DOCKET NO. D - PDF Free Download

BEFORE THE PUBLIC SERVICE COMMISSION OF THE STATE OF MONTANA DOCKET NO. D2018.2.12 Application for Authority to Increase Retail Electric Utility Service Rates and for Approval of Electric Service Schedules and Rules and Allocated Cost of Service and Rate Design APPLICATION, TARIFFS, AND INTERIM VOLUME I September 28, 2018

AL BROGAN ANN B. HILL SARAH N. NORCOTT NorthWestern Energy 208 N. Montana Avenue, Suite 205 Helena, Montana 59601 Tel. (406) 4438903 al.brogan@northwestern.com ann.hill@northwestern.com sarah.norcott@northwestern.com Attorneys for NorthWestern Energy DEPARTMENT OF PUBLIC SERVICE REGULATION BEFORE THE PUBLIC SERVICE COMMISSION OF THE STATE OF MONTANA IN THE MATTER OF NorthWestern Energy s ) REGULATORY DIVISION Application for Authority to Increase Retail ) Electric Utility Service Rates and For Approval ) DOCKET NO. D2018.2.12 of Electric Service Schedules and Rules and ) Allocated Cost of Service and Rate Design ) NORTHWESTERN ENERGY S APPLICATION NorthWestern Corporation d/b/a NorthWestern Energy ( NorthWestern or Applicant ) respectfully submits this Application for Authority to Increase Retail Electric Utility Service Rates and for Approval of Electric Service Schedules and Rules and Allocated Cost of Service and Rate Design ( Application ). 1 In support thereof, NorthWestern states as follows: 1 Pursuant to ARM 38.5.502, NorthWestern is filing a separate Application for Interim Rate Increase in conjunction with this Application. 1

Applicant s full name and address are: NorthWestern Energy 11 East Park Street Butte, MT 59701 I. II. Applicant is a Delaware corporation doing business as NorthWestern Energy in the states of Montana, South Dakota, and Nebraska as a public utility. III. The following described tariff sheets are the Electric Utility tariff sheets affected by the proposals in this Application that are presently in effect in Montana and on file with the Commission. Schedule Description Sheet Nos. REDS1 Residential Electric Delivery Service 52 nd Revised Sheet No. 10.1 GSEDS1 General Service Electric Delivery Service 29 th Revised Sheet No. 20.1 51 st Revised Sheet No. 20.2 GSEDS2 General Service Substation/Transmission 29 th Revised Sheet No. 21.1 Electric Delivery Service ISEDS1 Irrigation Pumping & Sprinkling Electric 52 nd Revised Sheet No. 30.1 Delivery Service ELDS1 Electric Lighting Delivery Service 29 th Revised Sheet No. 40.1 48 th Revised Sheet No. 40.2 ESS1 Electricity Supply Service 182 nd Revised Sheet No. 60.1 33 rd Revised Sheet No. 60.2 Rule No. 1 Definitions 1 st Revised Sheet No. R1.1 2

(Table Continued) Schedule Description Sheet Nos. Rule No. 3 Service Agreements Original Sheet No. R3.1 Rule No. 5 Service Conditions Original Sheet No. R5.1 1 st Revised Sheet No. R5.2 Original Sheet No. R5.3 Original Sheet No. R5.4 1 st Revised Sheet No. R5.5 Rule No. 6 Line Extensions 4 th Revised Sheet No. R6.1 4 th Revised Sheet No. R6.3 5 th Revised Sheet No. R6.4 Original Sheet No. R6.6 Rule No. 7 Customer s Installation Original Sheet No. R7.1 Rule No. 8 Utility s Installation 1 st Revised Sheet No. R8.1 2 nd Revised Sheet No. R8.2 1 st Revised Sheet No. R8.3 Rule No. 13 Termination of Service 1 st Revised Sheet No. R13.1 Original Sheet No. R13.2 Original Sheet No. R13.3 Original Sheet No. R13.4 Original Sheet No. R13.5 Original Sheet No. R13.6 Original Sheet No. R13.7 Original Sheet No. R13.8 Original Sheet No. R13.9 Original Sheet No. R13.10 The following described tariff sheets are new Electric Utility tariff sheets affected by the proposals in this Application. 3

Schedule Description Sheet Nos. RENM1 Residential Electric Net Metering Service Original Sheet No. 15.1 Original Sheet No. 15.2 Original Sheet No. 15.3 Original Sheet No. 15.4 Rule No. 13 Termination of Service Original Sheet No. R13.11 The applicable rates and rate changes, excluding the changes to the Rules for these tariff sheets, are summarized in Appendix A, which is attached. Due to changes in the rules some language appears on new pages. A complete set of the proposed revised tariffs is provided in a separate tab following this Application. IV. NorthWestern s currently authorized rates for its Electric Utility service are no longer just and reasonable rates as they do not allow NorthWestern to recover its costs of providing electric supply or delivery service nor do they provide NorthWestern an opportunity to earn a fair and reasonable return on its investments. V. NorthWestern has prepared, and files with this Application, its cost of providing Electric Utility service in Montana based upon a 2017 test year, adjusted for known and measurable changes. The filed cost of service includes the information required in the Commission s Minimum Rate Case Filing Standards set forth in ARM 38.5.103 through 38.5.182 and 38.5.190. NorthWestern also incorporates an application for approval of an allocated cost of service and rate design, which includes the establishment of a residential net metering class and rates for future private generators who interconnect to NorthWestern s system after Commission approval of the residential net metering class. 4

VI. The cost of service filed concurrently with this Application establishes that NorthWestern has a revenue deficiency for its Electric Utility of $34,861,573 consisting of a revenue deficiency for delivery service of $37,912,116, which is offset by supply service. As stated previously, Appendix A is a summary of the current base rates, excluding the tax tracker balance from Order No. 7580b in Docket No. D2017.11.86, and the proposed base rates. Appendix B, which is attached, summarizes the typical bill impact of the proposed rates for a residential customer using 750 kilowatt hours per month. VII. In 2018, NorthWestern purchased the membership interest in Two Dot Wind Farm, LLC and transferred the associated assets ( Two Dot Wind Farm ) to NorthWestern. Prior to the acquisition, NorthWestern purchased the output of the facility pursuant to a Qualifying Facility Power Purchase Agreement. NorthWestern presents evidence in this filing that shows that the purchase of the Two Dot Wind Farm results in a benefit to customers and just and reasonable rates. NorthWestern requests that the Commission authorize inclusion of the Two Dot Wind Farm in rate base and the proposed revenue requirement for it in base rates. VIII. In addition to filing its cost of service in support of this Application, NorthWestern files concurrently all necessary prefiled direct testimony, exhibits, and workpapers. 5

IX. When the Commission approved NorthWestern s acquisition of the Spion Kop Wind Project ( Spion ), it expressed concern about the risk of Spion underperforming relative to expectations and the limited sitespecific wind speed data. In 132 of Order No. 7159l in Docket No. D2011.5.41, the Commission required NorthWestern to to file annual compliance filings showing Spion Kop s net capacity factor and total energy output and required a rate adjustment if, at the end of three years, Spion s average annual total energy output was less than 118,000 megawatthours ( MWh ). At the end of three years, Spion s average annual total energy output was 136,565 MWh. NorthWestern has submitted compliance filings showing that Spion produced 139,970 MWh, 143,192 MWh, 126,532 MWh, 130,070 MWh, and 131,819 MWh for the 12month December through November reporting periods ending November 30 of 2013, 2014, 2015, 2016, and 2017 respectively. Spion s historical production has demonstrated that it has not underperformed expectations. NorthWestern requests that the Commission eliminate NorthWestern s obligation to make future annual compliance filings. WHEREFORE, NorthWestern respectfully requests that the Commission approve: 1. an increase in base electric rates in the amount of $34,861,573, a return on equity of 10.65%, and an overall rate of return of 7.42% for electric utility assets except for Colstrip Unit 4, which the Commission set at a 10.00% return on equity and 8.25% rate of return for the life of the plant in 264 of Order No. 6925f in Docket No. D2008.6.69; 2. NorthWestern s proposed allocated cost of service and rate design, including a new customer class for future residential net energy metering customers; 3. the inclusion of Two Dot Wind Farm in rate base; 4. capitalization of demand side management costs; 6

Docket No. D2018.2.12 Appendix A Page 1 of 3 1 2 3 4 5 A B C D E F G H I J K NorthWestern Energy Electric Utility Proposed Tariff Rates Docket D2018.2.12 Current Proposed Rates 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 Tariff Schedule Total Rate Tax Portion of Rate Rate Without Tax Total Rate Tax Portion Rate Rate Without Tax Change % Change Residential: Residential: Service Charge REDS1 4.10 $ $ $ 4.10 $ 5.60 $ $5.60 $ 1.50 36.59% Transmission ESS1 $ 0.009625 $ 0.002329 $ 0.007296 $ 0.011548 $ 0.006284 $ 0.005264 $ 0.001923 19.98% Distribution REDS1 $ 0.031676 $ 0.008964 $ 0.022712 $ 0.036429 $ 0.012339 $ 0.024090 $ 0.004753 15.01% Employee: Service Charge REDS1 $ 2.46 $ $ 2.46 $ 3.36 $ $3.36 $ 0.90 36.59% Transmission ESS1 $ 0.005775 $ 0.001397 $ 0.004378 $ 0.006929 $ 0.003771 $ 0.003158 $ 0.001154 19.98% Distribution REDS1 $ 0.019006 $ 0.005379 $ 0.013627 $ 0.021857 $ 0.007403 $ 0.014454 $ 0.002851 15.00% General Service 1: GS 1 Secondary Non Demand: Service Charge GSEDS1 5.85 $ $ $ 5.85 $ 6.95 $ $6.95 $ 1.10 18.80% Transmission ESS1 $ 0.008380 $ 0.002027 $ 0.006353 $ 0.010067 $ 0.005784 $ 0.004283 $ 0.001687 20.13% Distribution GSEDS1 $ 0.041882 $ 0.012466 $ 0.029416 $ 0.043819 $ 0.012790 $ 0.031029 $ 0.001937 4.62% GS 1 Secondary Demand: Service Charge GSEDS1 $ 7.35 $ $ 7.35 $ 8.70 $ $8.70 $ 1.35 18.37% Energy Distribution GSEDS1 $ 0.005358 $ 0.001434 $ 0.003924 $ 0.006205 $ 0.001624 $ 0.004581 $ 0.000847 15.81% Demand Transmission ESS1 $ 3.202190 $ 0.774972 $ 2.427218 $ 3.102074 $ 1.737241 $ 1.364833 $ (0.100116) 3.13% Demand Distribution GSEDS1 $ 6.527597 $ 1.579767 $ 4.947830 $ 7.825067 $ 2.048287 $ 5.776780 $ 1.297470 19.88% GS 1 Primary Non Demand: Service Charge GSEDS1 $ 6.30 $ $ 6.30 $ 8.80 $ $8.80 $ 2.50 39.68% Transmission ESS1 $ 0.008767 $ 0.002122 $ 0.006645 $ 0.009144 $ 0.004840 $ 0.004304 $ 0.000377 4.30% Distribution GSEDS1 $ 0.021699 $ 0.006463 $ 0.015236 $ 0.024154 $ 0.006628 $ 0.017526 $ 0.002455 11.31% GS 1 Primary Demand: Service Charge GSEDS1 $ 19.85 $ $ 19.85 $ 27.70 $ $27.70 $ 7.85 39.55% Energy Distribution GSEDS1 $ 0.007507 $ 0.001832 $ 0.005675 $ 0.009552 $ 0.001961 $ 0.007591 $ 0.002045 27.24% Demand Transmission ESS1 $ 3.892075 $ 0.941935 $ 2.950140 $ 3.541016 $ 1.973918 $ 1.567098 $ (0.351059) 9.02% Demand Distribution GSEDS1 $ 4.273725 $ 1.034300 $ 3.239425 $ 5.452490 $ 1.119242 $ 4.333248 $ 1.178765 27.58% General Service 2: GS 2 Substation: Monthly Cust Charge GSEDS2 160.50 $ $ $ 160.50 $ 225.00 $ $225.00 $ 64.50 40.19% Max Dmd Transmission ESS1 $ 4.007678 $ 0.969912 $ 3.037766 $ 2.740799 $ 1.537069 $ 1.203730 $ (1.266879) 31.61% Max Dmd Distribution GSEDS2 $ 1.587576 $ 0.391069 $ 1.196507 $ 2.189626 $ 0.553130 $ 1.636496 $ 0.602050 37.92% GS 2 Transmission: Monthly Cust Charge GSEDS2 $ 983.70 $ $ 983.70 $ 1,380.00 $ $1,380.00 $ 396.30 40.29% Max Dmd Transmission ESS1 $ 2.257187 $ 0.546270 $ 1.710917 $ 2.449841 $ 1.340627 $ 1.109214 $ 0.192654 8.54% Max Dmd Distribution GSEDS2 $ 1.155083 $ 0.349572 $ 0.805511 $ 1.188732 $ 0.127701 $ 1.061031 $ 0.033649 2.91%

Docket No. D2018.2.12 Appendix A Page 2 of 3 1 2 3 4 5 A B C D E F G H I J K NorthWestern Energy Electric Utility Proposed Tariff Rates Docket D2018.2.12 Current Proposed Rates 6 Tariff Schedule Total Rate Tax Portion of Rate Rate Without Tax Total Rate Tax Portion Rate Rate Without Tax Change % Change 47 Irrigation: 48 Irrigation Non Demand: 49 Seasonal Cust Chg ISEDS1 $ 43.05 $ $ 43.05 $ 47.35 $ $47.35 $ 4.30 9.99% 50 Energy Transmission ESS1 $ 0.012212 $ 0.002955 $ 0.009257 $ 0.009383 $ 0.004175 $ 0.005208 $ (0.002829) 23.17% 51 Energy Distribution ISEDS1 $ 0.028286 $ 0.009425 $ 0.018861 $ 0.035900 $ 0.024907 $ 0.010993 $ 0.007614 26.92% 52 Irrigation Demand: 53 Seasonal Cust Chg ISEDS1 $ 101.45 $ $ 101.45 $ 111.60 $ $111.60 $ 10.15 10.00% 54 Energy Distribution ISEDS1 $ 0.004998 $ 0.001863 $ 0.003135 $ 0.004797 $ 0.002423 $ 0.002374 $ (0.000201) 4.02% 55 Demand Transmission ESS1 $ 2.095177 $ 0.507061 $ 1.588116 $ 2.191794 $ 1.013810 $ 1.177984 $ 0.096617 4.61% 56 Demand Distribution ISEDS1 $ 7.635382 $ 1.847866 $ 5.787516 $ 8.856906 $ 4.473397 $ 4.383509 $ 1.221524 16.00% 57 58 Lighting: 59 Transmission ESS1 $ 0.003561 $ 0.000862 $ 0.002699 $ 0.006500 $ 0.003212 $ 0.003288 $ 0.002939 82.53% 60 Distribution ELDS1 $ 0.031850 $ 0.007709 $ 0.024141 $ 0.035268 $ 0.009126 $ 0.026142 $ 0.003418 10.73% 61 62 Ownership Charge (monthly): 63 Ownership Chg 200399 ELDS1 $ 3.16 $ 0.76 $ 2.40 $ 3.30 $ 0.80 $ 2.50 $ 0.14 4.43% 64 Ownership Chg 400599 ELDS1 $ 6.76 $ 1.64 $ 5.12 $ 7.02 $ 1.69 $ 5.33 $ 0.26 3.85% 65 Ownership Chg 600799 ELDS1 $ 10.50 $ 2.54 $ 7.96 $ 10.75 $ 2.47 $ 8.28 $ 0.25 2.38% 66 Ownership Chg 800999 ELDS1 $ 12.59 $ 3.04 $ 9.55 $ 12.92 $ 2.99 $ 9.93 $ 0.33 2.62% 67 Ownership Chg 10001199 ELDS1 $ 15.17 $ 3.68 $ 11.49 $ 15.60 $ 3.65 $ 11.95 $ 0.43 2.83% 68 Ownership Chg 12001399 ELDS1 $ 18.38 $ 4.44 $ 13.94 $ 18.93 $ 4.43 $ 14.50 $ 0.55 2.99% 69 Ownership Chg 14001599 ELDS1 $ 22.45 $ 5.43 $ 17.02 $ 23.01 $ 5.31 $ 17.70 $ 0.56 2.49% 70 Ownership Chg 16001799 ELDS1 $ 25.26 $ 6.11 $ 19.15 $ 25.92 $ 6.00 $ 19.92 $ 0.66 2.61% 71 Ownership Chg 18001999 ELDS1 $ 28.45 $ 6.87 $ 21.58 $ 29.10 $ 6.65 $ 22.45 $ 0.65 2.28% 72 Ownership Chg 20002199 ELDS1 $ 30.49 $ 7.38 $ 23.11 $ 31.19 $ 7.15 $ 24.04 $ 0.70 2.30% 73 Ownership Chg 22002399 ELDS1 $ 33.40 $ 8.08 $ 25.32 $ 34.16 $ 7.82 $ 26.34 $ 0.76 2.28% 74 Ownership Chg 24002599 ELDS1 $ 36.27 $ 8.76 $ 27.51 $ 37.17 $ 8.55 $ 28.62 $ 0.90 2.48% 75 Ownership Chg 26002799 ELDS1 $ 39.19 $ 9.48 $ 29.71 $ 40.08 $ 9.18 $ 30.90 $ 0.89 2.27% 76 Ownership Chg 28002999 ELDS1 $ 42.11 $ 10.19 $ 31.92 $ 43.07 $ 9.87 $ 33.20 $ 0.96 2.28% 77 Ownership Chg 30003199 ELDS1 $ 41.98 $ 9.69 $ 32.29 $ 42.97 $ 9.38 $ 33.59 $ 0.99 2.36% 78 Ownership Chg 32003399 ELDS1 $ 42.28 $ 9.76 $ 32.52 $ 43.28 $ 9.45 $ 33.83 $ 1.00 2.37% 79 Ownership Chg 34003599 ELDS1 $ 42.57 $ 9.82 $ 32.75 $ 43.58 $ 9.51 $ 34.07 $ 1.01 2.37% 80 Ownership Chg 36003799 ELDS1 $ 45.03 $ 10.40 $ 34.63 $ 46.09 $ 10.07 $ 36.02 $ 1.06 2.35% 81 Ownership Chg 38003999 ELDS1 $ 47.45 $ 10.96 $ 36.49 $ 48.57 $ 10.61 $ 37.96 $ 1.12 2.36% 82 Ownership Chg 40004199 ELDS1 $ 49.87 $ 11.51 $ 38.36 $ 51.05 $ 11.15 $ 39.90 $ 1.18 2.37% 83 Ownership Chg 42004399 ELDS1 $ 52.32 $ 12.08 $ 40.24 $ 53.56 $ 11.70 $ 41.86 $ 1.24 2.37% 84 Ownership Chg 44004599 ELDS1 $ 54.74 $ 12.63 $ 42.11 $ 56.03 $ 12.23 $ 43.80 $ 1.29 2.36% 85 Ownership Chg 46004799 ELDS1 $ 57.19 $ 13.21 $ 43.98 $ 58.53 $ 12.78 $ 45.75 $ 1.34 2.34% 86 Ownership Chg 48004999 ELDS1 $ 59.61 $ 13.76 $ 45.85 $ 61.01 $ 13.32 $ 47.69 $ 1.40 2.35% 87 Ownership Chg 50005199 ELDS1 $ 62.04 $ 14.31 $ 47.73 $ 63.53 $ 13.88 $ 49.65 $ 1.49 2.40% 88 Ownership Chg 52005399 ELDS1 $ 64.49 $ 14.90 $ 49.59 $ 66.01 $ 14.43 $ 51.58 $ 1.52 2.36% 89 Ownership Chg 54005599 ELDS1 $ 66.93 $ 15.46 $ 51.47 $ 68.51 $ 14.97 $ 53.54 $ 1.58 2.36% 90 Ownership Chg 56005799 ELDS1 $ 69.34 $ 16.00 $ 53.34 $ 70.97 $ 15.49 $ 55.48 $ 1.63 2.35% 91 Ownership Chg 58005999 ELDS1 $ 71.77 $ 16.56 $ 55.21 $ 73.46 $ 16.03 $ 57.43 $ 1.69 2.35% 92 93 94 Lighting Misc Charges 95 Operations Charge ELDS1 $ 0.66 $ 0.16 $ 0.50 $ 0.68 $ 0.16 $ 0.52 $ 0.02 3.03% 96 Maintenance Charge ELDS1 $ 0.64 $ 0.16 $ 0.48 $ 0.66 $ 0.16 $ 0.50 $ 0.02 3.13% 97 Billing Charge ELDS1 $ 0.26 $ 0.06 $ 0.20 $ 0.22 $ 0.01 $ 0.21 $ (0.04) 15.38%

Docket No. D2018.2.12 Appendix A Page 3 of 3 1 2 3 4 5 A B C D E F G H I J K NorthWestern Energy Electric Utility Proposed Tariff Rates Docket D2018.2.18 Current July 1, 2018 Proposed Rates 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 Net Electric Supply Rate ($/kwh) Tariff Schedule Total Rate Tax Portion of Rate Rate Without Tax Total Rate Tax Portion Rate Rate Without Tax Total Rate Change % Change Residential ESS1 $ 0.065891 $ 0.003985 $ 0.061906 $ 0.065698 $ 0.004515 $ 0.061183 $ (0.000193) 0.29% Employee ESS1 $ 0.039534 $ 0.002391 $ 0.037143 $ 0.039419 $ 0.002709 $ 0.036710 $ (0.000115) 0.29% GS1 Secondary NonDemand ESS1 $ 0.064029 $ 0.003985 $ 0.060044 $ 0.063875 $ 0.004563 $ 0.059312 $ (0.000154) 0.24% GS1 Secondary Demand ESS1 $ 0.065889 $ 0.003985 $ 0.061904 $ 0.063875 $ 0.004563 $ 0.059312 $ (0.002014) 3.06% GS1 Primary NonDemand ESS1 $ 0.064086 $ 0.003877 $ 0.060209 $ 0.061741 $ 0.004453 $ 0.057288 $ (0.002345) 3.66% GS1 Primary Demand ESS1 $ 0.062438 $ 0.003877 $ 0.058561 $ 0.061741 $ 0.004453 $ 0.057288 $ (0.000697) 1.12% GS2 Substation ESS1 $ 0.063532 $ 0.003841 $ 0.059691 $ 0.060142 $ 0.004400 $ 0.055742 $ (0.003390) 5.34% GS2 Transmission ESS1 $ 0.063149 $ 0.003818 $ 0.059331 $ 0.060683 $ 0.004357 $ 0.056326 $ (0.002466) 3.91% Irrigation ESS1 $ 0.064029 $ 0.003985 $ 0.060044 $ 0.069074 $ 0.004632 $ 0.064442 $ 0.005045 7.88% Lighting ESS1 $ 0.064029 $ 0.003985 $ 0.060044 $ 0.063872 $ 0.004483 $ 0.059389 $ (0.000157) 0.25%

Docket No. D2018.2.12 Appendix B Page 1 of 1 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 Residential Services Bill Amount A B C D E F G H I J K L M N Usage in kwh 750 1Jul18 Total Bill 1Jul18 Total Bill Total Bill Bill Percentage Rate Amount Rate Amount Rate Amount Change Change Monthly Service Charge per Meter $ 4.10 $ 4.10 $ 4.10 $ 4.10 $5.60 $ 5.60 $ 1.50 36.59% Commodity Charges: (Monthly $/kwh) Current Rates Approved Including Deferred Tax Portion in Rates Distribution Charge $ 0.022712 $ 17.03 $ 0.022712 $ 17.03 $ 0.024090 $ 18.07 $ 1.04 6.11% Taxes Distribution $ 0.009627 $ 7.22 Transmission Charge $ 0.007296 5.47 Taxes Transmission $ 0.002526 $ 1.89 Supply $ 0.061906 46.43 Taxes Supply $ 0.004305 3.23 Deferred Supply $ 0.000004 CTCQF $ 0.003182 2.39 BPA Credit $ (0.002249) (1.69) USBC $ 0.001334 1.00 Total kwh Usage $ 0.110643 82.97 $ 0.007296 1 1 Current Rates Approved Excluding Deferred Tax Portion in Rates $ 0.061906 $ 0.003985 $ 0.000004 $ 0.003182 $ (0.002249) $ 0.001334 $ 0.109463 Residential Class Proposed Rates $ 0.008964 $ 6.72 $ 0.012339 $ 9.25 $ 2.53 37.65% $ $ 5.47 $ 0.005264 $ 3.95 $ (1.52) 27.79% $ 0.002329 $ 1.75 $ 0.006284 $ 4.71 $ 2.96 169.14% $ $ 46.43 $ 0.061183 $ 45.89 $ (0.54) 1.16% $ $ 2.99 $ 0.004515 $ 3.39 $ 0.40 13.38% $ $ $ 0.000004 $ $ 0.00% $ $ 2.39 $ 0.003182 $ 2.39 $ 0.00% $ $ (1.69) $ (0.002249) $ (1.69) $ 0.00% $ $ 1.00 $ 0.001334 $ 1.00 $ 0.00% $ $ 82.09 $ 0.115946 $ 86.96 $ 4.87 5.87% Total Bill (Energy Charges plus Service Charge) $ 87.07 $ 86.19 $ 92.56 $ 6.37 7.39%

Service List Docket D2018.2.12 Electric General Filing Robert Nelson Montana Consumer Counsel 111 N. Last Chance Gulch Ste 1B Helena MT 59620 Ann Hill NorthWestern Energy 208 N. Montana Ave Suite 205 Helena MT 59601 Charles Magraw 501 8 th Ave. Helena MT 59601 Will Rosquist Administrator, Regulatory Division Public Service Commission 1701 Prospect Box 202601 Helena MT 596202601 Joe Schwartzenberger NorthWestern Energy 11 E. Park Butte MT 59701 Tracy Lowney Killoy NorthWestern Energy 11 E. Park Butte MT 59701 Al Brogan NorthWestern Energy 208 N. Montana Ave Suite 205 Helena MT 59601 Thorvald A. Nelson Holland & Hart 6380 S. Fiddlers Green Circle Suite 500 Greenwood Village CO 80111 F. Diego Rivas NW Energy Coalition 1101 8 th Ave. Helena MT 59601 Laura Rennick Andersen MDEQ 1520 E. 6 th Avenue Helena MT 59601

MarkedUp Tariffs

ELECTRIC TARIFF 52 nd Revised Sheet No. 10.1 Canceling 51 st Revised Sheet No. 10.1 Schedule No. REDS1 RESIDENTIAL ELECTRIC DELIVERY SERVICE APPLICABILITY: Applicable to all domestic purposes in single private dwellings and individual family apartments for Customers receiving electric supply under Electricity Supply Service or through a Contract with a Competitive Electric Supplier (Electric Supplier). PROHIBITION: Residential Electric customers with a net metering system interconnected to NWE s distribution system on and after {insert date on which the Commission approves Rate Schedule No. RENM 1 Residential Electric Net Metering Service} are prohibited from service under this rate schedule and the Electricity Supply Service Tariff referenced below. These customers are required to take service under Schedule No. RENM1. Residential Electric customers with net metering systems interconnected prior to {insert date from above} may elect to take service under Schedule No. RENM1; however, these customers cannot then receive electric net metering service under Schedule No. REDS1 Residential Electric Delivery Service. TYPE OF SERVICE: Singlephase, 120 volts, 2 wire, or 120/240 volts, 3 wire, through one meter at one point of delivery. RATES: Electric Supply Charge: PLUS: Transmission Charges: Monthly Bill: In Accordance with the Electricity Supply Service Tariff or with a Contract Between the Customer and an Electric Supplier. In Accordance with the Electricity Supply Service Tariff if receiving supply under Electricity Supply Service; or In Accordance with Utility s FERC Approved Transmission Tariff if receiving supply from an Electric Supplier. PLUS: Delivery Service Charge (DSC): Customer specific DSC resulting from the sum of the following: Total Rate Tax Portion of Rate Rate Without Tax Monthly Customer Charge: $ 4.10 $ 5.60 $ 4.10 $ 5.60 Monthly Employee Customer Charge: $ 2.46 $ 3.36 $ 2.46 $ 3.36 Plus: Energy (Monthly $/kwh): Regular Customer $ 0.032339 $ 0.036429 $ 0.009627 $ 0.012339 $ 0.022712 $ 0.024090 Employee $ 0.019404 $ 0.021857 $ 0.005777 $ 0.007403 $ 0.013627 $ 0.014454 TAX PORTION OF RATE: This rate represents the amount charged to customers for state and local taxes and fees and is separately disclosed on customer s bill. (continued)

ELECTRIC TARIFF Original Revised Sheet No. 15.1 Canceling Revised Sheet No. 15.1 Schedule No. RENM1 RESIDENTIAL ELECTRIC NET METERING SERVICE APPLICABILITY: This schedule is applicable to all Residential Electric customers with a net metering system interconnected to NWE s distribution system on and after {insert date on which the Commission approves this rate schedule}. Tariff Rule No. 16 Electric Net Metering applies to all customers under this tariff. Residential Electric customers with net metering systems interconnected prior to {insert date from above} may elect to take service under Schedule No. RENM1; however, these customers cannot then receive electric net metering service under Schedule No. REDS1 Residential Electric Delivery Service. TYPE OF SERVICE: Singlephase, 120 volts, 2 wire, or 120/240 volts, 3 wire, through one meter at one point of delivery. RATES: Monthly Bill: Delivery Service Charge (DSC): Customer specific DSC resulting from the sum of the following: Total Rate Tax Portion of Rate Rate Without Tax Monthly Customer Charge: $ 5.60 $ 5.60 PLUS: Electric Supply Charge: Energy (Monthly $/kwh): All kwh @ $ 0.065698 $ 0.004515 $ 0.061183 PLUS: Supply Deferred Monthly Charge $/kwh: All kwh @ $ 0.000004 $ 0.000004 PLUS: Demand (Monthly $/kw): Distribution: All kw @ $ 7.24 $ 2.46 $ 4.78 Transmission: All kw @ $ 1.40 $ 0.76 $ 0.64 (continued)

ELECTRIC TARIFF Original Revised Sheet No. 15.2 Canceling Revised Sheet No. 15.2 Schedule No. RENM1 RESIDENTIAL ELECTRIC NET METERING SERVICE Electric Supply Charge: Transmission Charge: In Accordance with this Tariff or with a Contract Between the Customer and an Electric Supplier In Accordance with this Tariff or with Utility s FERC Approved Transmission Tariff if receiving supply from an Electric Supplier TAX PORTION OF RATE: This rate represents the amount charged to customers for state and local taxes and fees and is separately disclosed on customer s bill. PLUS: BPA Residential Exchange Credit: Energy (Monthly $/kwh): Residential Customer All kwh @ $ (0.002123) PLUS: Other Applicable Charges: All charges contained on other applicable rate schedules approved by the Public Service Commission of Montana. Low Income Discount: Customers who have satisfied the requirements for and are receiving energy assistance through the LIEAP program administered by the State of Montana, Department of Health and Human Services (IncomeQualified Customer) shall obtain a discount on their DSC bill. The DSC discount shall be an amount equal to (15%) from May 1 st to October 31 st and (25%) from November 1 st to April 30 th of total electric bill (Electric Supply, Transmission, all Delivery Charges, any Competitive Transition Charges (CTCs), universal system benefits programs (USBC) and any other applicable electric charges contained on other applicable rate schedules approved by the Public Service Commission of Montana) as if the customer were receiving electricity supply service, regardless of whether the customer is receiving electricity supply service or competitive electric supply service. This discount shall be adjusted with changes in any regulated rates. APPLICATION OF RATES: Monthly Bill Components: Each month, Customers bills shall include all relevant charges contained on other applicable rate schedules including, but not limited to, competitive transition charges (CTC) and universal systems benefits programs (USBC). (continued)

SPECIAL TERMS AND CONDITIONS: 1. Definitions: ELECTRIC TARIFF Original Revised Sheet No. 15.3 Canceling Revised Sheet No. 15.3 Rule No. RENM1 RESIDENTIAL ELECTRIC NET METERING SERVICE A. BPA Residential Exchange Credit: Credit from the Bonneville Power Administration in settlement of the Residential Exchange rights of regional residential and small farm customers to benefit from the Federal Columbia River Power System per the Northwest Power Act. B. Electric Delivery Service: Service provided to Customer to deliver electricity through the local electric distribution wires to the Customer s point of service. C. Electric Energy: The amount of electricity used measured in kilowatt hours (kwh). D. Electric Demand: The average kilowatts (kw) supplied during the onehour period of maximum use during the month, as determined by permanently installed indicating type meters. 2. Two or More Apartments: Where two or more apartments or residential dwelling units are wired to receive service through one meter, and the expected demand exceeds 10 kw, General Service 1 Rates shall be applicable. 3. Common Areas: Halls, basements, or other common use portions of an apartment building or multiple dwelling building shall be served under General Service 1 Rates. 4. Nonresidential Uses: Where a portion of a residential dwelling unit is used for nonresidential purposes, General Service 1 Rates shall apply to all service used for nonresidential purposes. If installation of a separate meter is impracticable, all service rendered will be billed under the rate schedule applicable to the predominate usage of the premise. 5. SinglePhase Motors: Incidental singlephase motors of not larger than three horsepower may be served under this Rate Schedule when used for domestic purposes. 6. ThreePhase Service: Customers requiring larger than three horsepower motors for domestic purposes may be served under this Rate Schedule with threephase power when such service is available. If an underground threephase extension or conversion is required, the additional cost over an overhead threephase extension or conversion shall be contributed as a nonrefundable contribution by the Customer(s). (continued)

ELECTRIC TARIFF Original Revised Sheet No. 15.4 Canceling Revised Sheet No. 15.4 Rule No. RENM1 RESIDENTIAL ELECTRIC NET METERING SERVICE 7. Surcharge on Advances or Contributions: Whenever, under the provisions of this Rate Schedule, an advance or contribution is required, the current surcharge as required by Utility operations shall be applied to such advance or contribution. This is to offset the effect caused by the Utility s delayed tax depreciation reimbursement of the current year tax on this advance or contribution. This surcharge is not applicable where such advances or contributions are the result of highway relocations or any government directed relocations that benefit the public and the government is not receiving utility service. SERVICE AND RATES SUBJECT TO COMMISSION JURISDICTION: All rates and service conditions under this Rate Schedule are governed by the rules and regulations of the Public Service Commission of Montana and are subject to revision as the Commission may duly authorize in the exercise of its jurisdiction.

ELECTRIC TARIFF 29 th Revised Sheet No. 20.1 Canceling 28 th Revised Sheet No. 20.1 Schedule No. GSEDS1 GENERAL SERVICE ELECTRIC DELIVERY SERVICE APPLICABILITY: Applicable to electric service served from either a primary distribution line of 2.4 kv or more, but less than 50 kv; or from a secondary distribution line of 120 volts or more, but less than 50 kv, that is served from such a primary distribution line for Customers receiving electric supply under Electricity Supply Service or through a Contract with a Competitive Electric Supplier (Electric Supplier). Such service to be supplied through one meter at one point of delivery unless otherwise specified by a special contract between the Utility and Customer. Not applicable to standby, breakdown, resale or shared service, irrigation pumping and sprinkling service, or residential service. TYPE OF SERVICE: Sixty hertz alternating current delivered at primary or secondary distribution voltages and at such phase as Utility may have available. RATES: Monthly Bill: Electric Supply Charge: PLUS: Transmission Charges: In Accordance with the Electricity Supply Service Tariff or with a Contract Between the Customer and an Electric Supplier. In Accordance with the Electricity Supply Service Tariff if receiving supply under Electricity Supply Service; or In Accordance with Utility s FERC Approved Transmission Tariff if receiving supply from an Electric Supplier. PLUS: Delivery Service Charge (DSC): Customer specific DSC resulting from the sum of the following: Total Rate Tax Portion of Rate Rate Without Tax Secondary Service: NonDemand Meter: Monthly Customer Charge: $ 5.85 $ 5.85 Plus: $ 6.95 $ 6.95 Energy (Monthly $/kwh): All kwh @ $ 0.042785 $ 0.013369 $ 0.029416 $ 0.043819 $ 0.012790 $ 0.031029 Demand Meter: Monthly Customer Charge: $ 7.35 $ 7.35 Plus: $ 8.70 $ 8.70 Energy (Monthly $/kwh): All kwh @ $ 0.005470 $ 0.001546 $ 0.003924 Demand (Monthly $/kw): $ 0.006205 $ 0.001624 $ 0.004581 All kw @ $ 6.660955 $ 1.713125 $ 4.947830 $ 7.825067 $ 2.048287 $ 5.776780 (continued)

ELECTRIC TARIFF 51 st Revised Sheet No. 20.2 Canceling 50 th Revised Sheet No. 20.2 Schedule No. GSEDS1 GENERAL SERVICE ELECTRIC DELIVERY SERVICE PLUS: BPA Residential Exchange Credit: (Residential Load Only See Definition) Energy (Monthly $/kwh): All kwh @ $ (0.002123) Other Applicable Charges: All charges contained on other applicable rate schedules approved by the Public Service Commission of Montana. RATES: Delivery Service Charge (DSC): Customer specific DSC resulting from the sum of the following: Total Rate Tax Portion of Rate Rate Without Tax Primary Service: NonDemand Meter: Monthly Customer Charge: $ 6.30 $ 6.30 Plus: $ 8.80 $ 8.80 Energy (Monthly $/kwh): All kwh @ $ 0.022168 $ 0.006932 $ 0.015236 $ 0.024154 $ 0.006628 $ 0.017526 Demand Meter: Monthly Customer Charge: $ 19.85 $ 19.85 Plus: $ 27.70 $ 27.70 Energy (Monthly $/kwh): All kwh @ $ 0.007661 $ 0.001986 $ 0.005675 Demand (Monthly $/kw): $ 0.009552 $ 0.001961 $ 0.007591 All kw @ $ 4.361037 $ 1.121612 $ 3.239425 $ 5.452490 $ 1.119242 $ 4.333248 TAX PORTION OF RATE: This rate represents the amount charged to customers for state and local taxes and fees and is separately disclosed on customer s bill. PLUS: Other Applicable Charges: All charges contained on other applicable rate schedules approved by the Public Service Commission of Montana. Monthly Bill Components: Each month, Customers bills shall include an Electric Supply Charge; a Transmission & Ancillary Services Charge(s); all relevant charges contained on other applicable rate schedules including, but not limited to, competitive transition charges (CTC) and universal systems benefits programs (USBC); and Delivery Services Charge(s) (DSC). Customers may be billed either entirely by the Utility, or in part by the Electric Supplier, in accordance with the Contract between the Utility and Electric Supplier, or the Electric Supplier and its Customer. (continued)

ELECTRIC TARIFF 29 th Revised Sheet No. 21.1 Canceling 28 th Revised Sheet No. 21.1 Schedule No. GSEDS2 GENERAL SERVICE SUBSTATION/TRANSMISSION LEVEL ELECTRIC DELIVERY SERVICE APPLICABILITY: Applicable to all electric service served either directly from a transmission line of 50 kv or higher, or directly from a substation that is served from such a transmission line for Customers receiving electric supply under Electricity Supply Service or through a Contract with a Competitive Electric Supplier (Electric Supplier). Such service to be supplied through one meter at one point of delivery unless otherwise specified by a special contract between the Utility and Customer. Not applicable to standby, breakdown, resale or shared service, irrigation pumping and sprinkling service, or residential service (except as provided for in Schedule No. ECCGP1, 7). TYPE OF SERVICE: Sixty hertz alternating current delivered at such phase as Utility may have available. RATES: Monthly Bill: Electric Supply Charge: PLUS: Transmission Charges: In Accordance with the Electricity Supply Service Tariff or with a Contract Between the Customer and an Electric Supplier. In Accordance with the Electricity Supply Service Tariff if receiving supply under Electricity Supply Service; or In Accordance with Utility s FERC Approved Transmission Tariff if receiving supply from an Electric Supplier. PLUS: Delivery Service Charge (DSC): Customer specific DSC resulting from the sum of the following: Total Rate Tax Portion of Rate Rate Without Tax Substation Level: Monthly Customer Charge: $ 160.50 $ 160.50 Plus: $ 225.00 $ 225.00 Maximum Demand (Monthly $/kw): All kw @ $ 1.620106 $ 0.423599 $ 1.196507 $ 2.189626 $ 0.553130 $ 1.636496 Transmission Level: Monthly Customer Charge: $ 983.70 $ 983.70 Plus: $ 1,380.00 $ 1,380.00 Maximum Demand (Monthly $/kw): All kw @ $ 1.179689 $ 0.374178 $ 0.805511 $ 1.188732 $ 0.127701 $ 1.061031 TAX PORTION OF RATE: This rate represents the amount charged to customers for state and local taxes and fees and is separately disclosed on customer s bill. (continued)

ELECTRIC TARIFF 52 nd Revised Sheet No. 30.1 Canceling 51 st Revised Sheet No. 30.1 Schedule No. ISEDS1 IRRIGATION PUMPING & SPRINKLING ELECTRIC DELIVERY SERVICE APPLICABILITY: Applicable to Irrigation and Pumping Service Customers using this service exclusively for the operation of irrigation pumping and sprinkling equipment billed during the irrigation season, normally the May through October billing periods, who receive electric supply under Electricity Supply Service or through a Contract with a Competitive Electric Supplier (Electric Supplier). Such service to be supplied through one meter at one point of delivery unless otherwise specified by a special contract between the Utility and Customer. TYPE OF SERVICE: Sixty hertz alternating current delivered at such phase as Utility may have available. RATES: Monthly Bill: Electric Supply Charge: PLUS: Transmission Charges: PLUS: In Accordance with the Electricity Supply Service Tariff or with a Contract Between the Customer and an Electric Supplier. In Accordance with the Electricity Supply Service Tariff if receiving supply under Electricity Supply Service; or In Accordance with Utility s FERC Approved Transmission Tariff if receiving supply from an Electric Supplier. Tax Portion of Rate Rate Without Tax Total Rate NonDemand Meter: Seasonal Customer Charge: $ 43.05 $ 43.05 Plus: $ 47.35 $ 47.35 Energy (Monthly $/kwh): $ 0.028897 $ 0.03590 $ 0.010036 $ 0.024907 $ 0.018861$ 0.010993 Demand Meter: Seasonal Customer Charge: $ 101.45 $ 111.60 $ 101.45 $ 111.60 Plus: Energy (Monthly $/kwh): $ 0.005110 $ 0.004797 $ 0.001975 $ 0.002423 $ 0.003135 $ 0.002374 Demand (Monthly $/kw): $ 7.791372 $ 8.856906 $ 2.003856 $ 4.473397 $ 5.787516 $ 4.383509 TAX PORTION OF RATE: This rate represents the amount charged to customers for state and local taxes and fees and is separately disclosed on customer s bill. PLUS: BPA Residential Exchange Credit: Energy (Monthly $/kwh): All kwh @ $ (0.002123) (continued)

ELECTRIC TARIFF 29 th Revised Sheet No. 40.1 Canceling 28 th Revised Sheet No. 40.1 Schedule No. ELDS1 ELECTRIC LIGHTING DELIVERY SERVICE APPLICABILITY: Applicable for lighting purposes including, but not limited to, streets, highways, alleys, parks, public grounds, or other publicly dedicated outdoor ways and places, posttop lighting, and yard lighting, where lights are operated from dusk to dawn throughout the year; and all other miscellaneous outdoor lighting installations throughout the Utility s entire electric service area for Customers receiving electric supply under Electricity Supply Service or through a Contract with a Competitive Electric Supplier (Electric Supplier). TYPE OR SERVICE: Sixty hertz, alternating current delivered at such voltage or current as may be available at the Utility s option. RATES: Monthly Bill: Electric Supply Charge: PLUS: Transmission Charges: In Accordance with the Electricity Supply Service Tariff or with a Contract Between the Customer and an Electric Supplier. In Accordance with the Electricity Supply Service Tariff if receiving supply under Electricity Supply Service; or In Accordance with Utility s FERC Approved Transmission Tariff if receiving supply from an Electric Supplier. PLUS: Total Rate Tax Portion of Rate Rate Without Tax Energy Charge (Monthly $/kwh): $ 0.032500 $ 0.035268 $ 0.008359 $ 0.009126 $ 0.024141$ 0.026142 PLUS: Ownership Charge (Monthly $/Unit): Cost Range Total Unit Rate Tax Portion of Rate Unit Rate Without Tax $ 200 $ 399 $ 3.22 $ 3.30 $ 0.82 $ 0.80 $ 2.40 $ 2.50 400 599 $ 6.89 $ 7.02 $ 1.77 $ 1.69 $ 5.12 $ 5.33 600 799 $ 10.71 $ 10.75 $ 2.75 $ 2.47 $ 7.96 $ 8.28 800 999 $ 12.85 $ 12.92 $ 3.30 $ 2.99 $ 9.55 $ 9.93 1,000 1,199 $ 15.48 $ 15.60 $ 3.99 $ 3.65 $ 11.49 $ 11.95 1,200 1,399 $ 18.76 $ 18.93 $ 4.82 $ 4.43 $ 13.94 $ 14.50 1,400 1,599 $ 22.91 $ 23.01 $ 5.89 $ 5.31 $ 17.02 $ 17.70 1,600 1,799 $ 25.78 $ 25.92 $ 6.63 $ 6.00 $ 19.15 $ 19.92 1,800 1,999 $ 29.03 $ 29.10 $ 7.45 $ 6.65 $ 21.58 $ 22.45 2,000 2,199 $ 31.11 $ 31.19 $ 8.00 $ 7.15 $ 23.11 $ 24.04 (continued)

ELECTRIC TARIFF 48 th Revised Sheet No. 40.2 Canceling 47 th Revised Sheet No. 40.2 Schedule No. ELDS1 ELECTRIC LIGHTING DELIVERY SERVICE RATES: PLUS: Cost Range Total Unit Rate Tax Portion of Rate Unit Rate Without Tax 2,200 2,399 $ 34.08 $ 34.16 $ 8.76 $ 7.82 $ 25.32 $ 26.34 2,400 2,599 $ 37.01 $ 37.17 $ 9.50 $ 8.55 $ 27.51 $ 28.62 2,600 2,799 $ 40.00 $ 40.08 $ 10.29 $ 9.18 $ 29.71 $ 30.90 2,800 2,999 $ 42.98 $ 43.07 $ 11.06 $ 9.87 $ 31.92 $ 33.20 3,000 3,199 $ 42.83 $ 42.97 $ 10.54 $ 9.38 $ 32.29 $ 33.59 3,200 3,399 $ 43.14 $ 43.28 $ 10.62 $ 9.45 $ 32.52 $ 33.83 3,400 3,599 $ 43.44 $ 43.58 $ 10.69 $ 9.51 $ 32.75 $ 34.07 3,600 3,799 $ 45.94 $ 46.09 $ 11.31 $ 10.07 $ 34.63 $ 36.02 3,800 3,999 $ 48.41 $ 48.57 $ 11.92 $ 10.61 $ 36.49 $ 37.96 4,000 4,199 $ 50.88 $ 51.05 $ 12.52 $ 11.15 $ 38.36 $ 39.90 4,200 4,399 $ 53.37 $ 53.56 $ 13.13 $ 11.70 $ 40.24 $ 41.86 4,400 4,599 $ 55.85 $ 56.03 $ 13.74 $ 12.23 $ 42.11 $ 43.80 4,600 4,799 $ 58.34 $ 58.53 $ 14.36 $ 12.78 $ 43.98 $ 45.75 4,800 4,999 $ 60.82 $ 61.01 $ 14.97 $ 13.32 $ 45.85 $ 47.69 5,000 5,199 $ 63.30 $ 63.53 $ 15.57 $ 13.88 $ 47.73 $ 49.65 5,200 5,399 $ 65.80 $ 66.01 $ 16.21 $ 14.43 $ 49.59 $ 51.58 5,400 5,599 $ 68.29 $ 68.51 $ 16.82 $ 14.97 $ 51.47 $ 53.54 5,600 5,799 $ 70.74 $ 70.97 $ 17.40 $ 15.49 $ 53.34 $ 55.48 5,800 5,999 $ 73.22 $ 73.46 $ 18.01 $ 16.03 $ 55.21 $ 57.43 Tax Portion Rate Without ($/Unit/month) Total Rate of Rate Tax Operations Charge: $ 0.67 $ 0.68 $ 0.17 $ 0.16 $ 0.50 $ 0.52 Maintenance Charge: $ 0.65 $ 0.66 $ 0.17 $ 0.16 $ 0.48 $ 0.50 Billing Charge: $ 0.27 $ 0.22 $ 0.07 $ 0.01 $ 0.20 $ 0.21 TAX PORTION OF RATE: This rate represents the amount charged to customers for state and local taxes and fees and is separately disclosed on customer s bill. PLUS: BPA Residential Exchange Credit: (Residential Load Only See Definition) Energy (Monthly $/kwh): All kwh @ $ (0.002123) (continued)

ELECTRIC TARIFF 182 nd Revised Sheet No. 60.1 Canceling 181 st Revised Sheet No. 60.1 Schedule No. ESS1 ELECTRICITY SUPPLY SERVICE APPLICABLITY: Applicable to all electricity supply customers of the Utility. Electric supply provided under this tariff is for the Customer s end use; and is prohibited from being remarketed by the Customer. PURPOSE: The purpose of this Rate Schedule is to recover the market costs of electric supply costs associated with Electricity Supply requirements, and to recover current MPSCbased retail transmission costs. RATES: Supply Monthly Billing: Each month, the Electricity Supply Service Supply Charge and the Deferred Electricity Supply Charge shall be the product of the actual monthly consumption, in kwh, delivered at the Customer s meter, times the applicable Supply rate set forth as follows: Supply Monthly $/kwh Supply Total Rate Tax Portion of Rate Without Tax Rates Classes: Rate Residential $ 0.067034 $ 0.065698 $ 0.004305 $ 0.004515 $ 0.062729 $ 0.061183 Residential Employee $ 0.040220 $ 0.039419 $ 0.002584 $ 0.002709 $ 0.037636 $ 0.036710 General Service 1 Secondary NonDemand $ 0.065094 $ 0.063875 $ 0.004305 $ 0.004563 $ 0.060789 $ 0.059312 General Service 1 Secondary Demand $ 0.067032 $ 0.063875 $ 0.004305 $ 0.004563 $ 0.062727 $ 0.059312 General Service 1 Primary NonDemand $ 0.065198 $ 0.061741 $ 0.004188 $ 0.004453 $ 0.061010 $ 0.057288 General Service 1 Primary Demand $ 0.063479 $ 0.061741 $ 0.004188 $ 0.004453 $ 0.059291 $ 0.057288 General Service 2 Substation $ 0.064634 $ 0.060142 $ 0.004150 $ 0.004400 $ 0.060484 $ 0.055742 General Service 2 Transmission $ 0.064246 $ 0.060683 $ 0.004126 $ 0.004357 $ 0.060120 $ 0.056326 Irrigation $ 0.065094 $ 0.004305 $ 0.060789 $ 0.069074 Lighting $ 0.065094 $ 0.063872 PLUS: Supply Deferred Monthly Charge $/kwh Supply Deferred Rates Classes: Charge Residential $ 0.000004 Residential Employee $ 0.000002 General Service 1 Secondary NonDemand $ 0.000004 (continued) $ 0.004632 $ 0.004305 $ 0.004483 $ 0.064442 $ 0.060789 $ 0.059389

ELECTRIC TARIFF 2 nd Revised Sheet No. 60.2 Canceling 1 st Revised Sheet No. 60.2 Schedule No. ESS1 ELECTRICITY SUPPLY SERVICE Rates Classes: Supply Deferred Charge General Service 1 Secondary Demand $ 0.000004 General Service 1 Primary NonDemand $ 0.000004 General Service 1 Primary Demand $ 0.000004 General Service 2 Substation $ 0.000004 General Service 2 Transmission $ 0.000003 Irrigation $ 0.000004 Lighting $ 0.000004 Transmission Monthly Billing: Each month, the Electricity Supply Service Transmission shall be the product of the actual monthly consumption, in kwh, or actual monthly demand, in kw, delivered at the Customer s meter, times the applicable Transmission rate as set forth below: PLUS: Transmission (Monthly $kwh or /kw) Transmission Tax Rate Rates Classes: Total Rate Portion o Without Tax f Rate Residential /kwh $ 0.009822 $ 0.002526 $ 0.007296 $ 0.011548 $ 0.006284 $ 0.005264 Residential Employee /kwh $ 0.005893 $ 0.001515 $ 0.004378 $ 0.006929 $ 0.003771 $ 0.003158 General Service 1 Secondary NonDemand /kwh $ 0.008552 $ 0.002199 $ 0.006353 $ 0.010067 $ 0.005784 $ 0.004283 General Service 1 Secondary Demand /kw $ 3.267611 $ 0.840393 $ 2.427218 $ 3.102074 $ 1.737241 $ 1.364833 General Service 1 Primary NonDemand /kwh $ 0.008946 $ 0.002301 $ 0.006645 $ 0.009144 $ 0.004840 $ 0.004304 General Service 1 Primary Demand /kw $ 3.971590 $ 1.021450 $ 2.950140 $ 3.541016 $ 1.973918 $ 1.567098 General Service 2 Substation /kw $ 4.089554 $ 1.051788 $ 3.037766 $ 2.740799 $ 1.537069 $ 1.203730 General Service 2 Transmission /kw $ 2.303301 $ 0.592384 $ 1.710917 $ 2.449841 $ 1.340627 $ 1.109214 Irrigation NonDemand /kwh $ 0.012461 $ 0.003204 $ 0.009257 $ 0.009383 $ 0.004175 $ 0.005208 Irrigation Demand /kw $ 2.137981 $ 0.549865 $ 1.588116 $ 2.191794 $ 1.013810 $ 1.177984 Lighting /kwh $ 0.003633 $ 0.000934 $ 0.002699 (continued)

ELECTRIC TARIFF 1 st Revised Sheet No. R1.1 Canceling Original Revised Sheet No. R1.1 Rule No. 1 DEFINITIONS 11 Average Error in Registration The term "average error in registration" as used herein shall mean the average of the meter error at light load (approximately ten percent (10%) of meter rating) and at full load (approximately 100 percent of meter rating). 12 Commission The word "Commission" or "MPSC" as used herein shall mean the Public Service Commission of Montana. 13 Customer The word "Customer" as used herein shall mean any individual, partnership, association, firm, public or private corporation, or governmental agency purchasing electric service from the Utility. A person who requests disconnection of service at his or her current address in order to move service to his or her new address with no break in the service is an existing customer, not an applicant for new service. 14 Customer's Installation The term "Customer's installation" as used herein shall mean all wiring, appliances, and apparatus on Customer's side of the point of delivery except the Utility's meter and other equipment owned by the Utility. 15 Electric Service The term "electric service" or "service" as used herein shall mean the supplying of or availability, at the point of delivery, of electric power and energy, and also the electric power and energy delivered or used. 16 Loads of Uncertain Duration The term Loads of Uncertain Duration shall mean any operation in an established location that is expected to exist for less than five years. Examples of Loads of Uncertain Duration include but are not limited to mines, lumber mills, gravel pits, and asphalt plants. 17 Meter The word "meter" or "meters" as used herein shall mean the complete installation, including auxiliary devices and equipment, if any, used to measure the power and energy supplied to a Customer. 178 Point of Delivery The term "point of delivery' as used herein shall mean the point at which the Utility's facilities connect physically to Customer's facilities, the location of which shall be designated by or satisfactory to the Utility, unless otherwise defined in the service agreement. 189 Residential Dwelling Unit The term "residential dwelling unit" as used herein shall mean any room or combination of rooms, including trailers and mobile homes, with facilities for cooking, designed for occupancy by one family. 1910 Service Agreement The term "service agreement" as used herein shall mean the agreement or contract between the Utility and the Customer pursuant to which service is supplied and taken. 1101 Utility The word "Utility" as used herein shall mean NorthWestern Energy in the course of its business of supplying electric service to customers in Montana.

ELECTRIC TARIFF Original Revised Sheet No. R3.1 Canceling Revised Sheet No. R3.1 Rule No. 3 SERVICE AGREEMENTS 31 Application for Service The Utility may require a Customer or prospective Customer to sign one of the Utility's standard application or service agreement forms. The application or agreement shall be binding only after acceptance of service by a duly authorized representative of the Utility and once accepted by the Utility, all terms and conditions therein shall be binding on the Customer. In the case of acceptance ofwhere an service by a Customer prior to the signing of such agreement is not required by the Utility, Customer shall pay for the service so furnished in accordance with the applicable rate schedule or schedules in force at the time of service and shall abide by and be subject to these all Commissionapproved Electric Tariff rules. A Customer requiring the construction of a line extension, as described in Rule No. 6, may be required to sign a service agreement whereby service is contracted for a period of not less than two years.

51 Supply of Service ELECTRIC TARIFF Original Revised Sheet No. R5.1 Canceling Revised Sheet No. R5.1 Rule No. 5 SERVICE CONDITIONS A. To the extent permitted by law or agreement, service shall be supplied only under and pursuant to these rules and any modifications or additions thereto lawfully made and under such applicable rates, schedules, and contracts as may from time to tome be lawfully established. Service shall be supplied under the applicable rates, schedules, and contracts only at such points of delivery as are within the free extension limits, or such extended limits as are provided for in Rule No. 6, from the Utility's facilities which are adequate and suitable as to voltage, phase, and capacity for the service desired. B. When, to make service available to a prospective Customer, the Utility must extend its lines beyond the free extension limit or increase or change transformer capacity or other facilities, a special service agreement my be required. C. If an extension is of such length and the prospective business, which may be developed, by it is so meager as to make it doubtful whether the business from the extension would yield a reasonable return, the facts may be reported to the Commission for investigation and determination as to the reasonableness of such extension. D. Where separate points of delivery exist for supplying service to a single Customer, or separate meters are maintained for measurement of service to a single Customer, each point of delivery or metering shall be separately billed under the applicable rates, schedules, or contracts, unless such contracts specify otherwise. 52 Permits A Customer or prospective Customer must furnish all easements, cleared rightsofway, and permits necessary to enable the Utility to supply the service requiredrequested by Customer. The Utility may elect to obtain rightsofway, easements, and permits across and along public property, but the Customer or prospective Customer is not thereby relieved of the obligation to clear it initially. Customer shall grant the easement to the Utility, its successors, assigns, and apportionees. 53 Utility's Responsibility The Utility is responsible only to the Customer for supplying electric service. If a service agreement with Customer exists, service is provided in accordance with conditions set forth in thate service agreement with the Customer, irrespective of ownership of the premises served. The Utility shall not be responsible for inconvenience, damage, or injury to persons or property resulting from the Utility's termination or discontinuance of service to any premises in accordance with Rule No. 59 or Rule No. 13 or interruptions to service pursuant to Rule No. 82B. (continued)

54 Kind of Service Available ELECTRIC TARIFF 1 st Revised Sheet No. R5.2 Canceling Original Revised Sheet No. R5.2 Rule No. 5 SERVICE CONDITIONS A. The voltage, phase, frequency, and capacity of the Utility's facilities may vary in different areas. As protection against the installation of unsuitable lamps, appliances, motors, motor starters, and other equipment, Customers are advised to ascertain from the Utility the type of service available at their point of delivery. The type of service available under different rates and schedules varies, so the Customer should consult the Utility prior to purchasing and installing equipment to ascertain the type of service available under rates or schedules which will result in the lowest probable operating cost to Customer. B. Residential service shall be singlephase in character. If a residential Customer requires threephase service and if existing utility facilities are such that it can be supplied, the service application shall so state and such service shall be provided as prescribed under the applicable rate schedule. C. The Utility may serve Xray equipment through a commercial or industrial Customer's regularly installed meter and service where these are of adequate capacity and where existing distribution facilities are adequate. When a Customer requires a separate transformer, or separate service and meter, or any special facilities to serve Customer's Xray equipment, a special service agreement or contract may be required. 55 Use of Service A. Service shall be used by the Customer only for the purposes specified in the service agreement, contract, applicable rates, or schedules; and the Customer shall not remeter, sell, or permit others to use such service, except when expressly authorized to do so by the rates, schedules, or contract under which the service is supplied. B. In no case may a Customer extend its electric facilities across or under a street, alley, lane, court, avenue, or other public or private space under different ownership in order to obtain a rate advantage by taking service for two or more premises through one meter. 56 Seasonal, Construction, ShortTerm, or Temporary Service and Service to Individual Mobile Homes and Trailers (See Rule No. 511) A. The Utility may require the Customer to pay in advance the estimated cost of connecting and disconnecting and installing and removing, less salvage credits, the facilities required for rendering such service. Individual mobile homes and trailers shall not be entitled to a free line extension under the terms of Rule No. 6 until they have been classified as permanent in accordance with one of the following two paragraphs. (continued)

ELECTRIC TARIFF Original Revised Sheet No. R5.3 Canceling Revised Sheet No. R5.3 Rule No. 5 SERVICE CONDITIONS B. Should an individual mobile home or trailer remain in one location for 12 consecutive months, it shall be considered a permanent Customer and the deposit for estimated connection and disconnection charges, exclusive of line extension contribution required under Rule No. 6, shall be refunded upon request by the Customer. (For service to trailer courts see Rule No. 710.) C. A mobile home affixed to a permanent foundation and with modern allweather provision for water and sewer facilities will be considered permanent. The provision for water and sewer requires either connection to city or town provided utilities, or to a State of Montana approved water well and septic tank system. D. Contractors, builders, or owners are required to execute a contract for the use of electricity for building and other purposes in construction work at a location not served by the Utility with electricity. Another Customer shall not allow a contractor, builder, or owner to use that Customer's service unless the contractor, builder, or owner obtains the Utility's permission specifying the other premises where the electric service is to be used. Permanent service will not be turned on at any new premises until payment has been made for all construction service. E. Service to structures with seasonal occupancy including but not limited to seasonal cabins and, summer homes, etc., will be supplied only if Customer agrees to pay for service to that structure for 12 months of the year. 57 Other Loads of Uncertain Duration, Including Mining and Lumbering (See Rule No. 511) A. The Utility may require a Customer with Loads of Uncertain Duration to advance the entire cost of installing facilities used in rendering such service and shall credit the account of the Customer, the Customer s successor, or assignee with an amount equal to 20 percent of the Customer s annual electric utility bill until the cost of the free line extension allowance provided under the terms of Rule No. 6 has been refunded; provided, however, that the refund period for the Customer, the Customer s successor, or assignee at this location shall not extend more than five (5) years from date of initial service regardless of the amount of the unrecovered advance. The customer credits will be calculated on an annual basis, and such credits will be applied to the Customer s, the Customer s successor s, or assignee s account on an annual basis only, or after discontinuance of service. Rule Nos. 511 and 512 also apply to Loads of Uncertain Duration. (continued)

ELECTRIC TARIFF 1 st Revised Sheet No. R5.4 Canceling Original Revised Sheet No. R5.4 Rule No. 5 SERVICE CONDITIONS B. Service to carnivals and circuses or other similar temporary events The Utility shall collect from the Customer, in advance, the estimated cost of connecting and disconnecting service and the cost of installing and removing, less salvage credits, the facilities required for rendering such service, in addition to the deposit required for electric service. Energy charges shall be prorated for that portion of the month that service is rendered, but no proration will be applied to the demand charge. C. Any amount collected from a Customer which is in excess of the actual cost of installing and removing the facilities required for rendering such service will be refunded to the Customer within 30 days after service is disconnected and facilities have been removed. 58 Free Service The Utility shall not supply free electric service to any Customer. 59 Refusal and Termination of Service by Utility A. The Utility may refuse service to any delinquent Customer owing the Utility for service at a present or previous location in the Utility s service area until such past balance has been paid or a satisfactory arrangement has been made for paying it. B. The Utility may refuse service to an applicant for service on the basis of the delinquency of another Customer only under the following circumstances: 1. In the case of a residential Customer: a. If the applicant was a spouse or coresponsible party on the account of the delinquent Customer at the time the delinquency occurred; or b. If the applicant was a parent of the delinquent Customer and the delinquent Customer was a minor at the same time the delinquency occurred. 2. In the case of nonresidential Customer, the Utility may refuse service to an applicant on the basis of such past delinquency only if the applicant has a legal obligation to pay the delinquency. C. The Utility may refuse service if the party applicant for service refuses to establish credit as required under Rule No. 4. 510 Renting of Rooms Where four or less rooms, not intended to constitute a separate family suite, within a residence are rented to the public for domestic purposes only by one owning or occupying

ELECTRIC TARIFF 1 st Revised Sheet No. R5.5 Canceling Original Revised Sheet No. R5.5 Rule No. 5 SERVICE CONDITIONS the residence and where a single meter is installed, a single application of the rate shall apply to the entire service. 511 Reconnect Charges If a Customer requests reconnection of service outside of business hours, Customer shall pay a fee of $150.00. NorthWestern s business hours for purposes of this Rule 5 11 are Monday through Friday from 7:30am to 5pm prevailing MST excluding State and Utilityrecognized holidays. There shall be no reconnection charge if the disconnection of service was required to address safetyrelated conditions. 512 Surcharge on Advances or Contributions: Whenever, under the provisions of this Rate Schedule, an advance or contribution is required, the current surcharge as required by Utility operations shall be applies to such advance or contribution. This is to offset the effect caused by the Utility s delayed tax depreciation reimbursement of the current year tax on this advance or contribution. This surcharge is not applicable where advances or contributions are the result of highway relocations or any government directed relocations that benefit the public and the government is not receiving utility service.

ELECTRIC TARIFF 4 th Revised Sheet No. R6.1 Canceling 3 rd Revised Sheet No. R6.1 Rule No. 6 LINE EXTENSIONS 61 Line Extension Allowance Upon application for electric service, the Utility shall make an extension of a primary and/or secondary line to the Applicant for Service (except that the applicant shall furnish all necessary rightsofway) as follows: A. In the case of an application for Residential Service, a maximum line extension allowance of $5400 plus the service drop (not to exceed 150 feet overhead or 100 feet underground), transformer and meter. B. In the case of an application for General Service (GS), a maximum line extension allowance of: 1. GS and Irrigation nondemand metered service: $0.045/kWh times the Utility's estimate of the annual kwh consumption of the Customer plus the service drop (not to exceed 150 feet overhead or 100 feet underground), transformer and meter; 2. GS and Irrigation demand metered service less than 1 MW: $0.04/kWh times the Utility's estimate of the annual kwh consumption of the Customer plus the service drop (not to exceed 150 feet overhead or 100 feet underground), transformer and meter; 3. GS and Irrigation demand metered service equal to or greater than 1 MW: calculated based on the Revenue/Cost Ratio described below; or 4. Industrial Customers or projects requiring transmission or substation facilities: calculated based on the Revenue/Cost Ratio described below. Revenue/Cost Ratio: The comparison between the expected annual revenue to be received from the Customer and the annual cost of serving the Customer. A Revenue/Cost Ratio greater than one (1) will result in some level of line extension cost allowance; a Ratio less than or equal to one (1) will result in no line extension cost allowance. C. For purposes of this Tariff, a primary line is an electric utility line that operates at over 600 volts. A secondary line is an electric utility line that operates at voltages less than 600 volts and supplies energy to more than one electric service. Unless otherwise indicated, line extension refers to a primary line extension, a secondary line extension, or both. D. For purposes of this Tariff, a Single Family Residential Service means electric service to a singlefamily house, trailer, manufactured home, or mobile home, excluding any outbuildings, improvements, irrigation pumps, facilities, or other structures located on the property. (continued)

ELECTRIC TARIFF 4 th Revised Sheet No. R6.3 Canceling 3 rd Revised Sheet No. R6.3 Rule No. 6 LINE EXTENSIONS customers will be included for purposes of calculating refunds; however the refund to which they are no longer entitled will not be refunded to other customers. General Service and other nonsingle Family Residential Customers i. Advances will be refunded to the original line extension customer, their successors or assignees, and any subsequent customers connecting to the same line. When a subsequent customer requests connection to the original line extension, the remaining cost obligation of customers already connected to the extension (existing customers) and the cost obligation of the subsequent customer are determined as described in Rule No. 62 (A)(1), and as if the subsequent customer was connected to the line extension. The refund to each existing customer is based on their remaining cost obligation. ii. Refunds shall not exceed the customer s proportionate share of the cost of the original line extension. iii. No refunds will be made or credits allowed until the additional Applicant for Service has become an active electric Customer of the Utility. iv. At the end of the 60month period referred to above, no further refunds shall be made. 3. A Customer who hires a contractor to complete an extension pursuant to Paragraph 614 of this Rule No. 6 is not eligible for a refund. 63 Advances and Refunds for Subsequent Line Extensions When a subsequent customer requires a line extension that taps the original line extension during the applicable refund period, the Utility shall collect from the subsequent customer an advance equal to the customer s proportional share of the original advance for the original line extension determined under Rule No. 62 (A)(1), plus the advance for the subsequent line extension. Advances for subsequent customers connecting to the subsequent line extension will be determined based on the original advance for the subsequent line extension. For determination of refunds, see Rule No. 62 (A)(2). 64 Applicability This Rule applies to all prospective, permanent Customers, except street, posttop, outdoor, or yard lighting service, and service for resale, provided the proposed line extension can be built from an adequate, existing line across rightsofway which shall be supplied and cleared by the Customer. Extensions which are not capable of further revenue development, or to loads of uncertain duration, or extensions for temporary service, or which would involve any unusual conditions, are governed by the provisions of Rule No. 5. 65 Construction Standards The engineering, design, materials, and method of constructing the line extension shall be determined by the Utility in accordance with its service standards. The location and route of the line extension, from an existing, adequate line, shall be established by the Utility. The Utility may refuse to build a threephase extension in cases where the customer load does not (continued)

ELECTRIC TARIFF 5 th Revised Sheet No. R6.4 Canceling 4 th Revised Sheet No. R6.4 Rule No. 6 LINE EXTENSIONS require this type of extension. The line extension and all related facilities shall, at all times, be owned, maintained, and operated by the Utility. 66 Line Extension Cost A. The cost of an extension, as used herein, shall include the total construction expense associated with the extension, including overhead charges, based on the minimum sized facilities needed to serve the extension. The cost shall also include the cost of any addition to, or moving of, existing facilities necessary to serve the extension. The cost of an extension shall not include meters or distribution transformers. The line extension allowance shall be in accordance with Rule No. 61. In unusual circumstances where facilities could be extended from multiple existing locations, or where multiple routes could be taken from one location, the cost of an extension shall be based on the shortest technically feasible route as determined by the Utility where there is an available rightofway and/or Utility easements and access to facilities. B. In cases where underground facilities are required by law or these regulations, a Customer is precluded from the election of overhead service. C. The Utility may temporarily serve Customers by overhead electric facilities in undeveloped portions of such designated area provided, however, that as such subdivision is developed, the temporary overhead facilities shall be removed and underground facilities shall be installed by the Utility. The Customer is responsible for the installation and removal costs associated with temporary facilities. D. The Utility will perform one line extension engineering cost estimate per Applicant for Service, per year at the same location, free of charge. The Applicant for Service will be assessed a charge at the rate of $61.0068.12 per hour for additional line extension cost estimates. Minimum charge is $61.0068.12. Any line extension engineering costs collected which result in establishment of service shall be credited to Customer s line extension responsibility. 67 Extensions to Subdivisions or Housing Projects Where a line extension is requested for a subdivision or housing project, the Utility may require the principal thereof to advance the entire cost of construction, and will subsequently refund this amount as specified in Rule No. 61, less the additional costs required to serve each Customer at this location, within 60 months from the date the original line extension is completed. 68 Customer Agreement The Utility will require the Applicant for Service requesting a line extension to enter into a Customer Agreement to connect to the Utility s electric system. (continued)

ELECTRIC TARIFF Original Revised Sheet No. R6.6 Canceling Revised Sheet No. R6.6 Rule No. 6 LINE EXTENSIONS additional facilities will be used for general system improvement or reasonable orderly development. 613 Surcharge on Advances or Contributions Whenever, under the provisions of this Rule, an advance or contribution is required, the current surcharge as required by Utility operations shall be applied to such advance or contribution. This surcharge is to offset the effect caused by the Utility s delayed tax depreciation reimbursement of the current year tax on this advance or contribution. This surcharge is not applicable where such contributions or advances are the result of highway relocations or any governmentdirected relocations that benefit the public and the government is not receiving utility service. 614 Contractor to Install Extension A retail Customer that has an individual load with an average monthly demand of less than 5,000 kilowatts may hire a contractor to extend electric facilities on the retail Customer s property to a residential, commercial or other added structure if the Utility first provides a cost estimate to extend its facilities to the new structure(s) and at the request of the Customer, the contractor has provided an alternative cost estimate. If the retail customer hires a contractor to install the extension, the Customer must pay the Utility for any costs incurred by the Utility for necessary inspections or onsite visits during construction and installation. All provisions of 695123, MCA, not mentioned herein apply and must be complied with.

ELECTRIC TARIFF Original Revised Sheet No. R7.1 Canceling Revised Sheet No. R7.1 Rule No. 7 CUSTOMER S INSTALLATION 71 Location of Customer's Point of Delivery and Utility Meter Set Customer must provide service entrance terminals (point of delivery) at a point readily accessible to the Utility's distribution facilities and provide a point for mounting the Utility's meter such points to be determined by, or satisfactory to, the Utility. Customer's service entrance and meter installation shall comply with the National Electrical Code and the Utility's service standards. 72 Customer's Responsibility Customer shall be responsible for the electrical installation, appliances, apparatus, and equipment on Customer's side of the point of delivery, and for the electric power and energy after it passes said point of delivery. Customer shall also be responsible for providing any permits required by governmental agencies. 73 Changes in Installation Customer shall notify the Utility of any proposed changes or increases in the installation which might overload or adversely affect the Utility's facilities. If Customer desires to exceed the maximum demand specified in Customer's currently effective service agreement, a new service agreement with the Utility shall be executed. 74 Power Factor Customer's installation shall comply with the following power factor requirements: A. The Utility reserves the right to require a Customer to install adequate equipment so that at all times the Customer can operate its facilities to maintain a power factor between 90% lagging and 90% leading. The Utility may refuse service to any fluorescent or other lighting equipment having similar load characteristics, unless such equipment is equipped with power factor corrective devices so as to operate at a power factor of ninety percent (90%) lagging or higher. B. The Utility may refuse service to any electric welder or other equipment having similar load characteristics, unless such equipment is equipped with power factor corrective devices so as to operate at a power factor of seventyfive percent (75%) lagging or higher at rated full load. C. Customer shall select and use motors and other power equipment so as to obtain the highest practicable power factor for Customer's installation according to good accepted practice. The Utility may refuse service to a Customer when low power factor equipment interferes with Customer's service or service to other customers. D. Should the Utility elect to serve loads of known low power factor characteristics, it may adjust the bills for service thereto, but only in accordance with a formula approved by the Commission and incorporated in the rates, schedules, or contracts of the Utility. (continued)

81 Utility's Responsibility ELECTRIC TARIFF 1 st Revised Sheet No. R8.1 Canceling Original Revised Sheet No. R8.1 Rule No. 8 UTILITY S INSTALLATION A. The Utility shall install and maintain its lines and facilities on its side of the point of delivery; but it shall not be required to install or maintain any lines or facilities, except meters, on Customer's side of the point of delivery. Only the Utility's duly authorized employees or agents shall be permitted to connect and disconnect the Utility's facilities to Customer's service terminal. B. The Utility shall make connection to Customer's service terminals and, where necessary, extend its service drop and supply one set of service drop attachment fittings for securing the service drop to Customer's premises. C. Surcharge on Advances or Contributions: Whenever, under the provisions of this Rule, an advance or contribution is required, the current surcharge as required by Utility operations shall be applied to such advance or contribution. This is to offset the effect caused by the Utility s delayed tax depreciation reimbursement of the current year tax on this advance or contribution. This surcharge is not applicable where such advances or contributions are the result of highway relocations or any government directed relocations that benefit the public and the government is not receiving utility service. 82 Continuity of Service A. The Utility shall make a reasonable effort to avoid interruptions of service and, when such interruptions occur, shall reestablish service with reasonable diligence. B. The Utility shall not be liable to Customer or others for failure or interruption of electric service due to acts of God, governmental regulations, court or Commission orders, acts of the public enemy, strikes or labor difficulties, accidents, weather conditions, acts of third parties, droughts, or, without limitation by the foregoing, any other cause beyond the reasonable control of the Utility. C. In the case of emergencyies or circumstances beyond the reasonable control of the Utility, the Utility shall have the right to temporarily interrupt service to some Customers or some areas in order to continue service to hospitals, fire protection stations, national defense installations and similar services, or to prevent an interruption of service to a large area of the Utility's system or the systems of interconnected utilities. (continued)

ELECTRIC TARIFF 2 nd Revised Sheet No. R8.2 Canceling 1 st Revised Sheet No. R8.2 Rule No. 8 UTILITY S INSTALLATION 83 Interruption of Service for Repairs and Changes When it is necessary for the Utility to make repairs to, or change, its plant, generating equipment, transmission or distribution system, meters, or other property, the Utility may, without incurring any liability therefore, interrupt service for such periods as may be reasonably necessary and in such manner as to minimize inconvenience to Customers. 84 Adjustment of Rate for Interruptions Interruptions of service covered by preceding Rule No. 83 shall not render the Utility liable for any adjustment in bills if the interruption is less than 24 hours. 85 Voltages The Utility shall adopt nominal standard alternating current voltages for its entire distribution system, or for each of the several areas into which the system may be divided. The Utility shall, upon request from the Commission, a Customer, or a prospective Customer, furnish a statement of the nominal standard voltages for any specific area. A. The voltages and permissible range of variation shall be as specified in the current version of the American National Standards Institute (ANSI) C84.1. This Rule shall not apply: 1. To transmission systems not used to directly serve Customers; 2. Where Customers specifically request a voltage other than standard nominal system voltages as specified in ANSI C84.1; or 3. In instances where voltage is in excess of 34,500 volts. B. Voltage variations greater than those specified above may be allowed where contracts or rate schedules so provide, where service is supplied directly from a transmission line, in areas where Customers are widely scattered, or where the revenue does not justify close voltage regulation. 86 Voltage Variations Variations in voltage in excess of those specified shall not be considered a violation of preceding Rule No. 85 if such variations are caused by: A. Large starting current requirements of motors, welders, Xray machines, or other power apparatus on the Customer's premises;. B. Actions of the elements;. C. Infrequent and unavoidable fluctuations of short duration due to operation of the Utility's system; or. (continued)

ELECTRIC TARIFF 1 st Revised Sheet No. R8.3 Canceling Original Revised Sheet No. R8.3 Rule No. 8 UTILITY S INSTALLATION D. Circumstances beyond control of the Utility. 87 Voltage Tests The Utility shall own one or more portable indicating voltmeters and one or more portable graphic recording voltmeters of an approved type having a range corresponding to the voltage supplied. The Utility shall make a voltage measurement, when requested by a Customer, to determine if the voltage at the point of delivery to Customer is within the Commission's requirements as set forth in Rule No. 85A. 88 Frequency: Sixty cycles shall be standard frequency for alternating current. The Commission shall determine the suitability of any other frequency that the Utility may wish to adopt. The Utility shall maintain its frequency within five percent, plus or minus, of standard at all time during which service is supplied; except that infrequent excess fluctuations of short duration shall not be considered a violation of this Rule.

131 Definitions For purposes of this Rule: ELECTRIC TARIFF 1 st Revised Sheet No. R13.1 Canceling Original Revised Sheet No. R13.1 Rule No. 13 TERMINATION OF SERVICE A. Appliances essential for maintenance of health means any electric energyusing device, which is certified by a licensed physician as being essential to prevent or to provide relief from serious illness or to sustain the life of a member of the household and for which there is no reasonable alternative. B. Customer means any purchaser of electric service supplied by the Utility for residential purposes. A person who requests disconnection of service at his or her current address in order to move service to his or her new address with no break in the service is an existing customer, not an applicant for new service. C. Delinquent account means an account for residential service that remains unpaid for at least thirty (30) days after the bill is rendered. The exact due date shall be printed on the face of the bill. D. Discontinuance of service means a cessation of service voluntarily requested by a Customer. E. Elderly means any residential electric consumer aged 62 or older, who resides at the service address. F. Handicapped means any residential electric consumer who resides at the service address and has any physical or mental impairment which substantially limits one or more of such person's life activities, and such person: 1. Is certified as being physically disabled by a licensed physician; or 2. Is certified as being mentally disabled by a licensed psychiatrist or registered psychologist, Veterans Administration, Social Security Administration, or local board of health. G. Landlord Customer means one or more individuals or an organization listed on the Utility's records as the party responsible for payment of the electric service provided to one or more residential units of a building, which is occupied by a tenant. H. Person unable to pay or to pay only in installments means any purchaser of electric service for residential purposes, who is a recipient of public assistance and/or has an income at or below federal poverty guidelines. I. Residential building means a building containing one or more dwelling units occupied by one or more tenants, but excluding hotels and motels not used primarily for residential purposes. (continued)

ELECTRIC TARIFF Original Revised Sheet No. R13.2 Canceling Revised Sheet No. R13.2 Rule No. 13 TERMINATION OF SERVICE J. Tenant means any person or group of persons whose dwelling unit in a residential building is provided electricity, pursuant to a rental agreement, but who is not the Customer of the Utility. K. Termination of service means a cessation of service effectuated by the Utility and not voluntarily requested by a Customer. 132 Grounds for Termination of Service Subject to the requirements of these Rules, the Utility may terminate service to a Customer for any of the following reasons: A. Nonpayment of a delinquent account; B. Misrepresentation of identity for the purposes of obtaining utility service; C. Unauthorized interference, diversion, or use of the Utility's service situated or delivered on or about Customer's premises, or when any evidence of tampering with the meter or interference with the proper functioning thereof is found; D. Failure to comply with the terms and conditions of a deferred payment agreement made in accordance with these Rules; E. Refusal to grant a duly authorized representative of the Utility access to equipment upon the premises of the Customer at reasonable times for the purposes of inspection, maintenance, or replacement when the Utility has given Customer reasonable notice of the need for such access and the time of visitation; or F. Violation of other rules of the Commission or Utility which adversely affects the safety of customers or other persons, or the integrity of the Utility's delivery system. 133 Prohibited Grounds for Termination of Service Neither of the following shall constitute grounds for the Utility to terminate service: A. The failure of any person, other than the Customer against whom termination is sought, to pay any charges due to the Utility; or B. The failure of a Customer to pay for merchandise, appliances, or other services not contained in tariffs approved by the Commission. (continued)

ELECTRIC TARIFF Original Revised Sheet No. R13.3 Canceling Revised Sheet No. R13.3 Rule No. 13 TERMINATION OF SERVICE 134 Statement of Termination Policy A current general statement of the Utility's termination policy shall be posted in all local business offices of the Utility, shall be made available upon request to all existing Customers, and shall be provided to all new Customers when they initiate service. This statement must be written in clear and understandable language and must include the following information: A. The time allowed to pay outstanding bills; B. A statement that arrangements for installment payment of delinquent bills can be made at any time prior to termination of service; C. The title and telephone number of the Utility employee to whom inquiries and disputes may be directed; D. The time allowed to initiate a dispute; E. Instructions for designating a third party to receive a copy of termination notices; F. Instructions for designating elderly or handicapped status or a medical emergency; G. Instructions for designating the presence of special appliances essential for maintenance of health or safety; H. Details of the method of termination as described below in Rule No. 1313; and I. Availability of a copy of the Commission's rules on termination of service. 135 Notice Prior to and at the Time of Termination A. Except as provided for below in Rule Nos. 135 B. 2 or 137, the Utility may not terminate service to any residential, commercial, firm industrial, or other Customer unless written notice is served. B. Termination notice shall be served as follows: 1. If no response to the first notice is received within ten (10) days of mailing, the Utility must send a second notice by first class or certified mail (return receipt requested). The second notice must be sent by the Utility or personally served on the Customer at least ten (10) days prior to the date of the proposed termination. (continued)

ELECTRIC TARIFF Original Revised Sheet No. R13.4 Canceling Revised Sheet No. R13.4 Rule No. 13 TERMINATION OF SERVICE 2. The Utility may terminate utility services upon serving written or telephone notice five (5) business days prior to the proposed termination date when a Customer: a. Remits an insufficient funds check as payment to the Utility after receiving the first notice of termination; or b. Breaches a payment agreement made pursuant to Rule No. 1315 below. 3. The provisions of above Rule No. 135 B. 1 shall govern notice of termination to Landlord Customers, except that the first notice must be sent at least thirty (30) days prior to the date of the proposed termination. 4. The Utility shall give written notice of the proposed termination for nonpayment to each residential unit reasonably likely to be occupied by an affected tenant of a Landlord Customer subject to termination. Such notice shall not be rendered earlier than five (5) business days following initial notification to the Landlord Customer. However, if the Landlord Customer disputes the amount owing, such notice shall not be rendered until the dispute has been resolved. In no event shall such notice be served upon the tenants less than fifteen (15) days prior to the termination of service to the Landlord Customer because of nonpayment. Upon affidavit, the Commission may, for good cause shown by the Utility, reduce the minimum time between notification of the Landlord Customer and notification of the tenants. 5. Prior to termination of service, the Utility must make a diligent attempt to contact the Customer, either in person or by telephone, to apprise Customer of the proposed action. If telephone or personal contact is not made, the Utility employee shall leave notice in a place conspicuous to the Customer that service will be terminated two business days thereafter unless the delinquent charges have been paid. C. When service is terminated, the Utility employee terminating service shall leave notice upon the premises in a place conspicuous to the Customer that service has been terminated which gives the address and telephone number of the Utility where Customer may arrange to have service restored. The Utility shall have personnel available after the time of termination and during normal business hours authorized to reconnect service if the conditions cited as grounds for termination are corrected to the Utility's satisfaction and upon payment of any reconnection charge specified in the Utility's filed tariffs. (continued)

ELECTRIC TARIFF Original Revised Sheet No. R13.5 Canceling Revised Sheet No. R13.5 Rule No. 13 TERMINATION OF SERVICE 136 Contents of Written Notice The written notices required by these Rules must contain: A. The Utility's statement of termination policy; B. An identification of the Customer and service account affected by the proposed termination; C. A statement of reasons for termination; D. The date of proposed termination; E. The amount of the reconnection fee, if any; F. A summary of rights and remedies, including procedures to dispute the termination notice, provisions relating to elderly and handicapped consumers and those suffering a medical emergency, provisions for Customers who are unable to pay their bills and steps necessary to make a claim of inability to pay, availability of installment payment arrangements, and sources of financial assistance. G. Designation of the bill in question as actual or estimated; H. Except for notification of tenants, amount owed and time period over which amount was incurred; I. Instructions on how service can be restored; and J. In the case of a Landlord Customer, the date on or after which the Utility will notify tenants of the proposed termination; K. In the case of notification of tenants: 1. The amount of an average monthly bill for utility service to the premises and the largest bill for utility service to the premises in the previous 12 months; and 2. A statement that Commission procedures and the laws of Montana may give the tenant certain rights with respect to which the tenant may wish to consult an attorney or Montana Legal Services. (continued)

ELECTRIC TARIFF Original Revised Sheet No. R13.6 Canceling Revised Sheet No. R13.6 Rule No. 13 TERMINATION OF SERVICE 137 Grounds for Termination of Service Without Written Notice The Utility may terminate service without prior notice only: A. If a condition immediately dangerous or hazardous to life, physical safety, or property exists; B. Upon order by any court, the Commission, or any other duly authorized public authority; C. If such service is obtained fraudulently or without authorization of the Utility; or D. For violations of, and/or noncompliance with, any applicable federal, state, municipal or other local laws, regulations, and codes. 138 Customer's Right to Dispute a Termination Notice A. The Utility must provide a reasonable procedure for Customers to dispute the termination of service. If the Utility decides such a dispute against a Customer, it must do so in writing and must advise the Customer that Customer may appeal the decision to the Commission. If the Commission is not able to resolve the compliant informally, the Customer may institute formal complaint proceedings under ARM 38.2.2101. B. In its investigation of the proposed termination or during any hearing regarding the proposed termination, the Commission may make inquiry of the parties as to the following matters, among others: 1. The extent to which Customer has control over their source of money for payments, including such matters as the lateness of public assistance checks; 2. Weather conditions; 3. The existence of illness of residents in the affected units; 4. The ages of the persons residing in the affected units; and 5. The existence of, or potential for, termination of service by other companies. C. The Commission may consider and give due weight to the above matters in any decision rendered on the appeal. (continued)

ELECTRIC TARIFF Original Revised Sheet No. R13.7 Canceling Revised Sheet No. R13.7 Rule No. 13 TERMINATION OF SERVICE 139 Termination Notice for Nonpayment When Prohibited A notice of termination of service may not be issued for nonpayment of a delinquent account if the entire amount is disputed by the Customer and the Customer is currently negotiating the dispute with the Utility or has filed a complaint with the Commission. The Utility may, however, issue a notice of termination of service with respect to that portion of any delinquent account, which is not disputed by the Customer. 1310 Termination of Service During Winter Months A. During the period of November 1 to April 1, and on any day when the reported ambient air temperature at 8:00 a.m. is at or below freezing or if the U.S. Weather Service forecasts a snowstorm or freezing temperatures for the succeeding 24hour period, no termination of residential service may take place if a Customer establishes that they are unable to pay or are able to pay only in installments, that they or a member of the household is at least 62 years old, or that they or a member of the household is handicapped. B. No termination of service may take place during the period of November 1 to April 1 except with specific prior approval of the Commission. C. Notwithstanding the provisions of preceding subparagraphs A and B immediately above, the Utility may discontinue service where a hazardous or dangerous condition exists or as otherwise provided for in Rule No. 137. 1311 Medical Emergencies A. Except as provided herein service may not be terminated to a residence where a licensed health care professional certifies to the Utility that the absence of service will aggravate an existing medical condition which would threaten the health of any permanent resident. A licensed health care professional means a licensed physician physician assistantcertified advanced practice registered nurse or registered nurse provided for in ARM 37.106.2805 and Title 37, MCA. All certifications must be in writing and provide the name and address of the person with the medical condition that would be aggravated by a termination of service. The certification must include the printed name, signature office address, and telephone number of the certifying licensed health care professional. A medical condition certificate is valid for 180 days from the date it is signed and dated by the licensed health care professional and may be renewed on a semiannual basis. (continued)

ELECTRIC TARIFF Original Revised Sheet No. R13.8 Canceling Revised Sheet No. R13.8 Rule No. 13 TERMINATION OF SERVICE B. To avoid the accumulation of a substantial arrearage during the term of the medical certificate, the Utility and the Customer, or an authorized representative of the Customer, shall negotiate an equitable payment arrangement that is reasonable and consistent with the Customer s ability to pay. If the Customer fails to make payments as established, resulting in an arrearage of $500 or more, the customer is required to enter into and comply with a monthly payment arrangement equal to the average of the last 12 months billing plus 1/12 of the arrearage. Failure to enter into a monthly payment arrangement and make payments will result in disconnection proceedings being initiated as set out in Rule No. 1311(C). C. The Utility must provide written notice of the initiation of disconnection proceedings to the Customer. If the missed payments are not received within ten days of mailing the Utility must send a second notice. From the date of the second notice the customer must pay at least onethird of the delinquent charges to avoid termination of service. The second notice must be sent by the Utility at least ten days prior to the date of the proposed termination. All written notices must be sent by first class or certified mail. Prior to termination of service, the Utility must make a diligent attempt to contact the Customer either in person or by telephone to apprise the Customer of the proposed action. If telephone or personal contact is not made the utility employee shall leave notice in a place conspicuous to the customer that service will be terminated on the next business day. If the required payment is made a new payment arrangement will be recalculated consistent with Rule No. 1311(B). Under no circumstances shall disconnection proceedings occur on accounts with an arrearage of less than $500. Nothing in this rule prevents the Utility from continuing service to a delinquent medically protected account. D. The Utility must notify the Commission in writing of the proposed termination at the beginning of the disconnection process. The Commission may intervene and require a different payment arrangement or delay termination of services if the circumstances warrant. Before the Commission will consider approving an alternate payment arrangement, the Customer must apply, if eligible, for financial aid through organizations providing Utility bill payment assistance and must respond to Commission requests for information. The payment arrangement set by the Commission is binding upon both the Customer and the Utility. Failure to comply with the payment arrangement may result in disconnection proceedings being initiated as set out in Rule No. 1311(C). E. From November 1 through March 31, the utility may not terminate a medical exception account protected from disconnection by the criteria established in Rule No. 1310. (continued)

ELECTRIC TARIFF Original Revised Sheet No. R13.8 Canceling Revised Sheet No. R13.8 Rule No. 13 TERMINATION OF SERVICE A. Service may not be terminated to a residence where a physician or local board of health certifies to the Utility that the absence of service will aggravate an existing medical emergency of any permanent resident. All certifications must be in writing. The certificate must provide the name and address of the person with a medical emergency that would be aggravated by a termination of service and the office address and telephone number of the certifying physician or local board of health. All written certification must be signed by a physician or by a person with knowledge of the facts at the local board of health. A medical emergency certificate expires in thirty (30) days but may be renewed on a monthly basis. B. To avoid the burden of substantial arrearage at the end of the medical emergency, the Utility and the Customer, or a representative of the Customer, shall negotiate an equitable payment plan that is reasonable and consistent with Customer's ability to pay. If the parties cannot reach a satisfactory agreement, either party may seek such an agreement through the Commission. (continued)

ELECTRIC TARIFF Original Revised Sheet No. R13.9 Canceling Revised Sheet No. R13.9 Rule No. 13 TERMINATION OF SERVICE 1312 Time of Termination Service shall not be terminated on a day, or a day immediately preceding a day, when the services of the Utility are not available to the general public for the purpose of reconnecting terminated service. Service may be terminated only between the hours of 8:00 a.m. and 12:00 noon. The provisions of this paragraph do not apply to discontinuance of service voluntarily requested by a Customer. 1313 Method of Termination A. Actual termination may not take place until two business days after personal or telephone notice or, in the alternative, two business days after notice has been posted in a place conspicuous to the Customer when Customer was not contacted personally or by telephone. B. The Utility's representative (employee) shall, at the time of termination, attempt to inform the occupant of the affected residence that service is to be terminated. The employee shall present the occupant with a statement of charges due and shall request verification that the delinquent charges have not been paid or are not subject to a dispute previously registered with the Utility or the Commission. Upon the presentation of evidence, which reasonably indicates that the charge has been paid or is subject to a dispute previously registered with the Utility or the Commission, service shall not be terminated. C. The employee shall be authorized to accept payment. If payment in full of all delinquent charges is tendered, service shall not be terminated. D. Payment may be tendered in any reasonable manner including personal check. Payment by personal check in not reasonable if Customer has paid the Utility with checks returned for insufficient funds twice or more within the previous two (2) years. 1314 ThirdParty Notification If a Customer designates a third person to receive customer notifications of termination of service, the Utility shall forward a duplicate of such notices to the designated third party. The third party so notified will not be liable for the account of the Customer, unless such third party has agreed to be a guarantor for the Customer. 1315 Payment Arrangements A. When a Customer cannot pay a bill in full, the Utility may continue to serve the Customer if Customer and the Utility can agree on a reasonable portion of the outstanding bill to be paid immediately, and the manner in which the balance of the outstanding bill shall be paid. (continued)

ELECTRIC TARIFF Original Revised Sheet No. R13.10 Canceling Revised Sheet No. R13.10 Rule No. 13 TERMINATION OF SERVICE B. In deciding on the reasonableness of a particular agreement, the Utility shall take into account the Customer's ability to pay, the size of the unpaid balance, Customer's payment history, and the amount of time and reasons why the debt is outstanding. C. If a Customer fails to make the payment agreed upon by the date that it is due, the Utility may, but is not obligated to, enter into a second such agreement. D. No such agreement or settlement shall be binding upon a Customer if it requires the Customer to forego any right provided for elsewhere in these Rules. 1316 Identification of Landlord Customers The Utility shall determine, prior to termination, whether a tenant occupies the residence subject to termination. At the time service is requested or anytime thereafter, a Landlord Customer must notify the Utility if a tenant will occupy the premises receiving service. 1317 Notice to Commission of Terminations Affecting Tenants A. Notwithstanding anything contained elsewhere in these Rules, prior to any termination for nonpayment that would affect tenants, the Utility shall notify the Commission in writing of the proposed termination. Upon notice and investigation of such proposed termination, or during any hearing pursuant to the complaint procedures provided for in ARM 38.2.2101 et seq., the Commission may make inquiry of the parties as to the following matters, among others: 1. The amount the tenants have paid to the Utility in relation to the amount equal to one month's bill and the arrearage on any earlier bill due form tenants; 2. The number of vacant units in the building; 3. The extent to which the tenants have control over their source of money for rent payments, including such matters as the lateness of public assistance checks, direct rent payments by the Welfare Department to the tenants' landlord, or participation by the tenants in a leased housing or rental assistance program; 4. Whether the tenants are engaged in rent withholding against their landlord; 5. The amount of payments recently received by the Utility from the landlord and the size of the past due bill of the landlord; 6. Whether the Utility has pursued collection remedies, other than threatened termination of service, against the landlord; (continued)

ELECTRIC TARIFF Original Revised Sheet No. R13.11 Canceling Revised Sheet No. R13.11 Rule No. 13 TERMINATION OF SERVICE 7. Weather conditions; 8. The existence of illness of persons residing in the affected units; 9. The ages of the persons residing in the affected units; 10. The availability of other housing to the tenants; and 11. The existence of, or potential for, termination of service by other companies. B. The Commission may consider and give due weight to the above matters in any decision rendered on the complaint. 1318 Exemptions If hardships result from the application of any of these termination Rules, or if unusual difficulty is involved in complying with any of these Rules, application may be made by the Utility to the Commission for permanent or temporary exemption from its provision, but such application shall be supported by full and complete justification for such action. 1319 Restoration of Service Whenever service is terminated under the provisions of this Rule (except Rule No. 137), the Utility will restore service after the Customer has fulfilled the requirements for restoration as set forth in the termination notice prescribed by Rule No. 136. Where service has been terminated under the provisions of Rule No. 137, conditions for restoration of service will be determined on a casebycase basis. 1320 Discontinuance of Service by Customer Customer shall give the Utility at least 24hours' notice, Saturdays, Sundays, and holidays excluded, to discontinue service, unless a longer time for notice of discontinuance is provided for in the service agreement.

Interim

AL BROGAN ANN B. HILL SARAH N. NORCOTT NorthWestern Energy 208 N. Montana Ave., Suite 205 Helena, Montana 59601 Tel. (406) 4438903 al.brogan@northwestern.com ann.hill@northwestern.com sarah.norcott@northwestern.com Attorneys for NorthWestern Energy DEPARTMENT OF PUBLIC SERVICE REGULATION BEFORE THE PUBLIC SERVICE COMMISSION OF THE STATE OF MONTANA IN THE MATTER OF NorthWestern Energy s ) REGULATORY DIVISION Application for Authority to Increase Retail ) Electric Utility Service Rates and For Approval ) DOCKET NO. D2018.2.12 of Electric Service Schedules and Rules ) and Allocated Cost of Service and Rate Design ) APPLICATION FOR INTERIM INCREASE IN ELECTRIC UTILITY RATES NorthWestern Corporation d/b/a NorthWestern Energy ( NorthWestern or Applicant ) respectfully moves that the Montana Public Service Commission ( Commission ) authorize interim rate relief to be effective November 1, 2018. 1 As demonstrated in the testimony, exhibits, and supporting workpapers included in NorthWestern s filing, its current rates are no longer just and reasonable, as they do not allow NorthWestern an opportunity to recover its total cost of providing electric service to its customers. NorthWestern is entitled to interim rate relief as set forth in this 1 NorthWestern requests approval within 30 days, but effective, for billing purposes, on November 1, 2018.

Application and the supporting material, found in the Interim Section of the filing, provided pursuant to ARM 38.5.505 and 38.5.506. I. The interim increase is comprised of an increase of $29,103,483, or 11.04%, for electric delivery service and a decrease of ($15,256,527), or (5.84%), for electric generation service. The overall requested interim revenue requirement increase is $13,846,956 for total electric service. The typical bill impact of the proposed interim rates for a residential customer using 750 kilowatt hours per month would be an increase of 2.03% or approximately $1.75 per month. II. Delivery service rates are increased on a uniform percentage basis for all classes. Generation rates are decreased on a uniform percentage basis for all core customer classes. III. The following tariff sheets are the Electric Utility tariff sheets affected by the proposals in this Application that are in effect in Montana and on file with the Commission. Schedule Description Sheet Nos. REDS1 Residential Electric Delivery Service 52 nd Revised Sheet No. 10.1 GSEDS1 General Service Electric Delivery Service 29 th Revised Sheet No. 20.1 51 st Revised Sheet No. 20.2 GSEDS2 General Service Substation/Transmission Level Electric Delivery Service 29 th Revised Sheet No. 21.1 ISEDS1 Irrigation Pumping & Sprinkling Electric Delivery Service 52 nd Revised Sheet No. 30.1 ELDS1 Electric Lighting Delivery Service 29 th Revised Sheet No. 40.1 48 th Revised Sheet No. 40.2 ESS1 Electricity Supply Service 182 nd Revised Sheet No. 60.1 33 rd Revised Sheet No. 60.2 2

IV. In contrast to the request for final rate approval, the interim rates have been calculated based on the last approved rate of return on equity as shown in the table below. The interim request includes several other adjustments, which are detailed in the Interim Section of the Applicant s filing. The acquisition of Two Dot Wind Farm, LLC is not included in the interim calculation. Electric Utility Return on Equity Rate of Return Transmission & Distribution 10.25% Docket No 2009.9.129, 7.22% Order No. 7046i Colstrip Unit 4 10.00% Docket No. D2008.6.69 8.25% Order No. 6925f Dave Gates Generating Station 10.25% Docket No. D2008.8.95 7.10% Order No. 6943e Spion Kop Wind 10.00% Docket No. D2011.5.41 7.10% Order No. 7159l Hydro Assets 9.80% Docket No. D2013.12.85 Order No. 7323k 7.00% V. Approval of interim rates is a reasonable means of providing interim relief to NorthWestern. Commission approval of an interim rate increase will not result in any harm to customers, since the rebate provisions of 693304, MCA protect ratepayers until there is a Final Order in this docket. See Conclusions of Law, 4, Order No. 7115b, Docket No. D2010.8.82, In the Matter of MontanaDakota Utilities Co., Application for Auth. to Establish Increased Rates for Elec. Serv. VI. NorthWestern Satisfies the Standards for the Grant of Interim Rate Relief The controlling regulation for consideration of a request for an interim rate increase in a general rate increase proceeding is set forth at ARM 38.5.506(1). That regulation provides, Consideration of an application to increase rates on an interim basis in a general rate increase 3

proceeding will be guided by generally established principles of utility rate regulation. That standard is in contrast to the standards set forth for considering requested interim rate relief in a tracking case. In a tracking case, the Commission must evaluate the requested interim rate relief using the guidance provided in four specific factors. See ARM 38.5.506(3). In a general rate increase proceeding, the Commission evaluates requested interim rate relief using generally established principles of utility rate regulation, which encompasses a broader range of factors. ARM 38.5.506(1). As this is a general rate increase proceeding and not a tracker, the Commission is to evaluate NorthWestern s request using generally established principles of utility rate regulation. Application of these principles demonstrate that the Commission should grant NorthWestern s request for an interim rate increase in this proceeding. 2 First, NorthWestern s Application demonstrates a serious electric utility services revenue deficiency of $34,861,573. That deficiency was calculated based on the test period, which is the 12months ended December 2017, adjusted for normalized and known and measurable changes in accordance with ARM 38.5.106. The Application is supported by the prefiled testimony of 22 witnesses, 3 exhibits, workpapers, Statements, and all of the material required under the Commission s regulations. The Application is comprehensive and demonstrates that the expense 2 There is an immense amount of legal authority that stands for the proposition that utility commissions should grant requests for interim rate increases where, as is the case here, the utility demonstrates through its request for permanent rate relief that there is a revenue shortfall and that customers are protected because the interim rates are refundable with interest. The reason for this rule is that a utility cannot recover past losses in future rates. Therefore, unless a public utility commission is prepared to quickly issue a final order on the request for permanent rate relief, interim rates protect both customers as the rates are refundable with interest, and the utility, because, in the absence of interim rate relief, the utility has no ability to recover the losses it will incur between the time it files its request for permanent rate relief and the time the Commission issues a final order. A sample of the authorities is listed in footnote 5 of this Application. Nevertheless, even if the Commission were to incorrectly apply the limited legal standard for a tracking case, NorthWestern satisfies the guidance under ARM 38.5.506(3) as demonstrated in this Application. 3 Two of the witnesses have two pieces of prefiled direct testimony. Therefore, there is a total of 24 pieces of prefiled direct testimonies. 4

items are clearly identifiable costs to the utility; that the proposed rate increase matches the known increased expenses; and the request for both permanent and interim rate relief is fully supported by extensive evidence. Second, the current rates are no longer just and reasonable as they do not allow NorthWestern to recover its costs of providing electric service. Similarly, the current rates do not provide NorthWestern with the opportunity to earn a fair and reasonable return on its investments. This issue is critical because the Commission is unlikely to issue a final order in this case for at least nine months. The Commission has not established a procedural schedule or a hearing date, and this case is substantial in magnitude. This is demonstrated by (1) the number of witnesses who have filed prefiled direct testimony (22), 4 (2) the comprehensive Statements and workpapers, (3) the likely number of intervenors, and (4) the scope of the matters to be resolved, which includes not just traditional revenue requirement issues but additional issues such as net metering, required by the Montana Legislature s 2017 passage of House Bill 219. Moreover, in an effort to assist the Commission in promptly issuing a procedural order in this case, NorthWestern and a number of entities who have already submitted comments in this docket, started in August 2018 to discuss a proposed procedural schedule (the Commission s Chief Counsel has been included in the email communications). Under the most recent proposals, the hearing in this matter will not take place before May 2019. While the 9month period envisioned by the Legislature for resolving requests for rate changes falls at the end of June, a May hearing followed by the normal rounds of posthearing briefing demonstrates that it will be difficult for the Commission to issue a final order any earlier than July 2019. Therefore, the current rates, which are no longer just and reasonable, will be in effect for an unreasonably 4 There is a total of 24 individual pieces of prefiled testimony. See Footnote 3. 5

long period of time. These reasons further support granting NorthWestern s requested interim rate relief. Third, customers are protected should the Commission grant NorthWestern s request. The proposed interim rates will be both interim and refundable. Therefore, customers are fully protected because customers will receive refunds, with interest, if the Commission ultimately issues an order establishing permanent rates that are less than the proposed interim rates. Moreover, the request for interim rate relief is $13,846,956, only about 40 percent of the permanent requested rate relief. Not only is the impact on customers modest ($1.75 per month for the average residential customer), but because the interim rate relief is a small percentage of the requested permanent rate relief, customers are unlikely to experience a large rate increase followed by a large rate decrease should the Commission ultimately reduce NorthWestern s proposed permanent rate relief. These reasons further support NorthWestern s request for interim rate relief. Fourth, NorthWestern will be irreparably harmed if the interim rate request is not granted. It is wellestablished that in the context of a general rate case, a utility cannot recoup past losses in future rates. This is black letter law and a fundamental ratemaking principle. 5 5 A.J. Industries, Inc. v. Alaska Pub. Serv. Com n, 470 P.2d 537 (1970) (request granted for a preliminary injunction allowing for an interim rate because it is clear that if the allegations of the petitioner are ultimately determined to be correct, the petitioner will have suffered great harm. Furthermore, the harm suffered by the petitioner will be irreparable, since it appears to be well settled that a public utility cannot recoup past losses ); Alaska Pub. Util. Com n. v. GAAB, 534 P.2d 549 (Alaska 1975) (grant of injunction allowing interim rate to go into effect because proposed rates are refundable, utility had no means of recovering lost interim revenues if ultimately successful), citing Prendergast v. New York Telephone Co., 262 U.S. 43 (1923); Federal Telecommunications Law, Second Edition 1999 (Huber, Kellogg and Thorne) at 3.12.3 ( Nor may a carrier recoup a shortfall if filed rates prove to be too low. Indeed, it has traditionally been a cardinal principal of ratemaking that a utility may not set rates to recoup past losses ), citing Nader v. FCC, 520 F.2d 182 (D.C. Cir. 1975); Galveston Electric Co. v. Galveston, 258 U.S. 388, 395, 42 S.Ct. 351, 66 L.Ed. 678 (1922) (a utility cannot include past losses in establishing future rates); Board of Commrs. v. New York Tel. Co., 271 U.S. 23, 3132 (1926) (excess past depreciation cannot be applied to overcome deficits in future earnings caused by otherwise confiscatory rates). 6

The following people have been served with the interim filing: Jed Henthorne Owen Orndorff Energy West Inc. CELP 1 1 st Ave. S 1087 W. River St. Suite 200 Great Falls MT 59401 Boise ID 837027035 The following people have been served with the entire filing, which includes the interim: Service List Docket D2018.2.12 Electric General Filing Robert Nelson Montana Consumer Counsel 111 N. Last Chance Gulch Ste 1B Helena MT 59620 Ann Hill NorthWestern Energy 208 N. Montana Ave Suite 205 Helena MT 59601 Charles Magraw 501 8 th Ave. Helena MT 59601 Will Rosquist Administrator, Regulatory Division Public Service Commission 1701 Prospect Box 202601 Helena MT 596202601 Joe Schwartzenberger NorthWestern Energy 11 E. Park Butte MT 59701 Tracy Lowney Killoy NorthWestern Energy 11 E. Park Butte MT 59701 Al Brogan NorthWestern Energy 208 N. Montana Ave Suite 205 Helena MT 59601 Thorvald A. Nelson Holland & Hart 6380 S. Fiddlers Green Circle Suite 500 Greenwood Village CO 80111 F. Diego Rivas NW Energy Coalition 1101 8 th Ave. Helena MT 59601 Laura Rennick Andersen MDEQ 1520 E. 6 th Avenue Helena MT 59601

DEPARTMENT OF PUBLIC SERVICE REGULATION BEFORE THE PUBLIC SERVICE COMMISSION OF THE STATE OF MONTANA IN THE MATTER of NorthWestern Energy s ) REGULATORY DIVISION Application for Authority to Increase Retail ) Electric Utility Service Rates and for Approval ) DOCKET NO. D2018.2.12 of Electric Service Schedules and Rules and ) Allocated Cost of Service and Rate Design ) NOTICE OF INTERIM RATE ADJUSTMENT REQUEST NorthWestern Corporation d/b/a NorthWestern Energy ( NorthWestern or Applicant ) serves notice pursuant to the Administrative Rules of Montana, Section 38.5.503, that it has filed with the Montana Public Service Commission ( Commission ) a request for an interim increase in electric utility delivery rates and an interim decrease in generation rates in the abovecaptioned docket. The interim request for the electric delivery service is an increase of $29,103,483 and for electric generation service is a decrease of ($15,256,527). The net requested interim revenue requirement increase is $13,846,956 for total electric service. This Notice is based on the Application and the workpapers in this docket. This docket commenced on September 28, 2018, when the Applicant filed prefiled direct testimony, exhibits, and supporting workpapers with the Commission, including interim workpapers. Pursuant to 693304, MCA, Applicant requests an interim increase in delivery rates and decrease in generation rates to be implemented pending a final decision in this docket. This request for interim adjustment to electric utility service rates was made because the rates presently in effect are no longer just and reasonable as they do not allow NorthWestern an opportunity to recover in rates its total cost of providing electric service to its customers. This is 1

demonstrated in the prefiled direct testimony, exhibits, and supporting workpapers included in Applicant s filing in this docket. The interim electric service rates have been calculated based upon adjustments, methodologies, and rates of return resulting from NorthWestern s last approved rate cases Docket No. D2009.9.129 for Electric Utility Delivery Services; Docket No. D2008.6.69 for Colstrip Unit 4; Docket No. D2008.8.95 for Dave Gates Generating Station; Docket No. D2011.5.41 for Spion Kop Wind; and Docket No. D2013.12.85 for Hydro Assets. Rates implementing the requested interim increases and decreases are shown in the Interim Section of Applicant s filing. Delivery service rates are increased on a uniform percentage basis for all classes. Generation rates are decreased on a uniform percentage basis for all core customer classes. Applicant submits that Applicant s customers are fully protected during the period the interim increase is in effect by the rebate and interest provisions found in 693304, MCA. The interim request and supporting documents can be examined at NorthWestern s General Office, 11 East Park Street, Butte, Montana; at the office of the Montana Consumer Counsel ( MCC ), 111 North Last Chance Gulch, Suite 1B, Helena, Montana; or at the office of the Commission, 1701 Prospect Avenue, Helena, Montana. The MCC is available to assist in the representation of consumer interests in this matter, and its phone number is 4064442771. Any response which any person wishes to have the Commission take into consideration in its decision on this interim rate relief matter should be delivered to the Commission at the above address as soon as possible or mailed to the Commission at P.O. Box 202601, Helena, MT 596202601. To emphasize, any response should be made speedily. Any portion of the interim adjustment approved by the Commission pending hearing and final decision may, pursuant to 693304, MCA, be subject to rebate or surcharge with interest 2

if the final decision in this docket is to approve a final rate which is different than the interim rate. Dated: September 28, 2018 3

DEPARTMENT OF PUBLIC SERVICE REGULATION BEFORE THE PUBLIC SERVICE COMMISSION OF THE STATE OF MONTANA Service Date: IN THE MATTER of NorthWestern Energy s ) REGULATORY DIVISION Application for Authority to Increase Retail ) Electric Utility Service Rates and for Approval ) DOCKET NO. D2018.2.12 of Electric Service Schedules and Rules and ) ORDER NO. Allocated Cost of Service and Rate Design ) INTERIM ORDER Introduction 1. On September 28, 2018, NorthWestern Energy ( NorthWestern ) filed with the Montana Public Service Commission ( Commission ) an application for authority to increase its electric service rates in Montana. 2. Concurrent with its general electric rate increase application, NorthWestern requested an interim increase in electric revenues of $13,846,956. NorthWestern s interim request represents an increase of 11.04% for electric delivery service and a decrease of 5.84% for electric generation service. 3. NorthWestern based the interim electric rate increase request on the Commission s administrative rules regarding interim rate increase requests (ARM 38.5.501, et seq.). 4. The standards set forth in ARM 38.5.506(1) serve as the basis for the Interim Order. Consideration of an application to increase rates on an interim basis in a general rate increase proceeding will be guided by generally established principles of utility rate regulation. Discussion and Findings of Fact 5. The Commission accepts NorthWestern s proposed interim adjustments. 1

Conclusions of Law 6. NorthWestern provides electric service within Montana and as such is a public utility within the meaning of 693301, MCA. 7. The Commission properly exercises jurisdiction over NorthWestern s rates and operations pursuant to Title 69, Chapter 3, MCA. 8. The Commission, at its discretion, within the scope of 693304, MCA may grant requests for interim rate relief pending a hearing or final decision on a matter. 9. The rate levels approved in this Interim Order are a reasonable means of providing interim relief to NorthWestern. The rebate provisions of 693304, MCA protect ratepayers until there is a Final Order in this docket. Order 10. NorthWestern shall file tariffs in compliance with this Interim Order. 11. NorthWestern is authorized to collect on an interim basis an additional $13,846,956 in electric revenues. 12. Nothing in this Interim Order precludes the Commission from adopting in a subsequent Interim Order or Final Order a revenue requirement different from that contained in the Interim Order. DONE AND DATED this day of October, 2018, by a vote of 2

NorthWestern Energy Electric Utility Interim Filing INDEX Description Page No. Income Statement Total Electric Interim 1 Income Statement Electric Transmission & Distribution Interim 2 6 Income Statement Total Generation (Excluding Two Dot) Interim 7 12 Income Statement Colstrip Unit 4 Interim 13 17 Income Statement Dave Gates Generating Station Interim 18 22 Income Statement Spion Kop Wind Generation Interim 23 27 Income Statement Hydro Generation Interim 28 32 Income Statement Montana Generation Interim 33 37 Income Statement Electric Supply NonPCCAM Interim 38 42 Income Tax Workpapers Total Electric Interim 43 51 Income Tax Workpapers Electric Transmission & Distribution Interim Income Tax Workpapers Total Generation (Excluding Two Dot) Interim 52 60 61 69 Income Tax Workpapers Colstrip Unit 4 Interim 70 78 Income Tax Workpapers Dave Gates Generating Station Interim 79 87 Income Tax Workpapers Spion Kop Wind Generation Interim 88 96 Income Tax Workpapers Hydro Generation Interim 97 105 Income Tax Workpapers Montana Generation Interim 106 114 i

Description Page No. Income Tax Workpapers Electric Supply NonPCCAM Interim 115 123 Derivation of Uniform Percentage Change Electric Transmission & Distribution Interim 124 128 Operating Revenues Electric Transmission & Distribution Interim 129 143 Derivation of Uniform Percentage Change Total Generation (Excl Two Dot) Interim 144 148 Operating Revenues Total Generation (Excluding Two Dot) Interim 149 160 Rate Base Interim 161 Working Capital Adjustment Total Electric Interim 162 Working Capital Adjustment Electric Transmission & Distribution Interim 163 Working Capital Adjustment Colstrip Unit 4 Interim 164 Working Capital Adjustment Dave Gates Generating Station Interim Working Capital Adjustment Spion Kop Wind Generation Interim 165 166 Working Capital Adjustment Hydro Generation Interim 167 Pictorial Exhibits Interim Summary of Revenue Requirement 168 Income Statement Pictorial Exhibits Transmission & Distribution 169 195 Income Statement Pictorial Exhibits Total Generation 196 225 Income Statement Pictorial Exhibits Colstrip Unit 4 226 247 Income Statement Pictorial Exhibits DGGS 248 272 ii

Description Page No. Income Statement Pictorial Exhibits Spion Kop 273 288 Income Statement Pictorial Exhibits Hydro 289 311 Income Statement Pictorial Exhibits Miscellaneous Generation and Expense 312 327 iii

Docket No. D2018.2.12 Page 1 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 A B C D E F H NORTHWESTERN ENERGY ELECTRIC TOTAL UTILITY INCOME STATEMENT ACTUAL 12 MONTHS ENDED DECEMBER 2017 ADJUSTED INTERIM TRANSMISSION & DISTRIBUTION GENERATION TWO DOT PCCAM TOTAL REVENUES: RATE SCHEDULE REVENUES $263,531,298 261,216,207 0 0 524,747,505 SALES FOR RESALE 108,861 0 0 0 108,861 PROVISION FOR RATE REFUND 0 0 0 0 0 TRANSMISSION 53,346,877 0 0 0 53,346,877 MISCELLANEOUS REVENUES 3,492,605 1,547,144 0 0 5,039,749 GROSS REVENUES (LINE 2 THRU 6) 320,479,641 262,763,351 0 0 583,242,992 COST OF SERVICE: STEAM POWER OPERATION 0 6,227,146 0 0 6,227,146 STEAM POWER MAINTENANCE 0 7,560,165 0 0 7,560,165 HYDRO POWER OPERATION 1 13,137,274 0 0 13,137,275 HYDRO POWER MAINTENANCE (1) 5,890,260 0 0 5,890,259 OTHER POWER GENERATION OPERATION 0 3,956,773 0 0 3,956,772 OTHER POWER GENERATION MAINTENANCE 0 2,070,010 0 0 2,070,010 POWER SUPPLY 925,966 2,523,897 0 0 3,449,863 TRANSMISSION OPERATION 16,002,563 0 0 0 16,002,563 TRANSMISSION MAINTENANCE 4,940,519 0 0 0 4,940,519 DISTRIBUTION OPERATION 15,679,555 548,060 0 0 16,227,615 DISTRIBUTION MAINTENANCE 18,668,148 0 0 0 18,668,148 CUSTOMER ACCOUNTS EXPENSE 8,272,923 2,418,728 0 0 10,691,651 CUSTOMER SERVICE AND INFORMATION EXPENSE 3,273,634 1,482,079 0 0 4,755,713 SALES EXPENSE 0 0 0 0 0 ADMINISTRATIVE AND GENERAL EXPENSE 35,562,335 19,491,186 0 0 55,053,521 TOTAL O & M EXPENSE (LINE 10 THRU 22) 103,325,644 65,305,577 0 0 168,631,221 DEPRECIATION 68,872,461 31,387,187 0 0 100,259,648 AMORTIZATION OF ELECTRIC PLANT 4,071,010 1,229,314 0 0 5,300,325 AMORTIZATION OF PLANT ACQ. ADJ. 0 9,012,657 0 0 9,012,657 * AMORTIZATION RE:BPA RESIDENTIAL EXCHANGE 0 0 0 0 0 * AMORTIZATION RE:PROPERTY TAXES 0 0 0 0 0 * AMORTIZATION RE:COMPENSATED ABSENCES 0 0 0 0 0 * PENSION DIFFERENTIAL (2,079,450) (823,933) 0 0 (2,903,383) * MPSC/MCC TAXES 1,075,570 0 0 0 1,075,570 * SO2 ALLOWANCES 0 (1) 0 0 (1) TAXES OTHER THAN INCOME TAXES 102,648,373 30,062,553 0 0 132,710,926 INCOME TAXES FEDERAL U.S. 0 0 0 0 0 INCOME TAXES OTHER 0 0 0 0 0 DEFERRED INCOME TAXES (8,181,689) 19,308,793 0 0 11,127,105 SUBTOTAL (LINE 25 THRU 36) 166,406,276 90,176,570 0 0 256,582,846 TOTAL COST OF SERVICE (LINE 23 + 37) 269,731,920 155,482,147 0 0 425,214,067 UTILITY OPERATING INCOME (LINE 7 39) 50,747,721 107,281,204 0 0 158,028,925 ELECTRIC UTILITY RATE BASE 998,965,961 1,315,567,012 0 0 2,314,532,973 RATE OF RETURN EARNED (%) MPSC BASIS (LINE 41 / 43) 5.08% 8.15% 0.00% 0.00% 6.83% REQUIRED REVENUE INCREASE 29,103,483 (15,256,527) 13,846,956

Docket No. D2018.2.12 Page 2 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 A B C D E F G H I J NORTHWESTERN ENERGY ELECTRIC TRANSMISSION & DISTRIBUTION UTILITY INCOME STATEMENT ACTUAL 12 MONTHS ENDED DECEMBER 2017 ADJUSTED ELECTRIC REVENUE SALES & GENERATION TRANSMISSION & & REVENUE ADMINISTRATIVE CORPORATE ELECTRIC UTILITY AND SUPPLY DISTRIBUTION RELATED TRANSMISSION & GENERAL LABOR ALLOCATION FUNCTION UTILITY ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT REVENUES: RATE SCHEDULE REVENUES $712,487,926 ($440,045,563) $272,442,363 ($8,911,064.99) SALES FOR RESALE 25,524,104 (25,415,244) 108,860 0 PROVISION FOR RATE REFUND 2,365,681 (2,365,681) (0) 0 TRANSMISSION 48,856,869 798,226 49,655,096 3,691,781 MISCELLANEOUS REVENUES 11,703,879 (2,943,339) 8,760,540 (5,267,935.3) GROSS REVENUES (LINE 2 THRU 6) $800,938,459 ($469,971,600) $330,966,859 ($10,487,218) $0 $0 $0 $0 COST OF SERVICE: STEAM POWER OPERATION 25,443,588 ($25,443,588) $0 STEAM POWER MAINTENANCE 7,560,165 ($7,560,165) 0 HYDRO POWER OPERATION 12,879,333 ($12,879,332) 1 $0 HYDRO POWER MAINTENANCE 5,777,994 ($5,777,995) (1) 0 OTHER POWER GENERATION OPERATION 13,064,253 ($13,064,253) (0) 0 OTHER POWER GENERATION MAINTENANCE 3,171,342 ($3,171,342) (0) 0 POWER SUPPLY 182,595,843 (181,659,394) 936,449 (24,281) 34,370 (20,573) TRANSMISSION OPERATION 16,416,431 (364,124) 16,052,307 57,629 TRANSMISSION MAINTENANCE 4,918,832 0 4,918,832 21,687 DISTRIBUTION OPERATION 19,177,533 (521,564) 18,655,969 (417,900) (26,102) DISTRIBUTION MAINTENANCE 18,064,985 0 18,064,985 603,163 CUSTOMER ACCOUNTS EXPENSE 10,700,251 (2,283,996) 8,416,255 (175,354) 159,232 (127,209) CUSTOMER SERVICE AND INFORMATION EXPENSE 4,711,769 (1,395,320) 3,316,449 40,957 (83,772) SALES EXPENSE 464,338 (131,771) 332,567 (332,566) 0 0 ADMINISTRATIVE AND GENERAL EXPENSE 72,634,109 (21,300,452) 51,333,657 (9,830,235) (5,154,706) 101,248 (887,628) TOTAL O & M EXPENSE (LINE 10 THRU 22) 397,580,766 ($275,553,298) $122,027,468 ($10,005,589) ($24,281) ($5,487,272) $600,386 ($1,145,284) DEPRECIATION $102,381,617 ($34,710,241) $67,671,376 AMORTIZATION OF ELECTRIC PLANT 4,701,085 (1,105,444) 3,595,641 AMORTIZATION OF PLANT ACQ. ADJ. 7,014,087 (7,014,087) 0 * AMORTIZATION RE:BPA RESIDENTIAL EXCHANGE (7,372,612) 0 (7,372,612) * AMORTIZATION RE:PROPERTY TAXES 4,958,642 1,072,409 6,031,051 * AMORTIZATION RE:INVESTMENT TAX CREDITS 0 0 0 * PENSION DIFFERENTIAL (8,695,937) 2,467,766 (6,228,172) * MPSC/MCC TAXES 0 0 0 * SO2 ALLOWANCES (1) 1 0 TAXES OTHER THAN INCOME TAXES 128,208,897 (30,766,953) 97,441,944 36,084 40,249 INCOME TAXES FEDERAL U.S. (3,535,059) 3,521,493 (13,566) 0 0 0 0 0 INCOME TAXES OTHER 0 0 0 0 0 0 0 0 DEFERRED INCOME TAXES 17,262,633 (27,875,034) (10,612,401) (136,327) 6,394 1,444,936 (168,695) 301,582 SUBTOTAL (LINE 25 THRU 36) $244,923,351 ($94,410,090) $150,513,262 ($100,243) $6,394 $1,444,936 ($128,446) $301,582 TOTAL COST OF SERVICE (LINE 23 + 37) $642,504,117 ($369,963,387) $272,540,730 ($10,105,832) ($17,887) ($4,042,336) $471,940 ($843,702) UTILITY OPERATING INCOME (LINE 7 39) $158,434,342 ($100,008,213) $58,426,129 ($381,386) $17,887 $4,042,336 ($471,940) $843,702 ELECTRIC UTILITY RATE BASE $2,340,979,206 $1,325,237,902 1,015,741,304 $0 $0 $0 $0 $0 RATE OF RETURN EARNED (%) MPSC BASIS (LINE 41 / 43) 5.75% REQUIRED REVENUE INCREASE $23,064,650 $519,219 ($24,351) ($5,503,231) $642,499 ($1,148,615)

Docket No. D2018.2.12 Page 3 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 A B NORTHWESTERN ENERGY ELECTRIC TRANSMISSION & DISTRIBUTION UTILITY INCOME STATEMENT ACTUAL 12 MONTHS ENDED DECEMBER 2017 ADJUSTED REVENUES: RATE SCHEDULE REVENUES SALES FOR RESALE PROVISION FOR RATE REFUND TRANSMISSION MISCELLANEOUS REVENUES GROSS REVENUES (LINE 2 THRU 6) COST OF SERVICE: STEAM POWER OPERATION STEAM POWER MAINTENANCE HYDRO POWER OPERATION HYDRO POWER MAINTENANCE OTHER POWER GENERATION OPERATION OTHER POWER GENERATION MAINTENANCE POWER SUPPLY TRANSMISSION OPERATION TRANSMISSION MAINTENANCE DISTRIBUTION OPERATION DISTRIBUTION MAINTENANCE CUSTOMER ACCOUNTS EXPENSE CUSTOMER SERVICE AND INFORMATION EXPENSE SALES EXPENSE ADMINISTRATIVE AND GENERAL EXPENSE TOTAL O & M EXPENSE (LINE 10 THRU 22) DEPRECIATION AMORTIZATION OF ELECTRIC PLANT AMORTIZATION OF PLANT ACQ. ADJ. * AMORTIZATION RE:BPA RESIDENTIAL EXCHANGE * AMORTIZATION RE:PROPERTY TAXES * AMORTIZATION RE:INVESTMENT TAX CREDITS * PENSION DIFFERENTIAL * MPSC/MCC TAXES * SO2 ALLOWANCES TAXES OTHER THAN INCOME TAXES INCOME TAXES FEDERAL U.S. INCOME TAXES OTHER DEFERRED INCOME TAXES SUBTOTAL (LINE 25 THRU 36) TOTAL COST OF SERVICE (LINE 23 + 37) UTILITY OPERATING INCOME (LINE 7 39) ELECTRIC UTILITY RATE BASE RATE OF RETURN EARNED (%) MPSC BASIS (LINE 41 / 43) REQUIRED REVENUE INCREASE K L M N O P Q DSIP STIPULATION AND PROPERTY INTENTIONALLY HAZARD AMORTIZATION DEPRECIATION MARKET CREDIT AMORTIZATION TAXES LEFT TREES ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT BLANK ADJUSTMENT $0 $0 $0 $0 $0 $0 $0 (2,532,412) 0 3,500,000 ($2,532,412) $0 $0 $0 $0 $0 $3,500,000 (391,570) 475,369 7,372,612 (6,031,051) 0 4,148,721 1,075,570 5,130,096 0 0 0 0 0 0 0 0 0 0 0 0 0 0 666,847 (14,514) 0 (1,728,953) (1,350,883) 0 (921,638) $666,847 $69,285 $0 $4,836,899 $3,779,213 $0 ($921,638) ($1,865,565) $69,285 $0 $4,836,899 $3,779,213 $0 $2,578,362 $1,865,565 ($69,285) $0 ($4,836,899) ($3,779,213) $0 ($2,578,362) $0 $0 (24,367,156) 3,226,710 $0 ($2,539,778) $94,324 ($2,461,467) $6,910,898 $5,145,016 $0 $3,510,179

Docket No. D2018.2.12 Page 4 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 A B NORTHWESTERN ENERGY ELECTRIC TRANSMISSION & DISTRIBUTION UTILITY INCOME STATEMENT ACTUAL 12 MONTHS ENDED DECEMBER 2017 ADJUSTED REVENUES: RATE SCHEDULE REVENUES SALES FOR RESALE PROVISION FOR RATE REFUND TRANSMISSION MISCELLANEOUS REVENUES GROSS REVENUES (LINE 2 THRU 6) COST OF SERVICE: STEAM POWER OPERATION STEAM POWER MAINTENANCE HYDRO POWER OPERATION HYDRO POWER MAINTENANCE OTHER POWER GENERATION OPERATION OTHER POWER GENERATION MAINTENANCE POWER SUPPLY TRANSMISSION OPERATION TRANSMISSION MAINTENANCE DISTRIBUTION OPERATION DISTRIBUTION MAINTENANCE CUSTOMER ACCOUNTS EXPENSE CUSTOMER SERVICE AND INFORMATION EXPENSE SALES EXPENSE ADMINISTRATIVE AND GENERAL EXPENSE TOTAL O & M EXPENSE (LINE 10 THRU 22) DEPRECIATION AMORTIZATION OF ELECTRIC PLANT AMORTIZATION OF PLANT ACQ. ADJ. * AMORTIZATION RE:BPA RESIDENTIAL EXCHANGE * AMORTIZATION RE:PROPERTY TAXES * AMORTIZATION RE:INVESTMENT TAX CREDITS * PENSION DIFFERENTIAL * MPSC/MCC TAXES * SO2 ALLOWANCES TAXES OTHER THAN INCOME TAXES INCOME TAXES FEDERAL U.S. INCOME TAXES OTHER DEFERRED INCOME TAXES SUBTOTAL (LINE 25 THRU 36) TOTAL COST OF SERVICE (LINE 23 + 37) UTILITY OPERATING INCOME (LINE 7 39) ELECTRIC UTILITY RATE BASE RATE OF RETURN EARNED (%) MPSC BASIS (LINE 41 / 43) REQUIRED REVENUE INCREASE R S T U V W X MOVE NAVIGANT INTENTIONALLY INTENTIONALLY INTENTIONALLY WORKING INTEREST NEM STUDY TO LEFT LEFT LEFT CAPITAL INCOME TAX SYNCHRONIZATION RATE CASE EXPENSES BLANK BLANK BLANK ADJUSTMENT ADJUSTMENT ADJUSTMENT (107,372) $0 $0 $0 $0 $0 $0 $0 ($107,372) $0 $0 $0 $0 $0 $0 0 0 0 0 0 13,566 0 0 0 0 0 0 0 0 28,274 0 0 0 0 9,596,531 (2,657,737) $28,274 $0 $0 $0 $0 $9,610,097 ($2,657,737) ($79,098) $0 $0 $0 $0 $9,610,097 ($2,657,737) $79,098 $0 $0 $0 $0 ($9,610,097) $2,657,737 4,081,815 (661,441) ($107,685) $0 $0 $0 $412,340 $13,016,358 ($3,618,240)

Docket No. D2018.2.12 Page 5 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 A B NORTHWESTERN ENERGY ELECTRIC TRANSMISSION & DISTRIBUTION UTILITY INCOME STATEMENT ACTUAL 12 MONTHS ENDED DECEMBER 2017 ADJUSTED REVENUES: RATE SCHEDULE REVENUES SALES FOR RESALE PROVISION FOR RATE REFUND TRANSMISSION MISCELLANEOUS REVENUES GROSS REVENUES (LINE 2 THRU 6) COST OF SERVICE: STEAM POWER OPERATION STEAM POWER MAINTENANCE HYDRO POWER OPERATION HYDRO POWER MAINTENANCE OTHER POWER GENERATION OPERATION OTHER POWER GENERATION MAINTENANCE POWER SUPPLY TRANSMISSION OPERATION TRANSMISSION MAINTENANCE DISTRIBUTION OPERATION DISTRIBUTION MAINTENANCE CUSTOMER ACCOUNTS EXPENSE CUSTOMER SERVICE AND INFORMATION EXPENSE SALES EXPENSE ADMINISTRATIVE AND GENERAL EXPENSE TOTAL O & M EXPENSE (LINE 10 THRU 22) DEPRECIATION AMORTIZATION OF ELECTRIC PLANT AMORTIZATION OF PLANT ACQ. ADJ. * AMORTIZATION RE:BPA RESIDENTIAL EXCHANGE * AMORTIZATION RE:PROPERTY TAXES * AMORTIZATION RE:INVESTMENT TAX CREDITS * PENSION DIFFERENTIAL * MPSC/MCC TAXES * SO2 ALLOWANCES TAXES OTHER THAN INCOME TAXES INCOME TAXES FEDERAL U.S. INCOME TAXES OTHER DEFERRED INCOME TAXES SUBTOTAL (LINE 25 THRU 36) TOTAL COST OF SERVICE (LINE 23 + 37) UTILITY OPERATING INCOME (LINE 7 39) ELECTRIC UTILITY RATE BASE RATE OF RETURN EARNED (%) MPSC BASIS (LINE 41 / 43) REQUIRED REVENUE INCREASE Y Z AA AB AC AD AE AF INTERIM ADJUSTMENTS TOTAL TEST PERIOD ADJUST TO HAZARD INTENTIONALLY INTENTIONALLY WORKING UPDATES & @ PRESENT ROE FROM DEPRECIATION TREES LEFT LEFT CAPITAL ADJUSTMENTS RATES DOCKET 2009.9.129 ADJUSTMENT ADJUSTMENT BLANK BLANK ADJUSTMENT ($8,911,065) $263,531,298 0 108,861 0 3,691,781 53,346,877 (5,267,935) 3,492,605 ($10,487,218) $320,479,641 $0 $0 $0 $0 $0 $0 $0 $0 0 0 0 1 0 (1) 0 (0) 0 (0) (10,483) 925,966 (49,743) 16,002,563 21,687 4,940,519 (2,976,414) 15,679,555 4,103,163 22,168,148 (3,500,000) (143,331) 8,272,923 (42,815) 3,273,634 (332,566) 0 (15,771,322) 35,562,335 ($15,201,824) $106,825,644 $0 $0 ($3,500,000) $0 $0 $0 ($391,570) $67,279,806 1,592,655 475,369 4,071,010 0 0 7,372,612 0 (6,031,051) 0 0 0 4,148,721 (2,079,450) 1,075,570 1,075,570 0 0 5,206,429 102,648,373 13,566 0 0 0 0 0 0 0 0 0 0 0 0 0 5,065,817 (5,546,584) 0 (275,840) 921,638 0 0 0 $16,935,464 $167,448,725 $0 $1,316,815 $921,638 $0 $0 $0 $1,733,639 $274,274,369 $0 $1,316,815 ($2,578,362) $0 $0 $0 ($12,220,857) $46,205,272 $0 ($1,316,815) $2,578,362 $0 $0 $0 ($17,720,072) $998,021,233 (796,328) 820,905 4.63% $14,847,466 $37,912,116 ($2,717,410) $1,714,437 ($3,510,179) $0 $0 $80,689

Docket No. D2018.2.12 Page 6 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 A B NORTHWESTERN ENERGY ELECTRIC TRANSMISSION & DISTRIBUTION UTILITY INCOME STATEMENT ACTUAL 12 MONTHS ENDED DECEMBER 2017 ADJUSTED REVENUES: RATE SCHEDULE REVENUES SALES FOR RESALE PROVISION FOR RATE REFUND TRANSMISSION MISCELLANEOUS REVENUES GROSS REVENUES (LINE 2 THRU 6) COST OF SERVICE: STEAM POWER OPERATION STEAM POWER MAINTENANCE HYDRO POWER OPERATION HYDRO POWER MAINTENANCE OTHER POWER GENERATION OPERATION OTHER POWER GENERATION MAINTENANCE POWER SUPPLY TRANSMISSION OPERATION TRANSMISSION MAINTENANCE DISTRIBUTION OPERATION DISTRIBUTION MAINTENANCE CUSTOMER ACCOUNTS EXPENSE CUSTOMER SERVICE AND INFORMATION EXPENSE SALES EXPENSE ADMINISTRATIVE AND GENERAL EXPENSE TOTAL O & M EXPENSE (LINE 10 THRU 22) DEPRECIATION AMORTIZATION OF ELECTRIC PLANT AMORTIZATION OF PLANT ACQ. ADJ. * AMORTIZATION RE:BPA RESIDENTIAL EXCHANGE * AMORTIZATION RE:PROPERTY TAXES * AMORTIZATION RE:INVESTMENT TAX CREDITS * PENSION DIFFERENTIAL * MPSC/MCC TAXES * SO2 ALLOWANCES TAXES OTHER THAN INCOME TAXES INCOME TAXES FEDERAL U.S. INCOME TAXES OTHER DEFERRED INCOME TAXES SUBTOTAL (LINE 25 THRU 36) TOTAL COST OF SERVICE (LINE 23 + 37) UTILITY OPERATING INCOME (LINE 7 39) ELECTRIC UTILITY RATE BASE RATE OF RETURN EARNED (%) MPSC BASIS (LINE 41 / 43) REQUIRED REVENUE INCREASE AG AH AI AJ INTERIM ADJUSTMENTS INTERIM INTERIM INTEREST TOTAL TEST PERIOD INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES $ $263,531,298 108,861 53,346,877 3,492,605 $0 $0 $0 $320,479,641 0 0 1 (1) (0) (0) 925,966 16,002,563 4,940,519 15,679,555 (3,500,000) 18,668,148 8,272,923 3,273,634 0 35,562,335 $0 $0 ($3,500,000) $103,325,644 1,592,655 68,872,461 4,071,010 0 (2,079,450) 1,075,570 0 102,648,373 0 0 0 0 (1,166,673) (2,114,229) (2,635,104) (8,181,689) ($1,166,673) ($2,114,229) ($1,042,449) $166,406,276 ($1,166,673) ($2,114,229) $ (4,542,449) $269,731,920 $1,166,673 $2,114,229 $ 4,542,449 $50,747,721 920,151 $ 944,729 $998,965,961 5.08% ($1,497,862) ($2,878,308) $ (8,808,633) $29,103,483

Docket No. D2018.2.12 Page 7 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 A B C D E F G H NORTHWESTERN ENERGY TOTAL GENERATION (EXCLUDING TWO DOT) INCOME STATEMENT ACTUAL 12 MONTHS ENDED DECEMBER 2017 ADJUSTED INTERIM REVENUE REMOVE REMOVE ADD FIXED & REVENUE GENERATION DEFERRED REVENUE CREDITS NONPCCAM GENERATION RELATED (EXCL TWO DOT) REVENUES & VARIABLE SUPPLY AND SUPPLY ADJUSTMENT REVENUES: RATE SCHEDULE REVENUES $284,443,470 ($823,960) $23,900,160 $0 $261,367,270 ($151,063) SALES FOR RESALE $0 $0 $0 $0 0 $0 PROVISION FOR RATE REFUND $2,365,681 $0 $0 $0 2,365,681 ($2,365,681) TRANSMISSION $0 $0 $0 $0 0 $0 MISCELLANEOUS REVENUES $1,547,812 $0 $0 $0 1,547,812 ($667) GROSS REVENUES (LINE 2 THRU 6) $288,356,963 ($823,960) $23,900,160 $0 $265,280,763 ($2,517,412) COST OF SERVICE: STEAM POWER OPERATION 25,443,588 0 19,216,442 0 6,227,146 0 STEAM POWER MAINTENANCE 7,560,165 0 0 0 7,560,165 0 HYDRO POWER OPERATION 12,879,332 0 0 0 12,879,332 0 HYDRO POWER MAINTENANCE 5,777,995 0 0 0 5,777,995 0 OTHER POWER GENERATION OPERATION 11,157,390 0 7,208,745 0 3,948,645 0 OTHER POWER GENERATION MAINTENANCE 3,171,342 0 0 0 3,171,342 0 POWER SUPPLY 893,435 (823,960) 209,130 10,043,918 11,552,183 0 TRANSMISSION OPERATION 0 0 0 0 0 0 TRANSMISSION MAINTENANCE 0 0 0 0 0 0 DISTRIBUTION OPERATION 521,564 0 0 0 521,564 0 DISTRIBUTION MAINTENANCE 0 0 0 0 0 0 CUSTOMER ACCOUNTS EXPENSE 2,283,996 0 0 0 2,283,996 0 CUSTOMER SERVICE AND INFORMATION EXPENSE 1,395,320 0 0 0 1,395,320 0 SALES EXPENSE 131,771 0 0 0 131,771 0 ADMINISTRATIVE AND GENERAL EXPENSE 21,131,529 0 0 168,923 21,300,452 0 TOTAL O & M EXPENSE (LINE 10 THRU 22) 92,347,428 (823,960) 26,634,317 10,212,841 76,749,912 0 DEPRECIATION 34,710,241 0 0 0 34,710,241 0 AMORTIZATION OF ELECTRIC PLANT 1,105,444 0 0 0 1,105,444 0 AMORTIZATION OF PLANT ACQ. ADJ. 7,014,087 0 0 0 7,014,087 0 * AMORTIZATION RE:BPA RESIDENTIAL EXCHANGE 0 0 0 0 0 0 * AMORTIZATION RE:PROPERTY TAXES (1,072,409) 0 (1,072,409) 0 0 0 * AMORTIZATION RE:INVESTMENT TAX CREDITS 0 0 0 0 0 0 * PENSION DIFFERENTIAL (2,467,766) 0 0 0 (2,467,766) 0 * MPSC/MCC TAXES 0 0 0 0 0 0 * SO2 ALLOWANCES (1) 0 0 0 (1) 0 TAXES OTHER THAN INCOME TAXES 30,095,097 0 0 107,053 30,202,150 (545,199) INCOME TAXES FEDERAL U.S. (3,521,493) 0 (3,521,445) 0 (48) 0 INCOME TAXES OTHER 0 0 0 0 0 0 DEFERRED INCOME TAXES 28,316,218 0 (703,844) (441,184) 28,578,878 (519,333) SUBTOTAL (LINE 25 THRU 36) 94,179,417 0 (5,297,698) (334,130) 99,142,985 (1,064,532) TOTAL COST OF SERVICE (LINE 23 + 37) 186,526,845 (823,960) 21,336,619 9,878,711 175,892,897 (1,064,532) UTILITY OPERATING INCOME (LINE 7 39) $101,830,118 ($0) $2,563,541 ($9,878,711) $89,387,866 ($1,452,880) ELECTRIC UTILITY RATE BASE 1,325,237,902 $1,325,237,902 RATE OF RETURN EARNED (%) MPSC BASIS (LINE 41 / 43) 6.75% REQUIRED REVENUE INCREASE 15,608,454 1,977,946

Docket No. D2018.2.12 Page 8 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 A B NORTHWESTERN ENERGY TOTAL GENERATION (EXCLUDING TWO DOT) INCOME STATEMENT ACTUAL 12 MONTHS ENDED DECEMBER 2017 ADJUSTED INTERIM REVENUES: RATE SCHEDULE REVENUES SALES FOR RESALE PROVISION FOR RATE REFUND TRANSMISSION MISCELLANEOUS REVENUES GROSS REVENUES (LINE 2 THRU 6) COST OF SERVICE: STEAM POWER OPERATION STEAM POWER MAINTENANCE HYDRO POWER OPERATION HYDRO POWER MAINTENANCE OTHER POWER GENERATION OPERATION OTHER POWER GENERATION MAINTENANCE POWER SUPPLY TRANSMISSION OPERATION TRANSMISSION MAINTENANCE DISTRIBUTION OPERATION DISTRIBUTION MAINTENANCE CUSTOMER ACCOUNTS EXPENSE CUSTOMER SERVICE AND INFORMATION EXPENSE SALES EXPENSE ADMINISTRATIVE AND GENERAL EXPENSE TOTAL O & M EXPENSE (LINE 10 THRU 22) DEPRECIATION AMORTIZATION OF ELECTRIC PLANT AMORTIZATION OF PLANT ACQ. ADJ. * AMORTIZATION RE:BPA RESIDENTIAL EXCHANGE * AMORTIZATION RE:PROPERTY TAXES * AMORTIZATION RE:INVESTMENT TAX CREDITS * PENSION DIFFERENTIAL * MPSC/MCC TAXES * SO2 ALLOWANCES TAXES OTHER THAN INCOME TAXES INCOME TAXES FEDERAL U.S. INCOME TAXES OTHER DEFERRED INCOME TAXES SUBTOTAL (LINE 25 THRU 36) TOTAL COST OF SERVICE (LINE 23 + 37) UTILITY OPERATING INCOME (LINE 7 39) ELECTRIC UTILITY RATE BASE RATE OF RETURN EARNED (%) MPSC BASIS (LINE 41 / 43) REQUIRED REVENUE INCREASE I J K L M N O SALES & ADMINISTRATIVE CORPORATE PROPERTY CAPITALIZE & GENERAL LABOR ALLOCATION DEPRECIATION AMORTIZATION TAXES DSM ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT COSTS $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 257,942 0 0 0 0 0 0 112,265 0 0 0 0 0 0 8,128 0 0 0 0 0 0 (127,798) 0 0 0 0 0 0 (214,174) 20,573 0 0 0 (7,762,146) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 394 26,102 0 0 0 0 0 0 0 0 0 0 0 0 7,522 127,209 0 0 0 0 0 2,986 83,772 0 0 0 0 (131,771) 0 0 0 0 0 0 (2,395,124) (60,203) 886,593 0 0 0 0 (2,526,895) (12,938) 1,144,249 0 0 0 (7,762,146) 0 0 0 (778,840) 0 0 0 0 0 0 123,870 0 0 0 0 0 0 1,998,570 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1,643,833 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 (920) 0 0 0 406,522 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 665,395 3,649 (301,309) (282,156) (432,862) (107,048) 2,043,967 665,395 2,729 (301,309) 1,061,445 1,210,971 299,474 2,043,967 (1,861,500) (10,209) 842,940 1,061,445 1,210,971 299,474 (5,718,179) $1,861,500 $10,209 ($842,940) ($1,061,445) ($1,210,971) ($299,474) $5,718,179 (2,534,244) (13,900) 1,147,578 1,445,050 1,648,617 407,704 (7,784,722)

Docket No. D2018.2.12 Page 9 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 A B NORTHWESTERN ENERGY TOTAL GENERATION (EXCLUDING TWO DOT) INCOME STATEMENT ACTUAL 12 MONTHS ENDED DECEMBER 2017 ADJUSTED INTERIM REVENUES: RATE SCHEDULE REVENUES SALES FOR RESALE PROVISION FOR RATE REFUND TRANSMISSION MISCELLANEOUS REVENUES GROSS REVENUES (LINE 2 THRU 6) COST OF SERVICE: STEAM POWER OPERATION STEAM POWER MAINTENANCE HYDRO POWER OPERATION HYDRO POWER MAINTENANCE OTHER POWER GENERATION OPERATION OTHER POWER GENERATION MAINTENANCE POWER SUPPLY TRANSMISSION OPERATION TRANSMISSION MAINTENANCE DISTRIBUTION OPERATION DISTRIBUTION MAINTENANCE CUSTOMER ACCOUNTS EXPENSE CUSTOMER SERVICE AND INFORMATION EXPENSE SALES EXPENSE ADMINISTRATIVE AND GENERAL EXPENSE TOTAL O & M EXPENSE (LINE 10 THRU 22) DEPRECIATION AMORTIZATION OF ELECTRIC PLANT AMORTIZATION OF PLANT ACQ. ADJ. * AMORTIZATION RE:BPA RESIDENTIAL EXCHANGE * AMORTIZATION RE:PROPERTY TAXES * AMORTIZATION RE:INVESTMENT TAX CREDITS * PENSION DIFFERENTIAL * MPSC/MCC TAXES * SO2 ALLOWANCES TAXES OTHER THAN INCOME TAXES INCOME TAXES FEDERAL U.S. INCOME TAXES OTHER DEFERRED INCOME TAXES SUBTOTAL (LINE 25 THRU 36) TOTAL COST OF SERVICE (LINE 23 + 37) UTILITY OPERATING INCOME (LINE 7 39) ELECTRIC UTILITY RATE BASE RATE OF RETURN EARNED (%) MPSC BASIS (LINE 41 / 43) REQUIRED REVENUE INCREASE P Q R S T U V INTENTIONALLY INTENTIONALLY INTENTIONALLY INTENTIONALLY INTENTIONALLY INTENTIONALLY MAINTENANCE LEFT LEFT LEFT LEFT LEFT LEFT ADJUSTMENT BLANK BLANK BLANK BLANK BLANK BLANK $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 (973,534) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 (973,534) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 256,356 0 0 0 0 0 0 256,356 0 0 0 0 0 0 (717,178) 0 0 0 0 0 0 $717,178 $0 $0 $0 $0 $0 $0 (976,365) 0 0 0 0 0 0

Docket No. D2018.2.12 Page 10 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 A B NORTHWESTERN ENERGY TOTAL GENERATION (EXCLUDING TWO DOT) INCOME STATEMENT ACTUAL 12 MONTHS ENDED DECEMBER 2017 ADJUSTED INTERIM REVENUES: RATE SCHEDULE REVENUES SALES FOR RESALE PROVISION FOR RATE REFUND TRANSMISSION MISCELLANEOUS REVENUES GROSS REVENUES (LINE 2 THRU 6) COST OF SERVICE: STEAM POWER OPERATION STEAM POWER MAINTENANCE HYDRO POWER OPERATION HYDRO POWER MAINTENANCE OTHER POWER GENERATION OPERATION OTHER POWER GENERATION MAINTENANCE POWER SUPPLY TRANSMISSION OPERATION TRANSMISSION MAINTENANCE DISTRIBUTION OPERATION DISTRIBUTION MAINTENANCE CUSTOMER ACCOUNTS EXPENSE CUSTOMER SERVICE AND INFORMATION EXPENSE SALES EXPENSE ADMINISTRATIVE AND GENERAL EXPENSE TOTAL O & M EXPENSE (LINE 10 THRU 22) DEPRECIATION AMORTIZATION OF ELECTRIC PLANT AMORTIZATION OF PLANT ACQ. ADJ. * AMORTIZATION RE:BPA RESIDENTIAL EXCHANGE * AMORTIZATION RE:PROPERTY TAXES * AMORTIZATION RE:INVESTMENT TAX CREDITS * PENSION DIFFERENTIAL * MPSC/MCC TAXES * SO2 ALLOWANCES TAXES OTHER THAN INCOME TAXES INCOME TAXES FEDERAL U.S. INCOME TAXES OTHER DEFERRED INCOME TAXES SUBTOTAL (LINE 25 THRU 36) TOTAL COST OF SERVICE (LINE 23 + 37) UTILITY OPERATING INCOME (LINE 7 39) ELECTRIC UTILITY RATE BASE RATE OF RETURN EARNED (%) MPSC BASIS (LINE 41 / 43) REQUIRED REVENUE INCREASE W X Y Z AA WORKING INTEREST TOTAL TEST PERIOD CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES $0 $0 $0 (151,063) $261,216,207 $0 $0 $0 0 $0 $0 $0 $0 (2,365,681) $0 $0 $0 $0 0 $0 $0 $0 $0 (667) $1,547,144 $0 $0 $0 ($2,517,412) $262,763,351 0 0 0 0 $6,227,146 0 0 0 0 $7,560,165 0 0 0 257,942 $13,137,274 0 0 0 112,265 $5,890,260 0 0 0 8,128 $3,956,773 0 0 0 (1,101,332) $2,070,010 0 0 0 (7,955,748) $3,596,436 0 0 0 0 $0 0 0 0 0 $0 0 0 0 26,496 $548,060 0 0 0 0 $0 0 0 0 134,731 $2,418,728 0 0 0 86,758 $1,482,079 0 0 0 (131,771) ($0) 0 0 0 (1,568,733) $19,731,719 0 0 0 (10,131,264) 66,618,648 0 0 0 778839.7541 $33,931,401 0 0 0 123870.457 $1,229,314 0 0 0 1998570 $9,012,657 0 0 0 0 $0 0 0 0 0 $0 0 0 0 0 $0 0 0 0 1643832.96 ($823,933) 0 0 0 0 $0 0 0 0 0 ($1) 0 0 0 (139,597) $30,062,553 0 48 0 48 $0 0 0 0 0 $0 0 (13,950,680) 3,693,366 (8,930,655) $19,648,224 0 (13,950,632) 3,693,366 (6,082,770) 93,060,215 0 (13,950,632) 3,693,366 (16,214,034) 159,678,863 $0 $13,950,632 ($3,693,366) $13,696,622 $103,084,488 $1,436,665 ($1,550,257) ($113,592) $1,325,124,310 7.78% 149,149 (19,149,297) 5,028,143 (18,654,341) ($3,045,887)

Docket No. D2018.2.12 Page 11 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 A B NORTHWESTERN ENERGY TOTAL GENERATION (EXCLUDING TWO DOT) INCOME STATEMENT ACTUAL 12 MONTHS ENDED DECEMBER 2017 ADJUSTED INTERIM REVENUES: RATE SCHEDULE REVENUES SALES FOR RESALE PROVISION FOR RATE REFUND TRANSMISSION MISCELLANEOUS REVENUES GROSS REVENUES (LINE 2 THRU 6) COST OF SERVICE: STEAM POWER OPERATION STEAM POWER MAINTENANCE HYDRO POWER OPERATION HYDRO POWER MAINTENANCE OTHER POWER GENERATION OPERATION OTHER POWER GENERATION MAINTENANCE POWER SUPPLY TRANSMISSION OPERATION TRANSMISSION MAINTENANCE DISTRIBUTION OPERATION DISTRIBUTION MAINTENANCE CUSTOMER ACCOUNTS EXPENSE CUSTOMER SERVICE AND INFORMATION EXPENSE SALES EXPENSE ADMINISTRATIVE AND GENERAL EXPENSE TOTAL O & M EXPENSE (LINE 10 THRU 22) DEPRECIATION AMORTIZATION OF ELECTRIC PLANT AMORTIZATION OF PLANT ACQ. ADJ. * AMORTIZATION RE:BPA RESIDENTIAL EXCHANGE * AMORTIZATION RE:PROPERTY TAXES * AMORTIZATION RE:INVESTMENT TAX CREDITS * PENSION DIFFERENTIAL * MPSC/MCC TAXES * SO2 ALLOWANCES TAXES OTHER THAN INCOME TAXES INCOME TAXES FEDERAL U.S. INCOME TAXES OTHER DEFERRED INCOME TAXES SUBTOTAL (LINE 25 THRU 36) TOTAL COST OF SERVICE (LINE 23 + 37) UTILITY OPERATING INCOME (LINE 7 39) ELECTRIC UTILITY RATE BASE RATE OF RETURN EARNED (%) MPSC BASIS (LINE 41 / 43) REQUIRED REVENUE INCREASE AB AC AD AE AF AG AH INTERIM ADJUSTMENTS ADJUST NONPCCAM MONTANA INTENTIONALLY INTENTIONALLY WORKING ROE FROM ALL DEPRECIATION SUPPLY GENERATION LEFT LEFT CAPITAL GENERATION ORDERS ADJUSTMENT ADJUSTMENT ADJUSTMENT BLANK BLANK ADJUSTMENT $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 ($566,439) ($506,099) $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 ($174,664) ($65,869) $0 $0 $0 $0 $0 ($741,103) ($571,968) $0 $0 $0 $0 ($2,544,214) $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $534,285 $195,151 ($6,070) $0 $0 $0 $0 ($2,009,929) $195,151 ($6,070) $0 $0 $0 $0 ($2,009,929) ($545,952) ($578,038) $0 $0 $0 $0 $2,009,929 $545,952 $578,038 $0 $0 $0 $0 $1,272,107 $0 $0 $0 $0 $337,826 (5,528,431) (2,610,660) (743,258) (786,940) 0 0 32,344

Docket No. D2018.2.12 Page 12 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 A B NORTHWESTERN ENERGY TOTAL GENERATION (EXCLUDING TWO DOT) INCOME STATEMENT ACTUAL 12 MONTHS ENDED DECEMBER 2017 ADJUSTED INTERIM REVENUES: RATE SCHEDULE REVENUES SALES FOR RESALE PROVISION FOR RATE REFUND TRANSMISSION MISCELLANEOUS REVENUES GROSS REVENUES (LINE 2 THRU 6) COST OF SERVICE: STEAM POWER OPERATION STEAM POWER MAINTENANCE HYDRO POWER OPERATION HYDRO POWER MAINTENANCE OTHER POWER GENERATION OPERATION OTHER POWER GENERATION MAINTENANCE POWER SUPPLY TRANSMISSION OPERATION TRANSMISSION MAINTENANCE DISTRIBUTION OPERATION DISTRIBUTION MAINTENANCE CUSTOMER ACCOUNTS EXPENSE CUSTOMER SERVICE AND INFORMATION EXPENSE SALES EXPENSE ADMINISTRATIVE AND GENERAL EXPENSE TOTAL O & M EXPENSE (LINE 10 THRU 22) DEPRECIATION AMORTIZATION OF ELECTRIC PLANT AMORTIZATION OF PLANT ACQ. ADJ. * AMORTIZATION RE:BPA RESIDENTIAL EXCHANGE * AMORTIZATION RE:PROPERTY TAXES * AMORTIZATION RE:INVESTMENT TAX CREDITS * PENSION DIFFERENTIAL * MPSC/MCC TAXES * SO2 ALLOWANCES TAXES OTHER THAN INCOME TAXES INCOME TAXES FEDERAL U.S. INCOME TAXES OTHER DEFERRED INCOME TAXES SUBTOTAL (LINE 25 THRU 36) TOTAL COST OF SERVICE (LINE 23 + 37) UTILITY OPERATING INCOME (LINE 7 39) ELECTRIC UTILITY RATE BASE RATE OF RETURN EARNED (%) MPSC BASIS (LINE 41 / 43) REQUIRED REVENUE INCREASE AI AJ AK AL INTERIM ADJUSTMENTS INTERIM INTERIM INTEREST TOTAL TEST PERIOD INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES $0 $0 $ $261,216,207 $0 $0 $0 $0 $0 $0 $0 $0 1,547,144 $0 $0 $0 $262,763,351 $0 $0 6,227,146 $0 $0 7,560,165 $0 $0 13,137,274 $0 $0 5,890,260 $0 $0 3,956,773 $0 $0 2,070,010 $0 $0 (1,072,538) 2,523,897 $0 $0 $0 $0 $0 $0 548,060 $0 $0 $0 $0 2,418,728 $0 $0 1,482,079 $0 $0 (0) $0 $0 (240,533) 19,491,186 $0 $0 ($1,313,071) $65,305,577 $0 $0 (2,544,214) 31,387,187 $0 $0 1,229,314 $0 $0 9,012,657 $0 $0 $0 $0 $0 $0 $0 $0 (823,933) $0 $0 $0 $0 (1) $0 $0 30,062,553 $0 $0 $0 $0 ($624,182) ($438,614) (339,430) 19,308,793 ($624,182) ($438,614) ($2,883,644) $90,176,570 ($624,182) ($438,614) $ (4,196,716) $155,482,147 $624,182 $438,614 $ 4,196,716 $107,281,204 ($11,167,232) $ (9,557,298) $1,315,567,012 8.15% (1,976,567) (597,128) $ (12,210,640) ($15,256,527)

Docket No. D2018.2.12 Page 13 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 A B C D E F G H I NORTHWESTERN ENERGY COLSTRIP UNIT 4 INCOME STATEMENT ACTUAL 12 MONTHS ENDED DECEMBER 2017 ADJUSTED INTERIM REVENUE SALES & REMOVE REMOVE FIXED & REVENUE ADMINISTRATIVE COLSTRIP UNIT 4 DEFERRED REVENUE CREDITSCOLSTRIP UNIT 4 RELATED & GENERAL LABOR REVENUES & VARIABLE ADJUSTMENT ADJUSTMENT ADJUSTMENT REVENUES: RATE SCHEDULE REVENUES 97,432,620 ($2,723,439) $22,475,955 $77,680,105 ($685,850) SALES FOR RESALE 0 $0 PROVISION FOR RATE REFUND 0 $0 $0 TRANSMISSION 0 $0 MISCELLANEOUS REVENUES 0 $0 $0 GROSS REVENUES (LINE 2 THRU 6) $97,432,620 ($2,723,439) $22,475,955 $77,680,105 ($685,850) $0 $0 COST OF SERVICE: STEAM POWER OPERATION 25,443,588 19,216,442 $6,227,146 STEAM POWER MAINTENANCE 7,560,165 $7,560,165 OTHER POWER GENERATION OPERATION 0 $0 OTHER POWER GENERATION MAINTENANCE 0 $0 POWER SUPPLY 528,380 (2,723,439) 3,124,318 $127,501 ($12,877) TRANSMISSION OPERATION 0 $0 TRANSMISSION MAINTENANCE 0 $0 DISTRIBUTION OPERATION 142,120 $142,120 $394 DISTRIBUTION MAINTENANCE 0 $0 CUSTOMER ACCOUNTS EXPENSE 607,912 $607,912 $7,522 CUSTOMER SERVICE AND INFORMATION EXPENSE 361,240 $361,240 $2,986 SALES EXPENSE 37,649 $37,649 ($37,649) $0 ADMINISTRATIVE AND GENERAL EXPENSE 5,579,017 $5,579,017 (608,418) ($7,049) TOTAL O & M EXPENSE (LINE 10 THRU 22) 40,260,071 (2,723,439) 22,340,760 20,642,750 0 (646,067) (9,023) DEPRECIATION 13,062,285 $13,062,285 AMORTIZATION OF ELECTRIC PLANT 0 $0 AMORTIZATION OF PLANT ACQ. ADJ. 0 $0 * AMORTIZATION RE:BPA RESIDENTIAL EXCHANGE 0 $0 * AMORTIZATION RE:PROPERTY TAXES (203,924) (203,924) $0 * AMORTIZATION RE:INVESTMENT TAX CREDITS 0 $0 * PENSION DIFFERENTIAL (705,076) ($705,076) * MPSC/MCC TAXES 0 $0 * SO2 ALLOWANCES (1) ($1) TAXES OTHER THAN INCOME TAXES 4,291,542 $4,291,542 ($160,969) (642) INCOME TAXES FEDERAL U.S. 0 0 $0 0 0 0 INCOME TAXES OTHER 0 0 $0 0 0 0 DEFERRED INCOME TAXES 10,940,267 133,570 $10,806,696 (138,214) 170,126 2,545 SUBTOTAL (LINE 25 THRU 36) 27,385,093 0 (70,354) 27,455,446 (299,183) 170,126 1,903 TOTAL COST OF SERVICE (LINE 23 + 37) 67,645,163 (2,723,439) 22,270,406 48,098,196 (299,183) (475,941) (7,120) UTILITY OPERATING INCOME (LINE 7 39) $29,787,457 $0 $205,548 $29,581,909 ($386,666) $475,941 $7,120 ELECTRIC UTILITY RATE BASE 303,642,197 $303,642,197 RATE OF RETURN EARNED (%) MPSC BASIS (LINE 41 / 43) 9.74% REQUIRED REVENUE INCREASE ($6,169,081) $526,406 ($647,945) ($9,693)

Docket No. D2018.2.12 Page 14 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 A B NORTHWESTERN ENERGY COLSTRIP UNIT 4 INCOME STATEMENT ACTUAL 12 MONTHS ENDED DECEMBER 2017 ADJUSTED INTERIM REVENUES: RATE SCHEDULE REVENUES SALES FOR RESALE PROVISION FOR RATE REFUND TRANSMISSION MISCELLANEOUS REVENUES GROSS REVENUES (LINE 2 THRU 6) COST OF SERVICE: STEAM POWER OPERATION STEAM POWER MAINTENANCE OTHER POWER GENERATION OPERATION OTHER POWER GENERATION MAINTENANCE POWER SUPPLY TRANSMISSION OPERATION TRANSMISSION MAINTENANCE DISTRIBUTION OPERATION DISTRIBUTION MAINTENANCE CUSTOMER ACCOUNTS EXPENSE CUSTOMER SERVICE AND INFORMATION EXPENSE SALES EXPENSE ADMINISTRATIVE AND GENERAL EXPENSE TOTAL O & M EXPENSE (LINE 10 THRU 22) DEPRECIATION AMORTIZATION OF ELECTRIC PLANT AMORTIZATION OF PLANT ACQ. ADJ. * AMORTIZATION RE:BPA RESIDENTIAL EXCHANGE * AMORTIZATION RE:PROPERTY TAXES * AMORTIZATION RE:INVESTMENT TAX CREDITS * PENSION DIFFERENTIAL * MPSC/MCC TAXES * SO2 ALLOWANCES TAXES OTHER THAN INCOME TAXES INCOME TAXES FEDERAL U.S. INCOME TAXES OTHER DEFERRED INCOME TAXES SUBTOTAL (LINE 25 THRU 36) TOTAL COST OF SERVICE (LINE 23 + 37) UTILITY OPERATING INCOME (LINE 7 39) ELECTRIC UTILITY RATE BASE RATE OF RETURN EARNED (%) MPSC BASIS (LINE 41 / 43) REQUIRED REVENUE INCREASE J K L M N O P CORPORATE PROPERTY INTENTIONALLY INTENTIONALLY INTENTIONALLY ALLOCATION DEPRECIATION AMORTIZATION TAXES LEFT LEFT LEFT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT BLANK BLANK BLANK $0 $0 $0 $0 $0 $0 $0 0 0 0 0 0 0 0 0 0 0 0 0 619,949 228,253 0 469,667 95,160 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 (178,122) (123,675) (25,058) 0 0 0 0 670,080 345,992 70,102 0 0 0 0 670,080 345,992 70,102 0 0 0 $0 ($670,080) ($345,992) ($70,102) $0 $0 $0 $0 $912,247 $471,034 $95,437 $0 $0 $0

Docket No. D2018.2.12 Page 15 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 A B NORTHWESTERN ENERGY COLSTRIP UNIT 4 INCOME STATEMENT ACTUAL 12 MONTHS ENDED DECEMBER 2017 ADJUSTED INTERIM REVENUES: RATE SCHEDULE REVENUES SALES FOR RESALE PROVISION FOR RATE REFUND TRANSMISSION MISCELLANEOUS REVENUES GROSS REVENUES (LINE 2 THRU 6) COST OF SERVICE: STEAM POWER OPERATION STEAM POWER MAINTENANCE OTHER POWER GENERATION OPERATION OTHER POWER GENERATION MAINTENANCE POWER SUPPLY TRANSMISSION OPERATION TRANSMISSION MAINTENANCE DISTRIBUTION OPERATION DISTRIBUTION MAINTENANCE CUSTOMER ACCOUNTS EXPENSE CUSTOMER SERVICE AND INFORMATION EXPENSE SALES EXPENSE ADMINISTRATIVE AND GENERAL EXPENSE TOTAL O & M EXPENSE (LINE 10 THRU 22) DEPRECIATION AMORTIZATION OF ELECTRIC PLANT AMORTIZATION OF PLANT ACQ. ADJ. * AMORTIZATION RE:BPA RESIDENTIAL EXCHANGE * AMORTIZATION RE:PROPERTY TAXES * AMORTIZATION RE:INVESTMENT TAX CREDITS * PENSION DIFFERENTIAL * MPSC/MCC TAXES * SO2 ALLOWANCES TAXES OTHER THAN INCOME TAXES INCOME TAXES FEDERAL U.S. INCOME TAXES OTHER DEFERRED INCOME TAXES SUBTOTAL (LINE 25 THRU 36) TOTAL COST OF SERVICE (LINE 23 + 37) UTILITY OPERATING INCOME (LINE 7 39) ELECTRIC UTILITY RATE BASE RATE OF RETURN EARNED (%) MPSC BASIS (LINE 41 / 43) REQUIRED REVENUE INCREASE Q R S T U V W INTENTIONALLY INTENTIONALLY INTENTIONALLY INTENTIONALLY INTENTIONALLY WORKING LEFT LEFT LEFT LEFT LEFT CAPITAL INCOME TAX BLANK BLANK BLANK BLANK BLANK ADJUSTMENT ADJUSTMENT $0 $0 $0 $0 $0 $0 $0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 (4,340,701) 0 0 0 0 0 0 (4,340,701) 0 0 0 0 0 0 (4,340,701) $0 $0 $0 $0 $0 $0 $4,340,701 368,087 (28,677) $0 $0 $0 $0 $0 $41,326 (5,912,646)

Docket No. D2018.2.12 Page 16 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 A B NORTHWESTERN ENERGY COLSTRIP UNIT 4 INCOME STATEMENT ACTUAL 12 MONTHS ENDED DECEMBER 2017 ADJUSTED INTERIM REVENUES: RATE SCHEDULE REVENUES SALES FOR RESALE PROVISION FOR RATE REFUND TRANSMISSION MISCELLANEOUS REVENUES GROSS REVENUES (LINE 2 THRU 6) COST OF SERVICE: STEAM POWER OPERATION STEAM POWER MAINTENANCE OTHER POWER GENERATION OPERATION OTHER POWER GENERATION MAINTENANCE POWER SUPPLY TRANSMISSION OPERATION TRANSMISSION MAINTENANCE DISTRIBUTION OPERATION DISTRIBUTION MAINTENANCE CUSTOMER ACCOUNTS EXPENSE CUSTOMER SERVICE AND INFORMATION EXPENSE SALES EXPENSE ADMINISTRATIVE AND GENERAL EXPENSE TOTAL O & M EXPENSE (LINE 10 THRU 22) DEPRECIATION AMORTIZATION OF ELECTRIC PLANT AMORTIZATION OF PLANT ACQ. ADJ. * AMORTIZATION RE:BPA RESIDENTIAL EXCHANGE * AMORTIZATION RE:PROPERTY TAXES * AMORTIZATION RE:INVESTMENT TAX CREDITS * PENSION DIFFERENTIAL * MPSC/MCC TAXES * SO2 ALLOWANCES TAXES OTHER THAN INCOME TAXES INCOME TAXES FEDERAL U.S. INCOME TAXES OTHER DEFERRED INCOME TAXES SUBTOTAL (LINE 25 THRU 36) TOTAL COST OF SERVICE (LINE 23 + 37) UTILITY OPERATING INCOME (LINE 7 39) ELECTRIC UTILITY RATE BASE RATE OF RETURN EARNED (%) MPSC BASIS (LINE 41 / 43) REQUIRED REVENUE INCREASE X Y Z AA AB AC AD INTERIM ADJUSTMENTS INTEREST TOTAL TEST PERIOD ADJUST TO NONPCCAM MONTANA SYNCHRONIZATION UPDATES & @ PRESENT ROE FROM DEPRECIATION SUPPLY GENERATION ADJUSTMENT ADJUSTMENTS RATES DOCKET 2008.6.69 ADJUSTMENT ADJUSTMENT ADJUSTMENT (685,850) $76,994,255 0 $0 0 $0 0 $0 0 $0 $0 ($685,850) $76,994,255 $0 $0 $0 $0 0 $6,227,146 0 $7,560,165 0 $0 0 $0 (12,877) $114,625 0 $0 0 $0 394 $142,514 0 $0 7,522 $615,435 2,986 $364,226 (37,649) $0 (615,467) $4,963,550 0 (655,090) 19,987,659 $0 $0 $0 $0 619,949 $13,682,234 (414,386) 228,253 $228,253 0 $0 0 $0 0 $0 0 $0 469,667 ($235,409) 0 $0 0 ($1) (66,451) $4,225,091 0 0 $0 $0 $0 $0 $0 0 0 $0 $0 $0 $0 $0 479,244 (4,153,855) $6,652,841 $0 $87,021 $0 $0 479,244 (2,902,437) 24,553,009 $0 ($327,365) $0 $0 479,244 (3,557,528) 44,540,668 $0 ($327,365) $0 $0 ($479,244) $2,871,678 $32,453,587 $0 $327,365 $0 $0 339,409 $303,981,607 207,193 10.68% $652,442 ($3,871,392) ($10,040,473) $0 ($422,404) $0 $0

Docket No. D2018.2.12 Page 17 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 A B NORTHWESTERN ENERGY COLSTRIP UNIT 4 INCOME STATEMENT ACTUAL 12 MONTHS ENDED DECEMBER 2017 ADJUSTED INTERIM REVENUES: RATE SCHEDULE REVENUES SALES FOR RESALE PROVISION FOR RATE REFUND TRANSMISSION MISCELLANEOUS REVENUES GROSS REVENUES (LINE 2 THRU 6) COST OF SERVICE: STEAM POWER OPERATION STEAM POWER MAINTENANCE OTHER POWER GENERATION OPERATION OTHER POWER GENERATION MAINTENANCE POWER SUPPLY TRANSMISSION OPERATION TRANSMISSION MAINTENANCE DISTRIBUTION OPERATION DISTRIBUTION MAINTENANCE CUSTOMER ACCOUNTS EXPENSE CUSTOMER SERVICE AND INFORMATION EXPENSE SALES EXPENSE ADMINISTRATIVE AND GENERAL EXPENSE TOTAL O & M EXPENSE (LINE 10 THRU 22) DEPRECIATION AMORTIZATION OF ELECTRIC PLANT AMORTIZATION OF PLANT ACQ. ADJ. * AMORTIZATION RE:BPA RESIDENTIAL EXCHANGE * AMORTIZATION RE:PROPERTY TAXES * AMORTIZATION RE:INVESTMENT TAX CREDITS * PENSION DIFFERENTIAL * MPSC/MCC TAXES * SO2 ALLOWANCES TAXES OTHER THAN INCOME TAXES INCOME TAXES FEDERAL U.S. INCOME TAXES OTHER DEFERRED INCOME TAXES SUBTOTAL (LINE 25 THRU 36) TOTAL COST OF SERVICE (LINE 23 + 37) UTILITY OPERATING INCOME (LINE 7 39) ELECTRIC UTILITY RATE BASE RATE OF RETURN EARNED (%) MPSC BASIS (LINE 41 / 43) REQUIRED REVENUE INCREASE AE AF AG AH AI AJ AK INTERIM ADJUSTMENTS INTERIM INTERIM INTENTIONALLY INTENTIONALLY WORKING INTEREST TOTAL TEST PERIOD LEFT LEFT CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT BLANK BLANK ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES $ $76,994,255 $0 $0 $0 $0 $0 $0 $76,994,255 6,227,146 7,560,165 114,625 142,514 615,435 364,226 4,963,550 $0 $0 $0 $0 $0 $0 $19,987,659 (414,386) 13,267,847 228,253 (235,409) (1) 4,225,091 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 ($80,380) $26,455 33,096 6,685,937 $0 $0 $0 ($80,380) $26,455 ($381,290) $24,171,719 $0 $0 $0 ($80,380) $26,455 $ (381,290) $44,159,378 $0 $0 $0 $80,380 ($26,455) $381,290 $32,834,877 9,044 (3,646,726) $ (3,430,489) $300,551,118 10.92% $0 $0 $1,014 ($519,013) $36,016 $ (904,387) ($10,944,860)

Docket No. D2018.2.12 Page 18 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 A B C D E F G H I NORTHWESTERN ENERGY DAVE GATES GENERATING STATION INCOME STATEMENT ACTUAL 12 MONTHS ENDED DECEMBER 2017 ADJUSTED INTERIM REVENUE SALES & REMOVE REMOVE & REVENUE ADMINISTRATIVE DGGS DEFERRED REVENUE CREDITS FIXED DGGS RELATED & GENERAL LABOR REVENUES & VARIABLE ADJUSTMENT ADJUSTMENT ADJUSTMENT REVENUES: RATE SCHEDULE REVENUES $32,427,974 ($573,649) $3,757,474 $29,244,150 ($251,509) SALES FOR RESALE 0 0 PROVISION FOR RATE REFUND (176,050) (176,050) 176,050 TRANSMISSION 0 0 MISCELLANEOUS REVENUES 1,551,608 0 1,551,608 (4,463) GROSS REVENUES (LINE 2 THRU 6) $33,803,531 ($573,649) $3,757,474 $30,619,707 ($79,922) $0 $0 COST OF SERVICE: STEAM POWER OPERATION 0 0 STEAM POWER MAINTENANCE 0 0 OTHER POWER GENERATION OPERATION 9,055,658 7,208,745 1,846,914 5,297 OTHER POWER GENERATION MAINTENANCE 3,136,879 3,136,879 (127,798) POWER SUPPLY (3,405,910) (573,649) (2,945,830) 113,569 (27,576) TRANSMISSION OPERATION 0 0 TRANSMISSION MAINTENANCE 0 0 DISTRIBUTION OPERATION 52,205 52,205 DISTRIBUTION MAINTENANCE 0 0 CUSTOMER ACCOUNTS EXPENSE 237,209 237,209 0 CUSTOMER SERVICE AND INFORMATION EXPENSE 148,922 148,922 0 SALES EXPENSE 12,550 12,550 ($12,550) 0 ADMINISTRATIVE AND GENERAL EXPENSE 2,066,308 2,066,308 (250,639) (8,170) TOTAL O & M EXPENSE (LINE 10 THRU 22) 11,303,820 (573,649) 4,262,915 7,614,555 0 (263,188) (158,247) DEPRECIATION 6,250,133 6,250,133 AMORTIZATION OF ELECTRIC PLANT 122,829 122,829 AMORTIZATION OF PLANT ACQ. ADJ. 0 0 * AMORTIZATION RE:BPA RESIDENTIAL EXCHANGE 0 0 * AMORTIZATION RE:PROPERTY TAXES (164,182) (164,182) 0 * AMORTIZATION RE:INVESTMENT TAX CREDITS 0 0 * PENSION DIFFERENTIAL (235,025) (235,025) * MPSC/MCC TAXES 0 0 * SO2 ALLOWANCES 0 0 TAXES OTHER THAN INCOME TAXES 4,648,603 4,648,603 (14,689) (11,251) INCOME TAXES FEDERAL U.S. 0 0 0 0 0 INCOME TAXES OTHER 0 0 0 0 0 0 DEFERRED INCOME TAXES 639,282 (166,212) 805,494 (17,177) 69,304 44,633 SUBTOTAL (LINE 25 THRU 36) 11,261,640 0 (330,394) 11,592,034 (31,866) 69,304 33,382 TOTAL COST OF SERVICE (LINE 23 + 37) 22,565,460 (573,649) 3,932,521 19,206,588 (31,866) (193,884) (124,865) UTILITY OPERATING INCOME (LINE 7 39) $11,238,072 $0 ($175,047) $11,413,119 ($48,056) $193,884 $124,865 ELECTRIC UTILITY RATE BASE 170,995,420 $170,995,420 RATE OF RETURN EARNED (%) MPSC BASIS (LINE 41 / 43) 6.67% REQUIRED REVENUE INCREASE $1,735,430 $65,423 ($263,953) ($169,991)

Docket No. D2018.2.12 Page 19 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 A B NORTHWESTERN ENERGY DAVE GATES GENERATING STATION INCOME STATEMENT ACTUAL 12 MONTHS ENDED DECEMBER 2017 ADJUSTED INTERIM REVENUES: RATE SCHEDULE REVENUES SALES FOR RESALE PROVISION FOR RATE REFUND TRANSMISSION MISCELLANEOUS REVENUES GROSS REVENUES (LINE 2 THRU 6) COST OF SERVICE: STEAM POWER OPERATION STEAM POWER MAINTENANCE OTHER POWER GENERATION OPERATION OTHER POWER GENERATION MAINTENANCE POWER SUPPLY TRANSMISSION OPERATION TRANSMISSION MAINTENANCE DISTRIBUTION OPERATION DISTRIBUTION MAINTENANCE CUSTOMER ACCOUNTS EXPENSE CUSTOMER SERVICE AND INFORMATION EXPENSE SALES EXPENSE ADMINISTRATIVE AND GENERAL EXPENSE TOTAL O & M EXPENSE (LINE 10 THRU 22) DEPRECIATION AMORTIZATION OF ELECTRIC PLANT AMORTIZATION OF PLANT ACQ. ADJ. * AMORTIZATION RE:BPA RESIDENTIAL EXCHANGE * AMORTIZATION RE:PROPERTY TAXES * AMORTIZATION RE:INVESTMENT TAX CREDITS * PENSION DIFFERENTIAL * MPSC/MCC TAXES * SO2 ALLOWANCES TAXES OTHER THAN INCOME TAXES INCOME TAXES FEDERAL U.S. INCOME TAXES OTHER DEFERRED INCOME TAXES SUBTOTAL (LINE 25 THRU 36) TOTAL COST OF SERVICE (LINE 23 + 37) UTILITY OPERATING INCOME (LINE 7 39) ELECTRIC UTILITY RATE BASE RATE OF RETURN EARNED (%) MPSC BASIS (LINE 41 / 43) REQUIRED REVENUE INCREASE J K L M N O P CORPORATE PROPERTY INTENTIONALLY INTENTIONALLY ALLOCATION DEPRECIATION AMORTIZATION TAXES LEFT MAINTENANCE LEFT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT BLANK ADJUSTMENT BLANK $0 $0 $0 $0 $0 $0 $0 (973,534) 0 0 0 0 0 (973,534) 0 918,008 74,720 156,556 16,302 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 (208,473) (41,225) (4,293) 0 256,356 0 0 784,255 115,331 12,009 0 256,356 0 0 784,255 115,331 12,009 0 (717,178) 0 $0 ($784,255) ($115,331) ($12,009) $0 $717,178 $0 $0 $1,067,684 $157,012 $16,349 $0 ($976,365) $0

Docket No. D2018.2.12 Page 20 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 A B NORTHWESTERN ENERGY DAVE GATES GENERATING STATION INCOME STATEMENT ACTUAL 12 MONTHS ENDED DECEMBER 2017 ADJUSTED INTERIM REVENUES: RATE SCHEDULE REVENUES SALES FOR RESALE PROVISION FOR RATE REFUND TRANSMISSION MISCELLANEOUS REVENUES GROSS REVENUES (LINE 2 THRU 6) COST OF SERVICE: STEAM POWER OPERATION STEAM POWER MAINTENANCE OTHER POWER GENERATION OPERATION OTHER POWER GENERATION MAINTENANCE POWER SUPPLY TRANSMISSION OPERATION TRANSMISSION MAINTENANCE DISTRIBUTION OPERATION DISTRIBUTION MAINTENANCE CUSTOMER ACCOUNTS EXPENSE CUSTOMER SERVICE AND INFORMATION EXPENSE SALES EXPENSE ADMINISTRATIVE AND GENERAL EXPENSE TOTAL O & M EXPENSE (LINE 10 THRU 22) DEPRECIATION AMORTIZATION OF ELECTRIC PLANT AMORTIZATION OF PLANT ACQ. ADJ. * AMORTIZATION RE:BPA RESIDENTIAL EXCHANGE * AMORTIZATION RE:PROPERTY TAXES * AMORTIZATION RE:INVESTMENT TAX CREDITS * PENSION DIFFERENTIAL * MPSC/MCC TAXES * SO2 ALLOWANCES TAXES OTHER THAN INCOME TAXES INCOME TAXES FEDERAL U.S. INCOME TAXES OTHER DEFERRED INCOME TAXES SUBTOTAL (LINE 25 THRU 36) TOTAL COST OF SERVICE (LINE 23 + 37) UTILITY OPERATING INCOME (LINE 7 39) ELECTRIC UTILITY RATE BASE RATE OF RETURN EARNED (%) MPSC BASIS (LINE 41 / 43) REQUIRED REVENUE INCREASE Q R S T U V W INTENTIONALLY INTENTIONALLY INTENTIONALLY INTENTIONALLY INTENTIONALLY WORKING LEFT LEFT LEFT LEFT LEFT CAPITAL INCOME TAX BLANK BLANK BLANK BLANK BLANK ADJUSTMENT ADJUSTMENT $0 $0 $0 $0 $0 $0 $0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 (1,355,699) 0 0 0 0 0 0 (1,355,699) 0 0 0 0 0 0 (1,355,699) $0 $0 $0 $0 $0 $0 $1,355,699 239,852 (794,240) $0 $0 $0 $0 $0 $24,213 ($1,925,878)

Docket No. D2018.2.12 Page 21 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 A B NORTHWESTERN ENERGY DAVE GATES GENERATING STATION INCOME STATEMENT ACTUAL 12 MONTHS ENDED DECEMBER 2017 ADJUSTED INTERIM REVENUES: RATE SCHEDULE REVENUES SALES FOR RESALE PROVISION FOR RATE REFUND TRANSMISSION MISCELLANEOUS REVENUES GROSS REVENUES (LINE 2 THRU 6) COST OF SERVICE: STEAM POWER OPERATION STEAM POWER MAINTENANCE OTHER POWER GENERATION OPERATION OTHER POWER GENERATION MAINTENANCE POWER SUPPLY TRANSMISSION OPERATION TRANSMISSION MAINTENANCE DISTRIBUTION OPERATION DISTRIBUTION MAINTENANCE CUSTOMER ACCOUNTS EXPENSE CUSTOMER SERVICE AND INFORMATION EXPENSE SALES EXPENSE ADMINISTRATIVE AND GENERAL EXPENSE TOTAL O & M EXPENSE (LINE 10 THRU 22) DEPRECIATION AMORTIZATION OF ELECTRIC PLANT AMORTIZATION OF PLANT ACQ. ADJ. * AMORTIZATION RE:BPA RESIDENTIAL EXCHANGE * AMORTIZATION RE:PROPERTY TAXES * AMORTIZATION RE:INVESTMENT TAX CREDITS * PENSION DIFFERENTIAL * MPSC/MCC TAXES * SO2 ALLOWANCES TAXES OTHER THAN INCOME TAXES INCOME TAXES FEDERAL U.S. INCOME TAXES OTHER DEFERRED INCOME TAXES SUBTOTAL (LINE 25 THRU 36) TOTAL COST OF SERVICE (LINE 23 + 37) UTILITY OPERATING INCOME (LINE 7 39) ELECTRIC UTILITY RATE BASE RATE OF RETURN EARNED (%) MPSC BASIS (LINE 41 / 43) REQUIRED REVENUE INCREASE X Y Z AA AB AC AD INTERIM ADJUSTMENTS INTEREST TOTAL TEST PERIOD ADJUST TO NONPCCAM MONTANA SYNCHRONIZATION UPDATES & @ PRESENT ROE FROM DEPRECIATION SUPPLY GENERATION ADJUSTMENT ADJUSTMENTS RATES DOCKET 2008.8.95 ADJUSTMENT ADJUSTMENT ADJUSTMENT (251,509) $28,992,641 0 $0 176,050 $0 0 $0 (4,463) $1,547,144 $0 ($79,922) $30,539,785 $0 $0 $0 $0 0 $0 0 $0 5,297 $1,852,211 (1,101,332) $2,035,547 (27,576) $85,993 0 $0 0 $0 0 $52,205 0 $0 0 $237,209 0 $148,922 (12,550) ($0) (258,809) $1,807,499 0 (1,394,970) 6,219,585 $0 $0 $0 $0 918,008 $7,168,141 (1,087,765) 74,720 $197,549 0 $0 0 $0 0 $0 0 $0 156,556 ($78,470) $0 0 $0 (9,638) $4,638,965 0 0 $0 $0 $0 $0 $0 0 0 $0 $0 $0 $0 $0 1,563,584 307,010 $1,112,504 $0 $228,431 $0 $0 1,563,584 1,446,655 13,038,689 $0 ($859,334) $0 $0 1,563,584 51,686 19,258,274 $0 ($859,334) $0 $0 ($1,563,584) ($131,608) $11,281,511 $0 $859,334 $0 $0 ($554,389) $170,441,031 543,883 6.62% $2,128,661 123,155 $1,858,585 ($742,523) ($1,117,325) $0 $0

Docket No. D2018.2.12 Page 22 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 A B NORTHWESTERN ENERGY DAVE GATES GENERATING STATION INCOME STATEMENT ACTUAL 12 MONTHS ENDED DECEMBER 2017 ADJUSTED INTERIM REVENUES: RATE SCHEDULE REVENUES SALES FOR RESALE PROVISION FOR RATE REFUND TRANSMISSION MISCELLANEOUS REVENUES GROSS REVENUES (LINE 2 THRU 6) COST OF SERVICE: STEAM POWER OPERATION STEAM POWER MAINTENANCE OTHER POWER GENERATION OPERATION OTHER POWER GENERATION MAINTENANCE POWER SUPPLY TRANSMISSION OPERATION TRANSMISSION MAINTENANCE DISTRIBUTION OPERATION DISTRIBUTION MAINTENANCE CUSTOMER ACCOUNTS EXPENSE CUSTOMER SERVICE AND INFORMATION EXPENSE SALES EXPENSE ADMINISTRATIVE AND GENERAL EXPENSE TOTAL O & M EXPENSE (LINE 10 THRU 22) DEPRECIATION AMORTIZATION OF ELECTRIC PLANT AMORTIZATION OF PLANT ACQ. ADJ. * AMORTIZATION RE:BPA RESIDENTIAL EXCHANGE * AMORTIZATION RE:PROPERTY TAXES * AMORTIZATION RE:INVESTMENT TAX CREDITS * PENSION DIFFERENTIAL * MPSC/MCC TAXES * SO2 ALLOWANCES TAXES OTHER THAN INCOME TAXES INCOME TAXES FEDERAL U.S. INCOME TAXES OTHER DEFERRED INCOME TAXES SUBTOTAL (LINE 25 THRU 36) TOTAL COST OF SERVICE (LINE 23 + 37) UTILITY OPERATING INCOME (LINE 7 39) ELECTRIC UTILITY RATE BASE RATE OF RETURN EARNED (%) MPSC BASIS (LINE 41 / 43) REQUIRED REVENUE INCREASE AE AF AG AH AI AJ AK INTERIM ADJUSTMENTS INTERIM INTERIM INTENTIONALLY INTENTIONALLY WORKING INTEREST TOTAL TEST PERIOD LEFT LEFT CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT BLANK BLANK ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES $ $28,992,641 1,547,144 $0 $0 $0 $0 $0 $0 $30,539,785 1,852,211 2,035,547 85,993 52,205 237,209 148,922 (0) 1,807,499 $0 $0 $0 $0 $0 $0 $6,219,585 (1,087,765) 6,080,376 197,549 (78,470) 4,638,965 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 ($44,966) ($395,912) (212,447) 900,057 $0 $0 $0 ($44,966) ($395,912) ($1,300,213) $11,738,476 $0 $0 $0 ($44,966) ($395,912) $ (1,300,213) $17,958,061 $0 $0 $0 $44,966 $395,912 $1,300,213 $12,581,724 (3,460) 537,206 $ 1,077,629 $171,518,660 7.34% $0 $0 ($335) ($9,290) ($538,994) $ (2,408,467) ($549,882)

Docket No. D2018.2.12 Page 23 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 A B C D E F G H I NORTHWESTERN ENERGY SPION KOP WIND GENERATION INCOME STATEMENT ACTUAL 12 MONTHS ENDED DECEMBER 2017 ADJUSTED INTERIM REVENUE SALES & REMOVE REMOVE & REVENUE ADMINISTRATIVE SPION KOP DEFERRED REVENUE CREDITS FIXED SPION KOP RELATED & GENERAL LABOR REVENUES & VARIABLE ADJUSTMENT ADJUSTMENT ADJUSTMENT REVENUES: RATE SCHEDULE REVENUES $8,187,091 ($398,554) ($3,098,126) $11,683,771 ($497,720) SALES FOR RESALE 0 0 PROVISION FOR RATE REFUND 0 0 0 TRANSMISSION 0 0 MISCELLANEOUS REVENUES 0 0 0 GROSS REVENUES (LINE 2 THRU 6) $8,187,091 ($398,554) ($3,098,126) $11,683,771 ($497,720) $0 $0 COST OF SERVICE: STEAM POWER OPERATION 0 0 STEAM POWER MAINTENANCE 0 0 OTHER POWER GENERATION OPERATION 2,101,732 0 2,101,732 2,831 OTHER POWER GENERATION MAINTENANCE 34,463 34,463 0 POWER SUPPLY (414,945) (398,554) (22,978) 6,587 (2,262) TRANSMISSION OPERATION 0 0 TRANSMISSION MAINTENANCE 0 0 DISTRIBUTION OPERATION 0 0 DISTRIBUTION MAINTENANCE 0 0 CUSTOMER ACCOUNTS EXPENSE 0 0 CUSTOMER SERVICE AND INFORMATION EXPENSE 0 0 SALES EXPENSE 0 0 ADMINISTRATIVE AND GENERAL EXPENSE 86,170 86,170 (4,291) 196 TOTAL O & M EXPENSE (LINE 10 THRU 22) 1,807,419 (398,554) (22,978) 2,228,951 0 (4,291) 765 DEPRECIATION 3,298,924 3,298,924 AMORTIZATION OF ELECTRIC PLANT 3,216 3,216 AMORTIZATION OF PLANT ACQ. ADJ. 0 0 * AMORTIZATION RE:BPA RESIDENTIAL EXCHANGE 0 0 * AMORTIZATION RE:PROPERTY TAXES 69,589 69,589 0 * AMORTIZATION RE:INVESTMENT TAX CREDITS 0 0 * PENSION DIFFERENTIAL 0 0 * MPSC/MCC TAXES 0 0 * SO2 ALLOWANCES 0 0 TAXES OTHER THAN INCOME TAXES 400,200 400,200 (19,863) 54 INCOME TAXES FEDERAL U.S. (3,148,424) (3,148,376) (48) 0 0 0 INCOME TAXES OTHER 0 0 0 0 0 0 DEFERRED INCOME TAXES 650,785 (1,234,576) 1,885,361 (125,832) 1,130 (216) SUBTOTAL (LINE 25 THRU 36) 1,274,290 0 (4,313,363) 5,587,652 (145,695) 1,130 (162) TOTAL COST OF SERVICE (LINE 23 + 37) 3,081,709 (398,554) (4,336,340) 7,816,604 (145,695) (3,161) 603 UTILITY OPERATING INCOME (LINE 7 39) $5,105,382 $0 $1,238,215 $3,867,168 ($352,025) $3,161 ($603) ELECTRIC UTILITY RATE BASE 57,190,037 $57,190,037 RATE OF RETURN EARNED (%) MPSC BASIS (LINE 41 / 43) 6.76% REQUIRED REVENUE INCREASE $512,340 $479,245 ($4,304) $820

Docket No. D2018.2.12 Page 24 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 A B NORTHWESTERN ENERGY SPION KOP WIND GENERATION INCOME STATEMENT ACTUAL 12 MONTHS ENDED DECEMBER 2017 ADJUSTED INTERIM REVENUES: RATE SCHEDULE REVENUES SALES FOR RESALE PROVISION FOR RATE REFUND TRANSMISSION MISCELLANEOUS REVENUES GROSS REVENUES (LINE 2 THRU 6) COST OF SERVICE: STEAM POWER OPERATION STEAM POWER MAINTENANCE OTHER POWER GENERATION OPERATION OTHER POWER GENERATION MAINTENANCE POWER SUPPLY TRANSMISSION OPERATION TRANSMISSION MAINTENANCE DISTRIBUTION OPERATION DISTRIBUTION MAINTENANCE CUSTOMER ACCOUNTS EXPENSE CUSTOMER SERVICE AND INFORMATION EXPENSE SALES EXPENSE ADMINISTRATIVE AND GENERAL EXPENSE TOTAL O & M EXPENSE (LINE 10 THRU 22) DEPRECIATION AMORTIZATION OF ELECTRIC PLANT AMORTIZATION OF PLANT ACQ. ADJ. * AMORTIZATION RE:BPA RESIDENTIAL EXCHANGE * AMORTIZATION RE:PROPERTY TAXES * AMORTIZATION RE:INVESTMENT TAX CREDITS * PENSION DIFFERENTIAL * MPSC/MCC TAXES * SO2 ALLOWANCES TAXES OTHER THAN INCOME TAXES INCOME TAXES FEDERAL U.S. INCOME TAXES OTHER DEFERRED INCOME TAXES SUBTOTAL (LINE 25 THRU 36) TOTAL COST OF SERVICE (LINE 23 + 37) UTILITY OPERATING INCOME (LINE 7 39) ELECTRIC UTILITY RATE BASE RATE OF RETURN EARNED (%) MPSC BASIS (LINE 41 / 43) REQUIRED REVENUE INCREASE J K L M N O P CORPORATE PROPERTY INTENTIONALLY INTENTIONALLY INTENTIONALLY ALLOCATION DEPRECIATION AMORTIZATION TAXES LEFT LEFT LEFT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT BLANK BLANK BLANK $0 $0 $0 $0 $0 $0 $0 0 0 0 0 0 0 0 289,007 5,874 53,567 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 (61,925) 0 (14,106) 0 0 0 0 232,956 0 39,461 0 0 0 0 232,956 0 39,461 0 0 0 $0 ($232,956) $0 ($39,461) $0 $0 $0 $0 $317,146 $0 $53,723 $0 $0 $0

Docket No. D2018.2.12 Page 25 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 A B NORTHWESTERN ENERGY SPION KOP WIND GENERATION INCOME STATEMENT ACTUAL 12 MONTHS ENDED DECEMBER 2017 ADJUSTED INTERIM REVENUES: RATE SCHEDULE REVENUES SALES FOR RESALE PROVISION FOR RATE REFUND TRANSMISSION MISCELLANEOUS REVENUES GROSS REVENUES (LINE 2 THRU 6) COST OF SERVICE: STEAM POWER OPERATION STEAM POWER MAINTENANCE OTHER POWER GENERATION OPERATION OTHER POWER GENERATION MAINTENANCE POWER SUPPLY TRANSMISSION OPERATION TRANSMISSION MAINTENANCE DISTRIBUTION OPERATION DISTRIBUTION MAINTENANCE CUSTOMER ACCOUNTS EXPENSE CUSTOMER SERVICE AND INFORMATION EXPENSE SALES EXPENSE ADMINISTRATIVE AND GENERAL EXPENSE TOTAL O & M EXPENSE (LINE 10 THRU 22) DEPRECIATION AMORTIZATION OF ELECTRIC PLANT AMORTIZATION OF PLANT ACQ. ADJ. * AMORTIZATION RE:BPA RESIDENTIAL EXCHANGE * AMORTIZATION RE:PROPERTY TAXES * AMORTIZATION RE:INVESTMENT TAX CREDITS * PENSION DIFFERENTIAL * MPSC/MCC TAXES * SO2 ALLOWANCES TAXES OTHER THAN INCOME TAXES INCOME TAXES FEDERAL U.S. INCOME TAXES OTHER DEFERRED INCOME TAXES SUBTOTAL (LINE 25 THRU 36) TOTAL COST OF SERVICE (LINE 23 + 37) UTILITY OPERATING INCOME (LINE 7 39) ELECTRIC UTILITY RATE BASE RATE OF RETURN EARNED (%) MPSC BASIS (LINE 41 / 43) REQUIRED REVENUE INCREASE Q R S T U V W INTENTIONALLY INTENTIONALLY INTENTIONALLY INTENTIONALLY INTENTIONALLY WORKING LEFT LEFT LEFT LEFT LEFT CAPITAL INCOME TAX BLANK BLANK BLANK BLANK BLANK ADJUSTMENT ADJUSTMENT $0 $0 $0 $0 $0 $0 $0 0 0 0 0 0 0 0 0 0 0 0 0 0 48 0 0 0 0 0 0 0 0 0 0 0 0 0 (894,108) 0 0 0 0 0 0 (894,060) 0 0 0 0 0 0 (894,060) $0 $0 $0 $0 $0 $0 $894,060 3,920 314,373 $0 $0 $0 $0 $0 $395 (1,185,416)

Docket No. D2018.2.12 Page 26 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 A B NORTHWESTERN ENERGY SPION KOP WIND GENERATION INCOME STATEMENT ACTUAL 12 MONTHS ENDED DECEMBER 2017 ADJUSTED INTERIM REVENUES: RATE SCHEDULE REVENUES SALES FOR RESALE PROVISION FOR RATE REFUND TRANSMISSION MISCELLANEOUS REVENUES GROSS REVENUES (LINE 2 THRU 6) COST OF SERVICE: STEAM POWER OPERATION STEAM POWER MAINTENANCE OTHER POWER GENERATION OPERATION OTHER POWER GENERATION MAINTENANCE POWER SUPPLY TRANSMISSION OPERATION TRANSMISSION MAINTENANCE DISTRIBUTION OPERATION DISTRIBUTION MAINTENANCE CUSTOMER ACCOUNTS EXPENSE CUSTOMER SERVICE AND INFORMATION EXPENSE SALES EXPENSE ADMINISTRATIVE AND GENERAL EXPENSE TOTAL O & M EXPENSE (LINE 10 THRU 22) DEPRECIATION AMORTIZATION OF ELECTRIC PLANT AMORTIZATION OF PLANT ACQ. ADJ. * AMORTIZATION RE:BPA RESIDENTIAL EXCHANGE * AMORTIZATION RE:PROPERTY TAXES * AMORTIZATION RE:INVESTMENT TAX CREDITS * PENSION DIFFERENTIAL * MPSC/MCC TAXES * SO2 ALLOWANCES TAXES OTHER THAN INCOME TAXES INCOME TAXES FEDERAL U.S. INCOME TAXES OTHER DEFERRED INCOME TAXES SUBTOTAL (LINE 25 THRU 36) TOTAL COST OF SERVICE (LINE 23 + 37) UTILITY OPERATING INCOME (LINE 7 39) ELECTRIC UTILITY RATE BASE RATE OF RETURN EARNED (%) MPSC BASIS (LINE 41 / 43) REQUIRED REVENUE INCREASE X Y Z AA AB AC AD INTERIM ADJUSTMENTS INTEREST TOTAL TEST PERIOD ADJUST TO NONPCCAM MONTANA SYNCHRONIZATION UPDATES & @ PRESENT ROE FROM DEPRECIATION SUPPLY GENERATION ADJUSTMENT ADJUSTMENTS RATES DOCKET 2011.5.41 ADJUSTMENT ADJUSTMENT ADJUSTMENT (497,720) $11,186,051 0 $0 0 $0 0 $0 0 $0 $0 ($497,720) $11,186,051 $0 $0 $0 $0 0 $0 0 $0 2,831 $2,104,562 0 $34,463 (2,262) $4,325 0 $0 0 $0 0 $0 0 $0 0 $0 0 $0 0 $0 (4,095) $82,075 0 (3,526) 2,225,425 $0 $0 $0 $0 289,007 $3,587,931 (237,110) 5,874 $9,090 0 $0 0 $0 0 $0 0 $0 0 $0 0 $0 0 $0 33,758 $433,959 0 48 $0 $0 $0 $0 $0 0 0 $0 $0 $0 $0 $0 (113,449) (1,208,506) $676,855 $0 $49,793 $0 $0 (113,449) (879,819) 4,707,833 $0 ($187,317) $0 $0 (113,449) (883,345) 6,933,259 $0 ($187,317) $0 $0 $113,449 $385,625 $4,252,793 $0 $187,317 $0 $0 $318,292 $57,508,330 118,555 7.40% (154,449) (492,840) $19,500 ($250,534) ($243,554) $0 $0

Docket No. D2018.2.12 Page 27 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 A B NORTHWESTERN ENERGY SPION KOP WIND GENERATION INCOME STATEMENT ACTUAL 12 MONTHS ENDED DECEMBER 2017 ADJUSTED INTERIM REVENUES: RATE SCHEDULE REVENUES SALES FOR RESALE PROVISION FOR RATE REFUND TRANSMISSION MISCELLANEOUS REVENUES GROSS REVENUES (LINE 2 THRU 6) COST OF SERVICE: STEAM POWER OPERATION STEAM POWER MAINTENANCE OTHER POWER GENERATION OPERATION OTHER POWER GENERATION MAINTENANCE POWER SUPPLY TRANSMISSION OPERATION TRANSMISSION MAINTENANCE DISTRIBUTION OPERATION DISTRIBUTION MAINTENANCE CUSTOMER ACCOUNTS EXPENSE CUSTOMER SERVICE AND INFORMATION EXPENSE SALES EXPENSE ADMINISTRATIVE AND GENERAL EXPENSE TOTAL O & M EXPENSE (LINE 10 THRU 22) DEPRECIATION AMORTIZATION OF ELECTRIC PLANT AMORTIZATION OF PLANT ACQ. ADJ. * AMORTIZATION RE:BPA RESIDENTIAL EXCHANGE * AMORTIZATION RE:PROPERTY TAXES * AMORTIZATION RE:INVESTMENT TAX CREDITS * PENSION DIFFERENTIAL * MPSC/MCC TAXES * SO2 ALLOWANCES TAXES OTHER THAN INCOME TAXES INCOME TAXES FEDERAL U.S. INCOME TAXES OTHER DEFERRED INCOME TAXES SUBTOTAL (LINE 25 THRU 36) TOTAL COST OF SERVICE (LINE 23 + 37) UTILITY OPERATING INCOME (LINE 7 39) ELECTRIC UTILITY RATE BASE RATE OF RETURN EARNED (%) MPSC BASIS (LINE 41 / 43) REQUIRED REVENUE INCREASE AE AF AG AH AI AJ AK INTERIM ADJUSTMENTS INTERIM INTERIM INTENTIONALLY INTENTIONALLY WORKING INTEREST TOTAL TEST PERIOD LEFT LEFT CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT BLANK BLANK ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES $ $11,186,051 $0 $0 $0 $0 $0 $0 $11,186,051 2,104,562 34,463 4,325 82,075 $0 $0 $0 $0 $0 $0 $2,225,425 (237,110) 3,350,821 9,090 433,959 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $9,702 ($3,183) 56,312 733,167 $0 $0 $0 $9,702 ($3,183) ($180,798) $4,527,036 $0 $0 $0 $9,702 ($3,183) $ (180,798) $6,752,461 $0 $0 $0 ($9,702) $3,183 $180,798 $4,433,590 2,596 (929,804) $ (808,653) $56,699,677 7.82% $0 $0 $251 ($76,666) ($4,334) $ (574,837) ($555,337)

Docket No. D2018.2.12 Page 28 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 A B C D E F G H I J NORTHWESTERN ENERGY HYDRO GENERATION INCOME STATEMENT ACTUAL 12 MONTHS ENDED DECEMBER 2017 ADJUSTED INTERIM REVENUE SALES & REMOVE REMOVE & REVENUE ADMINISTRATIVE CORPORATE HYDRO DEFERRED REVENUE CREDITS FIXED HYDRO RELATED & GENERAL LABOR ALLOCATION REVENUES & VARIABLE ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT REVENUES: RATE SCHEDULE REVENUES $146,395,784 $2,871,683 $764,857 $142,759,244 $1,284,015 SALES FOR RESALE 0 0 0 PROVISION FOR RATE REFUND 2,541,732 2,541,732 (2,541,732) TRANSMISSION 0 0 MISCELLANEOUS REVENUES (3,796) 0 (3,796) 3,796 GROSS REVENUES (LINE 2 THRU 6) $148,933,720 $2,871,683 $764,857 $145,297,180 ($1,253,921) $0 $0 $0 COST OF SERVICE: STEAM POWER OPERATION 0 0 STEAM POWER MAINTENANCE 0 0 HYDRO POWER OPERATION 12,879,332 12,879,332 257,942 HYDRO POWER MAINTENANCE 5,777,995 5,777,995 112,265 OTHER POWER GENERATION OPERATION 0 0 0 OTHER POWER GENERATION MAINTENANCE 0 0 POWER SUPPLY 3,679,811 2,871,683 53,619 754,508 (186,068) 20,573 TRANSMISSION OPERATION 0 0 TRANSMISSION MAINTENANCE 0 0 DISTRIBUTION OPERATION 327,239 327,239 26,102 DISTRIBUTION MAINTENANCE 0 0 CUSTOMER ACCOUNTS EXPENSE 1,438,876 1,438,876 127,209 CUSTOMER SERVICE AND INFORMATION EXPENSE 885,159 885,159 83,772 SALES EXPENSE 81,573 81,573 (81,573) 0 ADMINISTRATIVE AND GENERAL EXPENSE 13,400,035 13,400,035 (1,597,645) (50,921) 886,593 TOTAL O & M EXPENSE (LINE 10 THRU 22) 38,470,018 2,871,683 53,619 35,544,716 0 (1,679,218) 133,218 1,144,249 DEPRECIATION 12,098,900 12,098,900 AMORTIZATION OF ELECTRIC PLANT 979,399 979,399 AMORTIZATION OF PLANT ACQ. ADJ. 7,014,087 7,014,087 * AMORTIZATION RE:BPA RESIDENTIAL EXCHANGE 0 0 * AMORTIZATION RE:PROPERTY TAXES (773,892) (773,892) 0 * AMORTIZATION RE:INVESTMENT TAX CREDITS 0 0 * PENSION DIFFERENTIAL (1,527,665) (1,527,665) * MPSC/MCC TAXES 0 0 * SO2 ALLOWANCES 0 0 TAXES OTHER THAN INCOME TAXES 20,754,751 20,754,751 (349,678) 9,472 INCOME TAXES FEDERAL U.S. (373,069) (373,069) 0 0 0 0 0 INCOME TAXES OTHER 0 0 0 0 0 0 DEFERRED INCOME TAXES 16,096,638 563,373 15,533,265 (238,110) 442,180 (37,574) (301,309) SUBTOTAL (LINE 25 THRU 36) 54,269,149 0 (583,588) 54,852,737 (587,788) 442,180 (28,102) (301,309) TOTAL COST OF SERVICE (LINE 23 + 37) 92,739,167 2,871,683 (529,968) 90,397,453 (587,788) (1,237,038) 105,116 842,940 UTILITY OPERATING INCOME (LINE 7 39) $56,194,552 $0 $1,294,825 $54,899,727 ($666,133) $1,237,038 ($105,116) ($842,940) ELECTRIC UTILITY RATE BASE 793,410,248 $793,410,248 RATE OF RETURN EARNED (%) MPSC BASIS (LINE 41 / 43) 6.92% REQUIRED REVENUE INCREASE $5,406,540 $906,872 ($1,684,102) $143,105 $1,147,578

Docket No. D2018.2.12 Page 29 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 A B NORTHWESTERN ENERGY HYDRO GENERATION INCOME STATEMENT ACTUAL 12 MONTHS ENDED DECEMBER 2017 ADJUSTED INTERIM REVENUES: RATE SCHEDULE REVENUES SALES FOR RESALE PROVISION FOR RATE REFUND TRANSMISSION MISCELLANEOUS REVENUES GROSS REVENUES (LINE 2 THRU 6) COST OF SERVICE: STEAM POWER OPERATION STEAM POWER MAINTENANCE HYDRO POWER OPERATION HYDRO POWER MAINTENANCE OTHER POWER GENERATION OPERATION OTHER POWER GENERATION MAINTENANCE POWER SUPPLY TRANSMISSION OPERATION TRANSMISSION MAINTENANCE DISTRIBUTION OPERATION DISTRIBUTION MAINTENANCE CUSTOMER ACCOUNTS EXPENSE CUSTOMER SERVICE AND INFORMATION EXPENSE SALES EXPENSE ADMINISTRATIVE AND GENERAL EXPENSE TOTAL O & M EXPENSE (LINE 10 THRU 22) DEPRECIATION AMORTIZATION OF ELECTRIC PLANT AMORTIZATION OF PLANT ACQ. ADJ. * AMORTIZATION RE:BPA RESIDENTIAL EXCHANGE * AMORTIZATION RE:PROPERTY TAXES * AMORTIZATION RE:INVESTMENT TAX CREDITS * PENSION DIFFERENTIAL * MPSC/MCC TAXES * SO2 ALLOWANCES TAXES OTHER THAN INCOME TAXES INCOME TAXES FEDERAL U.S. INCOME TAXES OTHER DEFERRED INCOME TAXES SUBTOTAL (LINE 25 THRU 36) TOTAL COST OF SERVICE (LINE 23 + 37) UTILITY OPERATING INCOME (LINE 7 39) ELECTRIC UTILITY RATE BASE RATE OF RETURN EARNED (%) MPSC BASIS (LINE 41 / 43) REQUIRED REVENUE INCREASE K L M N O P Q R PROPERTY INTENTIONALLY INTENTIONALLY INTENTIONALLY INTENTIONALLY INTENTIONALLY DEPRECIATION AMORTIZATION TAXES LEFT LEFT LEFT LEFT LEFT ADJUSTMENT ADJUSTMENT ADJUSTMENT BLANK BLANK BLANK BLANK BLANK (2,605,804) (184,977) 1,998,570 $0 $0 $0 $0 $0 $0 $0 $0 0 0 0 0 0 0 0 0 1,017,611 241,493 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 166,364 (267,962) (63,591) 0 0 0 0 0 (625,847) 749,649 177,902 0 0 0 0 0 (625,847) 749,649 177,902 0 0 0 0 0 $625,847 ($749,649) ($177,902) $0 $0 $0 $0 $0 ($852,027) $1,020,571 $242,195 $0 $0 $0 $0 $0

Docket No. D2018.2.12 Page 30 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 A B NORTHWESTERN ENERGY HYDRO GENERATION INCOME STATEMENT ACTUAL 12 MONTHS ENDED DECEMBER 2017 ADJUSTED INTERIM REVENUES: RATE SCHEDULE REVENUES SALES FOR RESALE PROVISION FOR RATE REFUND TRANSMISSION MISCELLANEOUS REVENUES GROSS REVENUES (LINE 2 THRU 6) COST OF SERVICE: STEAM POWER OPERATION STEAM POWER MAINTENANCE HYDRO POWER OPERATION HYDRO POWER MAINTENANCE OTHER POWER GENERATION OPERATION OTHER POWER GENERATION MAINTENANCE POWER SUPPLY TRANSMISSION OPERATION TRANSMISSION MAINTENANCE DISTRIBUTION OPERATION DISTRIBUTION MAINTENANCE CUSTOMER ACCOUNTS EXPENSE CUSTOMER SERVICE AND INFORMATION EXPENSE SALES EXPENSE ADMINISTRATIVE AND GENERAL EXPENSE TOTAL O & M EXPENSE (LINE 10 THRU 22) DEPRECIATION AMORTIZATION OF ELECTRIC PLANT AMORTIZATION OF PLANT ACQ. ADJ. * AMORTIZATION RE:BPA RESIDENTIAL EXCHANGE * AMORTIZATION RE:PROPERTY TAXES * AMORTIZATION RE:INVESTMENT TAX CREDITS * PENSION DIFFERENTIAL * MPSC/MCC TAXES * SO2 ALLOWANCES TAXES OTHER THAN INCOME TAXES INCOME TAXES FEDERAL U.S. INCOME TAXES OTHER DEFERRED INCOME TAXES SUBTOTAL (LINE 25 THRU 36) TOTAL COST OF SERVICE (LINE 23 + 37) UTILITY OPERATING INCOME (LINE 7 39) ELECTRIC UTILITY RATE BASE RATE OF RETURN EARNED (%) MPSC BASIS (LINE 41 / 43) REQUIRED REVENUE INCREASE S T U V W X Y Z INTENTIONALLY INTENTIONALLY INTENTIONALLY WORKING INTEREST TOTAL TEST PERIOD LEFT LEFT LEFT CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT BLANK BLANK BLANK ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES 1,284,015 $144,043,259 0 $0 (2,541,732) $0 0 $0 3,796 $0 $0 $0 $0 $0 $0 $0 ($1,253,921) $144,043,259 0 $0 0 $0 257,942 $13,137,274 112,265 $5,890,260 0 $0 0 $0 (165,495) $589,013 0 $0 0 $0 26,102 $353,341 0 $0 127,209 $1,566,084 83,772 $968,931 (81,573) ($0) (761,972) $12,638,062 0 0 0 0 0 0 (401,750) 35,142,966 (2,605,804) $9,493,096 (184,977) $794,422 1,998,570 $9,012,657 $0 $0 $0 1,017,611 ($510,054) $0 $0 (98,713) $20,656,038 0 0 0 0 0 0 0 $0 0 0 0 0 0 0 0 $0 0 0 0 0 (5,419,014) 2,064,962 (3,654,054) $11,879,210 0 0 0 0 (5,419,014) 2,064,962 (3,527,368) 51,325,369 0 0 0 0 (5,419,014) 2,064,962 (3,929,118) 86,468,335 $0 $0 $0 $0 $5,419,014 ($2,064,962) $2,675,197 $57,574,925 824,806 (1,041,712) ($216,905) $793,193,342 7.26% $0 $0 $0 $83,215 ($7,482,668) $2,811,236 (3,664,025) $1,742,515

Docket No. D2018.2.12 Page 31 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 A B NORTHWESTERN ENERGY HYDRO GENERATION INCOME STATEMENT ACTUAL 12 MONTHS ENDED DECEMBER 2017 ADJUSTED INTERIM REVENUES: RATE SCHEDULE REVENUES SALES FOR RESALE PROVISION FOR RATE REFUND TRANSMISSION MISCELLANEOUS REVENUES GROSS REVENUES (LINE 2 THRU 6) COST OF SERVICE: STEAM POWER OPERATION STEAM POWER MAINTENANCE HYDRO POWER OPERATION HYDRO POWER MAINTENANCE OTHER POWER GENERATION OPERATION OTHER POWER GENERATION MAINTENANCE POWER SUPPLY TRANSMISSION OPERATION TRANSMISSION MAINTENANCE DISTRIBUTION OPERATION DISTRIBUTION MAINTENANCE CUSTOMER ACCOUNTS EXPENSE CUSTOMER SERVICE AND INFORMATION EXPENSE SALES EXPENSE ADMINISTRATIVE AND GENERAL EXPENSE TOTAL O & M EXPENSE (LINE 10 THRU 22) DEPRECIATION AMORTIZATION OF ELECTRIC PLANT AMORTIZATION OF PLANT ACQ. ADJ. * AMORTIZATION RE:BPA RESIDENTIAL EXCHANGE * AMORTIZATION RE:PROPERTY TAXES * AMORTIZATION RE:INVESTMENT TAX CREDITS * PENSION DIFFERENTIAL * MPSC/MCC TAXES * SO2 ALLOWANCES TAXES OTHER THAN INCOME TAXES INCOME TAXES FEDERAL U.S. INCOME TAXES OTHER DEFERRED INCOME TAXES SUBTOTAL (LINE 25 THRU 36) TOTAL COST OF SERVICE (LINE 23 + 37) UTILITY OPERATING INCOME (LINE 7 39) ELECTRIC UTILITY RATE BASE RATE OF RETURN EARNED (%) MPSC BASIS (LINE 41 / 43) REQUIRED REVENUE INCREASE AA AB AC AD AE AF AG INTERIM ADJUSTMENTS ADJUST TO NONPCCAM MONTANA INTENTIONALLY INTENTIONALLY WORKING ROE FROM DEPRECIATION SUPPLY GENERATION LEFT LEFT CAPITAL DOCKET 2013.12.85 ADJUSTMENT ADJUSTMENT ADJUSTMENT BLANK BLANK ADJUSTMENT $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 (804,953) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 169,040 0 0 0 0 0 $0 ($635,913) $0 $0 $0 $0 $0 $0 ($635,913) $0 $0 $0 $0 $0 $0 $635,913 $0 $0 $0 $0 $0 402,476 329,646 ($4,535,374) ($827,377) $0 $0 $0 $0 $31,414

Docket No. D2018.2.12 Page 32 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 A B NORTHWESTERN ENERGY HYDRO GENERATION INCOME STATEMENT ACTUAL 12 MONTHS ENDED DECEMBER 2017 ADJUSTED INTERIM REVENUES: RATE SCHEDULE REVENUES SALES FOR RESALE PROVISION FOR RATE REFUND TRANSMISSION MISCELLANEOUS REVENUES GROSS REVENUES (LINE 2 THRU 6) COST OF SERVICE: STEAM POWER OPERATION STEAM POWER MAINTENANCE HYDRO POWER OPERATION HYDRO POWER MAINTENANCE OTHER POWER GENERATION OPERATION OTHER POWER GENERATION MAINTENANCE POWER SUPPLY TRANSMISSION OPERATION TRANSMISSION MAINTENANCE DISTRIBUTION OPERATION DISTRIBUTION MAINTENANCE CUSTOMER ACCOUNTS EXPENSE CUSTOMER SERVICE AND INFORMATION EXPENSE SALES EXPENSE ADMINISTRATIVE AND GENERAL EXPENSE TOTAL O & M EXPENSE (LINE 10 THRU 22) DEPRECIATION AMORTIZATION OF ELECTRIC PLANT AMORTIZATION OF PLANT ACQ. ADJ. * AMORTIZATION RE:BPA RESIDENTIAL EXCHANGE * AMORTIZATION RE:PROPERTY TAXES * AMORTIZATION RE:INVESTMENT TAX CREDITS * PENSION DIFFERENTIAL * MPSC/MCC TAXES * SO2 ALLOWANCES TAXES OTHER THAN INCOME TAXES INCOME TAXES FEDERAL U.S. INCOME TAXES OTHER DEFERRED INCOME TAXES SUBTOTAL (LINE 25 THRU 36) TOTAL COST OF SERVICE (LINE 23 + 37) UTILITY OPERATING INCOME (LINE 7 39) ELECTRIC UTILITY RATE BASE RATE OF RETURN EARNED (%) MPSC BASIS (LINE 41 / 43) REQUIRED REVENUE INCREASE AH AI AJ AK INTERIM ADJUSTMENTS INTERIM INTERIM INTEREST TOTAL TEST PERIOD INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES $ $144,043,259 $0 $0 $0 $144,043,259 13,137,274 5,890,260 589,013 353,341 1,566,084 968,931 (0) 12,638,062 $0 $0 $0 $35,142,966 (804,953) 8,688,143 794,422 9,012,657 (510,054) 20,656,038 0 0 0 0 (508,538) (65,974) (405,472) 11,473,738 ($508,538) ($65,974) ($1,210,425) $50,114,945 ($508,538) ($65,974) $ (1,210,425) $85,257,910 $508,538 $65,974 $1,210,425 $58,785,349 (7,127,908) $ (6,395,786) $786,797,557 7.47% ($1,371,598) ($89,816) $ (6,792,751) ($5,050,236)

Docket No. D2018.2.12 Page 33 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 A B C D E F G H I NORTHWESTERN ENERGY MONTANA GENERATION INCOME STATEMENT ACTUAL 12 MONTHS ENDED DECEMBER 2017 ADJUSTED INTERIM REVENUE SALES & & REVENUE ADMINISTRATIVE GENERATION EMPLOYEES INCOME TAXES GENERATION RELATED & GENERAL LABOR ADJUSTMENT ADJUSTMENT ADJUSTMENT REVENUES: RATE SCHEDULE REVENUES $0 $0 SALES FOR RESALE 0 0 PROVISION FOR RATE REFUND 0 0 TRANSMISSION 0 0 MISCELLANEOUS REVENUES 0 0 GROSS REVENUES (LINE 2 THRU 6) $0 $0 $0 $0 $0 $0 $0 COST OF SERVICE: STEAM POWER OPERATION 0 0 STEAM POWER MAINTENANCE 0 0 OTHER POWER GENERATION OPERATION 0 0 OTHER POWER GENERATION MAINTENANCE 0 0 POWER SUPPLY 506,099 506,099 TRANSMISSION OPERATION 0 0 TRANSMISSION MAINTENANCE 0 0 DISTRIBUTION OPERATION 0 0 DISTRIBUTION MAINTENANCE 0 0 CUSTOMER ACCOUNTS EXPENSE 0 0 CUSTOMER SERVICE AND INFORMATION EXPENSE 0 0 SALES EXPENSE 0 0 ADMINISTRATIVE AND GENERAL EXPENSE 0 0 65,869 TOTAL O & M EXPENSE (LINE 10 THRU 22) 506,099 0 0 506,099 0 65,869 0 DEPRECIATION 0 AMORTIZATION OF ELECTRIC PLANT 0 0 AMORTIZATION OF PLANT ACQ. ADJ. 0 0 * AMORTIZATION RE:BPA RESIDENTIAL EXCHANGE 0 0 * AMORTIZATION RE:PROPERTY TAXES 0 0 * AMORTIZATION RE:INVESTMENT TAX CREDITS 0 0 * PENSION DIFFERENTIAL 0 0 * MPSC/MCC TAXES 0 0 * SO2 ALLOWANCES 0 0 TAXES OTHER THAN INCOME TAXES 0 0 INCOME TAXES FEDERAL U.S. 0 0 0 0 0 0 INCOME TAXES OTHER 0 0 0 0 0 0 DEFERRED INCOME TAXES (10,754) 0 (10,754) 0 (17,345) 0 SUBTOTAL (LINE 25 THRU 36) (10,754) 0 0 (10,754) 0 (17,345) 0 TOTAL COST OF SERVICE (LINE 23 + 37) 495,345 0 0 495,345 0 48,524 0 UTILITY OPERATING INCOME (LINE 7 39) ($495,345) $0 $0 ($495,345) $0 ($48,524) $0 ELECTRIC UTILITY RATE BASE RATE OF RETURN EARNED (%) MPSC BASIS (LINE 41 / 43) REQUIRED REVENUE INCREASE $674,361 $0 $66,060 $0

Docket No. D2018.2.12 Page 34 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 A B NORTHWESTERN ENERGY MONTANA GENERATION INCOME STATEMENT ACTUAL 12 MONTHS ENDED DECEMBER 2017 ADJUSTED INTERIM REVENUES: RATE SCHEDULE REVENUES SALES FOR RESALE PROVISION FOR RATE REFUND TRANSMISSION MISCELLANEOUS REVENUES GROSS REVENUES (LINE 2 THRU 6) COST OF SERVICE: STEAM POWER OPERATION STEAM POWER MAINTENANCE OTHER POWER GENERATION OPERATION OTHER POWER GENERATION MAINTENANCE POWER SUPPLY TRANSMISSION OPERATION TRANSMISSION MAINTENANCE DISTRIBUTION OPERATION DISTRIBUTION MAINTENANCE CUSTOMER ACCOUNTS EXPENSE CUSTOMER SERVICE AND INFORMATION EXPENSE SALES EXPENSE ADMINISTRATIVE AND GENERAL EXPENSE TOTAL O & M EXPENSE (LINE 10 THRU 22) DEPRECIATION AMORTIZATION OF ELECTRIC PLANT AMORTIZATION OF PLANT ACQ. ADJ. * AMORTIZATION RE:BPA RESIDENTIAL EXCHANGE * AMORTIZATION RE:PROPERTY TAXES * AMORTIZATION RE:INVESTMENT TAX CREDITS * PENSION DIFFERENTIAL * MPSC/MCC TAXES * SO2 ALLOWANCES TAXES OTHER THAN INCOME TAXES INCOME TAXES FEDERAL U.S. INCOME TAXES OTHER DEFERRED INCOME TAXES SUBTOTAL (LINE 25 THRU 36) TOTAL COST OF SERVICE (LINE 23 + 37) UTILITY OPERATING INCOME (LINE 7 39) ELECTRIC UTILITY RATE BASE RATE OF RETURN EARNED (%) MPSC BASIS (LINE 41 / 43) REQUIRED REVENUE INCREASE J K L M N O P CORPORATE PROPERTY INTENTIONALLY INTENTIONALLY INTENTIONALLY ALLOCATION DEPRECIATION AMORTIZATION TAXES LEFT LEFT LEFT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT BLANK BLANK BLANK $0 $0 $0 $0 $0 $0 $0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0

Docket No. D2018.2.12 Page 35 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 A B NORTHWESTERN ENERGY MONTANA GENERATION INCOME STATEMENT ACTUAL 12 MONTHS ENDED DECEMBER 2017 ADJUSTED INTERIM REVENUES: RATE SCHEDULE REVENUES SALES FOR RESALE PROVISION FOR RATE REFUND TRANSMISSION MISCELLANEOUS REVENUES GROSS REVENUES (LINE 2 THRU 6) COST OF SERVICE: STEAM POWER OPERATION STEAM POWER MAINTENANCE OTHER POWER GENERATION OPERATION OTHER POWER GENERATION MAINTENANCE POWER SUPPLY TRANSMISSION OPERATION TRANSMISSION MAINTENANCE DISTRIBUTION OPERATION DISTRIBUTION MAINTENANCE CUSTOMER ACCOUNTS EXPENSE CUSTOMER SERVICE AND INFORMATION EXPENSE SALES EXPENSE ADMINISTRATIVE AND GENERAL EXPENSE TOTAL O & M EXPENSE (LINE 10 THRU 22) DEPRECIATION AMORTIZATION OF ELECTRIC PLANT AMORTIZATION OF PLANT ACQ. ADJ. * AMORTIZATION RE:BPA RESIDENTIAL EXCHANGE * AMORTIZATION RE:PROPERTY TAXES * AMORTIZATION RE:INVESTMENT TAX CREDITS * PENSION DIFFERENTIAL * MPSC/MCC TAXES * SO2 ALLOWANCES TAXES OTHER THAN INCOME TAXES INCOME TAXES FEDERAL U.S. INCOME TAXES OTHER DEFERRED INCOME TAXES SUBTOTAL (LINE 25 THRU 36) TOTAL COST OF SERVICE (LINE 23 + 37) UTILITY OPERATING INCOME (LINE 7 39) ELECTRIC UTILITY RATE BASE RATE OF RETURN EARNED (%) MPSC BASIS (LINE 41 / 43) REQUIRED REVENUE INCREASE Q R S T U V W INTENTIONALLY INTENTIONALLY INTENTIONALLY INTENTIONALLY INTENTIONALLY WORKING LEFT LEFT LEFT LEFT LEFT CAPITAL INCOME TAX BLANK BLANK BLANK BLANK BLANK ADJUSTMENT ADJUSTMENT $0 $0 $0 $0 $0 $0 $0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 34,171 0 0 0 0 0 0 34,171 0 0 0 0 0 0 34,171 $0 $0 $0 $0 $0 $0 ($34,171) $0 $0 $0 $0 $0 $0 $46,520 0

Docket No. D2018.2.12 Page 36 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 A B NORTHWESTERN ENERGY MONTANA GENERATION INCOME STATEMENT ACTUAL 12 MONTHS ENDED DECEMBER 2017 ADJUSTED INTERIM REVENUES: RATE SCHEDULE REVENUES SALES FOR RESALE PROVISION FOR RATE REFUND TRANSMISSION MISCELLANEOUS REVENUES GROSS REVENUES (LINE 2 THRU 6) COST OF SERVICE: STEAM POWER OPERATION STEAM POWER MAINTENANCE OTHER POWER GENERATION OPERATION OTHER POWER GENERATION MAINTENANCE POWER SUPPLY TRANSMISSION OPERATION TRANSMISSION MAINTENANCE DISTRIBUTION OPERATION DISTRIBUTION MAINTENANCE CUSTOMER ACCOUNTS EXPENSE CUSTOMER SERVICE AND INFORMATION EXPENSE SALES EXPENSE ADMINISTRATIVE AND GENERAL EXPENSE TOTAL O & M EXPENSE (LINE 10 THRU 22) DEPRECIATION AMORTIZATION OF ELECTRIC PLANT AMORTIZATION OF PLANT ACQ. ADJ. * AMORTIZATION RE:BPA RESIDENTIAL EXCHANGE * AMORTIZATION RE:PROPERTY TAXES * AMORTIZATION RE:INVESTMENT TAX CREDITS * PENSION DIFFERENTIAL * MPSC/MCC TAXES * SO2 ALLOWANCES TAXES OTHER THAN INCOME TAXES INCOME TAXES FEDERAL U.S. INCOME TAXES OTHER DEFERRED INCOME TAXES SUBTOTAL (LINE 25 THRU 36) TOTAL COST OF SERVICE (LINE 23 + 37) UTILITY OPERATING INCOME (LINE 7 39) ELECTRIC UTILITY RATE BASE RATE OF RETURN EARNED (%) MPSC BASIS (LINE 41 / 43) REQUIRED REVENUE INCREASE X Y Z AA AB AC AD INTERIM ADJUSTMENTS INTEREST TOTAL TEST PERIOD ADJUST TO NONPCCAM MONTANA SYNCHRONIZATION UPDATES & @ PRESENT ROE FROM DEPRECIATION SUPPLY GENERATION ADJUSTMENT ADJUSTMENTS RATES DOCKET 2009.9.129 ADJUSTMENT ADJUSTMENT ADJUSTMENT 0 $0 $0 0 $0 $0 0 $0 $0 0 $0 $0 0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $506,099 ($506,099) $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 65,869 $65,869 ($65,869) 0 65,869 571,968 $0 $0 $0 ($571,968) 0 $0 $0 0 $0 $0 0 $0 $0 0 $0 $0 0 $0 $0 0 $0 $0 0 $0 $0 0 $0 $0 0 $0 $0 0 $0 $0 0 0 $0 0 0 0 0 0 0 $0 0 0 0 0 0 $16,826 $6,072 0 0 0 (6,070) 0 16,826 6,072 $0 $0 $0 ($6,070) 0 82,695 578,040 $0 $0 $0 ($578,038) $0 ($82,695) ($578,040) $0 $0 $0 $578,038 $0 $0 $0 $112,580 $786,941 $0 $0 $0 ($786,940)

Docket No. D2018.2.12 Page 37 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 A B NORTHWESTERN ENERGY MONTANA GENERATION INCOME STATEMENT ACTUAL 12 MONTHS ENDED DECEMBER 2017 ADJUSTED INTERIM REVENUES: RATE SCHEDULE REVENUES SALES FOR RESALE PROVISION FOR RATE REFUND TRANSMISSION MISCELLANEOUS REVENUES GROSS REVENUES (LINE 2 THRU 6) COST OF SERVICE: STEAM POWER OPERATION STEAM POWER MAINTENANCE OTHER POWER GENERATION OPERATION OTHER POWER GENERATION MAINTENANCE POWER SUPPLY TRANSMISSION OPERATION TRANSMISSION MAINTENANCE DISTRIBUTION OPERATION DISTRIBUTION MAINTENANCE CUSTOMER ACCOUNTS EXPENSE CUSTOMER SERVICE AND INFORMATION EXPENSE SALES EXPENSE ADMINISTRATIVE AND GENERAL EXPENSE TOTAL O & M EXPENSE (LINE 10 THRU 22) DEPRECIATION AMORTIZATION OF ELECTRIC PLANT AMORTIZATION OF PLANT ACQ. ADJ. * AMORTIZATION RE:BPA RESIDENTIAL EXCHANGE * AMORTIZATION RE:PROPERTY TAXES * AMORTIZATION RE:INVESTMENT TAX CREDITS * PENSION DIFFERENTIAL * MPSC/MCC TAXES * SO2 ALLOWANCES TAXES OTHER THAN INCOME TAXES INCOME TAXES FEDERAL U.S. INCOME TAXES OTHER DEFERRED INCOME TAXES SUBTOTAL (LINE 25 THRU 36) TOTAL COST OF SERVICE (LINE 23 + 37) UTILITY OPERATING INCOME (LINE 7 39) ELECTRIC UTILITY RATE BASE RATE OF RETURN EARNED (%) MPSC BASIS (LINE 41 / 43) REQUIRED REVENUE INCREASE AE AF AG AH AI AJ AK INTERIM ADJUSTMENTS INTERIM INTERIM INTENTIONALLY INTENTIONALLY WORKING INTEREST TOTAL TEST PERIOD LEFT LEFT CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT BLANK BLANK ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES $ $0 $0 $0 $0 $0 $0 $0 $0 (506,099) (65,869) $0 $0 $0 $0 $0 ($571,968) $0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 (6,070) 2 $0 $0 $0 $0 $0 ($6,070) $2 $0 $0 $0 $0 $0 $ (578,038) $2 $0 $0 $0 $0 $0 $578,038 ($2) $ $0 $0 $0 $0 $0 $0 $ (786,940) $1

Docket No. D2018.2.12 Page 38 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 A B C D E F G H I NORTHWESTERN ENERGY ELECTRIC SUPPLY NONPCCAM INCOME STATEMENT ACTUAL 12 MONTHS ENDED DECEMBER 2017 ADJUSTED INTERIM REVENUE SALES & REMOVE REMOVE ELECTRIC & REVENUE ADMINISTRATIVE ELECTRIC SUPPLY PCCAM DEFERRED NONPCCAM RELATED & GENERAL LABOR EXPENSES ADJUSTMENT ADJUSTMENT ADJUSTMENT REVENUES: RATE SCHEDULE REVENUES $132,139,135 $120,520,952 $11,618,183 $0 0 SALES FOR RESALE 0 $0 PROVISION FOR RATE REFUND 0 $0 0 TRANSMISSION 0 $0 MISCELLANEOUS REVENUES 1,332,080 1,332,080 $0 GROSS REVENUES (LINE 2 THRU 6) $133,471,215 $121,853,032 $11,618,183 $0 $0 $0 $0 COST OF SERVICE: STEAM POWER OPERATION 0 0 STEAM POWER MAINTENANCE 0 0 OTHER POWER GENERATION OPERATION 1,906,863 1,906,863 0 OTHER POWER GENERATION MAINTENANCE 0.00 0 POWER SUPPLY 131,824,311 110,162,209 11,618,183 10,043,918 14,608 TRANSMISSION OPERATION 1,162,351 1,162,351 0 TRANSMISSION MAINTENANCE 0 0 DISTRIBUTION OPERATION 0 0 DISTRIBUTION MAINTENANCE 0 0 CUSTOMER ACCOUNTS EXPENSE 0 0 CUSTOMER SERVICE AND INFORMATION EXPENSE 0 0 SALES EXPENSE 0 0 ADMINISTRATIVE AND GENERAL EXPENSE 168,923 168,923 5,741 TOTAL O & M EXPENSE (LINE 10 THRU 22) 135,062,448 113,231,423 11,618,183 10,212,841 0 0 20,349 DEPRECIATION 0 0 AMORTIZATION OF ELECTRIC PLANT 0 0 AMORTIZATION OF PLANT ACQ. ADJ. 0 0 * AMORTIZATION RE:BPA RESIDENTIAL EXCHANGE 0 0 * AMORTIZATION RE:PROPERTY TAXES 0 0 * AMORTIZATION RE:INVESTMENT TAX CREDITS 0 0 * PENSION DIFFERENTIAL 0 0 * MPSC/MCC TAXES 0 0 * SO2 ALLOWANCES 0 0 TAXES OTHER THAN INCOME TAXES 671,856 564,803 107,053 1,447 INCOME TAXES FEDERAL U.S. 0 0 0 0 0 0 INCOME TAXES OTHER 0 0 0 0 0 0 DEFERRED INCOME TAXES (441,184) 0 (441,184) 0 0 (5,739) SUBTOTAL (LINE 25 THRU 36) 230,673 564,803 0 (334,130) 0 0 (4,292) TOTAL COST OF SERVICE (LINE 23 + 37) 135,293,121 113,796,226 11,618,183 9,878,711 0 0 16,057 UTILITY OPERATING INCOME (LINE 7 39) ($1,821,906) $8,056,805 $0 ($9,878,711) $0 $0 ($16,057) ELECTRIC UTILITY RATE BASE RATE OF RETURN EARNED (%) MPSC BASIS (LINE 41 / 43) REQUIRED REVENUE INCREASE $13,448,864 $0 $0 $21,859

Docket No. D2018.2.12 Page 39 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 A B NORTHWESTERN ENERGY ELECTRIC SUPPLY NONPCCAM INCOME STATEMENT ACTUAL 12 MONTHS ENDED DECEMBER 2017 ADJUSTED INTERIM REVENUES: RATE SCHEDULE REVENUES SALES FOR RESALE PROVISION FOR RATE REFUND TRANSMISSION MISCELLANEOUS REVENUES GROSS REVENUES (LINE 2 THRU 6) COST OF SERVICE: STEAM POWER OPERATION STEAM POWER MAINTENANCE OTHER POWER GENERATION OPERATION OTHER POWER GENERATION MAINTENANCE POWER SUPPLY TRANSMISSION OPERATION TRANSMISSION MAINTENANCE DISTRIBUTION OPERATION DISTRIBUTION MAINTENANCE CUSTOMER ACCOUNTS EXPENSE CUSTOMER SERVICE AND INFORMATION EXPENSE SALES EXPENSE ADMINISTRATIVE AND GENERAL EXPENSE TOTAL O & M EXPENSE (LINE 10 THRU 22) DEPRECIATION AMORTIZATION OF ELECTRIC PLANT AMORTIZATION OF PLANT ACQ. ADJ. * AMORTIZATION RE:BPA RESIDENTIAL EXCHANGE * AMORTIZATION RE:PROPERTY TAXES * AMORTIZATION RE:INVESTMENT TAX CREDITS * PENSION DIFFERENTIAL * MPSC/MCC TAXES * SO2 ALLOWANCES TAXES OTHER THAN INCOME TAXES INCOME TAXES FEDERAL U.S. INCOME TAXES OTHER DEFERRED INCOME TAXES SUBTOTAL (LINE 25 THRU 36) TOTAL COST OF SERVICE (LINE 23 + 37) UTILITY OPERATING INCOME (LINE 7 39) ELECTRIC UTILITY RATE BASE RATE OF RETURN EARNED (%) MPSC BASIS (LINE 41 / 43) REQUIRED REVENUE INCREASE J K L M N O P CORPORATE PROPERTY CAPITALIZE INTENTIONALLY INTENTIONALLY E ALLOCATION DEPRECIATION AMORTIZATION TAXES DSM LEFT LEFT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT COSTS BLANK BLANK $0 $0 $0 $0 $0 $0 $0 (7,762,146) 0 0 0 0 (7,762,146) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2,043,967 0 0 0 0 0 0 2,043,967 0 0 0 0 0 0 (5,718,179) 0 0 $0 $0 $0 $0 $5,718,179 $0 $0 $0 $0 $0 $0 ($7,784,722) $0 $0

Docket No. D2018.2.12 Page 40 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 A B NORTHWESTERN ENERGY ELECTRIC SUPPLY NONPCCAM INCOME STATEMENT ACTUAL 12 MONTHS ENDED DECEMBER 2017 ADJUSTED INTERIM REVENUES: RATE SCHEDULE REVENUES SALES FOR RESALE PROVISION FOR RATE REFUND TRANSMISSION MISCELLANEOUS REVENUES GROSS REVENUES (LINE 2 THRU 6) COST OF SERVICE: STEAM POWER OPERATION STEAM POWER MAINTENANCE OTHER POWER GENERATION OPERATION OTHER POWER GENERATION MAINTENANCE POWER SUPPLY TRANSMISSION OPERATION TRANSMISSION MAINTENANCE DISTRIBUTION OPERATION DISTRIBUTION MAINTENANCE CUSTOMER ACCOUNTS EXPENSE CUSTOMER SERVICE AND INFORMATION EXPENSE SALES EXPENSE ADMINISTRATIVE AND GENERAL EXPENSE TOTAL O & M EXPENSE (LINE 10 THRU 22) DEPRECIATION AMORTIZATION OF ELECTRIC PLANT AMORTIZATION OF PLANT ACQ. ADJ. * AMORTIZATION RE:BPA RESIDENTIAL EXCHANGE * AMORTIZATION RE:PROPERTY TAXES * AMORTIZATION RE:INVESTMENT TAX CREDITS * PENSION DIFFERENTIAL * MPSC/MCC TAXES * SO2 ALLOWANCES TAXES OTHER THAN INCOME TAXES INCOME TAXES FEDERAL U.S. INCOME TAXES OTHER DEFERRED INCOME TAXES SUBTOTAL (LINE 25 THRU 36) TOTAL COST OF SERVICE (LINE 23 + 37) UTILITY OPERATING INCOME (LINE 7 39) ELECTRIC UTILITY RATE BASE RATE OF RETURN EARNED (%) MPSC BASIS (LINE 41 / 43) REQUIRED REVENUE INCREASE Q R S T U V W INTENTIONALLY INTENTIONALLY INTENTIONALLY INTENTIONALLY INTENTIONALLY WORKING E LEFT LEFT LEFT LEFT LEFT CAPITAL INCOME TAX BLANK BLANK BLANK BLANK BLANK ADJUSTMENT ADJUSTMENT $0 $0 $0 $0 $0 $0 $0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 (1,975,328) 0 0 0 0 0 0 (1,975,328) 0 0 0 0 0 0 (1,975,328) $0 $0 $0 $0 $0 $0 $1,975,328 $0 $0 $0 $0 $0 $0 ($2,689,209)

Docket No. D2018.2.12 Page 41 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 A B NORTHWESTERN ENERGY ELECTRIC SUPPLY NONPCCAM INCOME STATEMENT ACTUAL 12 MONTHS ENDED DECEMBER 2017 ADJUSTED INTERIM REVENUES: RATE SCHEDULE REVENUES SALES FOR RESALE PROVISION FOR RATE REFUND TRANSMISSION MISCELLANEOUS REVENUES GROSS REVENUES (LINE 2 THRU 6) COST OF SERVICE: STEAM POWER OPERATION STEAM POWER MAINTENANCE OTHER POWER GENERATION OPERATION OTHER POWER GENERATION MAINTENANCE POWER SUPPLY TRANSMISSION OPERATION TRANSMISSION MAINTENANCE DISTRIBUTION OPERATION DISTRIBUTION MAINTENANCE CUSTOMER ACCOUNTS EXPENSE CUSTOMER SERVICE AND INFORMATION EXPENSE SALES EXPENSE ADMINISTRATIVE AND GENERAL EXPENSE TOTAL O & M EXPENSE (LINE 10 THRU 22) DEPRECIATION AMORTIZATION OF ELECTRIC PLANT AMORTIZATION OF PLANT ACQ. ADJ. * AMORTIZATION RE:BPA RESIDENTIAL EXCHANGE * AMORTIZATION RE:PROPERTY TAXES * AMORTIZATION RE:INVESTMENT TAX CREDITS * PENSION DIFFERENTIAL * MPSC/MCC TAXES * SO2 ALLOWANCES TAXES OTHER THAN INCOME TAXES INCOME TAXES FEDERAL U.S. INCOME TAXES OTHER DEFERRED INCOME TAXES SUBTOTAL (LINE 25 THRU 36) TOTAL COST OF SERVICE (LINE 23 + 37) UTILITY OPERATING INCOME (LINE 7 39) ELECTRIC UTILITY RATE BASE RATE OF RETURN EARNED (%) MPSC BASIS (LINE 41 / 43) REQUIRED REVENUE INCREASE X Y Z AA AB AC AD INTERIM ADJUSTMENTS INTEREST TOTAL TEST PERIOD ADJUST TO NONPCCAM MONTANA ESYNCHRONIZATION UPDATES & @ PRESENT ROE FROM DEPRECIATION SUPPLY GENERATION ADJUSTMENT ADJUSTMENTS RATES DOCKET 2009.9.129 ADJUSTMENT ADJUSTMENT ADJUSTMENT 0 $0 0 $0 $0 0 $0 0 $0 $0 $0 $0 $0 $0 $0 $0 0 $0 0 $0 0 $0 0 $0 (7,747,538) $2,296,381 (566,439) 0 $0 0 $0 0 $0 0 $0 0 $0 0 $0 0 $0 5,741 $174,664 ($174,664) 0 (7,741,797) 2,471,044 $0 $0 ($741,103) $0 0 $0 0 $0 0 $0 0 $0 0 $0 0 $0 0 $0 0 $0 0 $0 1,447 $108,500 0 0 $0 0 0 0 0 0 0 $0 0 0 0 0 (300,975) (238,075) ($679,259) 0 0 195,151 0 (300,975) (236,628) (570,758) $0 $0 $195,151 $0 (300,975) (7,978,425) 1,900,286 $0 $0 ($545,952) $0 $300,975 $7,978,425 ($1,900,286) $0 $0 $545,952 $0 ($409,747) (10,861,819) $2,587,045 $0 $0 ($743,258) $0

Docket No. D2018.2.12 Page 42 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 A B NORTHWESTERN ENERGY ELECTRIC SUPPLY NONPCCAM INCOME STATEMENT ACTUAL 12 MONTHS ENDED DECEMBER 2017 ADJUSTED INTERIM REVENUES: RATE SCHEDULE REVENUES SALES FOR RESALE PROVISION FOR RATE REFUND TRANSMISSION MISCELLANEOUS REVENUES GROSS REVENUES (LINE 2 THRU 6) COST OF SERVICE: STEAM POWER OPERATION STEAM POWER MAINTENANCE OTHER POWER GENERATION OPERATION OTHER POWER GENERATION MAINTENANCE POWER SUPPLY TRANSMISSION OPERATION TRANSMISSION MAINTENANCE DISTRIBUTION OPERATION DISTRIBUTION MAINTENANCE CUSTOMER ACCOUNTS EXPENSE CUSTOMER SERVICE AND INFORMATION EXPENSE SALES EXPENSE ADMINISTRATIVE AND GENERAL EXPENSE TOTAL O & M EXPENSE (LINE 10 THRU 22) DEPRECIATION AMORTIZATION OF ELECTRIC PLANT AMORTIZATION OF PLANT ACQ. ADJ. * AMORTIZATION RE:BPA RESIDENTIAL EXCHANGE * AMORTIZATION RE:PROPERTY TAXES * AMORTIZATION RE:INVESTMENT TAX CREDITS * PENSION DIFFERENTIAL * MPSC/MCC TAXES * SO2 ALLOWANCES TAXES OTHER THAN INCOME TAXES INCOME TAXES FEDERAL U.S. INCOME TAXES OTHER DEFERRED INCOME TAXES SUBTOTAL (LINE 25 THRU 36) TOTAL COST OF SERVICE (LINE 23 + 37) UTILITY OPERATING INCOME (LINE 7 39) ELECTRIC UTILITY RATE BASE RATE OF RETURN EARNED (%) MPSC BASIS (LINE 41 / 43) REQUIRED REVENUE INCREASE AE AF AG AH AI AJ AK INTERIM ADJUSTMENTS INTERIM INTERIM INTENTIONALLY INTENTIONALLY WORKING INTEREST TOTAL TEST PERIOD E LEFT LEFT CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT BLANK BLANK ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES $ $0 $0 $0 $0 $0 $0 $0 $0 (566,439) 1,729,942 (174,664) $0 $0 $0 $0 $0 ($741,103) $1,729,942 108,500 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 195,151 (484,108) $0 $0 $0 $0 $0 $195,151 ($375,607) $0 $0 $0 $0 $0 $ (545,952) $1,354,335 $0 $0 $0 $0 $0 $ 545,952 ($1,354,334) $ $0 $0 $0 $0 $0 $0 $ (743,258) $1,843,787

Docket No. D2018.2.12 Page 43 of 327 GENERAL RATE CASE A B C D E F G H I J K ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY ELECTRIC UTILITY REVENUE SALES & & REVENUE ADMINISTRATIVE CORPORATE DSIP STIPULATION AND TAXES OTHER TOTAL COMPANY RELATED TRANSMISSION & GENERAL LABOR ALLOCATION AMRTIZATION DEPRECIATION MARKET CREDIT AMORTIZATION THAN INCOME ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT 1 Operating Revenues 2 3 Operating Expenses 4 Book Depreciation 5 Amort. of Electric Plant & Acq Adjmt 6 Amort.Misc Items 7 Taxes other than Income 8 9 Subtotal Expenses 10 Net Utility Operating Income Before Inc Tax 11 12 Amortization of Excess Deferred TaxARAM 13 Amortization of Excess Deferred TaxUnprotected Rate Base 14 Amortization of Excess Deferred TaxUnprotected NonRate Bas 15 16 Deferred Income Taxes: 17 Injuries & Damages 18 Miscellaneous 19 Accrued Incentive Compensation 20 Accelerated Depreciation 21 Net Operating Loss 22 MPSC/MCC Taxes 23 Deferred Revenue 24 Customer Advances for Construction/CIAC 25 FAS106 & 112 Post Retirement Benefits 26 Costs of Refinancing Debt 27 Environmental Reserve 28 NonJurisdictional Items 29 SubtotalDeferred Income Tax 30 31 Income TaxesFederal 32 Income TaxesCorporation License Tax 33 Income TaxesForeign Taxes 34 SubtotalCurrent Income Tax 35 Net Utility Operating Income 36 Rate Base 37 Return on Rate Base 596,247,622 (13,004,630) 198,777,381 (10,005,589) (24,281) (8,014,168) 587,448 (1,035) (2,532,412) 102,381,617 (1,170,410) 11,715,172 2,597,810 (10,037,500) 8,209,685 127,644,094 (509,115) 39,329 5,536,619 430,480,764 (10,514,705) (24,281) (8,014,168) 626,777 (1,035) (2,532,412) 1,427,400 8,209,685 5,536,619 165,766,858 (2,489,926) 24,281 8,014,168 (626,777) 1,035 2,532,412 (1,427,400) (8,209,685) (5,536,619) 174,904 188,672 43,901,512 (296,670) (25,822,300) (655,660) 6,394 2,110,331 (165,046) 273 666,847 (2,161,815) (1,457,930) 71,138 1,872,859 (1,808,252) 59,222 (444,487) (210,098) (16,693) 17,966,477 (655,660) 6,394 2,110,331 (165,046) 273 666,847 (296,670) (2,161,815) (1,457,930) (13,614) (13,614) 147,813,995 (1,834,266) 17,887 5,903,837 (461,731) 762 1,865,565 (1,130,730) (6,047,870) (4,078,689) 2,340,979,206 (24,367,156) 3,226,710 0

Docket No. D2018.2.12 Page 44 of 327 GENERAL RATE CASE L M N O P Q R S T U V ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY ELECTRIC UTILITY 1 Operating Revenues 2 3 Operating Expenses 4 Book Depreciation 5 Amort. of Electric Plant & Acq Adjmt 6 Amort.Misc Items 7 Taxes other than Income 8 9 Subtotal Expenses 10 Net Utility Operating Income Before Inc Tax 11 12 Amortization of Excess Deferred TaxARAM 13 Amortization of Excess Deferred TaxUnprotected Rate Base 14 Amortization of Excess Deferred TaxUnprotected NonRate Bas 15 16 Deferred Income Taxes: 17 Injuries & Damages 18 Miscellaneous 19 Accrued Incentive Compensation 20 Accelerated Depreciation 21 Net Operating Loss 22 MPSC/MCC Taxes 23 Deferred Revenue 24 Customer Advances for Construction/CIAC 25 FAS106 & 112 Post Retirement Benefits 26 Costs of Refinancing Debt 27 Environmental Reserve 28 NonJurisdictional Items 29 SubtotalDeferred Income Tax 30 31 Income TaxesFederal 32 Income TaxesCorporation License Tax 33 Income TaxesForeign Taxes 34 SubtotalCurrent Income Tax 35 Net Utility Operating Income 36 Rate Base 37 Return on Rate Base REGULATORY HAZARD MOVE NAVIGANT CAPITALIZE TWO DOT WORKING INTEREST TOTAL TEST PERIOD PLANT TREES (NEM) STUDY TO DSM MAINTENANCE REVENUE CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT ADJUSTMENT ADJUSTMENT RATE CASE EXPENSES COSTS ADJUSTMENT REQUIREMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES 2,732,522 (10,272,108) 585,975,514 3,500,000 (107,372) (7,762,146) (973,534) 584,119 (24,748,970) 174,028,410 726,172 (444,238) 101,937,379 2,597,810 14,312,982 8,209,685 (1,827,814) 149,580 5,216,412 132,860,506 3,500,000 (107,372) (7,762,146) (973,534) 1,459,870 (9,169,301) 421,311,463 (3,500,000) 107,372 7,762,146 973,534 1,272,652 (1,102,807) 164,664,051 (1,403,791) (1,403,791) (1,403,791) 2,864,338 2,864,338 2,864,338 (1,073,482) (1,073,482) (1,073,482) (57,972) (57,972) 116,932 0 0 (62,535) (62,535) 126,137 1,052,187 (34,148,159) (33,392,642) 10,508,870 (921,638) 28,274 2,043,967 256,356 (984,246) 29,358,418 935,900 29,060,425 3,238,125 (23,579) (23,579) 47,559 (620,760) (620,760) 1,252,099 599,346 599,346 (1,208,906) (19,629) (19,629) 39,593 147,325 147,325 (297,162) 69,637 69,637 (140,461) 16,693 16,693 0 (921,638) 28,274 2,043,967 256,356 67,941 (4,354,150) 935,900 (3,896,626) 14,069,851 13,614 13,614 0 0 0 0 0 13,614 13,614 0 (2,578,362) 79,098 5,718,179 717,178 1,204,711 4,340,536 (935,900) $2,780,205 $150,594,200 17,533,971 5,517,280 (2,211,698) (300,893) 2,340,678,313 6.43%

Docket No. D2018.2.12 Page 45 of 327 GENERAL RATE CASE ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY ELECTRIC UTILITY 1 Operating Revenues 2 3 Operating Expenses 4 Book Depreciation 5 Amort. of Electric Plant & Acq Adjmt 6 Amort.Misc Items 7 Taxes other than Income 8 9 Subtotal Expenses 10 Net Utility Operating Income Before Inc Tax 11 12 Amortization of Excess Deferred TaxARAM 13 Amortization of Excess Deferred TaxUnprotected Rate Base 14 Amortization of Excess Deferred TaxUnprotected NonRate Bas 15 16 Deferred Income Taxes: 17 Injuries & Damages 18 Miscellaneous 19 Accrued Incentive Compensation 20 Accelerated Depreciation 21 Net Operating Loss 22 MPSC/MCC Taxes 23 Deferred Revenue 24 Customer Advances for Construction/CIAC 25 FAS106 & 112 Post Retirement Benefits 26 Costs of Refinancing Debt 27 Environmental Reserve 28 NonJurisdictional Items 29 SubtotalDeferred Income Tax 30 31 Income TaxesFederal 32 Income TaxesCorporation License Tax 33 Income TaxesForeign Taxes 34 SubtotalCurrent Income Tax 35 Net Utility Operating Income 36 Rate Base 37 Return on Rate Base INTERIM ADJUSTMENTS INTERIM INTERIM ADJUST TO HAZARD NONPCCAM MONTANA WORKING INTEREST TOTAL TEST PERIOD ROE FROM DEPRECIATION TREES TWO DOT SUPPLY GENERATION CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT DOCKET 2009.9.129 ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES (2,732,522) (2,732,522) 583,242,992 (3,500,000) (584,119) (741,103) (571,968) (5,397,190) 168,631,221 (951,559) (726,172) (1,677,731) 100,259,648 0 14,312,982 0 (1,827,814) (149,580) (149,580) 132,710,926 (951,559) (3,500,000) (1,459,870) (741,103) (571,968) (7,224,501) 414,086,962 951,559 3,500,000 (1,272,652) 741,103 571,968 4,491,978 169,156,030 0 (1,403,791) (2,864,338) (2,864,338) 0 1,073,482 1,073,482 0 0 116,932 0 0 0 126,137 258,445 (1,052,187) 9,832 (783,910) 9,724,960 921,638 984,246 195,151 (47,288) (2,453,113) (399,366) 2,838,759 0 47,559 (8,161) (8,161) 1,243,938 0 (1,208,906) 39,547 39,547 79,140 0 (297,162) 0 (140,461) 0 0 258,445 921,638 (67,941) 195,151 (6,070) (1,790,855) (2,453,113) (2,942,745) 11,127,106 0 0 0 0 0 0 0 0 693,114 2,578,362 (1,204,711) 545,952 578,038 1,790,855 2,453,113 $7,434,724 $158,028,924 475,780 (17,533,971) 1,158,731 (10,247,081) (26,146,541) 2,314,531,772 6.83%

Docket No. D2018.2.12 Page 46 of 327 GENERAL RATE CASE A B C D E F G H I J K ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY ELECTRIC UTILITY 38 ELECTRIC UTILITY CALCULATIONS 39 Operating Revenues 40 Operating Expenses 41 Subtotal 42 Depreciation & Amortization 43 Taxes other than Income 44 Net Utility Operating Income Before Inc Tax 45 Taxable Additions / (Deductions): 46 Nondeductible Meal Expense 47 Bad Debt Expense Accrual Net of Chargeoffs 48 Penalties 49 Meters 50 Customer Advances for Construction/CIAC 51 Repairs Expense 52 Accrued Incentive Compensation 53 MPSC/MCC Taxes 54 Costs of Refinancing Debt 55 Accelerated DepreciationExcess BLM Tx vs Bk Deprec 56 Accelerated DepreciationExcess Tx Rtn vs BLM Tx Dep 57 Removal Costs Net of Salvage 58 Deferred Revenue 59 FAS106 & 112 Post Retirement Benefits 60 Environmental Reserve 61 Injuries & Damages 62 Net Operating Loss 63 Excludable Foreign Income 64 MT Corporation License Tax 65 Deduct Interest Charges 66 Total Tax Additons / (Deductions) 67 Federal Taxable Income 68 Federal Income Tax @ 21% 69 Foreign Income Tax 70 Foreign Income Tax Credit 71 NonJurisdictional Items 72 Prior Period Adjustments 73 Audit Adjustments 74 Total Federal Income Tax 75 76 77 Montana Corporate License Tax 78 Federal Taxable Income B4 MT Corp Tx Deductn & NOL 79 Add: 80 Other 81 Other State Taxes Paid 82 83 Reduction for Unitary Allocation 84 85 Montana Taxable Income 86 Mont. Corp. Lic. Tax @ 6.75% 87 Net Tax Adjustment 88 Mont. Corp. License Tax 89 Actual 6.75% 90 91 Change in tax rates 92 NonJurisdictional Items 93 Net Tax Adjustment REVENUE SALES & & REVENUE ADMINISTRATIVE CORPORATE DSIP STIPULATION AND TAXES OTHER TOTAL COMPANY RELATED TRANSMISSION & GENERAL LABOR ALLOCATION AMRTIZATION DEPRECIATION MARKET CREDIT AMORTIZATION THAN INCOME ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT 596,247,622 (13,004,630) 198,777,381 (10,005,589) (24,281) (8,014,168) 587,448 (1,035) (2,532,412) 397,470,242 (2,999,041) 24,281 8,014,168 (587,448) 1,035 2,532,412 104,059,289 1,427,400 8,209,685 127,644,094 (509,115) 39,329 5,536,619 165,766,858 (2,489,926) 24,281 8,014,168 (626,777) 1,035 2,532,412 (1,427,400) (8,209,685) (5,536,619) 363,158 (48,808) (703,308) 4,590,927 (55,570,109) (479,016) (180,610) 1,128,498 15,223,687 14,687 (125,432,890) 1,412,713 (7,594,315) (4,754,955) (150,355) 533,414 (444,062) 65,559,633 2,489,926 (24,281) (8,014,168) 626,777 (1,035) (2,532,412) 8,209,685 5,536,619 (57,807,745) (165,766,858) 2,489,926 (24,281) (8,014,168) 626,777 (1,035) (2,532,412) 1,427,400 8,209,685 5,536,619 16,693 (30,307) (13,614) 0 (0) 0 (0)

Docket No. D2018.2.12 Page 47 of 327 GENERAL RATE CASE L M N O P Q R S T U V ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY ELECTRIC UTILITY 38 ELECTRIC UTILITY CALCULATIONS 39 Operating Revenues 40 Operating Expenses 41 Subtotal 42 Depreciation & Amortization 43 Taxes other than Income 44 Net Utility Operating Income Before Inc Tax 45 Taxable Additions / (Deductions): 46 Nondeductible Meal Expense 47 Bad Debt Expense Accrual Net of Chargeoffs 48 Penalties 49 Meters 50 Customer Advances for Construction/CIAC 51 Repairs Expense 52 Accrued Incentive Compensation 53 MPSC/MCC Taxes 54 Costs of Refinancing Debt 55 Accelerated DepreciationExcess BLM Tx vs Bk Deprec 56 Accelerated DepreciationExcess Tx Rtn vs BLM Tx Dep 57 Removal Costs Net of Salvage 58 Deferred Revenue 59 FAS106 & 112 Post Retirement Benefits 60 Environmental Reserve 61 Injuries & Damages 62 Net Operating Loss 63 Excludable Foreign Income 64 MT Corporation License Tax 65 Deduct Interest Charges 66 Total Tax Additons / (Deductions) 67 Federal Taxable Income 68 Federal Income Tax @ 21% 69 Foreign Income Tax 70 Foreign Income Tax Credit 71 NonJurisdictional Items 72 Prior Period Adjustments 73 Audit Adjustments 74 Total Federal Income Tax 75 76 77 Montana Corporate License Tax 78 Federal Taxable Income B4 MT Corp Tx Deductn & NOL 79 Add: 80 Other 81 Other State Taxes Paid 82 83 Reduction for Unitary Allocation 84 85 Montana Taxable Income 86 Mont. Corp. Lic. Tax @ 6.75% 87 Net Tax Adjustment 88 Mont. Corp. License Tax 89 Actual 6.75% 90 91 Change in tax rates 92 NonJurisdictional Items 93 Net Tax Adjustment REGULATORY HAZARD MOVE NAVIGANT CAPITALIZE TWO DOT WORKING INTEREST TOTAL TEST PERIOD PLANT TREES (NEM) STUDY TO DSM MAINTENANCE REVENUE CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT ADJUSTMENT ADJUSTMENT RATE CASE EXPENSES COSTS ADJUSTMENT REQUIREMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES 2,732,522 (10,272,108) 585,975,514 3,500,000 (107,372) (7,762,146) (973,534) 584,119 (24,748,970) 174,028,410 (3,500,000) 107,372 7,762,146 973,534 2,148,404 14,476,862 411,947,104 726,172 10,363,257 114,422,546 149,580 5,216,412 132,860,506 (3,500,000) 107,372 7,762,146 973,534 1,272,652 (1,102,807) 164,664,051 0 363,158 0 (48,808) 0 0 0 (703,308) 0 4,590,927 0 (55,570,109) 0 (479,016) 0 (180,610) 0 1,128,498 14,687 15,238,373 (5,010,412) 78,988,350 75,390,651 (50,042,239) 0 (7,594,315) 0 (4,754,955) 0 (150,355) 0 533,414 0 (444,062) 3,500,000 (107,372) (7,762,146) (973,534) 3,737,760 (78,988,350) (3,554,160) (77,856,691) (12,297,058) 0 0 0 0 3,554,160 3,554,160 (54,253,585) 3,500,000 (107,372) (7,762,146) (973,534) (1,272,652) 0 $1,102,807 ($164,664,051) 0 $ 0 $ 0 0 0 0 0 0 (16,693) (16,693) 0 30,307 30,307 0 0 0 13,614 13,614 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

Docket No. D2018.2.12 Page 48 of 327 GENERAL RATE CASE ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY ELECTRIC UTILITY 38 ELECTRIC UTILITY CALCULATIONS 39 Operating Revenues 40 Operating Expenses 41 Subtotal 42 Depreciation & Amortization 43 Taxes other than Income 44 Net Utility Operating Income Before Inc Tax 45 Taxable Additions / (Deductions): 46 Nondeductible Meal Expense 47 Bad Debt Expense Accrual Net of Chargeoffs 48 Penalties 49 Meters 50 Customer Advances for Construction/CIAC 51 Repairs Expense 52 Accrued Incentive Compensation 53 MPSC/MCC Taxes 54 Costs of Refinancing Debt 55 Accelerated DepreciationExcess BLM Tx vs Bk Deprec 56 Accelerated DepreciationExcess Tx Rtn vs BLM Tx Dep 57 Removal Costs Net of Salvage 58 Deferred Revenue 59 FAS106 & 112 Post Retirement Benefits 60 Environmental Reserve 61 Injuries & Damages 62 Net Operating Loss 63 Excludable Foreign Income 64 MT Corporation License Tax 65 Deduct Interest Charges 66 Total Tax Additons / (Deductions) 67 Federal Taxable Income 68 Federal Income Tax @ 21% 69 Foreign Income Tax 70 Foreign Income Tax Credit 71 NonJurisdictional Items 72 Prior Period Adjustments 73 Audit Adjustments 74 Total Federal Income Tax 75 76 77 Montana Corporate License Tax 78 Federal Taxable Income B4 MT Corp Tx Deductn & NOL 79 Add: 80 Other 81 Other State Taxes Paid 82 83 Reduction for Unitary Allocation 84 85 Montana Taxable Income 86 Mont. Corp. Lic. Tax @ 6.75% 87 Net Tax Adjustment 88 Mont. Corp. License Tax 89 Actual 6.75% 90 91 Change in tax rates 92 NonJurisdictional Items 93 Net Tax Adjustment INTERIM ADJUSTMENTS INTERIM INTERIM ADJUST TO HAZARD NONPCCAM MONTANA WORKING INTEREST TOTAL TEST PERIOD ROE FROM DEPRECIATION TREES TWO DOT SUPPLY GENERATION CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT DOCKET 2009.9.129 ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES (2,732,522) (2,732,522) 583,242,992 (3,500,000) (584,119) (741,103) (571,968) (5,397,190) 168,631,221 3,500,000 (2,148,404) 741,103 571,968 2,664,667 414,611,771 (951,559) (726,172) (1,677,731) 112,744,815 (149,580) (149,580) 132,710,926 951,559 3,500,000 (1,272,652) 741,103 571,968 4,491,978 169,156,030 1,000 1,000 364,158 0 (48,808) 0 0 0 (703,308) 0 4,590,927 (636,422) (636,422) (56,206,530) 0 (479,016) 0 (180,610) 0 1,128,498 279,132 49,878 329,009 15,567,383 (1,230,691) 5,010,412 (46,818) 3,732,903 (46,309,336) 0 (7,594,315) 30,994 30,994 (4,723,961) (150,182) (150,182) (300,537) 0 533,414 0 (444,062) (3,500,000) (3,737,760) (741,103) 179,581 9,315,912 1,516,631 (10,780,428) 0 0 0 0 (9,315,912) (9,315,912) (63,569,497) (951,559) (3,500,000) 1,272,652 (741,103) (571,968) ($4,491,978) ($169,156,030) $ $ 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

Docket No. D2018.2.12 Page 49 of 327 GENERAL RATE CASE A B C D E F G H I J K ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY ELECTRIC UTILITY COMPUTATION OF REQUIRED RETURN AND REVENUE INCREASE 1 Electric Utility Rate Base 2 Rate of Return 3 4 5 Net Operating Income 6 7 Net Operating Income for the Year 8 Ended 12/31/17 Adjusted for Known Changes 9 10 Required Incremental Increase in Net 11 Operating Income 12 13 Add: 14 MPSC Tax 15 Consumer Counsel Tax 16 Incremental Income Taxes 17 18 Required Revenue Increase 19 20 21 MPSC Tax (0.244%) 22 23 Consumer Counsel Tax (0.046%) 24 25 Taxable Income for State Income Tax 26 27 State Income Tax (6.75%) (Unitary Factor = 1.00) 28 29 Taxable Income for Federal Income Tax 30 31 Reduction of Fed.Inc.TaxDue to MCLT Expense 32 Federal Income Tax Expense (21%) 33 34 Required Incremental Increase in Net 35 Operating Income REVENUE SALES & & REVENUE ADMINISTRATIVE CORPORATE DSIP STIPULATION AND TAXES OTHER TOTAL COMPANY RELATED TRANSMISSION & GENERAL LABOR ALLOCATION AMRTIZATION DEPRECIATION MARKET CREDIT AMORTIZATION THAN INCOME ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT $2,340,979,206 $0 $0 $0 $0 $0 $0 $0 ($24,367,156) $3,226,710 $0 7.53% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 7.42% 7.42% 0.00% 176,220,887 0 0 0 0 0 0 0 (1,808,043) 239,422 0 147,813,995 (1,834,266) 17,887 5,903,837 (461,731) 762 1,865,565 (1,130,730) 0 (6,047,870) (4,078,689) $28,406,892 $1,834,266 ($17,887) ($5,903,837) $461,731 ($762) ($1,865,565) $1,130,730 ($1,808,043) $6,287,292 $4,078,689 94,362 6,093 (59) (19,611) 1,534 (3) (6,197) 3,756 (6,006) 20,885 13,549 17,790 1,149 (11) (3,697) 289 0 (1,168) 708 (1,132) 3,937 2,554 10,154,063 655,660 (6,394) (2,110,330) 165,046 (273) (666,848) 404,180 (646,286) 2,247,396 1,457,930 $38,673,107 $2,497,168 ($24,351) ($8,037,475) $628,600 ($1,038) ($2,539,778) $1,539,374 ($2,461,467) $8,559,510 $5,552,722 94,362 6,093 (59) (19,611) 1,534 (3) (6,197) 3,756 (6,006) 20,885 13,549 17,790 1,149 (11) (3,697) 289 0 (1,168) 708 (1,132) 3,937 2,554 $38,560,955 $2,489,926 ($24,281) ($8,014,167) $626,777 ($1,035) ($2,532,413) $1,534,910 ($2,454,329) $8,534,688 $5,536,619 2,602,864 168,070 (1,639) (540,956) 42,307 (70) (170,938) 103,606 (165,667) 576,091 373,722 $35,958,091 $2,321,856 ($22,642) ($7,473,211) $584,470 ($965) ($2,361,475) $1,431,304 ($2,288,662) $7,958,597 $5,162,897 (546,601) (35,295) 344 113,601 (8,884) 15 35,897 (21,757) 34,790 (120,979) (78,482) 8,097,800 522,885 (5,099) (1,682,975) 131,623 (218) (531,807) 322,331 (515,409) 1,792,284 1,162,690 $28,406,892 $1,834,266 ($17,887) ($5,903,837) $461,731 ($762) ($1,865,565) $1,130,730 ($1,808,043) $6,287,292 $4,078,689

Docket No. D2018.2.12 Page 50 of 327 GENERAL RATE CASE L M N O P Q R S T U V ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY ELECTRIC UTILITY COMPUTATION OF REQUIRED RETURN AND REVENUE INCREASE 1 Electric Utility Rate Base 2 Rate of Return 3 4 5 Net Operating Income 6 7 Net Operating Income for the Year 8 Ended 12/31/17 Adjusted for Known Changes 9 10 Required Incremental Increase in Net 11 Operating Income 12 13 Add: 14 MPSC Tax 15 Consumer Counsel Tax 16 Incremental Income Taxes 17 18 Required Revenue Increase 19 20 21 MPSC Tax (0.244%) 22 23 Consumer Counsel Tax (0.046%) 24 25 Taxable Income for State Income Tax 26 27 State Income Tax (6.75%) (Unitary Factor = 1.00) 28 29 Taxable Income for Federal Income Tax 30 31 Reduction of Fed.Inc.TaxDue to MCLT Expense 32 Federal Income Tax Expense (21%) 33 34 Required Incremental Increase in Net 35 Operating Income REGULATORY HAZARD MOVE NAVIGANT CAPITALIZE TWO DOT WORKING INTEREST TOTAL TEST PERIOD PLANT TREES (NEM) STUDY TO DSM MAINTENANCE REVENUE CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT ADJUSTMENT ADJUSTMENT RATE CASE EXPENSES COSTS ADJUSTMENT REQUIREMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES $0 $0 $0 $0 $0 $17,533,971 $5,517,280 ($2,211,698) $0 ($300,893) $2,340,678,313 0.00% 0.00% 0.00% 0.00% 0.00% 7.42% 7.48% 7.43% 0.00% 6.48% 7.53% 0 0 0 0 0 1,301,021 412,436 (164,347) 0 (19,511) 176,201,376 0 (2,578,362) 79,098 5,718,179 717,178 1,204,711 0 4,340,536 (935,900) 2,780,205 150,594,200 $0 $2,578,362 ($79,098) ($5,718,179) ($717,178) $96,310 $412,436 ($4,504,883) $935,900 ($2,799,716) $25,607,176 0 8,565 (263) (18,995) (2,382) 320 1,370 (14,964) 3,109 (9,299) 85,063 0 1,615 (50) (3,581) (449) 60 258 (2,821) 586 (1,753) 16,037 0 921,637 (28,274) (2,043,967) (256,356) 34,426 147,426 (1,610,274) 334,539 (1,000,762) 9,153,301 $0 $3,510,179 ($107,685) ($7,784,722) ($976,365) $131,116 $561,490 ($6,132,942) $1,274,134 ($3,811,530) $34,861,577 0 8,565 (263) (18,995) (2,382) 320 1,370 (14,964) 3,109 (9,299) 85,063 0 1,615 (50) (3,581) (449) 60 258 (2,821) 586 (1,753) 16,037 $0 $3,499,999 ($107,372) ($7,762,146) ($973,534) $130,736 $559,862 ($6,115,157) $1,270,439 (3,800,478) 34,760,477 0 236,250 (7,248) (523,945) (65,714) 8,825 37,791 (412,773) 85,755 (256,533) 2,346,331 $0 $3,263,749 ($100,124) ($7,238,201) ($907,820) $121,911 $522,071 ($5,702,384) $1,184,684 ($3,543,945) $32,414,146 0 (49,613) 1,522 110,028 13,800 (1,853) (7,936) 86,682 (18,009) 53,871 (492,730) 0 735,000 (22,548) (1,630,050) (204,442) 27,454 117,571 (1,284,183) 266,793 (798,100) 7,299,700 $0 $2,578,362 ($79,098) ($5,718,179) ($717,178) $96,310 $412,436 ($4,504,883) $935,900 ($2,799,716) $25,607,176

Docket No. D2018.2.12 Page 51 of 327 GENERAL RATE CASE ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY ELECTRIC UTILITY COMPUTATION OF REQUIRED RETURN AND REVENUE INCREASE 1 Electric Utility Rate Base 2 Rate of Return 3 4 5 Net Operating Income 6 7 Net Operating Income for the Year 8 Ended 12/31/17 Adjusted for Known Changes 9 10 Required Incremental Increase in Net 11 Operating Income 12 13 Add: 14 MPSC Tax 15 Consumer Counsel Tax 16 Incremental Income Taxes 17 18 Required Revenue Increase 19 20 21 MPSC Tax (0.244%) 22 23 Consumer Counsel Tax (0.046%) 24 25 Taxable Income for State Income Tax 26 27 State Income Tax (6.75%) (Unitary Factor = 1.00) 28 29 Taxable Income for Federal Income Tax 30 31 Reduction of Fed.Inc.TaxDue to MCLT Expense 32 Federal Income Tax Expense (21%) 33 34 Required Incremental Increase in Net 35 Operating Income INTERIM ADJUSTMENTS INTERIM INTERIM ADJUST TO HAZARD NONPCCAM MONTANA WORKING INTEREST TOTAL TEST PERIOD ROE FROM DEPRECIATION TREES TWO DOT SUPPLY GENERATION CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT DOCKET 2009.9.129 ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES $0 $475,780 $0 ($17,533,971) $0 $0 $1,158,731 ($10,247,081) $0 $4,654,909,192 $2,314,531,772 0.00% 7.32% 0.00% 0.00% 0.00% 0.00% 7.17% 7.43% 0.00% 0.17% 7.27% (7,357,910) 34,804 0 0 0 0 83,028 (761,248) 0 (8,001,326) 168,200,050 0 693,114 2,578,362 (1,204,711) 545,952 578,038 0 1,790,855 2,453,113 7,434,724 158,028,924 ($7,357,910) ($658,310) ($2,578,362) $1,204,711 ($545,952) ($578,038) $83,028 ($2,552,103) ($2,453,113) ($15,436,049) $10,171,127 (24,442) (2,187) (8,565) 4,002 (1,814) (1,920) 276 (8,478) (8,149) (51,277) 33,786 (4,608) (412) (1,615) 754 (342) (362) 52 (1,598) (1,536) (9,667) 6,370 (2,630,090) (235,314) (921,637) 430,625 (195,150) (206,620) 29,679 (912,251) (876,867) (5,517,625) 3,635,676 ($10,017,050) ($896,223) ($3,510,179) $1,640,092 ($743,258) ($786,940) $113,035 ($3,474,430) ($3,339,665) ($21,014,618) $13,846,959 (24,442) (2,187) (8,565) 4,002 (1,814) (1,920) 276 (8,478) (8,149) (51,277) 33,786 (4,608) (412) (1,615) 754 (342) (362) 52 (1,598) (1,536) (9,667) 6,370 ($9,988,000) ($893,624) ($3,499,999) $1,635,336 ($741,102) ($784,658) $112,707 ($3,464,354) ($3,329,980) (20,953,674) 13,806,803 (674,190) (60,320) (236,250) 110,385 (50,024) (52,964) 7,608 (233,844) (224,774) (1,414,373) 931,958 ($9,313,810) ($833,304) ($3,263,749) $1,524,951 ($691,078) ($731,694) $105,099 ($3,230,510) ($3,105,206) (19,539,301) 12,874,845 141,580 12,667 49,613 (23,181) 10,505 11,122 (1,598) 49,107 47,203 297,018 (195,712) (2,097,480) (187,661) (735,000) 343,421 (155,631) (164,778) 23,669 (727,514) (699,296) (4,400,270) 2,899,430 ($7,357,910) ($658,310) ($2,578,362) $1,204,711 ($545,952) ($578,038) $83,028 ($2,552,103) ($2,453,113) ($15,436,049) $10,171,127

Docket No. D2018.2.12 Page 52 of 327 GENERAL RATE CASE A B C D E F G H I J ELECTRIC REVENUE SALES & ACTUAL TWELVE MONTHS ENDED 2017 INTERIM GENERATION TRANSMISSION & & REVENUE ADMINISTRATIVE CORPORATE DSIP NORTHWESTERN ENERGY ELECTRIC UTILITY AND SUPPLY DISTRIBUTION RELATED TRANSMISSION & GENERAL LABOR ALLOCATION AMRTIZATION DEPRECIATION ELECTRIC TRANSMISSION & DISTRIBUTION UTILITY FUNCTION UTILITY ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT 1 Operating Revenues $800,938,459 ($469,971,600) $330,966,859 ($10,487,218) $0 $0 $0 $0 $0 $0 2 3 Operating Expenses 397,580,766 (275,553,298) 122,027,468 (10,005,589) (24,281) (5,487,272) 600,386 (1,145,284) (2,532,412) 4 Book Depreciation 102,381,617 (34,710,241) 67,671,376 (391,570) 5 Amort. of Electric Plant & Acq Adjmt 11,715,172 (8,119,530) 3,595,642 475,369 6 Amort.Misc Items (11,109,909) 3,540,176 (7,569,733) 7 Taxes other than Income 128,208,897 (30,766,953) 97,441,944 36,084 40,249 8 9 Subtotal Expenses $628,776,543 ($345,609,846) $283,166,697 ($9,969,505) ($24,281) ($5,487,272) $640,635 ($1,145,284) ($2,532,412) $83,799 10 Net Utility Operating Income Before Inc Tax $172,161,916 ($124,361,754) $47,800,162 ($517,713) $24,281 $5,487,272 ($640,635) $1,145,284 $2,532,412 ($83,799) 11 12 Amortization of Excess Deferred TaxARAM $0 0 0 0 0 0 0 0 13 Amortization of Excess Deferred TaxUnprotected Rate Base $0 0 0 0 0 0 0 0 14 Amortization of Excess Deferred TaxUnprotected NonRate Base $0 0 0 0 0 0 0 0 15 16 Deferred Income Taxes: 17 Injuries & Damages $136,037 0 0 0 0 0 0 0 18 Miscellaneous $0 0 0 0 0 0 0 0 19 Accrued Incentive Compensation $146,745 0 0 0 0 0 0 0 20 Accelerated Depreciation $27,675,306 0 0 0 0 0 0 (14,514) 21 Net Operating Loss ($33,227,762) (136,327) 6,394 1,444,936 (168,695) 301,582 666,847 0 22 MPSC/MCC Taxes $71,138 0 0 0 0 0 0 0 23 Deferred Revenue $1,455,311 0 0 0 0 0 0 0 24 Customer Advances for Construction/CIAC ($1,750,814) 0 0 0 0 0 0 0 25 FAS106 & 112 Post Retirement Benefits $52,634 0 0 0 0 0 0 0 26 Costs of Refinancing Debt ($50,070) 0 0 0 0 0 0 0 27 Environmental Reserve ($163,410) 0 0 0 0 0 0 0 28 NonJurisdictional Items ($4,957,516) 0 0 0 0 0 0 0 29 SubtotalDeferred Income Tax (10,612,401) (136,327) 6,394 1,444,936 (168,695) 301,582 666,847 (14,514) 30 31 Income TaxesFederal (13,566) 0 0 0 0 0 0 0 32 Income TaxesCorporation License Tax 0 0 0 0 0 0 0 0 33 Income TaxesForeign Taxes 0 0 0 0 0 0 0 0 34 SubtotalCurrent Income Tax (13,566) 0 0 0 0 0 0 0 35 Net Utility Operating Income $58,426,129 ($381,386) $17,887 $4,042,336 ($471,940) $843,702 $1,865,565 ($69,285) 36 Rate Base 1,015,741,304 $0 $0 $0 $0 $0 $0 $0 37 Return on Rate Base 5.75%

Docket No. D2018.2.12 Page 53 of 327 GENERAL RATE CASE K L C D E F M N O P ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY ELECTRIC TRANSMISSION & DISTRIBUTION UTILITY 1 Operating Revenues 2 3 Operating Expenses 4 Book Depreciation 5 Amort. of Electric Plant & Acq Adjmt 6 Amort.Misc Items 7 Taxes other than Income 8 9 Subtotal Expenses 10 Net Utility Operating Income Before Inc Tax 11 12 Amortization of Excess Deferred TaxARAM 13 Amortization of Excess Deferred TaxUnprotected Rate Base 14 Amortization of Excess Deferred TaxUnprotected NonRate Base 15 16 Deferred Income Taxes: 17 Injuries & Damages 18 Miscellaneous 19 Accrued Incentive Compensation 20 Accelerated Depreciation 21 Net Operating Loss 22 MPSC/MCC Taxes 23 Deferred Revenue 24 Customer Advances for Construction/CIAC 25 FAS106 & 112 Post Retirement Benefits 26 Costs of Refinancing Debt 27 Environmental Reserve 28 NonJurisdictional Items 29 SubtotalDeferred Income Tax 30 31 Income TaxesFederal 32 Income TaxesCorporation License Tax 33 Income TaxesForeign Taxes 34 SubtotalCurrent Income Tax 35 Net Utility Operating Income 36 Rate Base 37 Return on Rate Base STIPULATION AND TAXES OTHER REGULATORY HAZARD MOVE NAVIGANT WORKING INTEREST TOTAL MARKET CREDIT AMORTIZATION THAN INCOME PLANT TREES (NEM) STUDY TO CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT RATE CASE EXPENSES ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS $0 $0 $0 $0 $0 $0 $0 $0 $0 (10,487,218) 3,500,000 (107,372) (15,201,824) (391,570) 475,369 6,565,852 6,565,852 5,130,096 5,206,429 $0 $6,565,852 $5,130,096 $0 $3,500,000 ($107,372) $0 $0 $0 (3,345,744) $0 ($6,565,852) ($5,130,096) $0 ($3,500,000) $107,372 $0 $0 $0 (7,141,475) 0 0 0 0 0 0 0 (723,308) 0 (723,308) 0 0 0 0 0 0 0 2,358,435 0 2,358,435 0 0 0 0 0 0 0 (1,191,762) 0 (1,191,762) 0 0 0 0 0 0 0 (45,090) 0 (45,090) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 (48,639) 0 (48,639) 0 0 0 0 0 0 0 (27,682,940) 0 (27,697,454) 0 (1,728,953) (1,350,883) 0 (921,638) 28,274 0 31,844,640 (2,657,737) 27,328,440 0 0 0 0 0 0 0 (23,579) 0 (23,579) 0 0 0 0 0 0 0 (482,363) 0 (482,363) 0 0 0 0 0 0 0 580,308 0 580,308 0 0 0 0 0 0 0 (17,446) 0 (17,446) 0 0 0 0 0 0 0 16,596 0 16,596 0 0 0 0 0 0 0 54,162 0 54,162 0 0 0 0 0 0 0 4,957,516 0 4,957,516 0 (1,728,953) (1,350,883) 0 (921,638) 28,274 0 9,596,531 (2,657,737) 5,065,817 0 0 0 0 0 0 0 13,566 0 13,566 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 13,566 0 13,566 $0 ($4,836,899) ($3,779,213) $0 ($2,578,362) $79,098 $0 ($9,610,097) $2,657,737 ($12,220,857) ($24,367,156) $3,226,710 $0 $0 $0 $0 $4,081,934 ($661,441) $0 (17,719,953)

Docket No. D2018.2.12 Page 54 of 327 GENERAL RATE CASE Q R S T U V W X Y Z ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY ELECTRIC TRANSMISSION & DISTRIBUTION UTILITY 1 Operating Revenues 2 3 Operating Expenses 4 Book Depreciation 5 Amort. of Electric Plant & Acq Adjmt 6 Amort.Misc Items 7 Taxes other than Income 8 9 Subtotal Expenses 10 Net Utility Operating Income Before Inc Tax 11 12 Amortization of Excess Deferred TaxARAM 13 Amortization of Excess Deferred TaxUnprotected Rate Base 14 Amortization of Excess Deferred TaxUnprotected NonRate Base 15 16 Deferred Income Taxes: 17 Injuries & Damages 18 Miscellaneous 19 Accrued Incentive Compensation 20 Accelerated Depreciation 21 Net Operating Loss 22 MPSC/MCC Taxes 23 Deferred Revenue 24 Customer Advances for Construction/CIAC 25 FAS106 & 112 Post Retirement Benefits 26 Costs of Refinancing Debt 27 Environmental Reserve 28 NonJurisdictional Items 29 SubtotalDeferred Income Tax 30 31 Income TaxesFederal 32 Income TaxesCorporation License Tax 33 Income TaxesForeign Taxes 34 SubtotalCurrent Income Tax 35 Net Utility Operating Income 36 Rate Base 37 Return on Rate Base INTERIM ADJUSTMENTS INTERIM INTERIM TEST PERIOD ADJUST TO HAZARD WORKING INTEREST TOTAL TEST PERIOD @ PRESENT ROE FROM DEPRECIATION TREES CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT RATES DOCKET 2009.9.129 ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES 320,479,641 $0 $0 $0 $0 $0 $0 $0 $0 0 320,479,641 106,825,644 (3,500,000) (3,500,000) 103,325,644 67,279,806 1,592,655 1,592,655 68,872,461 4,071,011 0 4,071,011 (1,003,880) 0 (1,003,880) 102,648,373 0 102,648,373 279,820,954 $0 $1,592,655 ($3,500,000) $0 $0 $0 $0 $0 (1,907,345) 277,913,609 40,658,687 $0 ($1,592,655) $3,500,000 $0 $0 $0 $0 $0 1,907,345 42,566,032 (723,308) 0 0 0 0 0 0 0 0 0 (723,308) 2,358,435 0 0 0 0 0 0 (2,358,435) 0 (2,358,435) 0 (1,191,762) 0 0 0 0 0 0 1,191,762 0 1,191,762 0 90,947 0 0 0 0 0 0 0 0 0 90,947 98,106 0 0 0 0 0 0 0 0 0 98,106 (22,148) 0 (275,840) 0 0 0 0 0 0 (275,840) (297,988) (5,899,322) 0 0 921,638 0 0 0 0 (2,114,229) (1,192,591) (7,091,913) 47,559 0 0 0 0 0 0 0 0 0 47,559 972,948 0 0 0 0 0 0 0 0 0 972,948 (1,170,506) 0 0 0 0 0 0 0 0 0 (1,170,506) 35,188 0 0 0 0 0 0 0 0 0 35,188 (33,474) 0 0 0 0 0 0 0 0 0 (33,474) (109,248) 0 0 0 0 0 0 0 0 0 (109,248) (5,546,584) 0 (275,840) 921,638 0 0 0 (1,166,673) (2,114,229) (2,635,104) (8,181,689) $46,205,272 $0 ($1,316,815) $2,578,362 $0 $0 $0 $1,166,673 $2,114,229 $4,542,449 $50,747,721 998,021,351 $0 ($796,328) $0 $0 $0 $820,905 $920,151 $0 944,729 998,966,080 4.63% 5.08%

Docket No. D2018.2.12 Page 55 of 327 GENERAL RATE CASE A B C D E F G H I J ELECTRIC REVENUE SALES & ACTUAL TWELVE MONTHS ENDED 2017 INTERIM GENERATION TRANSMISSION & & REVENUE ADMINISTRATIVE CORPORATE DSIP NORTHWESTERN ENERGY ELECTRIC UTILITY AND SUPPLY DISTRIBUTION RELATED TRANSMISSION & GENERAL LABOR ALLOCATION AMRTIZATION DEPRECIATION ELECTRIC TRANSMISSION & DISTRIBUTION UTILITY FUNCTION UTILITY ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT 38 ELECTRIC UTILITY CALCULATIONS 39 Operating Revenues $330,966,859 ($10,487,218) $0 $0 $0 $0 $0 $0 40 Operating Expenses 122,027,468 (10,005,589) (24,281) (5,487,272) 600,386 (1,145,284) (2,532,412) 0 41 Subtotal $208,939,391 ($481,629) $24,281 $5,487,272 ($600,386) $1,145,284 $2,532,412 $0 42 Depreciation & Amortization 63,697,285 83,799 43 Taxes other than Income 97,441,944 36,084 40,249 44 Net Utility Operating Income Before Inc Tax $ 47,800,162 $ (517,713) $ 24,281 $ 5,487,272 $ (640,635) $ 1,145,284 $ 2,532,412 $ (83,799) 45 Taxable Additions / (Deductions): 46 Nondeductible Meal Expense $282,441 0 0 0 0 0 0 0 47 Bad Debt Expense Accrual Net of Chargeoffs ($48,808) 0 0 0 0 0 0 0 48 Penalties $0 0 0 0 0 0 0 0 49 Meters ($703,308) 0 0 0 0 0 0 0 50 Customer Advances for Construction/CIAC $4,445,099 0 0 0 0 0 0 0 51 Repairs Expense ($46,676,126) 0 0 0 0 0 0 0 52 Accrued Incentive Compensation ($372,568) 0 0 0 0 0 0 0 53 MPSC/MCC Taxes ($180,610) 0 0 0 0 0 0 0 54 Costs of Refinancing Debt $127,121 0 0 0 0 0 0 0 55 Accelerated DepreciationExcess BLM Tx vs Bk Deprec $12,490,382 0 0 0 0 0 0 14,687 56 Accelerated DepreciationExcess Tx Rtn vs BLM Tx Dep ($79,072,303) 0 0 0 0 0 0 69,112 57 Removal Costs Net of Salvage ($6,846,659) 0 0 0 0 0 0 0 58 Deferred Revenue ($3,694,855) 0 0 0 0 0 0 0 59 FAS106 & 112 Post Retirement Benefits ($133,630) 0 0 0 0 0 0 0 60 Environmental Reserve $414,877 0 0 0 0 0 0 0 61 Injuries & Damages ($345,381) 0 0 0 0 0 0 0 62 Net Operating Loss $84,361,186 517,713 (24,281) (5,487,272) 640,635 (1,145,284) (2,532,412) 0 63 Excludable Foreign Income $0 0 0 0 0 0 0 0 64 MT Corporation License Tax 0 0 0 0 0 0 0 0 65 Deduct Interest Charges ($11,847,020) 0 0 0 0 0 0 0 66 Total Tax Additons / (Deductions) ($47,800,162) $517,713 ($24,281) ($5,487,272) $640,635 ($1,145,284) ($2,532,412) $83,799 67 Federal Taxable Income $ $ $ $ $ $ $ $ 68 Federal Income Tax @ 21% $0 $0 $0 $0 $0 $0 $0 $0 69 Foreign Income Tax $0 0 0 0 0 0 0 0 70 Foreign Income Tax Credit $0 0 0 0 0 0 0 0 71 NonJurisdictional Items 4,957,516 0 0 0 0 0 0 0 72 Prior Period Adjustments ($4,971,082) 0 0 0 0 0 0 0 73 Audit Adjustments $0 0 0 0 0 0 0 0 74 Total Federal Income Tax (13,566) 0 0 0 0 0 0 0 75 76 77 Montana Corporate License Tax 78 Federal Taxable Income B4 MT Corp Tx Deductn & NOL $ (0) $ $ $ $ $ $ $ 79 Add: 80 Other $0 0 0 0 0 0 0 0 81 Other State Taxes Paid $0 0 0 0 0 0 0 0 82 83 Reduction for Unitary Allocation $0 0 0 0 0 0 0 0 84 85 Montana Taxable Income ($0) $0 $0 $0 $0 $0 $0 $0 86 Mont. Corp. Lic. Tax @ 6.75% $0 0 0 0 0 0 0 0 87 Net Tax Adjustment $0 $0 $0 $0 $0 $0 $0 $0 88 Mont. Corp. License Tax $0 $0 $0 $0 $0 $0 $0 $0 89 Actual 6.75% 0 0 0 0 0 0 0 0 90 91 Change in tax rates $0 0 0 0 0 0 0 0 92 NonJurisdictional Items $0 0 0 0 0 0 0 0 93 Net Tax Adjustment 0 0 0 0 0 0 0 0

Docket No. D2018.2.12 Page 56 of 327 GENERAL RATE CASE K L C D E F M N O P ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY ELECTRIC TRANSMISSION & DISTRIBUTION UTILITY 38 ELECTRIC UTILITY CALCULATIONS 39 Operating Revenues 40 Operating Expenses 41 Subtotal 42 Depreciation & Amortization 43 Taxes other than Income 44 Net Utility Operating Income Before Inc Tax 45 Taxable Additions / (Deductions): 46 Nondeductible Meal Expense 47 Bad Debt Expense Accrual Net of Chargeoffs 48 Penalties 49 Meters 50 Customer Advances for Construction/CIAC 51 Repairs Expense 52 Accrued Incentive Compensation 53 MPSC/MCC Taxes 54 Costs of Refinancing Debt 55 Accelerated DepreciationExcess BLM Tx vs Bk Deprec 56 Accelerated DepreciationExcess Tx Rtn vs BLM Tx Dep 57 Removal Costs Net of Salvage 58 Deferred Revenue 59 FAS106 & 112 Post Retirement Benefits 60 Environmental Reserve 61 Injuries & Damages 62 Net Operating Loss 63 Excludable Foreign Income 64 MT Corporation License Tax 65 Deduct Interest Charges 66 Total Tax Additons / (Deductions) 67 Federal Taxable Income 68 Federal Income Tax @ 21% 69 Foreign Income Tax 70 Foreign Income Tax Credit 71 NonJurisdictional Items 72 Prior Period Adjustments 73 Audit Adjustments 74 Total Federal Income Tax 75 76 77 Montana Corporate License Tax 78 Federal Taxable Income B4 MT Corp Tx Deductn & NOL 79 Add: 80 Other 81 Other State Taxes Paid 82 83 Reduction for Unitary Allocation 84 85 Montana Taxable Income 86 Mont. Corp. Lic. Tax @ 6.75% 87 Net Tax Adjustment 88 Mont. Corp. License Tax 89 Actual 6.75% 90 91 Change in tax rates 92 NonJurisdictional Items 93 Net Tax Adjustment STIPULATION AND TAXES OTHER REGULATORY HAZARD MOVE NAVIGANT WORKING INTEREST TOTAL MARKET CREDIT AMORTIZATION THAN INCOME PLANT TREES (NEM) STUDY TO CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT RATE CASE EXPENSES ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS $0 $0 $0 $0 $0 $0 $0 $0 $0 (10,487,218) 0 0 0 0 3,500,000 (107,372) 0 0 0 (15,201,824) $0 $0 $0 $0 ($3,500,000) $107,372 $0 $0 $0 4,714,606 6,565,852 6,649,652 5,130,096 5,206,429 $ $ (6,565,852) $ (5,130,096) $ $ (3,500,000) $ 107,372 $ $ $ (7,141,475) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 14,687 0 0 0 0 0 0 0 79,108,655 0 79,177,768 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 6,565,852 5,130,096 0 3,500,000 (107,372) 0 (79,108,655) 10,092,993 (61,957,987) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 (10,092,993) (10,092,993) $0 $6,565,852 $5,130,096 $0 $3,500,000 ($107,372) $0 $0 $0 $7,141,475 $ $ $ $ $ $ $ $ 0 $ $ 0 $0 $0 $0 $0 $0 $0 $0 $0 $0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 (4,957,516) 0 (4,957,516) 0 0 0 0 0 0 0 4,971,082 0 4,971,082 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 13,566 0 13,566 $ $ $ $ $ $ $ $ 0 $ 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 $0 $0 $0 $0 $0 $0 $0 $0 $0 0 0 0 0 0 0 0 0 0 0 0 $0 $0 $0 $0 $0 $0 $0 $0 $0 0 $0 $0 $0 $0 $0 $0 $0 $0 $0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

Docket No. D2018.2.12 Page 57 of 327 GENERAL RATE CASE ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY ELECTRIC TRANSMISSION & DISTRIBUTION UTILITY 38 ELECTRIC UTILITY CALCULATIONS 39 Operating Revenues 40 Operating Expenses 41 Subtotal 42 Depreciation & Amortization 43 Taxes other than Income 44 Net Utility Operating Income Before Inc Tax 45 Taxable Additions / (Deductions): 46 Nondeductible Meal Expense 47 Bad Debt Expense Accrual Net of Chargeoffs 48 Penalties 49 Meters 50 Customer Advances for Construction/CIAC 51 Repairs Expense 52 Accrued Incentive Compensation 53 MPSC/MCC Taxes 54 Costs of Refinancing Debt 55 Accelerated DepreciationExcess BLM Tx vs Bk Deprec 56 Accelerated DepreciationExcess Tx Rtn vs BLM Tx Dep 57 Removal Costs Net of Salvage 58 Deferred Revenue 59 FAS106 & 112 Post Retirement Benefits 60 Environmental Reserve 61 Injuries & Damages 62 Net Operating Loss 63 Excludable Foreign Income 64 MT Corporation License Tax 65 Deduct Interest Charges 66 Total Tax Additons / (Deductions) 67 Federal Taxable Income 68 Federal Income Tax @ 21% 69 Foreign Income Tax 70 Foreign Income Tax Credit 71 NonJurisdictional Items 72 Prior Period Adjustments 73 Audit Adjustments 74 Total Federal Income Tax 75 76 77 Montana Corporate License Tax 78 Federal Taxable Income B4 MT Corp Tx Deductn & NOL 79 Add: 80 Other 81 Other State Taxes Paid 82 83 Reduction for Unitary Allocation 84 85 Montana Taxable Income 86 Mont. Corp. Lic. Tax @ 6.75% 87 Net Tax Adjustment 88 Mont. Corp. License Tax 89 Actual 6.75% 90 91 Change in tax rates 92 NonJurisdictional Items 93 Net Tax Adjustment Q R S T U V W X Y Z INTERIM ADJUSTMENTS INTERIM INTERIM TEST PERIOD ADJUST TO HAZARD WORKING INTEREST TOTAL TEST PERIOD @ PRESENT ROE FROM DEPRECIATION TREES CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT RATES DOCKET 2009.9.129 ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES 320,479,641 $0 $0 $0 $0 $0 $0 $0 $0 0 320,479,641 106,825,644 0 0 (3,500,000) 0 0 0 0 0 (3,500,000) 103,325,644 213,653,997 $0 $0 $3,500,000 $0 $0 $0 $0 $0 3,500,000 217,153,997 70,346,936 1,592,655 1,592,655 71,939,592 102,648,373 0 102,648,373 40,658,687 $ $ (1,592,655) $ 3,500,000 $ $ $ $ $ 1,907,345 42,566,032 282,441 0 0 0 0 0 0 0 0 0 282,441 (48,808) 0 0 0 0 0 0 0 0 0 (48,808) (703,308) 0 0 0 0 0 0 0 0 0 (703,308) 4,445,099 0 0 0 0 0 0 0 0 0 4,445,099 (46,676,126) 0 0 0 0 0 0 0 0 0 (46,676,126) (372,568) 0 0 0 0 0 0 0 0 0 (372,568) (180,610) 0 0 0 0 0 0 0 0 0 (180,610) 127,121 0 0 0 0 0 0 0 0 0 127,121 12,505,069 0 279,132 0 0 0 0 0 0 279,132 12,784,200 105,465 0 1,313,524 0 0 0 0 0 0 1,313,524 1,418,989 (6,846,659) 0 0 0 0 0 0 0 0 0 (6,846,659) (3,694,855) 0 0 0 0 0 0 0 0 0 (3,694,855) (133,630) 0 0 0 0 0 0 0 0 0 (133,630) 414,877 0 0 0 0 0 0 0 0 0 414,877 (345,381) 0 0 0 0 0 0 0 0 0 (345,381) 22,403,199 0 0 (3,500,000) 0 0 0 0 8,028,970 4,528,970 26,932,169 (21,940,013) 0 0 0 0 0 0 0 (8,028,970) (8,028,970) (29,968,983) ($40,658,687) $0 $1,592,655 ($3,500,000) $0 $0 $0 $0 $0 ($1,907,345) ($42,566,032) $ $ $ $ $ $ $ $ $ $ $ 0 $0 $0 $0 $0 $0 $0 $0 $0 0 0 0 $ $ $ $ $ $ $ $ 0 0 0 $0 $0 $0 $0 $0 $0 $0 $0 0 0 0 $0 $0 $0 $0 $0 $0 $0 $0 0 0 0 $0 $0 $0 $0 $0 $0 $0 $0 0 0

Docket No. D2018.2.12 Page 58 of 327 GENERAL RATE CASE A B C D E F G H I J ELECTRIC REVENUE SALES & ACTUAL TWELVE MONTHS ENDED 2017 INTERIM GENERATION TRANSMISSION & & REVENUE ADMINISTRATIVE CORPORATE DSIP NORTHWESTERN ENERGY ELECTRIC UTILITY AND SUPPLY DISTRIBUTION RELATED TRANSMISSION & GENERAL LABOR ALLOCATION AMRTIZATION DEPRECIATION ELECTRIC TRANSMISSION & DISTRIBUTION UTILITY FUNCTION UTILITY ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT COMPUTATION OF REQUIRED RETURN AND REVENUE INCREASE 1 Electric Utility Rate Base $1,015,741,304 $0 $0 $0 $0 $0 $0 $0 2 Rate of Return 7.42% 7.42% 7.42% 7.42% 7.42% 7.42% 7.42% 7.42% 3 4 5 Net Operating Income 75,368,005 0 0 0 0 0 0 0 6 7 Net Operating Income for the Year 8 Ended 12/31/17 Adjusted for Known Changes 58,426,129 (381,386) 17,887 4,042,336 (471,940) 843,702 1,865,565 (69,285) 9 10 Required Incremental Increase in Net 11 Operating Income $16,941,876 $381,386 ($17,887) ($4,042,336) $471,940 ($843,702) ($1,865,565) $69,285 12 13 Add: 14 MPSC Tax 56,278 1,267 (59) (13,428) 1,568 (2,803) (6,197) 230 15 Consumer Counsel Tax 10,610 239 (11) (2,531) 296 (528) (1,168) 43 16 Incremental Income Taxes 6,055,886 136,327 (6,394) (1,444,936) 168,695 (301,582) (666,848) 24,766 17 18 Required Revenue Increase $23,064,650 $519,219 ($24,351) ($5,503,231) $642,499 ($1,148,615) ($2,539,778) $94,324 19 20 21 MPSC Tax (0.244%) 56,278 1,267 (59) (13,428) 1,568 (2,803) (6,197) 230 22 23 Consumer Counsel Tax (0.046%) 10,610 239 (11) (2,531) 296 (528) (1,168) 43 24 25 Taxable Income for State Income Tax $22,997,762 $517,713 ($24,281) ($5,487,272) $640,635 ($1,145,284) ($2,532,413) $94,051 26 27 State Income Tax (6.75%) (Unitary Factor = 1.00) 1,552,349 34,946 (1,639) (370,391) 43,243 (77,307) (170,938) 6,348 28 29 Taxable Income for Federal Income Tax $21,445,413 $482,767 ($22,642) ($5,116,881) $597,392 ($1,067,977) ($2,361,475) $87,703 30 31 Reduction of Fed.Inc.TaxDue to MCLT Expense (325,993) (7,339) 344 77,782 (9,081) 16,234 35,897 (1,333) 32 Federal Income Tax Expense (21%) 4,829,530 108,720 (5,099) (1,152,327) 134,533 (240,509) (531,807) 19,751 33 34 Required Incremental Increase in Net 35 Operating Income $16,941,876 $381,386 ($17,887) ($4,042,336) $471,940 ($843,702) ($1,865,565) $69,285

Docket No. D2018.2.12 Page 59 of 327 GENERAL RATE CASE K L C D E F M N O P ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY ELECTRIC TRANSMISSION & DISTRIBUTION UTILITY COMPUTATION OF REQUIRED RETURN AND REVENUE INCREASE 1 Electric Utility Rate Base 2 Rate of Return 3 4 5 Net Operating Income 6 7 Net Operating Income for the Year 8 Ended 12/31/17 Adjusted for Known Changes 9 10 Required Incremental Increase in Net 11 Operating Income 12 13 Add: 14 MPSC Tax 15 Consumer Counsel Tax 16 Incremental Income Taxes 17 18 Required Revenue Increase 19 20 21 MPSC Tax (0.244%) 22 23 Consumer Counsel Tax (0.046%) 24 25 Taxable Income for State Income Tax 26 27 State Income Tax (6.75%) (Unitary Factor = 1.00) 28 29 Taxable Income for Federal Income Tax 30 31 Reduction of Fed.Inc.TaxDue to MCLT Expense 32 Federal Income Tax Expense (21%) 33 34 Required Incremental Increase in Net 35 Operating Income STIPULATION AND TAXES OTHER REGULATORY HAZARD MOVE NAVIGANT WORKING INTEREST TOTAL MARKET CREDIT AMORTIZATION THAN INCOME PLANT TREES (NEM) STUDY TO CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT RATE CASE EXPENSES ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS ($24,367,156) $3,226,710 $0 $0 $0 $0 $4,081,934 ($661,441) $0 ($17,719,953) 7.42% 7.42% 7.42% 7.42% 7.42% 7.42% 7.42% 7.42% 7.42% 7.42% (1,808,043) 239,422 0 0 0 0 302,880 (49,079) 0 (1,314,820) 0 (4,836,899) (3,779,213) 0 (2,578,362) 79,098 0 (9,610,097) 2,657,737 (12,220,857) ($1,808,043) $5,076,321 $3,779,213 $0 $2,578,362 ($79,098) $302,880 $9,561,018 ($2,657,737) $10,906,037 (6,006) 16,863 12,554 0 8,565 (263) 1,006 31,760 (8,829) 36,228 (1,132) 3,179 2,367 0 1,615 (50) 190 5,988 (1,664) 6,833 (646,286) 1,814,535 1,350,882 0 921,637 (28,274) 108,264 3,417,592 (950,010) 3,898,368 ($2,461,467) $6,910,898 $5,145,016 $0 $3,510,179 ($107,685) $412,340 $13,016,358 ($3,618,240) $14,847,466 (6,006) 16,863 12,554 0 8,565 (263) 1,006 31,760 (8,829) 36,228 (1,132) 3,179 2,367 0 1,615 (50) 190 5,988 (1,664) 6,833 ($2,454,329) $6,890,856 $5,130,095 $0 $3,499,999 ($107,372) $411,144 $12,978,610 ($3,607,747) 14,804,405 (165,667) 465,133 346,281 0 236,250 (7,248) 27,752 876,056 (243,523) 999,296 ($2,288,662) $6,425,723 $4,783,814 $0 $3,263,749 ($100,124) $383,392 $12,102,554 ($3,364,224) $13,805,109 34,790 (97,678) (72,719) 0 (49,613) 1,522 (5,828) (183,972) 51,140 (209,854) (515,409) 1,447,080 1,077,320 0 735,000 (22,548) 86,340 2,725,508 (757,627) 3,108,926 ($1,808,043) $5,076,321 $3,779,213 $0 $2,578,362 ($79,098) $302,880 $9,561,018 ($2,657,737) $10,906,037

Docket No. D2018.2.12 Page 60 of 327 GENERAL RATE CASE ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY ELECTRIC TRANSMISSION & DISTRIBUTION UTILITY COMPUTATION OF REQUIRED RETURN AND REVENUE INCREASE 1 Electric Utility Rate Base 2 Rate of Return 3 4 5 Net Operating Income 6 7 Net Operating Income for the Year 8 Ended 12/31/17 Adjusted for Known Changes 9 10 Required Incremental Increase in Net 11 Operating Income 12 13 Add: 14 MPSC Tax 15 Consumer Counsel Tax 16 Incremental Income Taxes 17 18 Required Revenue Increase 19 20 21 MPSC Tax (0.244%) 22 23 Consumer Counsel Tax (0.046%) 24 25 Taxable Income for State Income Tax 26 27 State Income Tax (6.75%) (Unitary Factor = 1.00) 28 29 Taxable Income for Federal Income Tax 30 31 Reduction of Fed.Inc.TaxDue to MCLT Expense 32 Federal Income Tax Expense (21%) 33 34 Required Incremental Increase in Net 35 Operating Income Q R S T U V W X Y Z INTERIM ADJUSTMENTS INTERIM INTERIM TEST PERIOD ADJUST TO HAZARD WORKING INTEREST TOTAL TEST PERIOD @ PRESENT ROE FROM DEPRECIATION TREES CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT RATES DOCKET 2009.9.129 ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES $998,021,351 $998,021,351 ($796,328) $0 $0 $0 $820,905 $920,151 $0 $944,729 $998,966,080 7.42% 0.20% 7.22% 7.22% 7.22% 7.22% 7.22% 7.22% 7.22% 7.22% 7.22% 74,053,184 (1,996,043) (57,495) 0 0 0 59,269 66,435 0 68,209 72,125,351 46,205,272 0 (1,316,815) 2,578,362 0 0 0 1,166,673 2,114,229 4,542,449 50,747,721 $27,847,913 ($1,996,043) $1,259,320 ($2,578,362) $0 $0 $59,269 ($1,100,238) ($2,114,229) ($6,470,283) $21,377,630 92,506 (6,630) 4,183 (8,565) 0 0 197 (3,655) (7,023) (21,493) 71,013 17,443 (1,250) 789 (1,615) 0 0 37 (689) (1,324) (4,052) 13,391 9,954,254 (713,487) 450,145 (921,637) 0 0 21,186 (393,280) (755,732) (2,312,805) 7,641,449 $37,912,116 ($2,717,410) $1,714,437 ($3,510,179) $0 $0 $80,689 ($1,497,862) ($2,878,308) ($8,808,633) $29,103,483 92,506 (6,630) 4,183 (8,565) 0 0 197 (3,655) (7,023) (21,493) 71,013 17,443 (1,250) 789 (1,615) 0 0 37 (689) (1,324) (4,052) 13,391 37,802,167 ($2,709,530) $1,709,465 ($3,499,999) $0 $0 $80,455 ($1,493,518) ($2,869,961) (8,783,088) 29,019,079 2,551,645 (182,893) 115,389 (236,250) 0 0 5,431 (100,812) (193,722) (592,857) 1,958,788 $35,250,522 ($2,526,637) $1,594,076 ($3,263,749) $0 $0 $75,024 ($1,392,706) ($2,676,239) (8,190,231) 27,060,291 (535,847) 38,408 (24,232) 49,613 0 0 (1,141) 21,171 40,682 124,501 (411,346) 7,938,456 (569,002) 358,988 (735,000) 0 0 16,896 (313,639) (602,692) (1,844,449) 6,094,007 $27,847,913 ($1,996,043) $1,259,320 ($2,578,362) $0 $0 $59,269 ($1,100,238) ($2,114,229) ($6,470,283) $21,377,630

Docket No. D2018.2.12 Page 61 of 327 GENERAL RATE CASE A B C D E F G H REVENUE SALES & ACTUAL TWELVE MONTHS ENDED 2017 INTERIM REMOVE REMOVE REMOVE & REVENUE ADMINISTRATIVE CORPORATE NORTHWESTERN ENERGY TOTAL GENERATION DEFERRED DEFERRED REVENUE CREDITS FIXED RELATED & GENERAL LABOR ALLOCATION TOTAL GENERATION REVENUES & VARIABLE ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT 1 Operating Revenues 421,828,178 (823,960) 121,853,032 35,518,343 265,280,763 (2,517,412) 2 3 Operating Expenses 227,409,876 (823,960) 113,231,423 38,252,500 76,749,912 (2,526,895) (12,938) 1,144,249 4 Book Depreciation 34,710,241 34,710,241 5 Amort. of Electric Plant & Acq Adjmt 8,119,530 8,119,530 6 Amort.Misc Items (3,540,176) (1,072,409) (2,467,767) 7 Taxes other than Income 30,766,953 564,803 30,202,150 (545,199) (920) 8 9 Subtotal Expenses 297,466,424 (823,960) 113,796,226 37,180,091 147,314,067 (545,199) (2,526,895) (13,858) 1,144,249 10 Net Utility Operating Income Before Inc Tax 124,361,754 (0) 8,056,805 (1,661,748) 117,966,696 (1,972,213) 2,526,895 13,858 (1,144,249) 11 12 Amortization of Excess Deferred TaxARAM 13 Amortization of Excess Deferred TaxUnprotected Rate Base 14 Amortization of Excess Deferred TaxUnprotected NonRate Base 15 16 Deferred Income Taxes: 17 Injuries & Damages 38,867 18 Miscellaneous 19 Accrued Incentive Compensation 41,927 20 Accelerated Depreciation 16,226,206 21 Net Operating Loss 7,405,462 (519,333) 665,395 3,649 (301,309) 22 MPSC/MCC Taxes 23 Deferred Revenue 417,548 24 Customer Advances for Construction/CIAC (57,438) 25 FAS106 & 112 Post Retirement Benefits 6,588 26 Costs of Refinancing Debt (394,417) 27 Environmental Reserve (46,688) 28 NonJurisdictional Items 4,940,823 29 SubtotalDeferred Income Tax 28,578,878 (519,333) 665,395 3,649 (301,309) 30 31 Income TaxesFederal (48) 32 Income TaxesCorporation License Tax 33 Income TaxesForeign Taxes 34 SubtotalCurrent Income Tax (48) 35 Net Utility Operating Income 89,387,866 (1,452,880) 1,861,500 10,209 (842,940) 36 Rate Base 1,325,237,902 37 Return on Rate Base 0

Docket No. D2018.2.12 Page 62 of 327 GENERAL RATE CASE I J M N O ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY TOTAL GENERATION 1 Operating Revenues 2 3 Operating Expenses 4 Book Depreciation 5 Amort. of Electric Plant & Acq Adjmt 6 Amort.Misc Items 7 Taxes other than Income 8 9 Subtotal Expenses 10 Net Utility Operating Income Before Inc Tax 11 12 Amortization of Excess Deferred TaxARAM 13 Amortization of Excess Deferred TaxUnprotected Ra 14 Amortization of Excess Deferred TaxUnprotected No 15 16 Deferred Income Taxes: 17 Injuries & Damages 18 Miscellaneous 19 Accrued Incentive Compensation 20 Accelerated Depreciation 21 Net Operating Loss 22 MPSC/MCC Taxes 23 Deferred Revenue 24 Customer Advances for Construction/CIAC 25 FAS106 & 112 Post Retirement Benefits 26 Costs of Refinancing Debt 27 Environmental Reserve 28 NonJurisdictional Items 29 SubtotalDeferred Income Tax 30 31 Income TaxesFederal 32 Income TaxesCorporation License Tax 33 Income TaxesForeign Taxes 34 SubtotalCurrent Income Tax 35 Net Utility Operating Income 36 Rate Base 37 Return on Rate Base TAXES OTHER CAPITALIZE WORKING INTEREST DEPRECIATION AMORTIZATION THAN INCOME DSM MAINTENANCE CAPITAL INCOME TAX SYNCHRONIZATION ADJUSTMENT ADJUSTMENT ADJUSTMENT COSTS ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT (7,762,146) (973,534) (778,840) 2,122,440 1,643,833 406,522 1,343,601 1,643,833 406,522 (7,762,146) (973,534) (1,343,601) (1,643,833) (406,522) 7,762,146 973,534 (680,482) 505,903 118,279 (12,882) (13,897) (282,156) (6,465,218) (432,862) (107,047) 2,043,967 256,356 (2,486,222) 3,693,367 (138,396) 19,038 (2,184) 130,730 15,475 (4,940,823) (282,156) (432,862) (107,047) 2,043,967 256,356 (13,950,681) 3,693,367 48 48 (1,061,445) (1,210,971) (299,475) 5,718,179 717,178 13,950,633 (3,693,367) 1,435,346 (1,550,257)

Docket No. D2018.2.12 Page 63 of 327 GENERAL RATE CASE P Q ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY TOTAL GENERATION 1 Operating Revenues 2 3 Operating Expenses 4 Book Depreciation 5 Amort. of Electric Plant & Acq Adjmt 6 Amort.Misc Items 7 Taxes other than Income 8 9 Subtotal Expenses 10 Net Utility Operating Income Before Inc Tax 11 12 Amortization of Excess Deferred TaxARAM 13 Amortization of Excess Deferred TaxUnprotected Ra 14 Amortization of Excess Deferred TaxUnprotected No 15 16 Deferred Income Taxes: 17 Injuries & Damages 18 Miscellaneous 19 Accrued Incentive Compensation 20 Accelerated Depreciation 21 Net Operating Loss 22 MPSC/MCC Taxes 23 Deferred Revenue 24 Customer Advances for Construction/CIAC 25 FAS106 & 112 Post Retirement Benefits 26 Costs of Refinancing Debt 27 Environmental Reserve 28 NonJurisdictional Items 29 SubtotalDeferred Income Tax 30 31 Income TaxesFederal 32 Income TaxesCorporation License Tax 33 Income TaxesForeign Taxes 34 SubtotalCurrent Income Tax 35 Net Utility Operating Income 36 Rate Base 37 Return on Rate Base INTERIM ADJUSTMENTS INTERIM TOTAL TEST PERIOD ADJUST TO NONPCCAM MONTANA WORKING INTEREST TOTAL UPDATES & @ PRESENT ROE FROM DEPRECIATION SUPPLY GENERATION CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & ADJUSTMENTS RATES DOCKET 2008.6.69 ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS (2,517,412) 262,763,351 0 (10,131,264) 66,618,648 (741,103) (571,968) (1,313,071) (778,840) 33,931,401 (2,544,214) (2,544,214) 2,122,440 10,241,971 0 1,643,833 (823,934) 0 (139,597) 30,062,553 0 (7,283,428) 140,030,639 (2,544,214) (741,103) (571,968) (3,857,286) 4,766,016 122,732,712 2,544,214 741,103 571,968 3,857,286 (680,482) (680,482) 0 505,903 505,903 (505,903) (505,903) 118,279 118,279 (118,279) (118,279) (12,882) 25,985 0 0 0 0 (13,897) 28,030 0 (6,747,374) 9,478,832 534,285 9,832 544,117 2,815,961 10,221,423 195,151 (47,288) (438,614) (290,751) 0 0 0 (138,396) 279,152 (8,161) (8,161) 19,038 (38,400) 0 (2,184) 4,404 39,547 39,547 130,730 (263,687) 0 15,475 (31,213) 0 (4,940,823) 0 0 (8,930,654) 19,648,225 534,285 195,151 (6,070) (624,182) (438,614) (339,430) 48 0 0 0 0 0 0 0 0 48 0 0 $13,696,621 $103,084,487 2,009,929 545,952 578,038 624,182 438,614 $4,196,716 (114,911) 1,325,122,991 1,272,107 337,826 (11,167,232) (9,557,299) 7.78%

Docket No. D2018.2.12 Page 64 of 327 GENERAL RATE CASE A B C D E F G H REVENUE SALES & ACTUAL TWELVE MONTHS ENDED 2017 INTERIM REMOVE REMOVE REMOVE & REVENUE ADMINISTRATIVE CORPORATE NORTHWESTERN ENERGY TOTAL GENERATION DEFERRED DEFERRED REVENUE CREDITS FIXED RELATED & GENERAL LABOR ALLOCATION TOTAL GENERATION REVENUES & VARIABLE ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT 38 ELECTRIC UTILITY CALCULATIONS 39 Operating Revenues 265,280,763 (2,517,412) 40 Operating Expenses 76,749,912 (2,526,895) (12,938) 1,144,249 41 Subtotal 188,530,851 (2,517,412) 2,526,895 12,938 (1,144,249) 42 Depreciation & Amortization 40,362,004 43 Taxes other than Income 30,202,150 (545,199) (920) 44 Net Utility Operating Income Before Inc Tax 117,966,696 (1,972,213) 2,526,895 13,858 (1,144,249) 45 Taxable Additions / (Deductions): 46 Nondeductible Meal Expense 80,717 47 Bad Debt Expense Accrual Net of Chargeoffs 48 Penalties 49 Meters 50 Customer Advances for Construction/CIAC 145,827 51 Repairs Expense (8,893,983) 52 Accrued Incentive Compensation (106,448) 53 MPSC/MCC Taxes 54 Costs of Refinancing Debt 1,001,378 55 Accelerated DepreciationExcess BLM Tx vs Bk Deprec 2,733,305 56 Accelerated DepreciationExcess Tx Rtn vs BLM Tx Dep (46,360,587) 57 Removal Costs Net of Salvage (747,656) 58 Deferred Revenue (1,060,101) 59 FAS106 & 112 Post Retirement Benefits (16,725) 60 Environmental Reserve 118,536 61 Injuries & Damages (98,680) 62 Net Operating Loss (18,801,553) 1,972,213 (2,526,895) (13,858) 1,144,249 63 Excludable Foreign Income 64 MT Corporation License Tax 65 Deduct Interest Charges (45,960,725) 66 Total Tax Additons / (Deductions) (117,966,696) 1,972,213 (2,526,895) (13,858) 1,144,249 67 Federal Taxable Income 68 Federal Income Tax @ 21% 69 Foreign Income Tax 70 Foreign Income Tax Credit 71 NonJurisdictional Items (4,940,823) 72 Prior Period Adjustments 4,940,775 73 Audit Adjustments 74 Total Federal Income Tax (48) 75 76 77 Montana Corporate License Tax 78 Federal Taxable Income B4 MT Corp Tx Deductn & NOL 0 79 Add: 80 Other 81 Other State Taxes Paid 82 83 Reduction for Unitary Allocation 84 85 Montana Taxable Income 0 86 Mont. Corp. Lic. Tax @ 6.75% 87 Net Tax Adjustment 88 Mont. Corp. License Tax 89 Actual 6.75% 90 91 Change in tax rates 92 NonJurisdictional Items 93 Net Tax Adjustment

Docket No. D2018.2.12 Page 65 of 327 GENERAL RATE CASE I J M N O ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY TOTAL GENERATION 38 ELECTRIC UTILITY CALCULATIONS 39 Operating Revenues 40 Operating Expenses 41 Subtotal 42 Depreciation & Amortization 43 Taxes other than Income 44 Net Utility Operating Income Before Inc Tax 45 Taxable Additions / (Deductions): 46 Nondeductible Meal Expense 47 Bad Debt Expense Accrual Net of Chargeoffs 48 Penalties 49 Meters 50 Customer Advances for Construction/CIAC 51 Repairs Expense 52 Accrued Incentive Compensation 53 MPSC/MCC Taxes 54 Costs of Refinancing Debt 55 Accelerated DepreciationExcess BLM Tx vs Bk Depr 56 Accelerated DepreciationExcess Tx Rtn vs BLM Tx D 57 Removal Costs Net of Salvage 58 Deferred Revenue 59 FAS106 & 112 Post Retirement Benefits 60 Environmental Reserve 61 Injuries & Damages 62 Net Operating Loss 63 Excludable Foreign Income 64 MT Corporation License Tax 65 Deduct Interest Charges 66 Total Tax Additons / (Deductions) 67 Federal Taxable Income 68 Federal Income Tax @ 21% 69 Foreign Income Tax 70 Foreign Income Tax Credit 71 NonJurisdictional Items 72 Prior Period Adjustments 73 Audit Adjustments 74 Total Federal Income Tax 75 76 77 Montana Corporate License Tax 78 Federal Taxable Income B4 MT Corp Tx Deductn & NO 79 Add: 80 Other 81 Other State Taxes Paid 82 83 Reduction for Unitary Allocation 84 85 Montana Taxable Income 86 Mont. Corp. Lic. Tax @ 6.75% 87 Net Tax Adjustment 88 Mont. Corp. License Tax 89 Actual 6.75% 90 91 Change in tax rates 92 NonJurisdictional Items 93 Net Tax Adjustment TAXES OTHER CAPITALIZE WORKING INTEREST DEPRECIATION AMORTIZATION THAN INCOME DSM MAINTENANCE CAPITAL INCOME TAX SYNCHRONIZATION ADJUSTMENT ADJUSTMENT ADJUSTMENT COSTS ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT (7,762,146) (973,534) 7,762,146 973,534 1,343,601 1,643,833 406,522 (1,343,601) (1,643,833) (406,522) 7,762,146 973,534 1,343,601 (120,305) 1,643,833 406,522 (7,762,146) (973,534) 120,305 (14,025,887) 14,025,887 1,343,601 1,643,833 406,522 (7,762,146) (973,534) (0) (0) 4,940,823 (4,940,775) 48 (0) (0) (0) (0)

Docket No. D2018.2.12 Page 66 of 327 GENERAL RATE CASE P Q ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY TOTAL GENERATION 38 ELECTRIC UTILITY CALCULATIONS 39 Operating Revenues 40 Operating Expenses 41 Subtotal 42 Depreciation & Amortization 43 Taxes other than Income 44 Net Utility Operating Income Before Inc Tax 45 Taxable Additions / (Deductions): 46 Nondeductible Meal Expense 47 Bad Debt Expense Accrual Net of Chargeoffs 48 Penalties 49 Meters 50 Customer Advances for Construction/CIAC 51 Repairs Expense 52 Accrued Incentive Compensation 53 MPSC/MCC Taxes 54 Costs of Refinancing Debt 55 Accelerated DepreciationExcess BLM Tx vs Bk Depr 56 Accelerated DepreciationExcess Tx Rtn vs BLM Tx D 57 Removal Costs Net of Salvage 58 Deferred Revenue 59 FAS106 & 112 Post Retirement Benefits 60 Environmental Reserve 61 Injuries & Damages 62 Net Operating Loss 63 Excludable Foreign Income 64 MT Corporation License Tax 65 Deduct Interest Charges 66 Total Tax Additons / (Deductions) 67 Federal Taxable Income 68 Federal Income Tax @ 21% 69 Foreign Income Tax 70 Foreign Income Tax Credit 71 NonJurisdictional Items 72 Prior Period Adjustments 73 Audit Adjustments 74 Total Federal Income Tax 75 76 77 Montana Corporate License Tax 78 Federal Taxable Income B4 MT Corp Tx Deductn & NO 79 Add: 80 Other 81 Other State Taxes Paid 82 83 Reduction for Unitary Allocation 84 85 Montana Taxable Income 86 Mont. Corp. Lic. Tax @ 6.75% 87 Net Tax Adjustment 88 Mont. Corp. License Tax 89 Actual 6.75% 90 91 Change in tax rates 92 NonJurisdictional Items 93 Net Tax Adjustment INTERIM ADJUSTMENTS INTERIM TOTAL TEST PERIOD ADJUST TO NONPCCAM MONTANA WORKING INTEREST TOTAL UPDATES & @ PRESENT ROE FROM DEPRECIATION SUPPLY GENERATION CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & ADJUSTMENTS RATES DOCKET 2008.6.69 ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS (2,517,412) 262,763,351 0 (10,131,264) 66,618,648 (741,103) (571,968) (1,313,071) 7,613,852 196,144,703 741,103 571,968 1,313,071 2,987,434 43,349,438 (2,544,214) (2,544,214) (139,597) 30,062,553 0 4,766,016 122,732,712 2,544,214 741,103 571,968 3,857,286 0 80,717 1,000 1,000 0 0 0 0 0 0 0 0 0 0 145,827 0 0 (8,893,983) (636,422) (636,422) 0 (106,448) 0 0 0 0 0 1,001,378 0 0 2,733,305 49,878 49,878 1,223,296 (45,137,292) (2,544,214) (46,818) (2,591,033) 0 (747,656) 0 0 (1,060,101) 30,994 30,994 0 (16,725) (150,182) (150,182) 0 118,536 0 0 (98,680) 0 (20,015,198) (38,816,751) (741,103) 179,581 1,665,676 1,104,154 0 0 0 0 0 0 14,025,887 (31,934,838) (1,665,676) (1,665,676) ($4,766,016) ($122,732,712) (2,544,214) (741,103) (571,968) ($3,857,286) $ (0) $ $ 0 0 0 0 0 0 0 0 0 4,940,823 0 0 (4,940,775) 0 0 0 0 0 48 0 0 (0) (0) 0 0 0 0 0 0 0 0 0 0 (0) (0) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

Docket No. D2018.2.12 Page 67 of 327 GENERAL RATE CASE A B C D E F G H REVENUE SALES & ACTUAL TWELVE MONTHS ENDED 2017 INTERIM REMOVE REMOVE REMOVE & REVENUE ADMINISTRATIVE CORPORATE NORTHWESTERN ENERGY TOTAL GENERATION DEFERRED DEFERRED REVENUE CREDITS FIXED RELATED & GENERAL LABOR ALLOCATION TOTAL GENERATION REVENUES & VARIABLE ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT COMPUTATION OF REQUIRED RETURN AND REVENUE INCREASE 1 Electric Utility Rate Base $1,325,237,902 $0 $0 $0 $0 2 Rate of Return 7.61% 0.00% 0.00% 0.00% 0.00% 3 4 5 Net Operating Income 100,852,882 0 0 0 0 6 7 Net Operating Income for the Year 8 Ended 12/31/17 Adjusted for Known Changes 89,387,866 (1,452,880) 1,861,500 10,209 (842,940) 9 10 Required Incremental Increase in Net 11 Operating Income $11,465,016 $1,452,880 ($1,861,500) ($10,209) $842,940 12 13 Add: 14 MPSC Tax 38,085 4,826 (6,184) (34) 2,800 15 Consumer Counsel Tax 7,180 910 (1,166) (6) 528 16 Incremental Income Taxes 4,098,178 519,333 (665,394) (3,649) 301,310 17 18 Required Revenue Increase $15,608,459 $1,977,949 ($2,534,244) ($13,898) $1,147,578 19 20 21 MPSC Tax (0.244%) 38,085 4,826 (6,184) (34) 2,800 22 23 Consumer Counsel Tax (0.046%) 7,180 910 (1,166) (6) 528 24 25 Taxable Income for State Income Tax $15,563,194 $1,972,213 ($2,526,894) ($13,858) $1,144,250 26 27 State Income Tax (6.75%) (Unitary Factor = 1.00) 1,050,516 133,124 (170,565) (935) 77,237 28 29 Taxable Income for Federal Income Tax $14,512,678 $1,839,089 ($2,356,329) ($12,923) $1,067,013 30 31 Reduction of Fed.Inc.TaxDue to MCLT Expense (220,608) (27,956) 35,819 196 (16,220) 32 Federal Income Tax Expense (21%) 3,268,270 414,165 (530,648) (2,910) 240,293 33 34 Required Incremental Increase in Net 35 Operating Income $11,465,016 $1,452,880 ($1,861,500) ($10,209) $842,940

Docket No. D2018.2.12 Page 68 of 327 GENERAL RATE CASE I J M N O ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY TOTAL GENERATION COMPUTATION OF REQUIRED RETURN AND REVENUE INCREASE TAXES OTHER CAPITALIZE WORKING INTEREST DEPRECIATION AMORTIZATION THAN INCOME DSM MAINTENANCE CAPITAL INCOME TAX SYNCHRONIZATION ADJUSTMENT ADJUSTMENT ADJUSTMENT COSTS ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT 1 Electric Utility Rate Base 2 Rate of Return 3 4 5 Net Operating Income 6 7 Net Operating Income for the Year 8 Ended 12/31/17 Adjusted for Known Changes 9 10 Required Incremental Increase in Net 11 Operating Income 12 13 Add: 14 MPSC Tax 15 Consumer Counsel Tax 16 Incremental Income Taxes 17 18 Required Revenue Increase 19 20 21 MPSC Tax (0.244%) 22 23 Consumer Counsel Tax (0.046%) 24 25 Taxable Income for State Income Tax 26 27 State Income Tax (6.75%) (Unitary Factor = 1.00) 28 29 Taxable Income for Federal Income Tax 30 31 Reduction of Fed.Inc.TaxDue to MCLT Expense 32 Federal Income Tax Expense (21%) 33 34 Required Incremental Increase in Net 35 Operating Income $0 $0 $0 $0 $0 $0 $0 $0 $0 $1,435,346 ($1,550,257) $0 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 7.63% 7.44% 0.00% 0 0 0 0 0 0 0 0 0 109,556 (115,268) 0 (1,061,445) (1,210,971) (299,475) 5,718,179 717,178 0 0 0 0 0 13,950,633 (3,693,367) $1,061,445 $1,210,971 $299,475 ($5,718,179) ($717,178) $0 $0 $0 $0 $109,556 ($14,065,901) $3,693,367 3,526 4,023 995 (18,995) (2,382) 0 0 0 0 364 (46,724) 12,269 665 758 188 (3,581) (449) 0 0 0 0 69 (8,809) 2,313 379,414 432,863 107,047 (2,043,967) (256,356) 0 0 0 0 39,160 (5,027,866) 1,320,197 $1,445,050 $1,648,615 $407,705 ($7,784,722) ($976,365) $0 $0 $0 $0 $149,149 ($19,149,300) $5,028,146 3,526 4,023 995 (18,995) (2,382) 0 0 0 0 364 (46,724) 12,269 665 758 188 (3,581) (449) 0 0 0 0 69 (8,809) 2,313 $1,440,859 $1,643,834 $406,522 ($7,762,146) ($973,534) $0 $0 $0 $0 $148,716 ($19,093,767) $5,013,564 97,258 110,959 27,440 (523,945) (65,714) 0 0 0 0 10,038 (1,288,829) 338,416 $1,343,601 $1,532,875 $379,082 ($7,238,201) ($907,820) $0 $0 $0 $0 $138,678 ($17,804,938) $4,675,148 (20,424) (23,301) (5,762) 110,028 13,800 0 0 0 0 (2,108) 270,654 (71,067) 302,580 345,205 85,369 (1,630,050) (204,442) 0 0 0 0 31,230 (4,009,691) 1,052,848 $1,061,445 $1,210,971 $299,475 ($5,718,179) ($717,178) $0 $0 $0 $0 $109,556 ($14,065,901) $3,693,367

Docket No. D2018.2.12 Page 69 of 327 GENERAL RATE CASE P Q ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY TOTAL GENERATION COMPUTATION OF REQUIRED RETURN AND REVENUE INCREASE INTERIM ADJUSTMENTS INTERIM TOTAL TEST PERIOD ADJUST TO NONPCCAM MONTANA WORKING INTEREST TOTAL UPDATES & @ PRESENT ROE FROM DEPRECIATION SUPPLY GENERATION CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & ADJUSTMENTS RATES DOCKET 2008.6.69 ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS 1 Electric Utility Rate Base 2 Rate of Return 3 4 5 Net Operating Income 6 7 Net Operating Income for the Year 8 Ended 12/31/17 Adjusted for Known Changes 9 10 Required Incremental Increase in Net 11 Operating Income 12 13 Add: 14 MPSC Tax 15 Consumer Counsel Tax 16 Incremental Income Taxes 17 18 Required Revenue Increase 19 20 21 MPSC Tax (0.244%) 22 23 Consumer Counsel Tax (0.046%) 24 25 Taxable Income for State Income Tax 26 27 State Income Tax (6.75%) (Unitary Factor = 1.00) 28 29 Taxable Income for Federal Income Tax 30 31 Reduction of Fed.Inc.TaxDue to MCLT Expense 32 Federal Income Tax Expense (21%) 33 34 Required Incremental Increase in Net 35 Operating Income ($114,911) $1,325,122,991 $0 $1,272,107 $0 $0 $0 $0 $337,826 ($11,167,232) $0 ($9,557,299) 4.97% 7.61% 0.00% 7.26% 0.00% 0.00% 0.00% 0.00% 7.03% 7.41% 0.00% 49.94% (5,712) 100,847,173 (4,060,846) 92,299 0 0 0 0 23,759 (827,683) 0 (4,772,471) 13,696,621 103,084,487 0 2,009,929 545,952 578,038 0 0 0 624,182 438,614 4,196,716 ($13,702,333) ($2,237,317) ($4,060,846) ($1,917,630) ($545,952) ($578,038) $0 $0 $23,759 ($1,451,865) ($438,614) ($8,969,186) (45,516) (7,431) (13,489) (6,370) (1,814) (1,920) 0 0 79 (4,823) (1,457) (29,794) (8,580) (1,400) (2,543) (1,201) (342) (362) 0 0 15 (909) (275) (5,617) (4,897,908) (799,730) (1,451,552) (685,458) (195,150) (206,620) 0 0 8,493 (518,970) (156,783) (3,206,040) ($18,654,337) ($3,045,878) ($5,528,430) ($2,610,659) ($743,258) ($786,940) $0 $0 $32,346 ($1,976,567) ($597,129) ($12,210,637) (45,516) (7,431) (13,489) (6,370) (1,814) (1,920) 0 0 79 (4,823) (1,457) (29,794) (8,580) (1,400) (2,543) (1,201) (342) (362) 0 0 15 (909) (275) (5,617) (18,600,241) (3,037,047) ($5,512,398) ($2,603,088) ($741,102) ($784,658) $0 $0 $32,252 ($1,970,835) ($595,397) (12,175,226) (1,255,516) (205,000) (372,087) (175,708) (50,024) (52,964) 0 0 2,177 (133,031) (40,189) (821,826) ($17,344,725) ($2,832,047) ($5,140,311) ($2,427,380) ($691,078) ($731,694) $0 $0 $30,075 ($1,837,804) ($555,208) (11,353,400) 263,659 43,051 78,138 36,899 10,505 11,122 0 0 (457) 27,937 8,440 172,584 (3,906,051) (637,781) (1,157,603) (546,649) (155,631) (164,778) 0 0 6,773 (413,876) (125,034) (2,556,798) ($13,702,333) ($2,237,317) ($4,060,846) ($1,917,630) ($545,952) ($578,038) $0 $0 $23,759 ($1,451,865) ($438,614) ($8,969,186)

Docket No. D2018.2.12 Page 70 of 327 GENERAL RATE CASE A B C D E F G H I REVENUE SALES & ACTUAL TWELVE MONTHS ENDED 2017 INTERIM REMOVE REMOVE FIXED & REVENUE ADMINISTRATIVE CORPORATE NORTHWESTERN ENERGY COLSTRIP UNIT 4 DEFERRED VARIABLE COLSTRIP UNIT 4 RELATED & GENERAL LABOR ALLOCATION DEPRECIATION COLSTIP UNIT 4 REVENUES ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT 1 Operating Revenues $97,432,620 ($2,723,439) $22,475,955 $77,680,105 ($685,850) $0 $0 $0 $0 2 3 Operating Expenses 40,260,071 (2,723,439) 22,340,760 20,642,750 (646,067) (9,023) 4 Book Depreciation 13,062,285 13,062,285 619,949 5 Amort. of Electric Plant & Acq Adjmt 228,253 6 Amort.Misc Items (909,001) (203,924) (705,077) 7 Taxes other than Income 4,291,542 4,291,542 (160,969) (642) 8 9 Subtotal Expenses $56,704,897 ($2,723,439) $22,136,836 $37,291,500 ($160,969) ($646,067) ($9,665) $0 $848,202 10 Net Utility Operating Income Before Inc Tax $40,727,724 $0 $339,118 $40,388,605 ($524,880) $646,067 $9,665 $0 ($848,202) 11 12 Amortization of Excess Deferred TaxARAM $0 0 0 0 0 0 13 Amortization of Excess Deferred TaxUnprotected Rate Base $0 0 0 0 0 0 14 Amortization of Excess Deferred TaxUnprotected NonRate Base $0 0 0 0 0 0 15 16 Deferred Income Taxes: 17 Injuries & Damages $0 0 0 0 0 0 18 Miscellaneous $0 0 0 0 0 0 19 Accrued Incentive Compensation $0 0 0 0 0 0 20 Accelerated Depreciation $3,035,917 0 0 0 0 (178,122) 21 Net Operating Loss $7,392,331 (138,214) 170,126 2,545 0 0 22 MPSC/MCC Taxes $0 0 0 0 0 0 23 Deferred Revenue $0 0 0 0 0 0 24 Customer Advances for Construction/CIAC $0 0 0 0 0 0 25 FAS106 & 112 Post Retirement Benefits $0 0 0 0 0 0 26 Costs of Refinancing Debt ($380,112) 0 0 0 0 0 27 Environmental Reserve $0 0 0 0 0 0 28 NonJurisdictional Items $758,560 0 0 0 0 0 29 SubtotalDeferred Income Tax 10,806,696 (138,214) 170,126 2,545 0 (178,122) 30 31 Income TaxesFederal 0 0 0 0 0 0 32 Income TaxesCorporation License Tax 0 0 0 0 0 0 33 Income TaxesForeign Taxes 0 0 0 0 0 0 34 SubtotalCurrent Income Tax 0 0 0 0 0 0 35 Net Utility Operating Income $29,581,909 ($386,666) $475,941 $7,120 $0 ($670,080) 36 Rate Base $303,642,197 $0 $0 $0 $0 $0 37 Return on Rate Base 9.74%

Docket No. D2018.2.12 Page 71 of 327 GENERAL RATE CASE J K M N O P Q ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY COLSTIP UNIT 4 1 Operating Revenues 2 3 Operating Expenses 4 Book Depreciation 5 Amort. of Electric Plant & Acq Adjmt 6 Amort.Misc Items 7 Taxes other than Income 8 9 Subtotal Expenses 10 Net Utility Operating Income Before Inc Tax 11 12 Amortization of Excess Deferred TaxARAM 13 Amortization of Excess Deferred TaxUnprotected Rate Base 14 Amortization of Excess Deferred TaxUnprotected NonRate Ba 15 16 Deferred Income Taxes: 17 Injuries & Damages 18 Miscellaneous 19 Accrued Incentive Compensation 20 Accelerated Depreciation 21 Net Operating Loss 22 MPSC/MCC Taxes 23 Deferred Revenue 24 Customer Advances for Construction/CIAC 25 FAS106 & 112 Post Retirement Benefits 26 Costs of Refinancing Debt 27 Environmental Reserve 28 NonJurisdictional Items 29 SubtotalDeferred Income Tax 30 31 Income TaxesFederal 32 Income TaxesCorporation License Tax 33 Income TaxesForeign Taxes 34 SubtotalCurrent Income Tax 35 Net Utility Operating Income 36 Rate Base 37 Return on Rate Base TAXES OTHER WORKING INTEREST TOTAL TEST PERIOD ADJUST TO NONPCCAM AMORTIZATION THAN INCOME CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT ROE FROM DEPRECIATION SUPPLY ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES DOCKET 2008.6.69 ADJUSTMENT ADJUSTMENT $0 $0 $0 $0 $0 (685,850) 76,994,255 $0 $0 $0 (655,090) 19,987,659 619,949 13,682,234 (414,386) 228,253 228,253 469,667 469,667 (235,410) 95,160 (66,451) 4,225,091 $469,667 $95,160 $0 $0 $0 596,328 37,887,827 $0 ($414,386) $0 ($469,667) ($95,160) $0 $0 $0 (1,282,177) 39,106,428 $0 $414,386 $0 0 0 0 (151,991) 0 (151,991) (151,991) 0 0 0 0 0 0 (5,540) 0 (5,540) (5,540) 0 0 0 0 0 0 85,920 0 85,920 85,920 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 (1,324,790) 0 (1,502,912) 1,533,005 0 87,021 0 (123,675) (25,058) 0 (2,311,728) 479,244 (1,946,760) 5,445,571 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 125,988 0 125,988 (254,124) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 (758,560) 0 (758,560) 0 0 0 0 (123,675) (25,058) 0 (4,340,701) 479,244 (4,153,855) 6,652,841 0 87,021 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ($345,992) ($70,102) $0 $4,340,701 ($479,244) $2,871,678 $32,453,587 $0 $327,365 $0 $0 $0 $367,955 ($28,677) $0 339,277 303,981,475 $0 $207,193 $0 10.68%

Docket No. D2018.2.12 Page 72 of 327 GENERAL RATE CASE ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY COLSTIP UNIT 4 1 Operating Revenues 2 3 Operating Expenses 4 Book Depreciation 5 Amort. of Electric Plant & Acq Adjmt 6 Amort.Misc Items 7 Taxes other than Income 8 9 Subtotal Expenses 10 Net Utility Operating Income Before Inc Tax 11 12 Amortization of Excess Deferred TaxARAM 13 Amortization of Excess Deferred TaxUnprotected Rate Base 14 Amortization of Excess Deferred TaxUnprotected NonRate Ba 15 16 Deferred Income Taxes: 17 Injuries & Damages 18 Miscellaneous 19 Accrued Incentive Compensation 20 Accelerated Depreciation 21 Net Operating Loss 22 MPSC/MCC Taxes 23 Deferred Revenue 24 Customer Advances for Construction/CIAC 25 FAS106 & 112 Post Retirement Benefits 26 Costs of Refinancing Debt 27 Environmental Reserve 28 NonJurisdictional Items 29 SubtotalDeferred Income Tax 30 31 Income TaxesFederal 32 Income TaxesCorporation License Tax 33 Income TaxesForeign Taxes 34 SubtotalCurrent Income Tax 35 Net Utility Operating Income 36 Rate Base 37 Return on Rate Base INTERIM ADJUSTMENTS INTERIM INTERIM MONTANA WORKING INTEREST TOTAL TEST PERIOD GENERATION CAPITAL INCOME TAXSYNCHRONIZATION UPDATES & @ PRESENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES $0 $0 $0 $0 $0 $0 0 76,994,255 0 19,987,659 (414,386) 13,267,847 0 228,253 0 (235,410) 0 4,225,091 $0 $0 $0 $0 $0 $0 (414,386) 37,473,441 $0 $0 $0 $0 $0 $0 414,386 39,520,815 0 0 0 0 0 0 0 (151,991) 0 0 0 0 5,540 0 5,540 0 0 0 0 0 (85,920) 0 (85,920) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 87,021 1,620,026 0 0 0 0 0 26,455 26,455 5,472,026 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 (254,124) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 (80,380) 26,455 33,096 6,685,937 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 $0 $0 $0 $0 $80,380 ($26,455) $381,290 $32,834,877 $0 $0 $0 $9,044 ($3,646,726) $0 (3,430,489) 300,550,985 10.92%

Docket No. D2018.2.12 Page 73 of 327 GENERAL RATE CASE A B C D E F G H I REVENUE SALES & ACTUAL TWELVE MONTHS ENDED 2017 INTERIM REMOVE REMOVE FIXED & REVENUE ADMINISTRATIVE CORPORATE NORTHWESTERN ENERGY COLSTRIP UNIT 4 DEFERRED VARIABLE COLSTRIP UNIT 4 RELATED & GENERAL LABOR ALLOCATION DEPRECIATION COLSTIP UNIT 4 REVENUES ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT 38 ELECTRIC UTILITY CALCULATIONS 39 Operating Revenues $77,680,105 ($685,850) $0 $0 $0 $0 40 Operating Expenses 20,642,750 0 (646,067) (9,023) 0 0 41 Subtotal $57,037,355 ($685,850) $646,067 $9,023 $0 $0 42 Depreciation & Amortization 12,357,208 848,202 43 Taxes other than Income 4,291,542 (160,969) (642) 44 Net Utility Operating Income Before Inc Tax $ 40,388,605 $ (524,880) $ 646,067 $ 9,665 $ $ (848,202) 45 Taxable Additions / (Deductions): 46 Nondeductible Meal Expense $214 0 0 0 0 0 47 Bad Debt Expense Accrual Net of Chargeoffs $0 0 0 0 0 0 48 Penalties $0 0 0 0 0 0 49 Meters $0 0 0 0 0 0 50 Customer Advances for Construction/CIAC $0 0 0 0 0 0 51 Repairs Expense ($4,430,349) 0 0 0 0 0 52 Accrued Incentive Compensation $0 0 0 0 0 0 53 MPSC/MCC Taxes $0 0 0 0 0 0 54 Costs of Refinancing Debt $965,057 0 0 0 0 0 55 Accelerated DepreciationExcess BLM Tx vs Bk Deprec $2,207,080 0 0 0 0 0 56 Accelerated DepreciationExcess Tx Rtn vs BLM Tx Dep ($8,674,049) 0 0 0 0 848,202 57 Removal Costs Net of Salvage $0 0 0 0 0 0 58 Deferred Revenue $0 0 0 0 0 0 59 FAS106 & 112 Post Retirement Benefits $0 0 0 0 0 0 60 Environmental Reserve $0 0 0 0 0 0 61 Injuries & Damages $0 0 0 0 0 0 62 Net Operating Loss ($18,768,216) 524,880 (646,067) (9,665) 0 0 63 Excludable Foreign Income $0 0 0 0 0 0 64 MT Corporation License Tax 0 0 0 0 0 0 65 Deduct Interest Charges ($11,688,342) 0 0 0 0 0 66 Total Tax Additons / (Deductions) ($40,388,605) $524,880 ($646,067) ($9,665) $0 $848,202 67 Federal Taxable Income $ $ $ $ $ $ 68 Federal Income Tax @ 21% $0 $0 $0 $0 $0 $0 69 Foreign Income Tax $0 0 0 0 0 0 70 Foreign Income Tax Credit $0 0 0 0 0 0 71 NonJurisdictional Items (758,560) 0 0 0 0 0 72 Prior Period Adjustments $758,560 0 0 0 0 0 73 Audit Adjustments $0 0 0 0 0 0 74 Total Federal Income Tax 0 0 0 0 0 0 75 76 77 Montana Corporate License Tax 78 Federal Taxable Income B4 MT Corp Tx Deductn & NOL $ $ $ $ $ $ 79 Add: 80 Other $0 0 0 0 0 0 81 Other State Taxes Paid $0 0 0 0 0 0 82 83 Reduction for Unitary Allocation $0 0 0 0 0 0 84 85 Montana Taxable Income $0 $0 $0 $0 $0 $0 86 Mont. Corp. Lic. Tax @ 6.75% $0 0 0 0 0 0 87 Net Tax Adjustment $0 $0 $0 $0 $0 $0 88 Mont. Corp. License Tax $0 $0 $0 $0 $0 $0 89 Actual 6.75% 0 0 0 0 0 0 90 91 Change in tax rates $0 0 0 0 0 0 92 NonJurisdictional Items $0 0 0 0 0 0 93 Net Tax Adjustment 0 0 0 0 0 0

Docket No. D2018.2.12 Page 74 of 327 GENERAL RATE CASE J K M N O P Q ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY COLSTIP UNIT 4 38 ELECTRIC UTILITY CALCULATIONS 39 Operating Revenues 40 Operating Expenses 41 Subtotal 42 Depreciation & Amortization 43 Taxes other than Income 44 Net Utility Operating Income Before Inc Tax 45 Taxable Additions / (Deductions): 46 Nondeductible Meal Expense 47 Bad Debt Expense Accrual Net of Chargeoffs 48 Penalties 49 Meters 50 Customer Advances for Construction/CIAC 51 Repairs Expense 52 Accrued Incentive Compensation 53 MPSC/MCC Taxes 54 Costs of Refinancing Debt 55 Accelerated DepreciationExcess BLM Tx vs Bk Deprec 56 Accelerated DepreciationExcess Tx Rtn vs BLM Tx Dep 57 Removal Costs Net of Salvage 58 Deferred Revenue 59 FAS106 & 112 Post Retirement Benefits 60 Environmental Reserve 61 Injuries & Damages 62 Net Operating Loss 63 Excludable Foreign Income 64 MT Corporation License Tax 65 Deduct Interest Charges 66 Total Tax Additons / (Deductions) 67 Federal Taxable Income 68 Federal Income Tax @ 21% 69 Foreign Income Tax 70 Foreign Income Tax Credit 71 NonJurisdictional Items 72 Prior Period Adjustments 73 Audit Adjustments 74 Total Federal Income Tax 75 76 77 Montana Corporate License Tax 78 Federal Taxable Income B4 MT Corp Tx Deductn & NOL 79 Add: 80 Other 81 Other State Taxes Paid 82 83 Reduction for Unitary Allocation 84 85 Montana Taxable Income 86 Mont. Corp. Lic. Tax @ 6.75% 87 Net Tax Adjustment 88 Mont. Corp. License Tax 89 Actual 6.75% 90 91 Change in tax rates 92 NonJurisdictional Items 93 Net Tax Adjustment TAXES OTHER WORKING INTEREST TOTAL TEST PERIOD ADJUST TO NONPCCAM AMORTIZATION THAN INCOME CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT ROE FROM DEPRECIATION SUPPLY ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES DOCKET 2008.6.69 ADJUSTMENT ADJUSTMENT $0 $0 $0 $0 $0 (685,850) 76,994,255 $0 $0 $0 0 0 0 0 0 (655,090) 19,987,659 0 0 0 $0 $0 $0 $0 $0 (30,759) 57,006,596 $0 $0 $0 469,667 1,317,869 13,675,077 (414,386) 95,160 (66,451) 4,225,091 $ (469,667) $ (95,160) $ $ $ (1,282,177) 39,106,428 $ $ 414,386 $ 0 0 0 0 0 0 214 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 (4,430,349) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 965,057 0 0 0 0 0 0 0 0 0 2,207,080 0 0 0 0 0 0 525,824 0 1,374,026 (7,300,023) 0 (414,386) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 469,667 95,160 0 (525,824) (1,819,971) (1,911,820) (20,680,036) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1,819,971 1,819,971 (9,868,371) 0 0 0 $469,667 $95,160 $0 $0 $0 $1,282,177 ($39,106,428) $0 ($414,386) $0 $ $ $ $ 0 $ $ 0 $ $ $ $ $0 $0 $0 $0 $0 0 0 $0 $0 $0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 758,560 0 758,560 0 0 0 0 0 0 0 (758,560) 0 (758,560) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 $ $ $ $ 0 $ 0 0 $ $ $ 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 $0 $0 $0 $0 $0 0 0 $0 $0 $0 0 0 0 0 0 0 0 0 0 0 $0 $0 $0 $0 $0 0 0 $0 $0 $0 $0 $0 $0 $0 $0 0 0 $0 $0 $0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

Docket No. D2018.2.12 Page 75 of 327 GENERAL RATE CASE ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY COLSTIP UNIT 4 38 ELECTRIC UTILITY CALCULATIONS 39 Operating Revenues 40 Operating Expenses 41 Subtotal 42 Depreciation & Amortization 43 Taxes other than Income 44 Net Utility Operating Income Before Inc Tax 45 Taxable Additions / (Deductions): 46 Nondeductible Meal Expense 47 Bad Debt Expense Accrual Net of Chargeoffs 48 Penalties 49 Meters 50 Customer Advances for Construction/CIAC 51 Repairs Expense 52 Accrued Incentive Compensation 53 MPSC/MCC Taxes 54 Costs of Refinancing Debt 55 Accelerated DepreciationExcess BLM Tx vs Bk Deprec 56 Accelerated DepreciationExcess Tx Rtn vs BLM Tx Dep 57 Removal Costs Net of Salvage 58 Deferred Revenue 59 FAS106 & 112 Post Retirement Benefits 60 Environmental Reserve 61 Injuries & Damages 62 Net Operating Loss 63 Excludable Foreign Income 64 MT Corporation License Tax 65 Deduct Interest Charges 66 Total Tax Additons / (Deductions) 67 Federal Taxable Income 68 Federal Income Tax @ 21% 69 Foreign Income Tax 70 Foreign Income Tax Credit 71 NonJurisdictional Items 72 Prior Period Adjustments 73 Audit Adjustments 74 Total Federal Income Tax 75 76 77 Montana Corporate License Tax 78 Federal Taxable Income B4 MT Corp Tx Deductn & NOL 79 Add: 80 Other 81 Other State Taxes Paid 82 83 Reduction for Unitary Allocation 84 85 Montana Taxable Income 86 Mont. Corp. Lic. Tax @ 6.75% 87 Net Tax Adjustment 88 Mont. Corp. License Tax 89 Actual 6.75% 90 91 Change in tax rates 92 NonJurisdictional Items 93 Net Tax Adjustment INTERIM ADJUSTMENTS INTERIM INTERIM MONTANA WORKING INTEREST TOTAL TEST PERIOD GENERATION CAPITAL INCOME TAXSYNCHRONIZATION UPDATES & @ PRESENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES $0 $0 $0 $0 $0 $0 0 76,994,255 0 0 0 0 0 0 0 19,987,659 $0 $0 $0 $0 $0 $0 0 57,006,596 (414,386) 13,260,690 0 4,225,091 $ $ $ $ $ $ 414,386 39,520,815 0 0 0 0 0 0 0 214 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 (4,430,349) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 965,057 0 0 0 0 0 0 0 2,207,080 0 0 0 0 0 0 (414,386) (7,714,410) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 (100,464) (100,464) (20,780,500) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 100,464 100,464 (9,767,907) $0 $0 $0 $0 $0 $0 ($414,386) ($39,520,815) $ $ $ $ $ $ $ $ $0 $0 $0 $0 $0 $0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 $ $ $ $ $ $ 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 $0 $0 $0 $0 $0 $0 0 0 0 0 0 0 0 0 0 0 $0 $0 $0 $0 $0 $0 0 0 $0 $0 $0 $0 $0 $0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

Docket No. D2018.2.12 Page 76 of 327 GENERAL RATE CASE A B C D E F G H I REVENUE SALES & ACTUAL TWELVE MONTHS ENDED 2017 INTERIM REMOVE REMOVE FIXED & REVENUE ADMINISTRATIVE CORPORATE NORTHWESTERN ENERGY COLSTRIP UNIT 4 DEFERRED VARIABLE COLSTRIP UNIT 4 RELATED & GENERAL LABOR ALLOCATION DEPRECIATION COLSTIP UNIT 4 REVENUES ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT COMPUTATION OF REQUIRED RETURN AND REVENUE INCREASE 1 Electric Utility Rate Base $303,642,197 $0 $0 $0 $0 $0 2 Rate of Return 8.25% 8.25% 8.25% 8.25% 8.25% 8.25% 3 4 5 Net Operating Income 25,050,481 0 0 0 0 0 6 7 Net Operating Income for the Year 8 Ended 12/31/17 Adjusted for Known Changes 29,581,909 (386,666) 475,941 7,120 0 (670,080) 9 10 Required Incremental Increase in Net 11 Operating Income ($4,531,428) $386,666 ($475,941) ($7,120) $0 $670,080 12 13 Add: 14 MPSC Tax (15,053) 1,284 (1,581) (24) 0 2,226 15 Consumer Counsel Tax (2,838) 242 (298) (4) 0 420 16 Incremental Income Taxes (1,619,762) 138,214 (170,125) (2,545) 0 239,521 17 18 Required Revenue Increase ($6,169,081) $526,406 ($647,945) ($9,693) $0 $912,247 19 20 21 MPSC Tax (0.244%) (15,053) 1,284 (1,581) (24) 0 2,226 22 23 Consumer Counsel Tax (0.046%) (2,838) 242 (298) (4) 0 420 24 25 Taxable Income for State Income Tax ($6,151,190) $524,880 ($646,066) ($9,665) $0 $909,601 26 27 State Income Tax (6.75%) (Unitary Factor = 1.00) (415,205) 35,429 (43,609) (652) 0 61,398 28 29 Taxable Income for Federal Income Tax ($5,735,985) $489,451 ($602,457) ($9,013) $0 $848,203 30 31 Reduction of Fed.Inc.TaxDue to MCLT Expense 87,193 (7,440) 9,158 137 0 (12,894) 32 Federal Income Tax Expense (21%) (1,291,750) 110,225 (135,674) (2,030) 0 191,017 33 34 Required Incremental Increase in Net 35 Operating Income ($4,531,428) $386,666 ($475,941) ($7,120) $0 $670,080

Docket No. D2018.2.12 Page 77 of 327 GENERAL RATE CASE J K M N O P Q ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY COLSTIP UNIT 4 COMPUTATION OF REQUIRED RETURN AND REVENUE INCREASE 1 Electric Utility Rate Base 2 Rate of Return 3 4 5 Net Operating Income 6 7 Net Operating Income for the Year 8 Ended 12/31/17 Adjusted for Known Changes 9 10 Required Incremental Increase in Net 11 Operating Income 12 13 Add: 14 MPSC Tax 15 Consumer Counsel Tax 16 Incremental Income Taxes 17 18 Required Revenue Increase 19 20 21 MPSC Tax (0.244%) 22 23 Consumer Counsel Tax (0.046%) 24 25 Taxable Income for State Income Tax 26 27 State Income Tax (6.75%) (Unitary Factor = 1.00) 28 29 Taxable Income for Federal Income Tax 30 31 Reduction of Fed.Inc.TaxDue to MCLT Expense 32 Federal Income Tax Expense (21%) 33 34 Required Incremental Increase in Net 35 Operating Income TAXES OTHER WORKING INTEREST TOTAL TEST PERIOD ADJUST TO NONPCCAM AMORTIZATION THAN INCOME CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT ROE FROM DEPRECIATION SUPPLY ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES DOCKET 2008.6.69 ADJUSTMENT ADJUSTMENT $0 $0 $367,955 ($28,677) $0 $339,277 $303,981,475 $303,981,475 $207,193 $0 8.25% 8.25% 8.25% 8.25% 8.25% 8.25% 8.25% 0.00% 8.25% 8.25% 0 0 30,356 (2,366) 0 27,990 25,078,472 0 17,093 0 (345,992) (70,102) 0 4,340,701 (479,244) 2,871,678 32,453,587 0 327,365 0 $345,992 $70,102 $30,356 ($4,343,067) $479,244 ($2,843,688) ($7,375,116) $0 ($310,272) $0 1,149 233 101 (14,427) 1,592 (9,447) (24,500) 0 (1,031) 0 217 44 19 (2,720) 300 (1,780) (4,618) 0 (194) 0 123,676 25,058 10,850 (1,552,432) 171,306 (1,016,477) (2,636,239) 0 (110,907) 0 $471,034 $95,437 $41,326 ($5,912,646) $652,442 ($3,871,392) ($10,040,473) $0 ($422,404) $0 1,149 233 101 (14,427) 1,592 (9,447) (24,500) 0 (1,031) 0 217 44 19 (2,720) 300 (1,780) (4,618) 0 (194) 0 $469,668 $95,160 $41,206 ($5,895,499) $650,550 (3,860,165) (10,011,355) $0 ($421,179) $0 31,703 6,423 2,781 (397,946) 43,912 (260,561) (675,766) 0 (28,430) 0 $437,965 $88,737 $38,425 ($5,497,553) $606,638 ($3,599,604) ($9,335,589) $0 ($392,749) $0 (6,658) (1,349) (584) 83,569 (9,222) 54,717 141,910 0 5,970 0 98,631 19,984 8,653 (1,238,055) 136,616 (810,633) (2,102,383) 0 (88,447) 0 $345,992 $70,102 $30,356 ($4,343,067) $479,244 ($2,843,688) ($7,375,116) $0 ($310,272) $0

Docket No. D2018.2.12 Page 78 of 327 GENERAL RATE CASE ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY COLSTIP UNIT 4 COMPUTATION OF REQUIRED RETURN AND REVENUE INCREASE 1 Electric Utility Rate Base 2 Rate of Return 3 4 5 Net Operating Income 6 7 Net Operating Income for the Year 8 Ended 12/31/17 Adjusted for Known Changes 9 10 Required Incremental Increase in Net 11 Operating Income 12 13 Add: 14 MPSC Tax 15 Consumer Counsel Tax 16 Incremental Income Taxes 17 18 Required Revenue Increase 19 20 21 MPSC Tax (0.244%) 22 23 Consumer Counsel Tax (0.046%) 24 25 Taxable Income for State Income Tax 26 27 State Income Tax (6.75%) (Unitary Factor = 1.00) 28 29 Taxable Income for Federal Income Tax 30 31 Reduction of Fed.Inc.TaxDue to MCLT Expense 32 Federal Income Tax Expense (21%) 33 34 Required Incremental Increase in Net 35 Operating Income INTERIM ADJUSTMENTS INTERIM INTERIM MONTANA WORKING INTEREST TOTAL TEST PERIOD GENERATION CAPITAL INCOME TAXSYNCHRONIZATION UPDATES & @ PRESENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES $0 $0 $0 $9,044 ($3,646,726) $0 ($3,430,489) $300,550,985 8.25% 8.25% 8.25% 8.25% 8.25% 8.25% 8.25% 8.25% 0 0 0 746 (300,855) 0 (283,015) 24,795,456 0 0 0 0 80,380 (26,455) 381,290 32,834,877 $0 $0 $0 $746 ($381,235) $26,455 ($664,306) ($8,039,422) 0 0 0 2 (1,266) 88 (2,207) (26,707) 0 0 0 0 (239) 17 (416) (5,034) 0 0 0 266 (136,273) 9,456 (237,458) (2,873,697) $0 $0 $0 $1,014 ($519,013) $36,016 ($904,387) ($10,944,860) 0 0 0 2 (1,266) 88 (2,207) (26,707) 0 0 0 0 (239) 17 (416) (5,034) $0 $0 $0 $1,012 ($517,508) $35,911 (901,764) (10,913,119) 0 0 0 68 (34,932) 2,424 (60,870) (736,636) $0 $0 $0 $944 ($482,576) $33,487 (840,894) (10,176,483) 0 0 0 (14) 7,336 (509) 12,783 154,693 0 0 0 212 (108,677) 7,541 (189,371) (2,291,754) $0 $0 $0 $746 ($381,235) $26,455 ($664,306) ($8,039,422)

Docket No. D2018.2.12 Page 79 of 327 GENERAL RATE CASE A B C D E F G H I REVENUE SALES & ACTUAL TWELVE MONTHS ENDED 2017 INTERIM REMOVE REMOVE & REVENUE ADMINISTRATIVE CORPORATE NORTHWESTERN ENERGY DGGS DEFERRED VARIABLE DGGS FIXED DGGS RELATED & GENERAL LABOR ALLOCATION DEPRECIATION DAVE GATES GENERATING STATION REVENUES ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT 1 Operating Revenues $33,803,531 ($573,649) $3,757,474 $30,619,707 ($79,922) $0 $0 $0 $0 2 3 Operating Expenses 11,303,820 (573,649) 4,262,915 7,614,555 (263,188) (158,247) 4 Book Depreciation 6,250,133 6,250,133 918,008 5 Amort. of Electric Plant & Acq Adjmt 122,829 122,829 74,720 6 Amort.Misc Items (399,207) (164,182) (235,025) 7 Taxes other than Income 4,648,603 4,648,603 (14,689) (11,251) 8 9 Subtotal Expenses $21,926,177 ($573,649) $4,098,733 $18,401,094 ($14,689) ($263,188) ($169,498) $0 $992,728 10 Net Utility Operating Income Before Inc Tax $11,877,354 $0 ($341,259) $12,218,613 ($65,233) $263,188 $169,498 $0 ($992,728) 11 12 Amortization of Excess Deferred TaxARAM $0 0 0 0 0 0 13 Amortization of Excess Deferred TaxUnprotected Rate Base $0 0 0 0 0 0 14 Amortization of Excess Deferred TaxUnprotected NonRate Base $0 0 0 0 0 0 15 16 Deferred Income Taxes: 17 Injuries & Damages $4,858 0 0 0 0 0 18 Miscellaneous $0 0 0 0 0 0 19 Accrued Incentive Compensation $5,241 0 0 0 0 0 20 Accelerated Depreciation ($227,974) 0 0 0 0 (208,473) 21 Net Operating Loss ($525,610) (17,177) 69,304 44,633 0 0 22 MPSC/MCC Taxes $0 0 0 0 0 0 23 Deferred Revenue $46,090 0 0 0 0 0 24 Customer Advances for Construction/CIAC ($7,180) 0 0 0 0 0 25 FAS106 & 112 Post Retirement Benefits $30,400 0 0 0 0 0 26 Costs of Refinancing Debt ($1,788) 0 0 0 0 0 27 Environmental Reserve ($5,836) 0 0 0 0 0 28 NonJurisdictional Items $1,487,293 0 0 0 0 0 29 SubtotalDeferred Income Tax 805,494 (17,177) 69,304 44,633 0 (208,473) 30 31 Income TaxesFederal 0 0 0 0 0 0 32 Income TaxesCorporation License Tax 0 0 0 0 0 0 33 Income TaxesForeign Taxes 0 0 0 0 0 0 34 SubtotalCurrent Income Tax 0 0 0 0 0 0 35 Net Utility Operating Income $11,413,119 ($48,056) $193,884 $124,865 $0 ($784,255) 36 Rate Base $170,995,420 $0 $0 $0 $0 $0 37 Return on Rate Base 6.67%

Docket No. D2018.2.12 Page 80 of 327 GENERAL RATE CASE J M N O P Q ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY DAVE GATES GENERATING STATION 1 Operating Revenues 2 3 Operating Expenses 4 Book Depreciation 5 Amort. of Electric Plant & Acq Adjmt 6 Amort.Misc Items 7 Taxes other than Income 8 9 Subtotal Expenses 10 Net Utility Operating Income Before Inc Tax 11 12 Amortization of Excess Deferred TaxARAM 13 Amortization of Excess Deferred TaxUnprotected Rate Base 14 Amortization of Excess Deferred TaxUnprotected NonRate 15 16 Deferred Income Taxes: 17 Injuries & Damages 18 Miscellaneous 19 Accrued Incentive Compensation 20 Accelerated Depreciation 21 Net Operating Loss 22 MPSC/MCC Taxes 23 Deferred Revenue 24 Customer Advances for Construction/CIAC 25 FAS106 & 112 Post Retirement Benefits 26 Costs of Refinancing Debt 27 Environmental Reserve 28 NonJurisdictional Items 29 SubtotalDeferred Income Tax 30 31 Income TaxesFederal 32 Income TaxesCorporation License Tax 33 Income TaxesForeign Taxes 34 SubtotalCurrent Income Tax 35 Net Utility Operating Income 36 Rate Base 37 Return on Rate Base TAXES OTHER WORKING INTEREST TOTAL TEST PERIOD AMORTIZATION THAN INCOME MAINTENANCE CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 (79,922) 30,539,785 (973,534) (1,394,970) 6,219,585 918,008 7,168,141 74,720 197,549 156,556 156,556 (78,470) 16,302 (9,638) 4,638,965 $156,556 $16,302 $0 ($973,534) $0 $0 $0 $0 $0 $0 (255,324) 18,145,770 ($156,556) ($16,302) $0 $973,534 $0 $0 $0 $0 $0 $0 175,402 12,394,015 0 0 0 0 0 0 0 0 (213,986) 0 (213,986) (213,986) 0 0 0 0 0 0 0 0 80,754 0 80,754 80,754 0 0 0 0 0 0 0 0 (35,788) 0 (35,788) (35,788) 0 0 0 0 0 0 0 0 (1,610) 0 (1,610) 3,248 0 0 0 0 0 0 0 0 0 (1,737) 0 (1,737) 3,504 0 0 0 0 0 0 0 0 (141,174) 0 (349,647) (577,621) (41,225) (4,293) 0 256,356 0 0 0 0 465,582 1,563,584 2,336,764 1,811,154 0 0 0 0 0 0 0 0 0 (15,277) 0 (15,277) 30,813 0 0 0 0 0 0 0 0 2,380 0 2,380 (4,800) 0 0 0 0 0 0 0 0 (10,076) 0 (10,076) 20,324 0 0 0 0 0 0 0 0 593 0 593 (1,195) 0 0 0 0 0 0 0 0 1,934 0 1,934 (3,902) 0 0 0 0 0 0 0 0 (1,487,293) 0 (1,487,293) 0 (41,225) (4,293) 0 256,356 0 0 0 0 (1,355,699) 1,563,584 307,010 1,112,504 0 0 0 0 ($115,331) ($12,009) $0 $717,178 $0 $0 $0 $0 $1,355,699 ($1,563,584) ($131,608) $11,281,511 $0 $0 $0 $0 $0 $0 $0 $239,691 ($794,240) $0 (554,549) 170,440,871 6.62%

Docket No. D2018.2.12 Page 81 of 327 GENERAL RATE CASE ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY DAVE GATES GENERATING STATION 1 Operating Revenues 2 3 Operating Expenses 4 Book Depreciation 5 Amort. of Electric Plant & Acq Adjmt 6 Amort.Misc Items 7 Taxes other than Income 8 9 Subtotal Expenses 10 Net Utility Operating Income Before Inc Tax 11 12 Amortization of Excess Deferred TaxARAM 13 Amortization of Excess Deferred TaxUnprotected Rate Base 14 Amortization of Excess Deferred TaxUnprotected NonRate 15 16 Deferred Income Taxes: 17 Injuries & Damages 18 Miscellaneous 19 Accrued Incentive Compensation 20 Accelerated Depreciation 21 Net Operating Loss 22 MPSC/MCC Taxes 23 Deferred Revenue 24 Customer Advances for Construction/CIAC 25 FAS106 & 112 Post Retirement Benefits 26 Costs of Refinancing Debt 27 Environmental Reserve 28 NonJurisdictional Items 29 SubtotalDeferred Income Tax 30 31 Income TaxesFederal 32 Income TaxesCorporation License Tax 33 Income TaxesForeign Taxes 34 SubtotalCurrent Income Tax 35 Net Utility Operating Income 36 Rate Base 37 Return on Rate Base INTERIM ADJUSTMENTS INTERIM INTERIM ADJUST TO NONPCCAM MONTANA WORKING INTEREST TOTAL TEST PERIOD ROE FROM DEPRECIATION SUPPLY GENERATION CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT DOCKET 2008.8.95ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES $0 $0 $0 $0 $0 $0 $0 $0 $0 0 30,539,785 0 6,219,585 (1,087,765) (1,087,765) 6,080,376 0 197,549 0 (78,470) 0 4,638,965 $0 ($1,087,765) $0 $0 $0 $0 $0 $0 $0 (1,087,765) 17,058,005 $0 $1,087,765 $0 $0 $0 $0 $0 $0 $0 1,087,765 13,481,780 0 0 0 0 0 0 0 0 0 0 (213,986) 0 0 0 0 0 0 0 (80,754) 0 (80,754) 0 0 0 0 0 0 0 0 35,788 0 35,788 0 0 0 0 0 0 0 0 0 0 0 3,248 0 0 0 0 0 0 0 0 0 0 3,504 0 228,431 0 0 0 0 0 0 0 228,431 (349,190) 0 0 0 0 0 0 0 0 (395,912) (395,912) 1,415,242 0 0 0 0 0 0 0 0 0 0 30,813 0 0 0 0 0 0 0 0 0 0 (4,800) 0 0 0 0 0 0 0 0 0 0 20,324 0 0 0 0 0 0 0 0 0 0 (1,195) 0 0 0 0 0 0 0 0 0 0 (3,902) 0 228,431 0 0 0 0 0 (44,966) (395,912) (212,447) 900,057 $0 $859,334 $0 $0 $0 $0 $0 $44,966 $395,912 $1,300,213 $12,581,724 $0 $543,883 $0 $0 $0 $0 ($3,460) $537,206 $0 1,077,629 171,518,499 7.34%

Docket No. D2018.2.12 Page 82 of 327 GENERAL RATE CASE A B C D E F G H I REVENUE SALES & ACTUAL TWELVE MONTHS ENDED 2017 INTERIM REMOVE REMOVE & REVENUE ADMINISTRATIVE CORPORATE NORTHWESTERN ENERGY DGGS DEFERRED VARIABLE DGGS FIXED DGGS RELATED & GENERAL LABOR ALLOCATION DEPRECIATION DAVE GATES GENERATING STATION REVENUES ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT 38 ELECTRIC UTILITY CALCULATIONS 39 Operating Revenues $30,619,707 ($79,922) $0 $0 $0 $0 40 Operating Expenses 7,614,555 0 (263,188) (158,247) 0 0 41 Subtotal $23,005,152 ($79,922) $263,188 $158,247 $0 $0 42 Depreciation & Amortization 6,137,936 992,728 43 Taxes other than Income 4,648,603 (14,689) (11,251) 44 Net Utility Operating Income Before Inc Tax $ 12,218,613 $ (65,233) $ 263,188 $ 169,498 $ $ (992,728) 45 Taxable Additions / (Deductions): 46 Nondeductible Meal Expense $10,563 0 0 0 0 0 47 Bad Debt Expense Accrual Net of Chargeoffs $0 0 0 0 0 0 48 Penalties $0 0 0 0 0 0 49 Meters $0 0 0 0 0 0 50 Customer Advances for Construction/CIAC $18,228 0 0 0 0 0 51 Repairs Expense ($4,896,566) 0 0 0 0 0 52 Accrued Incentive Compensation ($13,306) 0 0 0 0 0 53 MPSC/MCC Taxes $0 0 0 0 0 0 54 Costs of Refinancing Debt $4,540 0 0 0 0 0 55 Accelerated DepreciationExcess BLM Tx vs Bk Deprec $565,474 0 0 0 0 0 56 Accelerated DepreciationExcess Tx Rtn vs BLM Tx Dep $651,354 0 0 0 0 992,728 57 Removal Costs Net of Salvage ($70,294) 0 0 0 0 0 58 Deferred Revenue ($117,016) 0 0 0 0 0 59 FAS106 & 112 Post Retirement Benefits ($77,182) 0 0 0 0 0 60 Environmental Reserve $14,817 0 0 0 0 0 61 Injuries & Damages ($12,335) 0 0 0 0 0 62 Net Operating Loss $1,334,458 65,233 (263,188) (169,498) 0 0 63 Excludable Foreign Income $0 0 0 0 0 0 64 MT Corporation License Tax 0 0 0 0 0 0 65 Deduct Interest Charges ($9,631,350) 0 0 0 0 0 66 Total Tax Additons / (Deductions) ($12,218,613) $65,233 ($263,188) ($169,498) $0 $992,728 67 Federal Taxable Income $ $ $ $ $ $ 68 Federal Income Tax @ 21% $0 $0 $0 $0 $0 $0 69 Foreign Income Tax $0 0 0 0 0 0 70 Foreign Income Tax Credit $0 0 0 0 0 0 71 NonJurisdictional Items (1,487,293) 0 0 0 0 0 72 Prior Period Adjustments $1,487,293 0 0 0 0 0 73 Audit Adjustments $0 0 0 0 0 0 74 Total Federal Income Tax 0 0 0 0 0 0 75 76 77 Montana Corporate License Tax 78 Federal Taxable Income B4 MT Corp Tx Deductn & NOL $ $ $ $ $ $ 79 Add: 80 Other $0 0 0 0 0 0 81 Other State Taxes Paid $0 0 0 0 0 0 82 83 Reduction for Unitary Allocation $0 0 0 0 0 0 84 85 Montana Taxable Income $0 $0 $0 $0 $0 $0 86 Mont. Corp. Lic. Tax @ 6.75% $0 0 0 0 0 0 87 Net Tax Adjustment $0 $0 $0 $0 $0 $0 88 Mont. Corp. License Tax $0 $0 $0 $0 $0 $0 89 Actual 6.75% 0 0 0 0 0 0 90 91 Change in tax rates $0 0 0 0 0 0 92 NonJurisdictional Items $0 0 0 0 0 0 93 Net Tax Adjustment 0 0 0 0 0 0

Docket No. D2018.2.12 Page 83 of 327 GENERAL RATE CASE J M N O P Q ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY DAVE GATES GENERATING STATION 38 ELECTRIC UTILITY CALCULATIONS 39 Operating Revenues 40 Operating Expenses 41 Subtotal 42 Depreciation & Amortization 43 Taxes other than Income 44 Net Utility Operating Income Before Inc Tax 45 Taxable Additions / (Deductions): 46 Nondeductible Meal Expense 47 Bad Debt Expense Accrual Net of Chargeoffs 48 Penalties 49 Meters 50 Customer Advances for Construction/CIAC 51 Repairs Expense 52 Accrued Incentive Compensation 53 MPSC/MCC Taxes 54 Costs of Refinancing Debt 55 Accelerated DepreciationExcess BLM Tx vs Bk Deprec 56 Accelerated DepreciationExcess Tx Rtn vs BLM Tx Dep 57 Removal Costs Net of Salvage 58 Deferred Revenue 59 FAS106 & 112 Post Retirement Benefits 60 Environmental Reserve 61 Injuries & Damages 62 Net Operating Loss 63 Excludable Foreign Income 64 MT Corporation License Tax 65 Deduct Interest Charges 66 Total Tax Additons / (Deductions) 67 Federal Taxable Income 68 Federal Income Tax @ 21% 69 Foreign Income Tax 70 Foreign Income Tax Credit 71 NonJurisdictional Items 72 Prior Period Adjustments 73 Audit Adjustments 74 Total Federal Income Tax 75 76 77 Montana Corporate License Tax 78 Federal Taxable Income B4 MT Corp Tx Deductn & NOL 79 Add: 80 Other 81 Other State Taxes Paid 82 83 Reduction for Unitary Allocation 84 85 Montana Taxable Income 86 Mont. Corp. Lic. Tax @ 6.75% 87 Net Tax Adjustment 88 Mont. Corp. License Tax 89 Actual 6.75% 90 91 Change in tax rates 92 NonJurisdictional Items 93 Net Tax Adjustment TAXES OTHER WORKING INTEREST TOTAL TEST PERIOD AMORTIZATION THAN INCOME MAINTENANCE CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 (79,922) 30,539,785 0 0 0 (973,534) 0 0 0 0 0 0 (1,394,970) 6,219,585 $0 $0 $0 $973,534 $0 $0 $0 $0 $0 $0 1,315,048 24,320,200 156,556 1,149,284 7,287,220 16,302 (9,638) 4,638,965 $ (156,556) $ (16,302) $ $ 973,534 $ $ $ $ $ $ 175,402 12,394,015 10,563 0 0 0 18,228 (4,896,566) (13,306) 0 4,540 565,474 0 0 0 0 0 0 0 0 1,106,498 0 2,099,226 2,750,580 (70,294) (117,016) (77,182) 14,817 (12,335) 156,556 16,302 0 (973,534) 0 0 0 0 (1,106,498) (5,937,849) (8,212,477) (6,878,019) 0 0 0 0 0 0 0 0 0 0 0 5,937,849 5,937,849 (3,693,501) $156,556 $16,302 $0 ($973,534) $0 $0 $0 $0 ($0) $0 ($175,402) ($12,394,015) $ $ $ $ $ $ $ $ $ (0) $ $ (0) $ $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 0 0 0 0 0 0 0 0 0 0 0 0 1,487,293 0 1,487,293 0 0 0 0 0 0 0 0 0 (1,487,293) 0 (1,487,293) 0 0 0 $ $ $ $ $ $ $ $ $ (0) $ (0) (0) 0 0 0 $0 $0 $0 $0 $0 $0 $0 $0 ($0) $0 (0) (0) 0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 0 0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 0 0 0 0 0 0

Docket No. D2018.2.12 Page 84 of 327 GENERAL RATE CASE ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY DAVE GATES GENERATING STATION 38 ELECTRIC UTILITY CALCULATIONS 39 Operating Revenues 40 Operating Expenses 41 Subtotal 42 Depreciation & Amortization 43 Taxes other than Income 44 Net Utility Operating Income Before Inc Tax 45 Taxable Additions / (Deductions): 46 Nondeductible Meal Expense 47 Bad Debt Expense Accrual Net of Chargeoffs 48 Penalties 49 Meters 50 Customer Advances for Construction/CIAC 51 Repairs Expense 52 Accrued Incentive Compensation 53 MPSC/MCC Taxes 54 Costs of Refinancing Debt 55 Accelerated DepreciationExcess BLM Tx vs Bk Deprec 56 Accelerated DepreciationExcess Tx Rtn vs BLM Tx Dep 57 Removal Costs Net of Salvage 58 Deferred Revenue 59 FAS106 & 112 Post Retirement Benefits 60 Environmental Reserve 61 Injuries & Damages 62 Net Operating Loss 63 Excludable Foreign Income 64 MT Corporation License Tax 65 Deduct Interest Charges 66 Total Tax Additons / (Deductions) 67 Federal Taxable Income 68 Federal Income Tax @ 21% 69 Foreign Income Tax 70 Foreign Income Tax Credit 71 NonJurisdictional Items 72 Prior Period Adjustments 73 Audit Adjustments 74 Total Federal Income Tax 75 76 77 Montana Corporate License Tax 78 Federal Taxable Income B4 MT Corp Tx Deductn & NOL 79 Add: 80 Other 81 Other State Taxes Paid 82 83 Reduction for Unitary Allocation 84 85 Montana Taxable Income 86 Mont. Corp. Lic. Tax @ 6.75% 87 Net Tax Adjustment 88 Mont. Corp. License Tax 89 Actual 6.75% 90 91 Change in tax rates 92 NonJurisdictional Items 93 Net Tax Adjustment INTERIM ADJUSTMENTS INTERIM INTERIM ADJUST TO NONPCCAM MONTANA WORKING INTEREST TOTAL TEST PERIOD ROE FROM DEPRECIATION SUPPLY GENERATION CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT DOCKET 2008.8.95ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES $0 $0 $0 $0 $0 $0 $0 $0 $0 0 30,539,785 0 0 0 0 0 0 0 0 0 0 6,219,585 $0 $0 $0 $0 $0 $0 $0 $0 $0 0 24,320,200 (1,087,765) (1,087,765) 6,199,455 0 4,638,965 $ $ 1,087,765 $ $ $ $ $ $ $ 1,087,765 13,481,780 0 0 0 0 0 0 0 0 0 0 10,563 0 0 0 0 0 0 0 0 0 0 18,228 0 0 0 0 0 0 0 0 0 0 (4,896,566) 0 0 0 0 0 0 0 0 0 0 (13,306) 0 0 0 0 0 0 0 0 0 0 4,540 0 0 0 0 0 0 0 0 0 0 565,474 0 (1,087,765) 0 0 0 0 0 0 0 (1,087,765) 1,662,815 0 0 0 0 0 0 0 0 0 0 (70,294) 0 0 0 0 0 0 0 0 0 0 (117,016) 0 0 0 0 0 0 0 0 0 0 (77,182) 0 0 0 0 0 0 0 0 0 0 14,817 0 0 0 0 0 0 0 0 0 0 (12,335) 0 0 0 0 0 0 0 0 1,503,510 1,503,510 (5,374,509) 0 0 0 0 0 0 0 0 (1,503,510) (1,503,510) (5,197,011) $0 ($1,087,765) $0 $0 $0 $0 $0 $0 $0 ($1,087,765) ($13,481,780) $ $ $ $ $ $ $ $ $ $ $ $0 $0 $0 $0 $0 $0 $0 $0 $0 0 0 $ $ $ $ $ $ $ $ $ 0 (0) $0 $0 $0 $0 $0 $0 $0 $0 $0 0 (0) $0 $0 $0 $0 $0 $0 $0 $0 $0 0 0 $0 $0 $0 $0 $0 $0 $0 $0 $0 0 0

Docket No. D2018.2.12 Page 85 of 327 GENERAL RATE CASE A B C D E F G H I REVENUE SALES & ACTUAL TWELVE MONTHS ENDED 2017 INTERIM REMOVE REMOVE & REVENUE ADMINISTRATIVE CORPORATE NORTHWESTERN ENERGY DGGS DEFERRED VARIABLE DGGS FIXED DGGS RELATED & GENERAL LABOR ALLOCATION DEPRECIATION DAVE GATES GENERATING STATION REVENUES ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT COMPUTATION OF REQUIRED RETURN AND REVENUE INCREASE 1 Electric Utility Rate Base $170,995,420 $0 $0 $0 $0 $0 2 Rate of Return 7.42% 7.42% 7.42% 7.42% 7.42% 7.42% 3 4 5 Net Operating Income 12,687,860 0 0 0 0 0 6 7 Net Operating Income for the Year 8 Ended 12/31/17 Adjusted for Known Changes 11,413,119 (48,056) 193,884 124,865 0 (784,255) 9 10 Required Incremental Increase in Net 11 Operating Income $1,274,741 $48,056 ($193,884) ($124,865) $0 $784,255 12 13 Add: 14 MPSC Tax 4,234 160 (644) (415) 0 2,605 15 Consumer Counsel Tax 798 30 (121) (78) 0 491 16 Incremental Income Taxes 455,657 17,177 (69,304) (44,633) 0 280,333 17 18 Required Revenue Increase $1,735,430 $65,423 ($263,953) ($169,991) $0 $1,067,684 19 20 21 MPSC Tax (0.244%) 4,234 160 (644) (415) 0 2,605 22 23 Consumer Counsel Tax (0.046%) 798 30 (121) (78) 0 491 24 25 Taxable Income for State Income Tax $1,730,398 $65,233 ($263,188) ($169,498) $0 $1,064,588 26 27 State Income Tax (6.75%) (Unitary Factor = 1.00) 116,802 4,403 (17,765) (11,441) 0 71,860 28 29 Taxable Income for Federal Income Tax $1,613,596 $60,830 ($245,423) ($158,057) $0 $992,728 30 31 Reduction of Fed.Inc.TaxDue to MCLT Expense (24,528) (925) 3,731 2,403 0 (15,091) 32 Federal Income Tax Expense (21%) 363,383 13,699 (55,270) (35,595) 0 223,564 33 34 Required Incremental Increase in Net 35 Operating Income $1,274,741 $48,056 ($193,884) ($124,865) $0 $784,255

Docket No. D2018.2.12 Page 86 of 327 GENERAL RATE CASE J M N O P Q ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY DAVE GATES GENERATING STATION COMPUTATION OF REQUIRED RETURN AND REVENUE INCREASE 1 Electric Utility Rate Base 2 Rate of Return 3 4 5 Net Operating Income 6 7 Net Operating Income for the Year 8 Ended 12/31/17 Adjusted for Known Changes 9 10 Required Incremental Increase in Net 11 Operating Income 12 13 Add: 14 MPSC Tax 15 Consumer Counsel Tax 16 Incremental Income Taxes 17 18 Required Revenue Increase 19 20 21 MPSC Tax (0.244%) 22 23 Consumer Counsel Tax (0.046%) 24 25 Taxable Income for State Income Tax 26 27 State Income Tax (6.75%) (Unitary Factor = 1.00) 28 29 Taxable Income for Federal Income Tax 30 31 Reduction of Fed.Inc.TaxDue to MCLT Expense 32 Federal Income Tax Expense (21%) 33 34 Required Incremental Increase in Net 35 Operating Income TAXES OTHER WORKING INTEREST TOTAL TEST PERIOD AMORTIZATION THAN INCOME MAINTENANCE CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES $0 $0 $0 $0 $0 $0 $0 $239,691 ($794,240) $0 ($554,549) $170,440,871 7.42% 7.42% 7.42% 7.42% 7.42% 7.42% 7.42% 7.42% 7.42% 7.42% 7.42% 7.42% 0 0 0 0 0 0 0 17,785 (58,933) 0 (41,148) 12,646,713 (115,331) (12,009) 0 717,178 0 0 0 0 1,355,699 (1,563,584) (131,608) 11,281,511 $115,331 $12,009 $0 ($717,178) $0 $0 $0 $17,785 ($1,414,632) $1,563,584 $90,461 $1,365,202 383 40 0 (2,382) 0 0 0 59 (4,699) 5,194 301 4,535 72 8 0 (449) 0 0 0 11 (886) 979 57 855 41,226 4,292 0 (256,356) 0 0 0 6,358 (505,661) 558,904 32,336 487,993 $157,012 $16,349 $0 ($976,365) $0 $0 $0 $24,213 ($1,925,878) $2,128,661 $123,155 $1,858,585 383 40 0 (2,382) 0 0 0 59 (4,699) 5,194 301 4,535 72 8 0 (449) 0 0 0 11 (886) 979 57 855 $156,557 $16,301 $0 ($973,534) $0 $0 $0 $24,143 ($1,920,293) $2,122,488 122,797 1,853,195 10,568 1,100 0 (65,714) 0 0 0 1,630 (129,620) 143,268 8,289 125,091 $145,989 $15,201 $0 ($907,820) $0 $0 $0 $22,513 ($1,790,673) $1,979,220 $114,508 $1,728,104 (2,219) (231) 0 13,800 0 0 0 (342) 27,220 (30,086) (1,740) (26,268) 32,877 3,423 0 (204,442) 0 0 0 5,070 (403,261) 445,722 25,787 389,170 $115,331 $12,009 $0 ($717,178) $0 $0 $0 $17,785 ($1,414,632) $1,563,584 $90,461 $1,365,202

Docket No. D2018.2.12 Page 87 of 327 GENERAL RATE CASE ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY DAVE GATES GENERATING STATION COMPUTATION OF REQUIRED RETURN AND REVENUE INCREASE 1 Electric Utility Rate Base 2 Rate of Return 3 4 5 Net Operating Income 6 7 Net Operating Income for the Year 8 Ended 12/31/17 Adjusted for Known Changes 9 10 Required Incremental Increase in Net 11 Operating Income 12 13 Add: 14 MPSC Tax 15 Consumer Counsel Tax 16 Incremental Income Taxes 17 18 Required Revenue Increase 19 20 21 MPSC Tax (0.244%) 22 23 Consumer Counsel Tax (0.046%) 24 25 Taxable Income for State Income Tax 26 27 State Income Tax (6.75%) (Unitary Factor = 1.00) 28 29 Taxable Income for Federal Income Tax 30 31 Reduction of Fed.Inc.TaxDue to MCLT Expense 32 Federal Income Tax Expense (21%) 33 34 Required Incremental Increase in Net 35 Operating Income INTERIM ADJUSTMENTS INTERIM INTERIM ADJUST TO NONPCCAM MONTANA WORKING INTEREST TOTAL TEST PERIOD ROE FROM DEPRECIATION SUPPLY GENERATION CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT DOCKET 2008.8.95ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES $170,440,871 $543,883 $0 $0 $0 $0 ($3,460) $537,206 $0 $1,077,629 $171,518,499 0.32% 7.10% 7.10% 7.10% 7.10% 7.10% 7.10% 7.10% 7.10% 7.10% 7.10% (545,411) 38,616 0 0 0 0 (246) 38,142 0 76,512 12,177,813 0 859,334 0 0 0 0 0 44,966 395,912 1,300,213 12,581,724 ($545,411) ($820,718) $0 $0 $0 $0 ($246) ($6,824) ($395,912) ($1,769,111) ($403,909) (1,812) (2,726) 0 0 0 0 (1) (23) (1,315) (5,877) (1,342) (342) (514) 0 0 0 0 0 (4) (248) (1,108) (253) (194,958) (293,367) 0 0 0 0 (88) (2,439) (141,519) (632,371) (144,378) ($742,523) ($1,117,325) $0 $0 $0 $0 ($335) ($9,290) ($538,994) ($2,408,467) ($549,882) (1,812) (2,726) 0 0 0 0 (1) (23) (1,315) (5,877) (1,342) (342) (514) 0 0 0 0 0 (4) (248) (1,108) (253) ($740,369) ($1,114,085) $0 $0 $0 $0 ($334) ($9,263) ($537,431) (2,401,482) (548,287) (49,975) (75,201) 0 0 0 0 (23) (625) (36,277) (162,101) (37,010) ($690,394) ($1,038,884) $0 $0 $0 $0 ($311) ($8,638) ($501,154) (2,239,381) (511,277) 10,495 15,792 0 0 0 0 5 131 7,618 34,041 7,773 (155,478) (233,958) 0 0 0 0 (70) (1,945) (112,860) (504,311) (115,141) ($545,411) ($820,718) $0 $0 $0 $0 ($246) ($6,824) ($395,912) ($1,769,111) ($403,909)

Docket No. D2018.2.12 Page 88 of 327 GENERAL RATE CASE A B C D E F H I J REVENUE SALES & ACTUAL TWELVE MONTHS ENDED 2017 INTERIM REMOVE REMOVE & REVENUE ADMINISTRATIVE NORTHWESTERN ENERGY SPION KOP DEFERRED VARIABLE SPION FIXED SPION KOP RELATED & GENERAL LABOR ALLOCATION DEPRECIATION SPION KOP WIND REVENUES ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT 1 Operating Revenues $8,187,091 ($398,554) ($3,098,126) $11,683,771 ($497,720) $0 $0 $0 $0 2 3 Operating Expenses 1,807,419 (398,554) (22,978) 2,228,951 (4,291) 765 4 Book Depreciation 3,298,924 3,298,924 289,007 5 Amort. of Electric Plant & Acq Adjmt 3,216 3,216 5,874 6 Amort.Misc Items 69,589 69,589 7 Taxes other than Income 400,200 400,200 (19,863) 54 8 9 Subtotal Expenses $5,579,348 ($398,554) $46,611 $5,931,291 ($19,863) ($4,291) $819 $0 $294,881 10 Net Utility Operating Income Before Inc Tax $2,607,743 $0 ($3,144,737) $5,752,480 ($477,857) $4,291 ($819) $0 ($294,881) 11 12 Amortization of Excess Deferred TaxARAM $0 0 0 0 0 0 13 Amortization of Excess Deferred TaxUnprotected Rate Base $0 0 0 0 0 0 14 Amortization of Excess Deferred TaxUnprotected NonRate Base $0 0 0 0 0 0 15 16 Deferred Income Taxes: 17 Injuries & Damages $0 0 0 0 0 0 18 Miscellaneous $0 0 0 0 0 0 19 Accrued Incentive Compensation $0 0 0 0 0 0 20 Accelerated Depreciation ($83,770) 0 0 0 0 (61,925) 21 Net Operating Loss $2,042,577 (125,832) 1,130 (216) 0 0 22 MPSC/MCC Taxes $0 0 0 0 0 0 23 Deferred Revenue $0 0 0 0 0 0 24 Customer Advances for Construction/CIAC $0 0 0 0 0 0 25 FAS106 & 112 Post Retirement Benefits $0 0 0 0 0 0 26 Costs of Refinancing Debt $0 0 0 0 0 0 27 Environmental Reserve $0 0 0 0 0 0 28 NonJurisdictional Items ($73,446) 0 0 0 0 0 29 SubtotalDeferred Income Tax 1,885,361 (125,832) 1,130 (216) 0 (61,925) 30 31 Income TaxesFederal (48) 0 0 0 0 0 32 Income TaxesCorporation License Tax 0 0 0 0 0 0 33 Income TaxesForeign Taxes 0 0 0 0 0 0 34 SubtotalCurrent Income Tax (48) 0 0 0 0 0 35 Net Utility Operating Income $3,867,168 ($352,025) $3,161 ($603) $0 ($232,956) 36 Rate Base $57,190,037 $0 $0 $0 $0 $0 37 Return on Rate Base 6.76%

Docket No. D2018.2.12 Page 89 of 327 GENERAL RATE CASE M N O P Q ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY SPION KOP WIND 1 Operating Revenues 2 3 Operating Expenses 4 Book Depreciation 5 Amort. of Electric Plant & Acq Adjmt 6 Amort.Misc Items 7 Taxes other than Income 8 9 Subtotal Expenses 10 Net Utility Operating Income Before Inc Tax 11 12 Amortization of Excess Deferred TaxARAM 13 Amortization of Excess Deferred TaxUnprotected Rate Base 14 Amortization of Excess Deferred TaxUnprotected NonRate Bas 15 16 Deferred Income Taxes: 17 Injuries & Damages 18 Miscellaneous 19 Accrued Incentive Compensation 20 Accelerated Depreciation 21 Net Operating Loss 22 MPSC/MCC Taxes 23 Deferred Revenue 24 Customer Advances for Construction/CIAC 25 FAS106 & 112 Post Retirement Benefits 26 Costs of Refinancing Debt 27 Environmental Reserve 28 NonJurisdictional Items 29 SubtotalDeferred Income Tax 30 31 Income TaxesFederal 32 Income TaxesCorporation License Tax 33 Income TaxesForeign Taxes 34 SubtotalCurrent Income Tax 35 Net Utility Operating Income 36 Rate Base 37 Return on Rate Base TAXES OTHER WORKING INTEREST TOTAL TEST PERIOD AMORTIZATION THAN INCOME CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 (497,720) 11,186,051 (3,526) 2,225,425 289,007 3,587,931 5,874 9,090 0 0 53,567 33,758 433,959 $0 $53,567 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 325,113 6,256,404 $0 ($53,567) $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 (822,833) 4,929,647 (314,504) 0 (314,504) (314,504) 0 0 0 0 (9,702) 0 (9,702) (9,702) 0 0 0 0 0 0 0 0 0 0 0 0 32,891 0 (29,034) (112,804) 0 (14,106) 0 0 0 0 0 0 0 0 0 (676,239) (113,449) (928,712) 1,113,865 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 73,446 0 73,446 0 0 (14,106) 0 0 0 0 0 0 0 0 0 (894,108) (113,449) (1,208,506) 676,855 48 0 48 0 0 0 0 0 0 0 0 0 48 0 48 0 $0 ($39,461) $0 $0 $0 $0 $0 $0 $0 $0 $0 $894,060 $113,449 $385,625 $4,252,793 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $3,907 $314,373 $0 318,280 57,508,317 7.40%

Docket No. D2018.2.12 Page 90 of 327 GENERAL RATE CASE ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY SPION KOP WIND 1 Operating Revenues 2 3 Operating Expenses 4 Book Depreciation 5 Amort. of Electric Plant & Acq Adjmt 6 Amort.Misc Items 7 Taxes other than Income 8 9 Subtotal Expenses 10 Net Utility Operating Income Before Inc Tax 11 12 Amortization of Excess Deferred TaxARAM 13 Amortization of Excess Deferred TaxUnprotected Rate Base 14 Amortization of Excess Deferred TaxUnprotected NonRate Bas 15 16 Deferred Income Taxes: 17 Injuries & Damages 18 Miscellaneous 19 Accrued Incentive Compensation 20 Accelerated Depreciation 21 Net Operating Loss 22 MPSC/MCC Taxes 23 Deferred Revenue 24 Customer Advances for Construction/CIAC 25 FAS106 & 112 Post Retirement Benefits 26 Costs of Refinancing Debt 27 Environmental Reserve 28 NonJurisdictional Items 29 SubtotalDeferred Income Tax 30 31 Income TaxesFederal 32 Income TaxesCorporation License Tax 33 Income TaxesForeign Taxes 34 SubtotalCurrent Income Tax 35 Net Utility Operating Income 36 Rate Base 37 Return on Rate Base INTERIM ADJUSTMENTS INTERIM INTERIM ADJUST TO NONPCCAM MONTANA WORKING INTEREST TOTAL TEST PERIOD ROE FROM DEPRECIATION SUPPLY GENERATION CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT DOCKET 2011.5.41 ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES $0 $0 $0 $0 $0 $0 $0 $0 $0 0 11,186,051 0 2,225,425 (237,110) (237,110) 3,350,821 0 9,090 0 0 0 433,959 $0 ($237,110) $0 $0 $0 $0 $0 $0 $0 (237,110) 6,019,294 $0 $237,110 $0 $0 $0 $0 $0 $0 $0 237,110 5,166,757 0 0 0 0 0 0 0 0 0 0 (314,504) 0 0 0 0 0 0 0 9,702 0 9,702 0 0 49,793 0 0 0 0 0 0 0 49,793 (63,011) 0 0 0 0 0 0 0 0 (3,183) (3,183) 1,110,682 0 49,793 0 0 0 0 0 9,702 (3,183) 56,312 733,167 $0 $187,317 $0 $0 $0 $0 $0 ($9,702) $3,183 $180,798 $4,433,590 $0 $118,555 $0 $0 $0 $0 $2,596 ($929,804) $0 (808,653) 56,699,665 7.82%

Docket No. D2018.2.12 Page 91 of 327 GENERAL RATE CASE A B C D E F H I J REVENUE SALES & ACTUAL TWELVE MONTHS ENDED 2017 INTERIM REMOVE REMOVE & REVENUE ADMINISTRATIVE NORTHWESTERN ENERGY SPION KOP DEFERRED VARIABLE SPION FIXED SPION KOP RELATED & GENERAL LABOR ALLOCATION DEPRECIATION SPION KOP WIND REVENUES ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT 38 ELECTRIC UTILITY CALCULATIONS 39 Operating Revenues $11,683,771 ($497,720) $0 $0 $0 $0 40 Operating Expenses 2,228,951 0 (4,291) 765 0 0 41 Subtotal $9,454,820 ($497,720) $4,291 ($765) $0 $0 42 Depreciation & Amortization 3,302,139 294,881 43 Taxes other than Income 400,200 (19,863) 54 44 Net Utility Operating Income Before Inc Tax $ 5,752,480 $ (477,857) $ 4,291 $ (819) $ $ (294,881) 45 Taxable Additions / (Deductions): 46 Nondeductible Meal Expense $0 0 0 0 0 0 47 Bad Debt Expense Accrual Net of Chargeoffs $0 0 0 0 0 0 48 Penalties $0 0 0 0 0 0 49 Meters $0 0 0 0 0 0 50 Customer Advances for Construction/CIAC $0 0 0 0 0 0 51 Repairs Expense $0 0 0 0 0 0 52 Accrued Incentive Compensation $0 0 0 0 0 0 53 MPSC/MCC Taxes $0 0 0 0 0 0 54 Costs of Refinancing Debt $0 0 0 0 0 0 55 Accelerated DepreciationExcess BLM Tx vs Bk Deprec ($1,500) 0 0 0 0 0 56 Accelerated DepreciationExcess Tx Rtn vs BLM Tx Dep $239,344 0 0 0 0 294,881 57 Removal Costs Net of Salvage $0 0 0 0 0 0 58 Deferred Revenue $0 0 0 0 0 0 59 FAS106 & 112 Post Retirement Benefits $0 0 0 0 0 0 60 Environmental Reserve $0 0 0 0 0 0 61 Injuries & Damages $0 0 0 0 0 0 62 Net Operating Loss ($5,185,850) 477,857 (4,291) 819 0 0 63 Excludable Foreign Income $0 0 0 0 0 0 64 MT Corporation License Tax 0 0 0 0 0 0 65 Deduct Interest Charges ($804,474) 0 0 0 0 0 66 Total Tax Additons / (Deductions) ($5,752,480) $477,857 ($4,291) $819 $0 $294,881 67 Federal Taxable Income $ $ $ $ $ $ 68 Federal Income Tax @ 21% $0 $0 $0 $0 $0 $0 69 Foreign Income Tax $0 0 0 0 0 0 70 Foreign Income Tax Credit $0 0 0 0 0 0 71 NonJurisdictional Items 73,446 0 0 0 0 0 72 Prior Period Adjustments ($73,494) 0 0 0 0 0 73 Audit Adjustments $0 0 0 0 0 0 74 Total Federal Income Tax (48) 0 0 0 0 0 75 76 77 Montana Corporate License Tax 78 Federal Taxable Income B4 MT Corp Tx Deductn & NOL $ $ $ $ $ $ 79 Add: 80 Other $0 0 0 0 0 0 81 Other State Taxes Paid $0 0 0 0 0 0 82 83 Reduction for Unitary Allocation $0 0 0 0 0 0 84 85 Montana Taxable Income $0 $0 $0 $0 $0 $0 86 Mont. Corp. Lic. Tax @ 6.75% $0 0 0 0 0 0 87 Net Tax Adjustment $0 $0 $0 $0 $0 $0 88 Mont. Corp. License Tax $0 $0 $0 $0 $0 $0 89 Actual 6.75% 0 0 0 0 0 0 90 91 Change in tax rates $0 0 0 0 0 0 92 NonJurisdictional Items $0 0 0 0 0 0 93 Net Tax Adjustment 0 0 0 0 0 0

Docket No. D2018.2.12 Page 92 of 327 GENERAL RATE CASE M N O P Q ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY SPION KOP WIND 38 ELECTRIC UTILITY CALCULATIONS 39 Operating Revenues 40 Operating Expenses 41 Subtotal 42 Depreciation & Amortization 43 Taxes other than Income 44 Net Utility Operating Income Before Inc Tax 45 Taxable Additions / (Deductions): 46 Nondeductible Meal Expense 47 Bad Debt Expense Accrual Net of Chargeoffs 48 Penalties 49 Meters 50 Customer Advances for Construction/CIAC 51 Repairs Expense 52 Accrued Incentive Compensation 53 MPSC/MCC Taxes 54 Costs of Refinancing Debt 55 Accelerated DepreciationExcess BLM Tx vs Bk Deprec 56 Accelerated DepreciationExcess Tx Rtn vs BLM Tx Dep 57 Removal Costs Net of Salvage 58 Deferred Revenue 59 FAS106 & 112 Post Retirement Benefits 60 Environmental Reserve 61 Injuries & Damages 62 Net Operating Loss 63 Excludable Foreign Income 64 MT Corporation License Tax 65 Deduct Interest Charges 66 Total Tax Additons / (Deductions) 67 Federal Taxable Income 68 Federal Income Tax @ 21% 69 Foreign Income Tax 70 Foreign Income Tax Credit 71 NonJurisdictional Items 72 Prior Period Adjustments 73 Audit Adjustments 74 Total Federal Income Tax 75 76 77 Montana Corporate License Tax 78 Federal Taxable Income B4 MT Corp Tx Deductn & NOL 79 Add: 80 Other 81 Other State Taxes Paid 82 83 Reduction for Unitary Allocation 84 85 Montana Taxable Income 86 Mont. Corp. Lic. Tax @ 6.75% 87 Net Tax Adjustment 88 Mont. Corp. License Tax 89 Actual 6.75% 90 91 Change in tax rates 92 NonJurisdictional Items 93 Net Tax Adjustment TAXES OTHER WORKING INTEREST TOTAL TEST PERIOD AMORTIZATION THAN INCOME CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 (497,720) 11,186,051 0 0 (3,526) 2,225,425 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 (494,194) 8,960,626 294,881 3,597,020 53,567 33,758 433,959 $ $ (53,567) $ $ $ $ $ $ $ $ $ $ $ (822,833) 4,929,647 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 (1,500) 2,940 0 297,821 537,165 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 53,567 0 0 0 0 0 0 0 0 0 (2,940) 430,831 955,843 (4,230,007) 0 0 0 0 0 0 0 0 0 (430,831) (430,831) (1,235,305) $0 $53,567 $0 $0 $0 $0 $0 $0 $0 $0 $0 ($0) $0 $822,833 ($4,929,647) $ $ $ $ $ $ $ $ $ $ $ $ (0) $ $ $ $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 0 0 0 0 0 0 0 0 0 0 (73,446) 0 (73,446) 0 73,494 0 73,494 0 0 0 0 0 48 0 48 0 $ $ $ $ $ $ $ $ $ $ $ $ (0) $ (0) (0) 0 0 0 0 0 0 0 0 0 0 0 0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 ($0) $0 (0) (0) 0 0 0 0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 0 0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

Docket No. D2018.2.12 Page 93 of 327 GENERAL RATE CASE ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY SPION KOP WIND 38 ELECTRIC UTILITY CALCULATIONS 39 Operating Revenues 40 Operating Expenses 41 Subtotal 42 Depreciation & Amortization 43 Taxes other than Income 44 Net Utility Operating Income Before Inc Tax 45 Taxable Additions / (Deductions): 46 Nondeductible Meal Expense 47 Bad Debt Expense Accrual Net of Chargeoffs 48 Penalties 49 Meters 50 Customer Advances for Construction/CIAC 51 Repairs Expense 52 Accrued Incentive Compensation 53 MPSC/MCC Taxes 54 Costs of Refinancing Debt 55 Accelerated DepreciationExcess BLM Tx vs Bk Deprec 56 Accelerated DepreciationExcess Tx Rtn vs BLM Tx Dep 57 Removal Costs Net of Salvage 58 Deferred Revenue 59 FAS106 & 112 Post Retirement Benefits 60 Environmental Reserve 61 Injuries & Damages 62 Net Operating Loss 63 Excludable Foreign Income 64 MT Corporation License Tax 65 Deduct Interest Charges 66 Total Tax Additons / (Deductions) 67 Federal Taxable Income 68 Federal Income Tax @ 21% 69 Foreign Income Tax 70 Foreign Income Tax Credit 71 NonJurisdictional Items 72 Prior Period Adjustments 73 Audit Adjustments 74 Total Federal Income Tax 75 76 77 Montana Corporate License Tax 78 Federal Taxable Income B4 MT Corp Tx Deductn & NOL 79 Add: 80 Other 81 Other State Taxes Paid 82 83 Reduction for Unitary Allocation 84 85 Montana Taxable Income 86 Mont. Corp. Lic. Tax @ 6.75% 87 Net Tax Adjustment 88 Mont. Corp. License Tax 89 Actual 6.75% 90 91 Change in tax rates 92 NonJurisdictional Items 93 Net Tax Adjustment INTERIM ADJUSTMENTS INTERIM INTERIM ADJUST TO NONPCCAM MONTANA WORKING INTEREST TOTAL TEST PERIOD ROE FROM DEPRECIATION SUPPLY GENERATION CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT DOCKET 2011.5.41 ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES $0 $0 $0 $0 $0 $0 $0 $0 $0 0 11,186,051 0 0 0 0 0 0 0 0 0 0 2,225,425 $0 $0 $0 $0 $0 $0 $0 $0 $0 0 8,960,626 (237,110) (237,110) 3,359,910 0 433,959 $ $ 237,110 $ $ $ $ $ $ $ 237,110 5,166,757 0 0 0 0 0 0 0 0 0 0 (1,500) 0 (237,110) 0 0 0 0 0 0 0 (237,110) 300,055 0 0 0 0 0 0 0 0 12,088 12,088 (4,217,919) 0 0 0 0 0 0 0 0 (12,088) (12,088) (1,247,393) $0 ($237,110) $0 $0 $0 $0 $0 $0 $0 ($237,110) ($5,166,757) $ $ $ $ $ $ $ $ $ $ $ $0 $0 $0 $0 $0 $0 $0 $0 $0 0 0 $ $ $ $ $ $ $ $ $ 0 (0) $0 $0 $0 $0 $0 $0 $0 $0 $0 0 (0) $0 $0 $0 $0 $0 $0 $0 $0 $0 0 0 $0 $0 $0 $0 $0 $0 $0 $0 $0 0 0

Docket No. D2018.2.12 Page 94 of 327 GENERAL RATE CASE A B C D E F H I J REVENUE SALES & ACTUAL TWELVE MONTHS ENDED 2017 INTERIM REMOVE REMOVE & REVENUE ADMINISTRATIVE NORTHWESTERN ENERGY SPION KOP DEFERRED VARIABLE SPION FIXED SPION KOP RELATED & GENERAL LABOR ALLOCATION DEPRECIATION SPION KOP WIND REVENUES ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT COMPUTATION OF REQUIRED RETURN AND REVENUE INCREASE 1 Electric Utility Rate Base $57,190,037 $0 $0 $0 $0 $0 2 Rate of Return 7.42% 7.42% 7.42% 7.42% 7.42% 7.42% 3 4 5 Net Operating Income 4,243,501 0 0 0 0 0 6 7 Net Operating Income for the Year 8 Ended 12/31/17 Adjusted for Known Changes 3,867,168 (352,025) 3,161 (603) 0 (232,956) 9 10 Required Incremental Increase in Net 11 Operating Income $376,333 $352,025 ($3,161) $603 $0 $232,956 12 13 Add: 14 MPSC Tax 1,250 1,169 (11) 2 0 774 15 Consumer Counsel Tax 236 220 (2) 0 0 146 16 Incremental Income Taxes 134,521 125,831 (1,130) 215 0 83,270 17 18 Required Revenue Increase $512,340 $479,245 ($4,304) $820 $0 $317,146 19 20 21 MPSC Tax (0.244%) 1,250 1,169 (11) 2 0 774 22 23 Consumer Counsel Tax (0.046%) 236 220 (2) 0 0 146 24 25 Taxable Income for State Income Tax $510,854 $477,856 ($4,291) $818 $0 $316,226 26 27 State Income Tax (6.75%) (Unitary Factor = 1.00) 34,483 32,255 (290) 55 0 21,345 28 29 Taxable Income for Federal Income Tax $476,371 $445,601 ($4,001) $763 $0 $294,881 30 31 Reduction of Fed.Inc.TaxDue to MCLT Expense (7,241) (6,774) 61 (12) 0 (4,482) 32 Federal Income Tax Expense (21%) 107,279 100,350 (901) 172 0 66,407 33 34 Required Incremental Increase in Net 35 Operating Income $376,333 $352,025 ($3,161) $603 $0 $232,956

Docket No. D2018.2.12 Page 95 of 327 GENERAL RATE CASE M N O P Q ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY SPION KOP WIND COMPUTATION OF REQUIRED RETURN AND REVENUE INCREASE 1 Electric Utility Rate Base 2 Rate of Return 3 4 5 Net Operating Income 6 7 Net Operating Income for the Year 8 Ended 12/31/17 Adjusted for Known Changes 9 10 Required Incremental Increase in Net 11 Operating Income 12 13 Add: 14 MPSC Tax 15 Consumer Counsel Tax 16 Incremental Income Taxes 17 18 Required Revenue Increase 19 20 21 MPSC Tax (0.244%) 22 23 Consumer Counsel Tax (0.046%) 24 25 Taxable Income for State Income Tax 26 27 State Income Tax (6.75%) (Unitary Factor = 1.00) 28 29 Taxable Income for Federal Income Tax 30 31 Reduction of Fed.Inc.TaxDue to MCLT Expense 32 Federal Income Tax Expense (21%) 33 34 Required Incremental Increase in Net 35 Operating Income TAXES OTHER WORKING INTEREST TOTAL TEST PERIOD AMORTIZATION THAN INCOME CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $3,907 $314,373 $0 $318,280 $57,508,317 7.42% 7.42% #### #### #### #### #### #### #### #### 7.42% 7.42% 7.42% 7.42% 7.42% 0 0 0 0 0 0 0 0 0 0 290 23,326 0 23,616 4,267,117 0 (39,461) 0 0 0 0 0 0 0 0 0 894,060 113,449 385,625 4,252,793 $0 $39,461 $0 $0 $0 $0 $0 $0 $0 $0 $290 ($870,734) ($113,449) ($362,009) $14,324 0 131 0 0 0 0 0 0 0 0 1 (2,892) (377) (1,203) 47 0 25 0 0 0 0 0 0 0 0 0 (545) (71) (227) 9 0 14,106 0 0 0 0 0 0 0 0 104 (311,245) (40,552) (129,401) 5,120 $0 $53,723 $0 $0 $0 $0 $0 $0 $0 $0 $395 ($1,185,416) ($154,449) ($492,840) $19,500 0 131 0 0 0 0 0 0 0 0 1 (2,892) (377) (1,203) 47 0 25 0 0 0 0 0 0 0 0 0 (545) (71) (227) 9 $0 $53,567 $0 $0 $0 $0 $0 $0 $0 $0 $394 ($1,181,979) ($154,001) (491,410) 19,444 0 3,616 0 0 0 0 0 0 0 0 27 (79,784) (10,395) (33,171) 1,312 $0 $49,951 $0 $0 $0 $0 $0 $0 $0 $0 $367 ($1,102,195) ($143,606) ($458,239) $18,132 0 (759) 0 0 0 0 0 0 0 0 (6) 16,755 2,183 6,966 (275) 0 11,249 0 0 0 0 0 0 0 0 83 (248,216) (32,340) (103,196) 4,083 $0 $39,461 $0 $0 $0 $0 $0 $0 $0 $0 $290 ($870,734) ($113,449) ($362,009) $14,324

Docket No. D2018.2.12 Page 96 of 327 GENERAL RATE CASE ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY SPION KOP WIND COMPUTATION OF REQUIRED RETURN AND REVENUE INCREASE 1 Electric Utility Rate Base 2 Rate of Return 3 4 5 Net Operating Income 6 7 Net Operating Income for the Year 8 Ended 12/31/17 Adjusted for Known Changes 9 10 Required Incremental Increase in Net 11 Operating Income 12 13 Add: 14 MPSC Tax 15 Consumer Counsel Tax 16 Incremental Income Taxes 17 18 Required Revenue Increase 19 20 21 MPSC Tax (0.244%) 22 23 Consumer Counsel Tax (0.046%) 24 25 Taxable Income for State Income Tax 26 27 State Income Tax (6.75%) (Unitary Factor = 1.00) 28 29 Taxable Income for Federal Income Tax 30 31 Reduction of Fed.Inc.TaxDue to MCLT Expense 32 Federal Income Tax Expense (21%) 33 34 Required Incremental Increase in Net 35 Operating Income INTERIM ADJUSTMENTS INTERIM INTERIM ADJUST TO NONPCCAM MONTANA WORKING INTEREST TOTAL TEST PERIOD ROE FROM DEPRECIATION SUPPLY GENERATION CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT DOCKET 2011.5.41 ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES $57,508,317 $118,555 $0 $0 $0 $0 $2,596 ($929,804) $0 ($808,653) $56,699,665 0.32% 7.10% 7.10% 7.10% 7.10% 7.10% 7.10% 7.10% 7.10% 7.10% 7.10% (184,027) 8,417 0 0 0 0 184 (66,016) 0 (57,414) 4,025,676 0 187,317 0 0 0 0 0 (9,702) 3,183 180,798 4,433,590 ($184,027) ($178,900) $0 $0 $0 $0 $184 ($56,314) ($3,183) ($422,240) ($407,916) (611) (594) 0 0 0 0 1 (187) (11) (1,402) (1,355) (115) (112) 0 0 0 0 0 (35) (2) (264) (255) (65,781) (63,948) 0 0 0 0 66 (20,130) (1,138) (150,931) (145,811) ($250,534) ($243,554) $0 $0 $0 $0 $251 ($76,666) ($4,334) ($574,837) ($555,337) (611) (594) 0 0 0 0 1 (187) (11) (1,402) (1,355) (115) (112) 0 0 0 0 0 (35) (2) (264) (255) ($249,808) ($242,848) $0 $0 $0 $0 $250 ($76,444) ($4,321) (573,171) (553,727) (16,862) (16,392) 0 0 0 0 17 (5,160) (292) (38,689) (37,377) ($232,946) ($226,456) $0 $0 $0 $0 $233 ($71,284) ($4,029) (534,482) (516,350) 3,541 3,442 0 0 0 0 (4) 1,084 61 8,124 7,849 (52,460) (50,998) 0 0 0 0 53 (16,054) (907) (120,366) (116,283) ($184,027) ($178,900) $0 $0 $0 $0 $184 ($56,314) ($3,183) ($422,240) ($407,916)

Docket No. D2018.2.12 Page 97 of 327 GENERAL RATE CASE A B C D E F G H I REVENUE SALES & ACTUAL TWELVE MONTHS ENDED 2017 INTERIM REMOVE REMOVE & REVENUE ADMINISTRATIVE CORPORATE NORTHWESTERN ENERGY HYDRO DEFERRED REVENUE CREDITS FIXED HYDRO RELATED & GENERAL LABOR ALLOCATION DEPRECIATION HYDROS REVENUES & VARIABLE ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT 1 Operating Revenues $148,933,720 $2,871,683 $764,857 $145,297,180 ($1,253,921) $0 $0 $0 $0 2 3 Operating Expenses 38,470,018 2,871,683 53,619 35,544,716 (1,679,218) 133,218 1,144,249 4 Book Depreciation 12,098,900 12,098,900 (2,605,804) 5 Amort. of Electric Plant & Acq Adjmt 7,993,486 7,993,486 1,813,593 6 Amort.Misc Items (2,301,557) (773,892) (1,527,665) 7 Taxes other than Income 20,754,751 20,754,751 (349,678) 9,472 8 9 Subtotal Expenses $77,015,598 $2,871,683 ($720,273) $74,864,188 ($349,678) ($1,679,218) $142,690 $1,144,249 ($792,211) 10 Net Utility Operating Income Before Inc Tax $71,918,121 $0 $1,485,129 $70,432,992 ($904,243) $1,679,218 ($142,690) ($1,144,249) $792,211 11 12 Amortization of Excess Deferred TaxARAM $0 0 0 0 0 0 13 Amortization of Excess Deferred TaxUnprotected Rate Base $0 0 0 0 0 0 14 Amortization of Excess Deferred TaxUnprotected NonRate Base $0 0 0 0 0 0 15 16 Deferred Income Taxes: 17 Injuries & Damages $34,009 0 0 0 0 0 18 Miscellaneous $0 0 0 0 0 0 19 Accrued Incentive Compensation $36,686 0 0 0 0 0 20 Accelerated Depreciation $13,396,274 0 0 0 0 166,364 21 Net Operating Loss $2,151,502 (238,110) 442,180 (37,574) (301,309) 0 22 MPSC/MCC Taxes $0 0 0 0 0 0 23 Deferred Revenue $359,250 0 0 0 0 0 24 Customer Advances for Construction/CIAC ($50,258) 0 0 0 0 0 25 FAS106 & 112 Post Retirement Benefits $35,341 0 0 0 0 0 26 Costs of Refinancing Debt ($12,517) 0 0 0 0 0 27 Environmental Reserve ($40,852) 0 0 0 0 0 28 NonJurisdictional Items ($376,170) 0 0 0 0 0 29 SubtotalDeferred Income Tax 15,533,265 (238,110) 442,180 (37,574) (301,309) 166,364 30 31 Income TaxesFederal 0 0 0 0 0 0 32 Income TaxesCorporation License Tax 0 0 0 0 0 0 33 Income TaxesForeign Taxes 0 0 0 0 0 0 34 SubtotalCurrent Income Tax 0 0 0 0 0 0 35 Net Utility Operating Income $54,899,727 ($666,133) $1,237,038 ($105,116) ($842,940) $625,847 36 Rate Base $793,410,248 $0 $0 $0 $0 $0 37 Return on Rate Base 6.92%

GENERAL RATE CASE Docket No. D2018.2.12 Page 98 of 327 J M N O P Q ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY HYDROS 1 Operating Revenues 2 3 Operating Expenses 4 Book Depreciation 5 Amort. of Electric Plant & Acq Adjmt 6 Amort.Misc Items 7 Taxes other than Income 8 9 Subtotal Expenses 10 Net Utility Operating Income Before Inc Tax 11 12 Amortization of Excess Deferred TaxARAM 13 Amortization of Excess Deferred TaxUnprotected Rate Base 14 Amortization of Excess Deferred TaxUnprotected NonRate B 15 16 Deferred Income Taxes: 17 Injuries & Damages 18 Miscellaneous 19 Accrued Incentive Compensation 20 Accelerated Depreciation 21 Net Operating Loss 22 MPSC/MCC Taxes 23 Deferred Revenue 24 Customer Advances for Construction/CIAC 25 FAS106 & 112 Post Retirement Benefits 26 Costs of Refinancing Debt 27 Environmental Reserve 28 NonJurisdictional Items 29 SubtotalDeferred Income Tax 30 31 Income TaxesFederal 32 Income TaxesCorporation License Tax 33 Income TaxesForeign Taxes 34 SubtotalCurrent Income Tax 35 Net Utility Operating Income 36 Rate Base 37 Return on Rate Base TAXES OTHER WORKING INTEREST TOTAL TEST PERIOD AMORTIZATION THAN INCOME CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 (1,253,921) 144,043,259 (401,750) 35,142,966 (2,605,804) 9,493,096 1,813,593 9,807,079 1,017,611 1,017,611 (510,054) 241,493 (98,713) 20,656,038 $1,017,611 $241,493 $0 $0 $0 $0 $0 $0 $0 $0 (275,064) 74,589,124 ($1,017,611) ($241,493) $0 $0 $0 $0 $0 $0 $0 $0 (978,857) 69,454,135 0 0 0 0 0 0 0 0 0 430,688 0 430,688 430,688 0 0 0 0 0 0 0 0 77,850 0 77,850 77,850 0 0 0 0 0 0 0 0 (11,272) 0 (11,272) 22,737 0 0 0 0 0 0 0 0 0 (12,160) 0 (12,160) 24,526 0 0 0 0 0 0 0 0 (4,916,554) 0 (4,750,190) 8,646,084 (267,962) (63,591) 0 0 0 0 0 0 (1,267,297) 2,064,962 331,299 2,482,801 0 0 0 0 0 0 0 0 0 (119,074) 0 (119,074) 240,176 0 0 0 0 0 0 0 0 16,658 0 16,658 (33,600) 0 0 0 0 0 0 0 0 (11,714) 0 (11,714) 23,627 0 0 0 0 0 0 0 0 4,149 0 4,149 (8,368) 0 0 0 0 0 0 0 0 13,540 0 13,540 (27,312) 0 0 0 0 0 0 0 0 376,170 0 376,170 0 (267,962) (63,591) 0 0 0 0 0 0 (5,419,014) 2,064,962 (3,654,054) 11,879,210 0 0 0 0 ($749,649) ($177,902) $0 $0 $0 $0 $0 $0 $5,419,014 ($2,064,962) $2,675,197 $57,574,925 $0 $0 $0 $0 $0 $0 $0 $823,792 ($1,041,712) $0 (217,919) 793,192,329 7.26%

GENERAL RATE CASE Docket No. D2018.2.12 Page 99 of 327 ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY HYDROS 1 Operating Revenues 2 3 Operating Expenses 4 Book Depreciation 5 Amort. of Electric Plant & Acq Adjmt 6 Amort.Misc Items 7 Taxes other than Income 8 9 Subtotal Expenses 10 Net Utility Operating Income Before Inc Tax 11 12 Amortization of Excess Deferred TaxARAM 13 Amortization of Excess Deferred TaxUnprotected Rate Base 14 Amortization of Excess Deferred TaxUnprotected NonRate B 15 16 Deferred Income Taxes: 17 Injuries & Damages 18 Miscellaneous 19 Accrued Incentive Compensation 20 Accelerated Depreciation 21 Net Operating Loss 22 MPSC/MCC Taxes 23 Deferred Revenue 24 Customer Advances for Construction/CIAC 25 FAS106 & 112 Post Retirement Benefits 26 Costs of Refinancing Debt 27 Environmental Reserve 28 NonJurisdictional Items 29 SubtotalDeferred Income Tax 30 31 Income TaxesFederal 32 Income TaxesCorporation License Tax 33 Income TaxesForeign Taxes 34 SubtotalCurrent Income Tax 35 Net Utility Operating Income 36 Rate Base 37 Return on Rate Base INTERIM ADJUSTMENTS INTERIM INTERIM ADJUST TO NONPCCAM MONTANA WORKING INTEREST TOTAL TEST PERIOD ROE FROM DEPRECIATION SUPPLY GENERATION CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT DOCKET 2013.12.85 ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES $0 $0 $0 $0 $0 $0 $0 $0 $0 0 144,043,259 0 35,142,966 (804,953) (804,953) 8,688,143 0 9,807,079 0 (510,054) 0 20,656,038 $0 ($804,953) $0 $0 $0 $0 $0 $0 $0 (804,953) 73,784,172 $0 $804,953 $0 $0 $0 $0 $0 $0 $0 804,953 70,259,088 0 0 0 0 0 0 0 (430,688) 0 (430,688) 0 0 0 0 0 0 0 0 (77,850) 0 (77,850) 0 0 0 0 0 0 0 0 0 0 0 22,737 0 0 0 0 0 0 0 0 0 0 24,526 0 169,040 0 0 0 0 0 0 0 169,040 8,815,124 0 0 0 0 0 0 0 0 (65,974) (65,974) 2,416,827 0 0 0 0 0 0 0 0 0 0 240,176 0 0 0 0 0 0 0 0 0 0 (33,600) 0 0 0 0 0 0 0 0 0 0 23,627 0 0 0 0 0 0 0 0 0 0 (8,368) 0 0 0 0 0 0 0 0 0 0 (27,312) 0 169,040 0 0 0 0 0 (508,538) (65,974) (405,472) 11,473,738 $0 $635,913 $0 $0 $0 $0 $0 $508,538 $65,974 $1,210,425 $58,785,349 $0 $402,476 $0 $0 $0 $0 $329,645 ($7,127,908) $0 (6,395,786) 786,796,542 7.47%

Docket No. D2018.2.12 Page 100 of 327 GENERAL RATE CASE A B C D E F G H I REVENUE SALES & ACTUAL TWELVE MONTHS ENDED 2017 INTERIM REMOVE REMOVE & REVENUE ADMINISTRATIVE CORPORATE NORTHWESTERN ENERGY HYDRO DEFERRED REVENUE CREDITS FIXED HYDRO RELATED & GENERAL LABOR ALLOCATION DEPRECIATION HYDROS REVENUES & VARIABLE ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT 38 ELECTRIC UTILITY CALCULATIONS 39 Operating Revenues $145,297,180 ($1,253,921) $0 $0 $0 $0 40 Operating Expenses 35,544,716 0 (1,679,218) 133,218 1,144,249 0 41 Subtotal $109,752,464 ($1,253,921) $1,679,218 ($133,218) ($1,144,249) $0 42 Depreciation & Amortization 18,564,721 (792,211) 43 Taxes other than Income 20,754,751 (349,678) 9,472 44 Net Utility Operating Income Before Inc Tax $ 70,432,992 $ (904,243) $ 1,679,218 $ (142,690) $ (1,144,249) $ 792,211 45 Taxable Additions / (Deductions): 46 Nondeductible Meal Expense $70,940 0 0 0 0 0 47 Bad Debt Expense Accrual Net of Chargeoffs $0 0 0 0 0 0 48 Penalties $0 0 0 0 0 0 49 Meters $0 0 0 0 0 0 50 Customer Advances for Construction/CIAC $127,599 0 0 0 0 0 51 Repairs Expense ($203,490) 0 0 0 0 0 52 Accrued Incentive Compensation ($93,142) 0 0 0 0 0 53 MPSC/MCC Taxes $0 0 0 0 0 0 54 Costs of Refinancing Debt $31,780 0 0 0 0 0 55 Accelerated DepreciationExcess BLM Tx vs Bk Deprec $12,129 0 0 0 0 0 56 Accelerated DepreciationExcess Tx Rtn vs BLM Tx Dep ($38,275,068) 0 0 0 0 (792,211) 57 Removal Costs Net of Salvage ($677,362) 0 0 0 0 0 58 Deferred Revenue ($912,091) 0 0 0 0 0 59 FAS106 & 112 Post Retirement Benefits ($89,726) 0 0 0 0 0 60 Environmental Reserve $103,719 0 0 0 0 0 61 Injuries & Damages ($86,345) 0 0 0 0 0 62 Net Operating Loss ($5,462,398) 904,243 (1,679,218) 142,690 1,144,249 0 63 Excludable Foreign Income $0 0 0 0 0 0 64 MT Corporation License Tax 0 0 0 0 0 0 65 Deduct Interest Charges ($24,979,538) 0 0 0 0 0 66 Total Tax Additons / (Deductions) ($70,432,992) $904,243 ($1,679,218) $142,690 $1,144,249 ($792,211) 67 Federal Taxable Income $ $ $ $ $ $ 68 Federal Income Tax @ 21% $0 $0 $0 $0 $0 $0 69 Foreign Income Tax $0 0 0 0 0 0 70 Foreign Income Tax Credit $0 0 0 0 0 0 71 NonJurisdictional Items 376,170 0 0 0 0 0 72 Prior Period Adjustments ($376,170) 0 0 0 0 0 73 Audit Adjustments $0 0 0 0 0 0 74 Total Federal Income Tax 0 0 0 0 0 0 75 76 77 Montana Corporate License Tax 78 Federal Taxable Income B4 MT Corp Tx Deductn & NOL $ $ $ $ $ $ 79 Add: 80 Other $0 0 0 0 0 0 81 Other State Taxes Paid $0 0 0 0 0 0 82 83 Reduction for Unitary Allocation $0 0 0 0 0 0 84 85 Montana Taxable Income $0 $0 $0 $0 $0 $0 86 Mont. Corp. Lic. Tax @ 6.75% $0 0 0 0 0 0 87 Net Tax Adjustment $0 $0 $0 $0 $0 $0 88 Mont. Corp. License Tax $0 $0 $0 $0 $0 $0 89 Actual 6.75% 0 0 0 0 0 0 90 91 Change in tax rates $0 0 0 0 0 0 92 NonJurisdictional Items $0 0 0 0 0 0 93 Net Tax Adjustment 0 0 0 0 0 0

GENERAL RATE CASE Docket No. D2018.2.12 Page 101 of 327 J M N O P Q ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY HYDROS 38 ELECTRIC UTILITY CALCULATIONS 39 Operating Revenues 40 Operating Expenses 41 Subtotal 42 Depreciation & Amortization 43 Taxes other than Income 44 Net Utility Operating Income Before Inc Tax 45 Taxable Additions / (Deductions): 46 Nondeductible Meal Expense 47 Bad Debt Expense Accrual Net of Chargeoffs 48 Penalties 49 Meters 50 Customer Advances for Construction/CIAC 51 Repairs Expense 52 Accrued Incentive Compensation 53 MPSC/MCC Taxes 54 Costs of Refinancing Debt 55 Accelerated DepreciationExcess BLM Tx vs Bk Deprec 56 Accelerated DepreciationExcess Tx Rtn vs BLM Tx Dep 57 Removal Costs Net of Salvage 58 Deferred Revenue 59 FAS106 & 112 Post Retirement Benefits 60 Environmental Reserve 61 Injuries & Damages 62 Net Operating Loss 63 Excludable Foreign Income 64 MT Corporation License Tax 65 Deduct Interest Charges 66 Total Tax Additons / (Deductions) 67 Federal Taxable Income 68 Federal Income Tax @ 21% 69 Foreign Income Tax 70 Foreign Income Tax Credit 71 NonJurisdictional Items 72 Prior Period Adjustments 73 Audit Adjustments 74 Total Federal Income Tax 75 76 77 Montana Corporate License Tax 78 Federal Taxable Income B4 MT Corp Tx Deductn & NOL 79 Add: 80 Other 81 Other State Taxes Paid 82 83 Reduction for Unitary Allocation 84 85 Montana Taxable Income 86 Mont. Corp. Lic. Tax @ 6.75% 87 Net Tax Adjustment 88 Mont. Corp. License Tax 89 Actual 6.75% 90 91 Change in tax rates 92 NonJurisdictional Items 93 Net Tax Adjustment TAXES OTHER WORKING INTEREST TOTAL TEST PERIOD AMORTIZATION THAN INCOME CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 (1,253,921) 144,043,259 0 0 0 0 0 0 0 0 0 0 (401,750) 35,142,966 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 (852,170) 108,900,294 1,017,611 225,400 18,790,121 241,493 (98,713) 20,656,038 $ (1,017,611) $ (241,493) $ $ $ $ $ $ $ $ (978,857) 69,454,135 70,940 0 0 0 127,599 (203,490) (93,142) 0 31,780 12,129 0 0 0 0 0 0 0 0 (2,104,553) 0 (2,896,764) (41,171,831) (677,362) (912,091) (89,726) 103,719 (86,345) 1,017,611 241,493 0 0 0 0 0 0 2,104,553 (7,841,876) (3,966,255) (9,428,653) 0 0 0 0 0 0 0 0 0 0 0 7,841,876 7,841,876 (17,137,662) $1,017,611 $241,493 $0 $0 $0 $0 $0 $0 ($0) $0 $978,857 ($69,454,135) $ $ $ $ $ $ $ $ $ (0) $ $ (0) $ $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 0 0 0 0 0 0 0 0 0 0 0 0 (376,170) 0 (376,170) 0 0 0 0 0 0 0 0 0 376,170 0 376,170 0 0 0 $ $ $ $ $ $ $ $ $ (0) $ (0) (0) 0 0 0 $0 $0 $0 $0 $0 $0 $0 $0 ($0) $0 (0) (0) 0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 0 0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 0 0 0 0 0 0

GENERAL RATE CASE ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY HYDROS 38 ELECTRIC UTILITY CALCULATIONS 39 Operating Revenues 40 Operating Expenses 41 Subtotal 42 Depreciation & Amortization 43 Taxes other than Income 44 Net Utility Operating Income Before Inc Tax 45 Taxable Additions / (Deductions): 46 Nondeductible Meal Expense 47 Bad Debt Expense Accrual Net of Chargeoffs 48 Penalties 49 Meters 50 Customer Advances for Construction/CIAC 51 Repairs Expense 52 Accrued Incentive Compensation 53 MPSC/MCC Taxes 54 Costs of Refinancing Debt 55 Accelerated DepreciationExcess BLM Tx vs Bk Deprec 56 Accelerated DepreciationExcess Tx Rtn vs BLM Tx Dep 57 Removal Costs Net of Salvage 58 Deferred Revenue 59 FAS106 & 112 Post Retirement Benefits 60 Environmental Reserve 61 Injuries & Damages 62 Net Operating Loss 63 Excludable Foreign Income 64 MT Corporation License Tax 65 Deduct Interest Charges 66 Total Tax Additons / (Deductions) 67 Federal Taxable Income 68 Federal Income Tax @ 21% 69 Foreign Income Tax 70 Foreign Income Tax Credit 71 NonJurisdictional Items 72 Prior Period Adjustments 73 Audit Adjustments 74 Total Federal Income Tax 75 76 77 Montana Corporate License Tax 78 Federal Taxable Income B4 MT Corp Tx Deductn & NOL 79 Add: 80 Other 81 Other State Taxes Paid 82 83 Reduction for Unitary Allocation 84 85 Montana Taxable Income 86 Mont. Corp. Lic. Tax @ 6.75% 87 Net Tax Adjustment 88 Mont. Corp. License Tax 89 Actual 6.75% 90 91 Change in tax rates 92 NonJurisdictional Items 93 Net Tax Adjustment Docket No. D2018.2.12 Page 102 of 327 INTERIM ADJUSTMENTS INTERIM INTERIM ADJUST TO NONPCCAM MONTANA WORKING INTEREST TOTAL TEST PERIOD ROE FROM DEPRECIATION SUPPLY GENERATION CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT DOCKET 2013.12.85 ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES $0 $0 $0 $0 $0 $0 $0 $0 $0 0 144,043,259 0 0 0 0 0 0 0 0 0 0 35,142,966 $0 $0 $0 $0 $0 $0 $0 $0 $0 0 108,900,294 (804,953) (804,953) 17,985,168 0 20,656,038 $ $ 804,953 $ $ $ $ $ $ $ 804,953 70,259,088 0 0 0 0 0 0 0 0 0 0 70,940 0 0 0 0 0 0 0 0 0 0 127,599 0 0 0 0 0 0 0 0 0 0 (203,490) 0 0 0 0 0 0 0 0 0 0 (93,142) 0 0 0 0 0 0 0 0 0 0 31,780 0 0 0 0 0 0 0 0 0 0 12,129 0 (804,953) 0 0 0 0 0 0 0 (804,953) (41,976,784) 0 0 0 0 0 0 0 0 0 0 (677,362) 0 0 0 0 0 0 0 0 0 0 (912,091) 0 0 0 0 0 0 0 0 0 0 (89,726) 0 0 0 0 0 0 0 0 0 0 103,719 0 0 0 0 0 0 0 0 0 0 (86,345) 0 0 0 0 0 0 0 0 250,542 250,542 (9,178,111) 0 0 0 0 0 0 0 0 (250,542) (250,542) (17,388,204) $0 ($804,953) $0 $0 $0 $0 $0 $0 $0 ($804,953) ($70,259,088) $ $ $ $ $ $ $ $ $ $ $ $0 $0 $0 $0 $0 $0 $0 $0 $0 0 0 $ $ $ $ $ $ $ $ $ 0 (0) $0 $0 $0 $0 $0 $0 $0 $0 $0 0 (0) $0 $0 $0 $0 $0 $0 $0 $0 $0 0 0 $0 $0 $0 $0 $0 $0 $0 $0 $0 0 0

Docket No. D2018.2.12 Page 103 of 327 GENERAL RATE CASE A B C D E F G H I REVENUE SALES & ACTUAL TWELVE MONTHS ENDED 2017 INTERIM REMOVE REMOVE & REVENUE ADMINISTRATIVE CORPORATE NORTHWESTERN ENERGY HYDRO DEFERRED REVENUE CREDITS FIXED HYDRO RELATED & GENERAL LABOR ALLOCATION DEPRECIATION HYDROS REVENUES & VARIABLE ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT COMPUTATION OF REQUIRED RETURN AND REVENUE INCREASE 1 Electric Utility Rate Base $793,410,248 $0 $0 $0 $0 $0 2 Rate of Return 7.42% 7.42% 7.42% 7.42% 7.42% 7.42% 3 4 5 Net Operating Income 58,871,040 0 0 0 0 0 6 7 Net Operating Income for the Year 8 Ended 12/31/17 Adjusted for Known Changes 54,899,727 (666,133) 1,237,038 (105,116) (842,940) 625,847 9 10 Required Incremental Increase in Net 11 Operating Income $3,971,313 $666,133 ($1,237,038) $105,116 $842,940 ($625,847) 12 13 Add: 14 MPSC Tax 13,192 2,213 (4,109) 349 2,800 (2,079) 15 Consumer Counsel Tax 2,487 417 (775) 66 528 (392) 16 Incremental Income Taxes 1,419,548 238,109 (442,180) 37,574 301,310 (223,709) 17 18 Required Revenue Increase $5,406,540 $906,872 ($1,684,102) $143,105 $1,147,578 ($852,027) 19 20 21 MPSC Tax (0.244%) 13,192 2,213 (4,109) 349 2,800 (2,079) 22 23 Consumer Counsel Tax (0.046%) 2,487 417 (775) 66 528 (392) 24 25 Taxable Income for State Income Tax $5,390,861 $904,242 ($1,679,218) $142,690 $1,144,250 ($849,556) 26 27 State Income Tax (6.75%) (Unitary Factor = 1.00) 363,883 61,036 (113,347) 9,632 77,237 (57,345) 28 29 Taxable Income for Federal Income Tax $5,026,978 $843,206 ($1,565,871) $133,058 $1,067,013 ($792,211) 30 31 Reduction of Fed.Inc.TaxDue to MCLT Expense (76,415) (12,818) 23,803 (2,023) (16,220) 12,042 32 Federal Income Tax Expense (21%) 1,132,080 189,891 (352,636) 29,965 240,293 (178,406) 33 34 Required Incremental Increase in Net 35 Operating Income $3,971,313 $666,133 ($1,237,038) $105,116 $842,940 ($625,847)

GENERAL RATE CASE Docket No. D2018.2.12 Page 104 of 327 J M N O P Q ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY HYDROS COMPUTATION OF REQUIRED RETURN AND REVENUE INCREASE 1 Electric Utility Rate Base 2 Rate of Return 3 4 5 Net Operating Income 6 7 Net Operating Income for the Year 8 Ended 12/31/17 Adjusted for Known Changes 9 10 Required Incremental Increase in Net 11 Operating Income 12 13 Add: 14 MPSC Tax 15 Consumer Counsel Tax 16 Incremental Income Taxes 17 18 Required Revenue Increase 19 20 21 MPSC Tax (0.244%) 22 23 Consumer Counsel Tax (0.046%) 24 25 Taxable Income for State Income Tax 26 27 State Income Tax (6.75%) (Unitary Factor = 1.00) 28 29 Taxable Income for Federal Income Tax 30 31 Reduction of Fed.Inc.TaxDue to MCLT Expense 32 Federal Income Tax Expense (21%) 33 34 Required Incremental Increase in Net 35 Operating Income TAXES OTHER WORKING INTEREST TOTAL TEST PERIOD AMORTIZATION THAN INCOME CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES $0 $0 $0 $0 $0 $0 $0 $823,792 ($1,041,712) $0 ($217,919) $793,192,329 7.42% 7.42% 7.42% 7.42% 7.42% 7.42% #### 7.42% 7.42% 7.42% 7.42% 7.42% 0 0 0 0 0 0 0 61,125 (77,295) 0 (16,170) 58,854,871 (749,649) (177,902) 0 0 0 0 0 0 5,419,014 (2,064,962) 2,675,197 57,574,925 $749,649 $177,902 $0 $0 $0 $0 $0 $61,125 ($5,496,309) $2,064,962 ($2,691,367) $1,279,946 2,490 591 0 0 0 0 0 203 (18,258) 6,859 (8,941) 4,251 469 111 0 0 0 0 0 38 (3,442) 1,293 (1,687) 800 267,963 63,591 0 0 0 0 0 21,849 (1,964,659) 738,122 (962,030) 457,518 $1,020,571 $242,195 $0 $0 $0 $0 $0 $83,215 ($7,482,668) $2,811,236 ($3,664,025) $1,742,515 2,490 591 0 0 0 0 0 203 (18,258) 6,859 (8,941) 4,251 469 111 0 0 0 0 0 38 (3,442) 1,293 (1,687) 800 $1,017,612 $241,493 $0 $0 $0 $0 $0 $82,974 ($7,460,968) $2,803,084 (3,653,397) 1,737,464 68,689 16,301 0 0 0 0 0 5,601 (503,615) 189,208 (246,603) 117,280 $948,923 $225,192 $0 $0 $0 $0 $0 $77,373 ($6,957,353) $2,613,876 ($3,406,794) $1,620,184 (14,425) (3,423) 0 0 0 0 0 (1,176) 105,759 (39,734) 51,785 (24,630) 213,699 50,713 0 0 0 0 0 17,424 (1,566,803) 588,648 (767,212) 364,868 $749,649 $177,902 $0 $0 $0 $0 $0 $61,125 ($5,496,309) $2,064,962 ($2,691,367) $1,279,946

GENERAL RATE CASE ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY HYDROS COMPUTATION OF REQUIRED RETURN AND REVENUE INCREASE 1 Electric Utility Rate Base 2 Rate of Return 3 4 5 Net Operating Income 6 7 Net Operating Income for the Year 8 Ended 12/31/17 Adjusted for Known Changes 9 10 Required Incremental Increase in Net 11 Operating Income 12 13 Add: 14 MPSC Tax 15 Consumer Counsel Tax 16 Incremental Income Taxes 17 18 Required Revenue Increase 19 20 21 MPSC Tax (0.244%) 22 23 Consumer Counsel Tax (0.046%) 24 25 Taxable Income for State Income Tax 26 27 State Income Tax (6.75%) (Unitary Factor = 1.00) 28 29 Taxable Income for Federal Income Tax 30 31 Reduction of Fed.Inc.TaxDue to MCLT Expense 32 Federal Income Tax Expense (21%) 33 34 Required Incremental Increase in Net 35 Operating Income Docket No. D2018.2.12 Page 105 of 327 INTERIM ADJUSTMENTS INTERIM INTERIM ADJUST TO NONPCCAM MONTANA WORKING INTEREST TOTAL TEST PERIOD ROE FROM DEPRECIATION SUPPLY GENERATION CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT DOCKET 2013.12.85 ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES $793,192,329 $402,476 $0 $0 $0 $0 $329,645 ($7,127,908) $0 ($6,395,786) $786,796,542 0.42% 7.00% 7.00% 7.00% 7.00% 7.00% 7.00% 7.00% 7.00% 7.00% 7.00% (3,331,408) 28,173 0 0 0 0 23,075 (498,954) 0 (447,705) 55,075,758 0 635,913 0 0 0 0 0 508,538 65,974 1,210,425 58,785,349 ($3,331,408) ($607,740) $0 $0 $0 $0 $23,075 ($1,007,492) ($65,974) ($4,989,539) ($3,709,593) (11,066) (2,019) 0 0 0 0 77 (3,347) (219) (16,574) (12,323) (2,086) (381) 0 0 0 0 14 (631) (41) (3,125) (2,325) (1,190,814) (217,237) 0 0 0 0 8,248 (360,128) (23,582) (1,783,513) (1,325,995) ($4,535,374) ($827,377) $0 $0 $0 $0 $31,414 ($1,371,598) ($89,816) ($6,792,751) ($5,050,236) (11,066) (2,019) 0 0 0 0 77 (3,347) (219) (16,574) (12,323) (2,086) (381) 0 0 0 0 14 (631) (41) (3,125) (2,325) ($4,522,222) ($824,977) $0 $0 $0 $0 $31,323 ($1,367,620) ($89,556) (6,773,052) (5,035,588) (305,250) (55,686) 0 0 0 0 2,114 (92,314) (6,045) (457,181) (339,901) ($4,216,972) ($769,291) $0 $0 $0 $0 $29,209 ($1,275,306) ($83,511) (6,315,871) (4,695,687) 64,103 11,694 0 0 0 0 (444) 19,386 1,269 96,008 71,378 (949,667) (173,245) 0 0 0 0 6,578 (287,200) (18,806) (1,422,340) (1,057,472) ($3,331,408) ($607,740) $0 $0 $0 $0 $23,075 ($1,007,492) ($65,974) ($4,989,539) ($3,709,593)

Docket No. D2018.2.12 Page 106 of 327 GENERAL RATE CASE A B C D E F G H I REVENUE SALES & ACTUAL TWELVE MONTHS ENDED 2017 INTERIM & REVENUE ADMINISTRATIVE CORPORATE NORTHWESTERN ENERGY GENERATION EMPLOYEES INCOME TAXES GENERATION RELATED & GENERAL LABOR ALLOCATION DEPRECIATION MONTANA GENERATION ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT 1 Operating Revenues $0 $0 $0 $0 $0 $0 $0 $0 $0 2 3 Operating Expenses 506,099 506,099 65,869 4 Book Depreciation 5 Amort. of Electric Plant & Acq Adjmt 6 Amort.Misc Items 7 Taxes other than Income 8 9 Subtotal Expenses $506,099 $0 $0 $506,099 $0 $65,869 $0 $0 $0 10 Net Utility Operating Income Before Inc Tax ($506,099) $0 $0 ($506,099) $0 ($65,869) $0 $0 $0 11 12 Amortization of Excess Deferred TaxARAM $0 0 0 0 0 0 13 Amortization of Excess Deferred TaxUnprotected Rate Base $0 0 0 0 0 0 14 Amortization of Excess Deferred TaxUnprotected NonRate Base $0 0 0 0 0 0 15 16 Deferred Income Taxes: 17 Injuries & Damages $0 0 0 0 0 0 18 Miscellaneous $0 0 0 0 0 0 19 Accrued Incentive Compensation $0 0 0 0 0 0 20 Accelerated Depreciation $105,759 0 0 0 0 0 21 Net Operating Loss ($40,780) 0 (17,345) 0 0 0 22 MPSC/MCC Taxes $0 0 0 0 0 0 23 Deferred Revenue $12,208 0 0 0 0 0 24 Customer Advances for Construction/CIAC $0 0 0 0 0 0 25 FAS106 & 112 Post Retirement Benefits ($59,153) 0 0 0 0 0 26 Costs of Refinancing Debt $0 0 0 0 0 0 27 Environmental Reserve $0 0 0 0 0 0 28 NonJurisdictional Items ($28,788) 0 0 0 0 0 29 SubtotalDeferred Income Tax (10,754) 0 (17,345) 0 0 0 30 31 Income TaxesFederal 0 0 0 0 0 0 32 Income TaxesCorporation License Tax 0 0 0 0 0 0 33 Income TaxesForeign Taxes 0 0 0 0 0 0 34 SubtotalCurrent Income Tax 0 0 0 0 0 0 35 Net Utility Operating Income ($495,345) $0 ($48,524) $0 $0 $0 36 Rate Base 37 Return on Rate Base #DIV/0!

GENERAL RATE CASE Docket No. D2018.2.12 Page 107 of 327 J M N O P Q ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY MONTANA GENERATION 1 Operating Revenues 2 3 Operating Expenses 4 Book Depreciation 5 Amort. of Electric Plant & Acq Adjmt 6 Amort.Misc Items 7 Taxes other than Income 8 9 Subtotal Expenses 10 Net Utility Operating Income Before Inc Tax 11 12 Amortization of Excess Deferred TaxARAM 13 Amortization of Excess Deferred TaxUnprotected Rate Base 14 Amortization of Excess Deferred TaxUnprotected NonRate 15 16 Deferred Income Taxes: 17 Injuries & Damages 18 Miscellaneous 19 Accrued Incentive Compensation 20 Accelerated Depreciation 21 Net Operating Loss 22 MPSC/MCC Taxes 23 Deferred Revenue 24 Customer Advances for Construction/CIAC 25 FAS106 & 112 Post Retirement Benefits 26 Costs of Refinancing Debt 27 Environmental Reserve 28 NonJurisdictional Items 29 SubtotalDeferred Income Tax 30 31 Income TaxesFederal 32 Income TaxesCorporation License Tax 33 Income TaxesForeign Taxes 34 SubtotalCurrent Income Tax 35 Net Utility Operating Income 36 Rate Base 37 Return on Rate Base TAXES OTHER WORKING INTEREST TOTAL TEST PERIOD AMORTIZATION THAN INCOME CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES $0 $0 $0 $0 $0 $0 $0 0 0 65,869 571,968 0 0 0 0 0 0 0 0 $0 $0 $0 $0 $0 $0 $0 65,869 571,968 $0 $0 $0 $0 $0 $0 $0 (65,869) (571,968) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 (115,591) 0 (115,591) (9,832) 0 0 0 0 0 105,414 0 88,069 47,289 0 0 0 0 0 0 0 0 0 0 0 0 0 0 (4,046) 0 (4,046) 8,162 0 0 0 0 0 0 0 0 0 0 0 0 0 0 19,606 0 19,606 (39,547) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 28,788 0 28,788 0 0 0 0 0 0 34,171 0 16,826 6,072 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 $0 $0 $0 $0 $0 ($34,171) $0 ($82,695) ($578,040) 0 0 0.00%

GENERAL RATE CASE Docket No. D2018.2.12 Page 108 of 327 ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY MONTANA GENERATION 1 Operating Revenues 2 3 Operating Expenses 4 Book Depreciation 5 Amort. of Electric Plant & Acq Adjmt 6 Amort.Misc Items 7 Taxes other than Income 8 9 Subtotal Expenses 10 Net Utility Operating Income Before Inc Tax 11 12 Amortization of Excess Deferred TaxARAM 13 Amortization of Excess Deferred TaxUnprotected Rate Base 14 Amortization of Excess Deferred TaxUnprotected NonRate 15 16 Deferred Income Taxes: 17 Injuries & Damages 18 Miscellaneous 19 Accrued Incentive Compensation 20 Accelerated Depreciation 21 Net Operating Loss 22 MPSC/MCC Taxes 23 Deferred Revenue 24 Customer Advances for Construction/CIAC 25 FAS106 & 112 Post Retirement Benefits 26 Costs of Refinancing Debt 27 Environmental Reserve 28 NonJurisdictional Items 29 SubtotalDeferred Income Tax 30 31 Income TaxesFederal 32 Income TaxesCorporation License Tax 33 Income TaxesForeign Taxes 34 SubtotalCurrent Income Tax 35 Net Utility Operating Income 36 Rate Base 37 Return on Rate Base INTERIM ADJUSTMENTS INTERIM INTERIM ADJUST TO NONPCCAM MONTANA WORKING INTEREST TOTAL TEST PERIOD ROE FROM DEPRECIATION SUPPLY GENERATION CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT DOCKET 2009.9.129 ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES $0 $0 $0 $0 $0 $0 $0 $0 $0 0 0 (571,968) (571,968) 0 0 0 0 0 0 0 0 0 $0 $0 $0 ($571,968) $0 $0 $0 $0 $0 (571,968) 0 $0 $0 $0 $571,968 $0 $0 $0 $0 $0 571,968 0 0 0 0 9,832 0 0 0 0 0 9,832 0 0 0 0 (47,288) 0 0 0 0 0 (47,288) 1 0 0 0 (8,161) 0 0 0 0 0 (8,161) 1 0 0 0 39,547 0 0 0 0 0 39,547 0 0 0 0 (6,070) 0 0 0 0 0 (6,070) 2 $0 $0 $0 $578,038 $0 $0 $0 $0 $0 $578,038 ($2) $0 $0 $0 $0 $0 $0 $0 $0 $0 0 0 0.00%

Docket No. D2018.2.12 Page 109 of 327 GENERAL RATE CASE A B C D E F G H I REVENUE SALES & ACTUAL TWELVE MONTHS ENDED 2017 INTERIM & REVENUE ADMINISTRATIVE CORPORATE NORTHWESTERN ENERGY GENERATION EMPLOYEES INCOME TAXES GENERATION RELATED & GENERAL LABOR ALLOCATION DEPRECIATION MONTANA GENERATION ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT 38 ELECTRIC UTILITY CALCULATIONS 39 Operating Revenues $0 $0 $0 $0 $0 $0 40 Operating Expenses 506,099 0 65,869 0 0 0 41 Subtotal ($506,099) $0 ($65,869) $0 $0 $0 42 Depreciation & Amortization 43 Taxes other than Income 44 Net Utility Operating Income Before Inc Tax $ (506,099) $ $ (65,869) $ $ $ 45 Taxable Additions / (Deductions): 46 Nondeductible Meal Expense ($1,000) 0 0 0 0 0 47 Bad Debt Expense Accrual Net of Chargeoffs $0 0 0 0 0 0 48 Penalties $0 0 0 0 0 0 49 Meters $0 0 0 0 0 0 50 Customer Advances for Construction/CIAC $0 0 0 0 0 0 51 Repairs Expense $636,422 0 0 0 0 0 52 Accrued Incentive Compensation $0 0 0 0 0 0 53 MPSC/MCC Taxes $0 0 0 0 0 0 54 Costs of Refinancing Debt $0 0 0 0 0 0 55 Accelerated DepreciationExcess BLM Tx vs Bk Deprec ($49,878) 0 0 0 0 0 56 Accelerated DepreciationExcess Tx Rtn vs BLM Tx Dep ($302,168) 0 0 0 0 0 57 Removal Costs Net of Salvage $0 0 0 0 0 0 58 Deferred Revenue ($30,994) 0 0 0 0 0 59 FAS106 & 112 Post Retirement Benefits $150,182 0 0 0 0 0 60 Environmental Reserve $0 0 0 0 0 0 61 Injuries & Damages $0 0 0 0 0 0 62 Net Operating Loss $103,537 0 65,869 0 0 0 63 Excludable Foreign Income $0 0 0 0 0 0 64 MT Corporation License Tax 0 0 0 0 0 0 65 Deduct Interest Charges $0 0 0 0 0 0 66 Total Tax Additons / (Deductions) $506,099 $0 $65,869 $0 $0 $0 67 Federal Taxable Income $ $ $ $ $ $ 68 Federal Income Tax @ 21% $0 $0 $0 $0 $0 $0 69 Foreign Income Tax $0 0 0 0 0 0 70 Foreign Income Tax Credit $0 0 0 0 0 0 71 NonJurisdictional Items 28,788 0 0 0 0 0 72 Prior Period Adjustments ($28,788) 0 0 0 0 0 73 Audit Adjustments $0 0 0 0 0 0 74 Total Federal Income Tax 0 0 0 0 0 0 75 76 77 Montana Corporate License Tax 78 Federal Taxable Income B4 MT Corp Tx Deductn & NOL $ 0 $ $ $ $ $ 79 Add: 80 Other $0 0 0 0 0 0 81 Other State Taxes Paid $0 0 0 0 0 0 82 83 Reduction for Unitary Allocation $0 0 0 0 0 0 84 85 Montana Taxable Income $0 $0 $0 $0 $0 $0 86 Mont. Corp. Lic. Tax @ 6.75% $0 0 0 0 0 0 87 Net Tax Adjustment $0 $0 $0 $0 $0 $0 88 Mont. Corp. License Tax $0 $0 $0 $0 $0 $0 89 Actual 6.75% 0 0 0 0 0 0 90 91 Change in tax rates $0 0 0 0 0 0 92 NonJurisdictional Items $0 0 0 0 0 0 93 Net Tax Adjustment 0 0 0 0 0 0

GENERAL RATE CASE Docket No. D2018.2.12 Page 110 of 327 J M N O P Q ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY MONTANA GENERATION 38 ELECTRIC UTILITY CALCULATIONS 39 Operating Revenues 40 Operating Expenses 41 Subtotal 42 Depreciation & Amortization 43 Taxes other than Income 44 Net Utility Operating Income Before Inc Tax 45 Taxable Additions / (Deductions): 46 Nondeductible Meal Expense 47 Bad Debt Expense Accrual Net of Chargeoffs 48 Penalties 49 Meters 50 Customer Advances for Construction/CIAC 51 Repairs Expense 52 Accrued Incentive Compensation 53 MPSC/MCC Taxes 54 Costs of Refinancing Debt 55 Accelerated DepreciationExcess BLM Tx vs Bk Deprec 56 Accelerated DepreciationExcess Tx Rtn vs BLM Tx Dep 57 Removal Costs Net of Salvage 58 Deferred Revenue 59 FAS106 & 112 Post Retirement Benefits 60 Environmental Reserve 61 Injuries & Damages 62 Net Operating Loss 63 Excludable Foreign Income 64 MT Corporation License Tax 65 Deduct Interest Charges 66 Total Tax Additons / (Deductions) 67 Federal Taxable Income 68 Federal Income Tax @ 21% 69 Foreign Income Tax 70 Foreign Income Tax Credit 71 NonJurisdictional Items 72 Prior Period Adjustments 73 Audit Adjustments 74 Total Federal Income Tax 75 76 77 Montana Corporate License Tax 78 Federal Taxable Income B4 MT Corp Tx Deductn & NOL 79 Add: 80 Other 81 Other State Taxes Paid 82 83 Reduction for Unitary Allocation 84 85 Montana Taxable Income 86 Mont. Corp. Lic. Tax @ 6.75% 87 Net Tax Adjustment 88 Mont. Corp. License Tax 89 Actual 6.75% 90 91 Change in tax rates 92 NonJurisdictional Items 93 Net Tax Adjustment TAXES OTHER WORKING INTEREST TOTAL TEST PERIOD AMORTIZATION THAN INCOME CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES $0 $0 $0 $0 $0 $0 $0 0 0 0 0 0 0 0 0 0 65,869 571,968 $0 $0 $0 $0 $0 $0 $0 (65,869) (571,968) 0 0 0 0 $ $ $ $ $ $ $ (65,869) (571,968) 0 0 0 0 0 0 0 0 (1,000) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 636,422 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 (49,878) 0 0 0 0 0 348,987 0 348,987 46,818 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 (30,994) 0 0 0 0 0 0 0 0 150,182 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 (348,987) 0 (283,118) (179,581) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 $0 $0 $0 $0 $0 ($0) $0 $65,869 $571,968 $ $ $ $ $ $ (0) $ $ $ $0 $0 $0 $0 $0 $0 $0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 (28,788) 0 (28,788) 0 0 0 0 0 0 28,788 0 28,788 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 $ $ $ $ $ $ (0) $ (0) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 $0 $0 $0 $0 $0 ($0) $0 (0) 0 0 0 0 0 0 0 0 0 0 $0 $0 $0 $0 $0 $0 $0 0 0 $0 $0 $0 $0 $0 $0 $0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

GENERAL RATE CASE ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY MONTANA GENERATION 38 ELECTRIC UTILITY CALCULATIONS 39 Operating Revenues 40 Operating Expenses 41 Subtotal 42 Depreciation & Amortization 43 Taxes other than Income 44 Net Utility Operating Income Before Inc Tax 45 Taxable Additions / (Deductions): 46 Nondeductible Meal Expense 47 Bad Debt Expense Accrual Net of Chargeoffs 48 Penalties 49 Meters 50 Customer Advances for Construction/CIAC 51 Repairs Expense 52 Accrued Incentive Compensation 53 MPSC/MCC Taxes 54 Costs of Refinancing Debt 55 Accelerated DepreciationExcess BLM Tx vs Bk Deprec 56 Accelerated DepreciationExcess Tx Rtn vs BLM Tx Dep 57 Removal Costs Net of Salvage 58 Deferred Revenue 59 FAS106 & 112 Post Retirement Benefits 60 Environmental Reserve 61 Injuries & Damages 62 Net Operating Loss 63 Excludable Foreign Income 64 MT Corporation License Tax 65 Deduct Interest Charges 66 Total Tax Additons / (Deductions) 67 Federal Taxable Income 68 Federal Income Tax @ 21% 69 Foreign Income Tax 70 Foreign Income Tax Credit 71 NonJurisdictional Items 72 Prior Period Adjustments 73 Audit Adjustments 74 Total Federal Income Tax 75 76 77 Montana Corporate License Tax 78 Federal Taxable Income B4 MT Corp Tx Deductn & NOL 79 Add: 80 Other 81 Other State Taxes Paid 82 83 Reduction for Unitary Allocation 84 85 Montana Taxable Income 86 Mont. Corp. Lic. Tax @ 6.75% 87 Net Tax Adjustment 88 Mont. Corp. License Tax 89 Actual 6.75% 90 91 Change in tax rates 92 NonJurisdictional Items 93 Net Tax Adjustment Docket No. D2018.2.12 Page 111 of 327 INTERIM ADJUSTMENTS INTERIM INTERIM ADJUST TO NONPCCAM MONTANA WORKING INTEREST TOTAL TEST PERIOD ROE FROM DEPRECIATION SUPPLY GENERATION CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT DOCKET 2009.9.129 ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES $0 $0 $0 $0 $0 $0 $0 $0 $0 0 0 0 0 0 (571,968) 0 0 0 0 0 (571,968) 0 $0 $0 $0 $571,968 $0 $0 $0 $0 $0 571,968 0 0 0 0 0 $ $ $ $ 571,968 $ $ $ $ $ 571,968 0 0 0 0 1,000 0 0 0 0 0 1,000 0 0 0 0 (636,422) 0 0 0 0 0 (636,422) 0 0 0 0 49,878 0 0 0 0 0 49,878 0 0 0 0 (46,818) 0 0 0 0 0 (46,818) 0 0 0 0 30,994 0 0 0 0 0 30,994 0 0 0 0 (150,182) 0 0 0 0 0 (150,182) 0 0 0 0 179,581 0 0 0 0 0 179,581 0 $0 $0 $0 ($571,968) $0 $0 $0 $0 $0 ($571,968) $0 $ $ $ $ $ $ $ $ $ $ $ $0 $0 $0 $0 $0 $0 $0 $0 $0 0 0 $ $ $ $ $ $ $ $ $ 0 0 $0 $0 $0 $0 $0 $0 $0 $0 $0 0 0 $0 $0 $0 $0 $0 $0 $0 $0 $0 0 0 $0 $0 $0 $0 $0 $0 $0 $0 $0 0 0

Docket No. D2018.2.12 Page 112 of 327 GENERAL RATE CASE A B C D E F G H I REVENUE SALES & ACTUAL TWELVE MONTHS ENDED 2017 INTERIM & REVENUE ADMINISTRATIVE CORPORATE NORTHWESTERN ENERGY GENERATION EMPLOYEES INCOME TAXES GENERATION RELATED & GENERAL LABOR ALLOCATION DEPRECIATION MONTANA GENERATION ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT COMPUTATION OF REQUIRED RETURN AND REVENUE INCREASE 1 Electric Utility Rate Base $0 $0 $0 $0 $0 $0 2 Rate of Return 7.42% 7.42% 7.42% 7.42% 7.42% 7.42% 3 4 5 Net Operating Income 0 0 0 0 0 0 6 7 Net Operating Income for the Year 8 Ended 12/31/17 Adjusted for Known Changes (495,345) 0 (48,524) 0 0 0 9 10 Required Incremental Increase in Net 11 Operating Income $495,345 $0 $48,524 $0 $0 $0 12 13 Add: 14 MPSC Tax 1,645 0 161 0 0 0 15 Consumer Counsel Tax 310 0 30 0 0 0 16 Incremental Income Taxes 177,061 0 17,345 0 0 0 17 18 Required Revenue Increase $674,361 $0 $66,060 $0 $0 $0 19 20 21 MPSC Tax (0.244%) 1,645 0 161 0 0 0 22 23 Consumer Counsel Tax (0.046%) 310 0 30 0 0 0 24 25 Taxable Income for State Income Tax $672,406 $0 $65,869 $0 $0 $0 26 27 State Income Tax (6.75%) (Unitary Factor = 1.00) 45,387 0 4,446 0 0 0 28 29 Taxable Income for Federal Income Tax $627,019 $0 $61,423 $0 $0 $0 30 31 Reduction of Fed.Inc.TaxDue to MCLT Expense (9,531) 0 (934) 0 0 0 32 Federal Income Tax Expense (21%) 141,205 0 13,833 0 0 0 33 34 Required Incremental Increase in Net 35 Operating Income $495,345 $0 $48,524 $0 $0 $0

GENERAL RATE CASE Docket No. D2018.2.12 Page 113 of 327 J M N O P Q ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY MONTANA GENERATION COMPUTATION OF REQUIRED RETURN AND REVENUE INCREASE 1 Electric Utility Rate Base 2 Rate of Return 3 4 5 Net Operating Income 6 7 Net Operating Income for the Year 8 Ended 12/31/17 Adjusted for Known Changes 9 10 Required Incremental Increase in Net 11 Operating Income 12 13 Add: 14 MPSC Tax 15 Consumer Counsel Tax 16 Incremental Income Taxes 17 18 Required Revenue Increase 19 20 21 MPSC Tax (0.244%) 22 23 Consumer Counsel Tax (0.046%) 24 25 Taxable Income for State Income Tax 26 27 State Income Tax (6.75%) (Unitary Factor = 1.00) 28 29 Taxable Income for Federal Income Tax 30 31 Reduction of Fed.Inc.TaxDue to MCLT Expense 32 Federal Income Tax Expense (21%) 33 34 Required Incremental Increase in Net 35 Operating Income TAXES OTHER WORKING INTEREST TOTAL TEST PERIOD AMORTIZATION THAN INCOME CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES $0 $0 $0 $0 $0 $0 $0 $0 $0 7.42% 7.42% 7.42% 7.42% 7.42% 7.42% 7.42% 7.42% 7.42% 0 0 0 0 0 0 0 0 0 0 0 0 0 0 (34,171) 0 (82,695) (578,040) $0 $0 $0 $0 $0 $34,171 $0 $82,695 $578,040 0 0 0 0 0 114 0 275 1,920 0 0 0 0 0 21 0 51 361 0 0 0 0 0 12,214 0 29,559 206,620 $0 $0 $0 $0 $0 $46,520 $0 $112,580 $786,941 0 0 0 0 0 114 0 275 1,920 0 0 0 0 0 21 0 51 361 $0 $0 $0 $0 $0 $46,385 $0 112,254 784,660 0 0 0 0 0 3,131 0 7,577 52,964 $0 $0 $0 $0 $0 $43,254 $0 $104,677 $731,696 0 0 0 0 0 (658) 0 (1,592) (11,123) 0 0 0 0 0 9,741 0 23,574 164,779 $0 $0 $0 $0 $0 $34,171 $0 $82,695 $578,040

GENERAL RATE CASE ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY MONTANA GENERATION COMPUTATION OF REQUIRED RETURN AND REVENUE INCREASE 1 Electric Utility Rate Base 2 Rate of Return 3 4 5 Net Operating Income 6 7 Net Operating Income for the Year 8 Ended 12/31/17 Adjusted for Known Changes 9 10 Required Incremental Increase in Net 11 Operating Income 12 13 Add: 14 MPSC Tax 15 Consumer Counsel Tax 16 Incremental Income Taxes 17 18 Required Revenue Increase 19 20 21 MPSC Tax (0.244%) 22 23 Consumer Counsel Tax (0.046%) 24 25 Taxable Income for State Income Tax 26 27 State Income Tax (6.75%) (Unitary Factor = 1.00) 28 29 Taxable Income for Federal Income Tax 30 31 Reduction of Fed.Inc.TaxDue to MCLT Expense 32 Federal Income Tax Expense (21%) 33 34 Required Incremental Increase in Net 35 Operating Income Docket No. D2018.2.12 Page 114 of 327 INTERIM ADJUSTMENTS INTERIM INTERIM ADJUST TO NONPCCAM MONTANA WORKING INTEREST TOTAL TEST PERIOD ROE FROM DEPRECIATION SUPPLY GENERATION CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT DOCKET 2009.9.129 ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 0.20% 7.22% 7.22% 7.22% 7.22% 7.22% 7.22% 7.22% 7.22% 7.22% 7.22% 0 0 0 578,038 0 0 0 0 0 578,038 (2) $0 $0 $0 ($578,038) $0 $0 $0 $0 $0 ($578,038) $2 0 0 0 (1,920) 0 0 0 0 0 (1,920) 0 0 0 0 (362) 0 0 0 0 0 (362) (1) 0 0 0 (206,620) 0 0 0 0 0 (206,620) 0 $0 $0 $0 ($786,940) $0 $0 $0 $0 $0 ($786,940) $1 0 0 0 (1,920) 0 0 0 0 0 (1,920) 0 0 0 0 (362) 0 0 0 0 0 (362) (1) $0 $0 $0 ($784,658) $0 $0 $0 $0 $0 (784,658) 2 0 0 0 (52,964) 0 0 0 0 0 (52,964) 0 $0 $0 $0 ($731,694) $0 $0 $0 $0 $0 (731,694) 2 0 0 0 11,122 0 0 0 0 0 11,122 (1) 0 0 0 (164,778) 0 0 0 0 0 (164,778) 1 $0 $0 $0 ($578,038) $0 $0 $0 $0 $0 ($578,038) $2

Docket No. D2018.2.12 Page 115 of 327 GENERAL RATE CASE A B C D E F G H I J REVENUE SALES & ACTUAL TWELVE MONTHS ENDED 2017 INTERIM REMOVE REMOVE ELECTRIC SUPPLY & REVENUE ADMINISTRATIVE CORPORATE NORTHWESTERN ENERGY ELECTRIC SUPPLY PCCAM DEFERRED NONPCCAM RELATED & GENERAL LABOR ALLOCATION DEPRECIATION AMORTIZATION ELECTRIC SUPPLY NONPCCAM ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT 1 Operating Revenues $133,471,215 $121,853,032 $11,618,183 $0 $0 $0 $0 $0 $0 $0 2 3 Operating Expenses 135,062,448 113,231,423 11,618,183 10,212,841 20,349 4 Book Depreciation 5 Amort. of Electric Plant & Acq Adjmt 6 Amort.Misc Items 7 Taxes other than Income 671,856 564,803 107,053 1,447 8 9 Subtotal Expenses $135,734,305 $113,796,226 $11,618,183 $10,319,895 $0 $0 $21,796 $0 $0 $0 10 Net Utility Operating Income Before Inc Tax ($2,263,089) $8,056,805 $0 ($10,319,895) $0 $0 ($21,796) $0 $0 $0 11 12 Amortization of Excess Deferred TaxARAM $0 0 0 0 0 0 0 13 Amortization of Excess Deferred TaxUnprotected Rate Base $0 0 0 0 0 0 0 14 Amortization of Excess Deferred TaxUnprotected NonRate Base $0 0 0 0 0 0 0 15 16 Deferred Income Taxes: 17 Injuries & Damages $0 0 0 0 0 0 0 18 Miscellaneous $0 0 0 0 0 0 0 19 Accrued Incentive Compensation $0 0 0 0 0 0 0 20 Accelerated Depreciation $0 0 0 0 0 0 0 21 Net Operating Loss ($3,614,558) 0 0 (5,739) 0 0 0 22 MPSC/MCC Taxes $0 0 0 0 0 0 0 23 Deferred Revenue $0 0 0 0 0 0 0 24 Customer Advances for Construction/CIAC $0 0 0 0 0 0 0 25 FAS106 & 112 Post Retirement Benefits $0 0 0 0 0 0 0 26 Costs of Refinancing Debt $0 0 0 0 0 0 0 27 Environmental Reserve $0 0 0 0 0 0 0 28 NonJurisdictional Items $3,173,374 0 0 0 0 0 0 29 SubtotalDeferred Income Tax (441,184) 0 0 (5,739) 0 0 0 30 31 Income TaxesFederal 0 0 0 0 0 0 0 32 Income TaxesCorporation License Tax 0 0 0 0 0 0 0 33 Income TaxesForeign Taxes 0 0 0 0 0 0 0 34 SubtotalCurrent Income Tax 0 0 0 0 0 0 0 35 Net Utility Operating Income ($9,878,711) $0 $0 ($16,057) $0 $0 $0 36 Rate Base $0 37 Return on Rate Base #DIV/0!

Docket No. D2018.2.12 Page 116 of 327 GENERAL RATE CASE M N O P Q ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY ELECTRIC SUPPLY NONPCCAM 1 Operating Revenues 2 3 Operating Expenses 4 Book Depreciation 5 Amort. of Electric Plant & Acq Adjmt 6 Amort.Misc Items 7 Taxes other than Income 8 9 Subtotal Expenses 10 Net Utility Operating Income Before Inc Tax 11 12 Amortization of Excess Deferred TaxARAM 13 Amortization of Excess Deferred TaxUnprotected Rate Base 14 Amortization of Excess Deferred TaxUnprotected NonRate 15 16 Deferred Income Taxes: 17 Injuries & Damages 18 Miscellaneous 19 Accrued Incentive Compensation 20 Accelerated Depreciation 21 Net Operating Loss 22 MPSC/MCC Taxes 23 Deferred Revenue 24 Customer Advances for Construction/CIAC 25 FAS106 & 112 Post Retirement Benefits 26 Costs of Refinancing Debt 27 Environmental Reserve 28 NonJurisdictional Items 29 SubtotalDeferred Income Tax 30 31 Income TaxesFederal 32 Income TaxesCorporation License Tax 33 Income TaxesForeign Taxes 34 SubtotalCurrent Income Tax 35 Net Utility Operating Income 36 Rate Base 37 Return on Rate Base TAXES OTHER CAPITALIZE WORKING INTEREST TOTAL TEST PERIOD THAN INCOME DSM CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT ADJUSTMENT COSTS ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES $0 $0 $0 $0 $0 $0 $0 $0 $0 0 0 (7,762,146) (7,741,797) 2,471,044 0 0 0 0 0 0 1,447 108,500 $0 ($7,762,146) $0 $0 $0 $0 $0 $0 $0 (7,740,350) 2,579,545 $0 $7,762,146 $0 $0 $0 $0 $0 $0 $0 7,740,350 (2,579,545) 0 2,043,967 0 0 0 0 0 1,198,046 (300,975) 2,935,299 (679,259) 0 0 0 0 0 0 0 (3,173,374) 0 (3,173,374) 0 0 2,043,967 0 0 0 0 0 (1,975,328) (300,975) (238,075) (679,259) $0 $5,718,179 $0 $0 $0 $0 $0 $1,975,328 $300,975 $7,978,425 ($1,900,286) 0.00% 0 0 0.00%

Docket No. D2018.2.12 Page 117 of 327 GENERAL RATE CASE ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY ELECTRIC SUPPLY NONPCCAM 1 Operating Revenues 2 3 Operating Expenses 4 Book Depreciation 5 Amort. of Electric Plant & Acq Adjmt 6 Amort.Misc Items 7 Taxes other than Income 8 9 Subtotal Expenses 10 Net Utility Operating Income Before Inc Tax 11 12 Amortization of Excess Deferred TaxARAM 13 Amortization of Excess Deferred TaxUnprotected Rate Base 14 Amortization of Excess Deferred TaxUnprotected NonRate 15 16 Deferred Income Taxes: 17 Injuries & Damages 18 Miscellaneous 19 Accrued Incentive Compensation 20 Accelerated Depreciation 21 Net Operating Loss 22 MPSC/MCC Taxes 23 Deferred Revenue 24 Customer Advances for Construction/CIAC 25 FAS106 & 112 Post Retirement Benefits 26 Costs of Refinancing Debt 27 Environmental Reserve 28 NonJurisdictional Items 29 SubtotalDeferred Income Tax 30 31 Income TaxesFederal 32 Income TaxesCorporation License Tax 33 Income TaxesForeign Taxes 34 SubtotalCurrent Income Tax 35 Net Utility Operating Income 36 Rate Base 37 Return on Rate Base INTERIM ADJUSTMENTS INTERIM INTERIM ADJUST TO NONPCCAM MONTANA WORKING INTEREST TOTAL TEST PERIOD ROE FROM DEPRECIATION SUPPLY GENERATION CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT DOCKET 2009.9.129 ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES $0 $0 $0 $0 $0 $0 $0 $0 $0 0 0 (741,103) (741,103) 1,729,942 0 0 0 0 0 0 0 108,500 $0 $0 ($741,103) $0 $0 $0 $0 $0 $0 (741,103) 1,838,442 $0 $0 $741,103 $0 $0 $0 $0 $0 $0 741,103 (1,838,442) 0 0 195,151 0 0 0 0 0 0 195,151 (484,108) 0 0 195,151 0 0 0 0 0 0 195,151 (484,108) $0 $0 $545,952 $0 $0 $0 $0 $0 $0 $545,952 ($1,354,334) $0 $0 $0 $0 $0 $0 $0 $0 $0 0 0 0.00%

Docket No. D2018.2.12 Page 118 of 327 GENERAL RATE CASE A B C D E F G H I J REVENUE SALES & ACTUAL TWELVE MONTHS ENDED 2017 INTERIM REMOVE REMOVE ELECTRIC SUPPLY & REVENUE ADMINISTRATIVE CORPORATE NORTHWESTERN ENERGY ELECTRIC SUPPLY PCCAM DEFERRED NONPCCAM RELATED & GENERAL LABOR ALLOCATION DEPRECIATION AMORTIZATION ELECTRIC SUPPLY NONPCCAM ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT 38 ELECTRIC UTILITY CALCULATIONS 39 Operating Revenues $0 $0 $0 $0 $0 $0 $0 40 Operating Expenses 10,212,841 0 0 20,349 0 0 0 41 Subtotal ($10,212,841) $0 $0 ($20,349) $0 $0 $0 42 Depreciation & Amortization 43 Taxes other than Income 107,053 1,447 44 Net Utility Operating Income Before Inc Tax $ (10,319,895) $ $ $ (21,796) $ $ $ 45 Taxable Additions / (Deductions): 46 Nondeductible Meal Expense $0 0 0 0 0 0 0 47 Bad Debt Expense Accrual Net of Chargeoffs $0 0 0 0 0 0 0 48 Penalties $0 0 0 0 0 0 0 49 Meters $0 0 0 0 0 0 0 50 Customer Advances for Construction/CIAC $0 0 0 0 0 0 0 51 Repairs Expense $0 0 0 0 0 0 0 52 Accrued Incentive Compensation $0 0 0 0 0 0 0 53 MPSC/MCC Taxes $0 0 0 0 0 0 0 54 Costs of Refinancing Debt $0 0 0 0 0 0 0 55 Accelerated DepreciationExcess BLM Tx vs Bk Deprec $0 0 0 0 0 0 0 56 Accelerated DepreciationExcess Tx Rtn vs BLM Tx Dep $0 0 0 0 0 0 0 57 Removal Costs Net of Salvage $0 0 0 0 0 0 0 58 Deferred Revenue $0 0 0 0 0 0 0 59 FAS106 & 112 Post Retirement Benefits $0 0 0 0 0 0 0 60 Environmental Reserve $0 0 0 0 0 0 0 61 Injuries & Damages $0 0 0 0 0 0 0 62 Net Operating Loss $9,176,917 0 0 21,796 0 0 0 63 Excludable Foreign Income $0 0 0 0 0 0 0 64 MT Corporation License Tax 0 0 0 0 0 0 0 65 Deduct Interest Charges $1,142,978 0 0 0 0 0 0 66 Total Tax Additons / (Deductions) $10,319,895 $0 $0 $21,796 $0 $0 $0 67 Federal Taxable Income $ $ $ $ $ $ $ 68 Federal Income Tax @ 21% $0 $0 $0 $0 $0 $0 $0 69 Foreign Income Tax $0 0 0 0 0 0 0 70 Foreign Income Tax Credit $0 0 0 0 0 0 0 71 NonJurisdictional Items (3,173,374) 0 0 0 0 0 0 72 Prior Period Adjustments $3,173,374 0 0 0 0 0 0 73 Audit Adjustments $0 0 0 0 0 0 0 74 Total Federal Income Tax 0 0 0 0 0 0 0 75 76 77 Montana Corporate License Tax 78 Federal Taxable Income B4 MT Corp Tx Deductn & NOL $ $ $ $ $ $ $ 79 Add: 80 Other $0 0 0 0 0 0 0 81 Other State Taxes Paid $0 0 0 0 0 0 0 82 83 Reduction for Unitary Allocation $0 0 0 0 0 0 0 84 85 Montana Taxable Income $0 $0 $0 $0 $0 $0 $0 86 Mont. Corp. Lic. Tax @ 6.75% $0 0 0 0 0 0 0 87 Net Tax Adjustment $0 $0 $0 $0 $0 $0 $0 88 Mont. Corp. License Tax $0 $0 $0 $0 $0 $0 $0 89 Actual 6.75% 0 0 0 0 0 0 0 90 91 Change in tax rates $0 0 0 0 0 0 0 92 NonJurisdictional Items $0 0 0 0 0 0 0 93 Net Tax Adjustment 0 0 0 0 0 0 0

Docket No. D2018.2.12 Page 119 of 327 GENERAL RATE CASE M N O P Q ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY ELECTRIC SUPPLY NONPCCAM 38 ELECTRIC UTILITY CALCULATIONS 39 Operating Revenues 40 Operating Expenses 41 Subtotal 42 Depreciation & Amortization 43 Taxes other than Income 44 Net Utility Operating Income Before Inc Tax 45 Taxable Additions / (Deductions): 46 Nondeductible Meal Expense 47 Bad Debt Expense Accrual Net of Chargeoffs 48 Penalties 49 Meters 50 Customer Advances for Construction/CIAC 51 Repairs Expense 52 Accrued Incentive Compensation 53 MPSC/MCC Taxes 54 Costs of Refinancing Debt 55 Accelerated DepreciationExcess BLM Tx vs Bk Deprec 56 Accelerated DepreciationExcess Tx Rtn vs BLM Tx Dep 57 Removal Costs Net of Salvage 58 Deferred Revenue 59 FAS106 & 112 Post Retirement Benefits 60 Environmental Reserve 61 Injuries & Damages 62 Net Operating Loss 63 Excludable Foreign Income 64 MT Corporation License Tax 65 Deduct Interest Charges 66 Total Tax Additons / (Deductions) 67 Federal Taxable Income 68 Federal Income Tax @ 21% 69 Foreign Income Tax 70 Foreign Income Tax Credit 71 NonJurisdictional Items 72 Prior Period Adjustments 73 Audit Adjustments 74 Total Federal Income Tax 75 76 77 Montana Corporate License Tax 78 Federal Taxable Income B4 MT Corp Tx Deductn & NOL 79 Add: 80 Other 81 Other State Taxes Paid 82 83 Reduction for Unitary Allocation 84 85 Montana Taxable Income 86 Mont. Corp. Lic. Tax @ 6.75% 87 Net Tax Adjustment 88 Mont. Corp. License Tax 89 Actual 6.75% 90 91 Change in tax rates 92 NonJurisdictional Items 93 Net Tax Adjustment TAXES OTHER CAPITALIZE WORKING INTEREST TOTAL TEST PERIOD THAN INCOME DSM CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT ADJUSTMENT COSTS ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES $0 $0 $0 $0 $0 $0 $0 $0 $0 0 0 0 (7,762,146) 0 0 0 0 0 0 0 (7,741,797) 2,471,044 $0 $7,762,146 $0 $0 $0 $0 $0 $0 $0 7,741,797 (2,471,044) 0 0 1,447 108,500 $ $ 7,762,146 $ $ $ $ $ $ $ 7,740,350 (2,579,545) 0 (7,762,146) 0 0 0 0 0 0 1,142,978 (6,597,372) 2,579,544 0 0 0 0 0 0 0 0 (1,142,978) (1,142,978) 0 $0 ($7,762,146) $0 $0 $0 $0 $0 $0 $0 ($7,740,350) $2,579,545 $ $ $ $ $ $ $ $ $ $ $ $0 $0 $0 $0 $0 $0 $0 $0 $0 0 0 0 0 0 0 0 0 0 3,173,374 0 3,173,374 0 0 0 0 0 0 0 0 (3,173,374) 0 (3,173,374) 0 $ $ $ $ $ $ $ $ $ 0 0 $0 $0 $0 $0 $0 $0 $0 $0 $0 0 0 $0 $0 $0 $0 $0 $0 $0 $0 $0 0 0 $0 $0 $0 $0 $0 $0 $0 $0 $0 0 0

Docket No. D2018.2.12 Page 120 of 327 GENERAL RATE CASE ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY ELECTRIC SUPPLY NONPCCAM 38 ELECTRIC UTILITY CALCULATIONS 39 Operating Revenues 40 Operating Expenses 41 Subtotal 42 Depreciation & Amortization 43 Taxes other than Income 44 Net Utility Operating Income Before Inc Tax 45 Taxable Additions / (Deductions): 46 Nondeductible Meal Expense 47 Bad Debt Expense Accrual Net of Chargeoffs 48 Penalties 49 Meters 50 Customer Advances for Construction/CIAC 51 Repairs Expense 52 Accrued Incentive Compensation 53 MPSC/MCC Taxes 54 Costs of Refinancing Debt 55 Accelerated DepreciationExcess BLM Tx vs Bk Deprec 56 Accelerated DepreciationExcess Tx Rtn vs BLM Tx Dep 57 Removal Costs Net of Salvage 58 Deferred Revenue 59 FAS106 & 112 Post Retirement Benefits 60 Environmental Reserve 61 Injuries & Damages 62 Net Operating Loss 63 Excludable Foreign Income 64 MT Corporation License Tax 65 Deduct Interest Charges 66 Total Tax Additons / (Deductions) 67 Federal Taxable Income 68 Federal Income Tax @ 21% 69 Foreign Income Tax 70 Foreign Income Tax Credit 71 NonJurisdictional Items 72 Prior Period Adjustments 73 Audit Adjustments 74 Total Federal Income Tax 75 76 77 Montana Corporate License Tax 78 Federal Taxable Income B4 MT Corp Tx Deductn & NOL 79 Add: 80 Other 81 Other State Taxes Paid 82 83 Reduction for Unitary Allocation 84 85 Montana Taxable Income 86 Mont. Corp. Lic. Tax @ 6.75% 87 Net Tax Adjustment 88 Mont. Corp. License Tax 89 Actual 6.75% 90 91 Change in tax rates 92 NonJurisdictional Items 93 Net Tax Adjustment INTERIM ADJUSTMENTS INTERIM INTERIM ADJUST TO NONPCCAM MONTANA WORKING INTEREST TOTAL TEST PERIOD ROE FROM DEPRECIATION SUPPLY GENERATION CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT DOCKET 2009.9.129 ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES $0 $0 $0 $0 $0 $0 $0 $0 $0 0 0 0 0 (741,103) 0 0 0 0 0 0 (741,103) 1,729,942 $0 $0 $741,103 $0 $0 $0 $0 $0 $0 741,103 (1,729,942) 0 0 0 108,500 $ $ $ 741,103 $ $ $ $ $ $ 741,103 (1,838,442) 0 0 (741,103) 0 0 0 0 0 0 (741,103) 1,838,442 $0 $0 ($741,103) $0 $0 $0 $0 $0 $0 ($741,103) $1,838,442 $ $ $ $ $ $ $ $ $ $ $ $0 $0 $0 $0 $0 $0 $0 $0 $0 0 0 $ $ $ $ $ $ $ $ $ 0 0 $0 $0 $0 $0 $0 $0 $0 $0 $0 0 0 $0 $0 $0 $0 $0 $0 $0 $0 $0 0 0 $0 $0 $0 $0 $0 $0 $0 $0 $0 0 0

Docket No. D2018.2.12 Page 121 of 327 GENERAL RATE CASE A B C D E F G H I J REVENUE SALES & ACTUAL TWELVE MONTHS ENDED 2017 INTERIM REMOVE REMOVE ELECTRIC SUPPLY & REVENUE ADMINISTRATIVE CORPORATE NORTHWESTERN ENERGY ELECTRIC SUPPLY PCCAM DEFERRED NONPCCAM RELATED & GENERAL LABOR ALLOCATION DEPRECIATION AMORTIZATION ELECTRIC SUPPLY NONPCCAM ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT COMPUTATION OF REQUIRED RETURN AND REVENUE INCREASE 1 Electric Utility Rate Base $0 $0 $0 $0 $0 $0 $0 2 Rate of Return 7.42% 7.42% 7.42% 7.42% 7.42% 7.42% 7.42% 3 4 5 Net Operating Income 0 0 0 0 0 0 0 6 7 Net Operating Income for the Year 8 Ended 12/31/17 Adjusted for Known Changes (9,878,711) 0 0 (16,057) 0 0 0 9 10 Required Incremental Increase in Net 11 Operating Income $9,878,711 $0 $0 $16,057 $0 $0 $0 12 13 Add: 14 MPSC Tax 32,815 0 0 53 0 0 0 15 Consumer Counsel Tax 6,186 0 0 10 0 0 0 16 Incremental Income Taxes 3,531,152 0 0 5,739 0 0 0 17 18 Required Revenue Increase $13,448,864 $0 $0 $21,859 $0 $0 $0 19 20 21 MPSC Tax (0.244%) 32,815 0 0 53 0 0 0 22 23 Consumer Counsel Tax (0.046%) 6,186 0 0 10 0 0 0 24 25 Taxable Income for State Income Tax $13,409,863 $0 $0 $21,796 $0 $0 $0 26 27 State Income Tax (6.75%) (Unitary Factor = 1.00) 905,166 0 0 1,471 0 0 0 28 29 Taxable Income for Federal Income Tax $12,504,697 $0 $0 $20,325 $0 $0 $0 30 31 Reduction of Fed.Inc.TaxDue to MCLT Expense (190,085) 0 0 (309) 0 0 0 32 Federal Income Tax Expense (21%) 2,816,071 0 0 4,577 0 0 0 33 34 Required Incremental Increase in Net 35 Operating Income $9,878,711 $0 $0 $16,057 $0 $0 $0

Docket No. D2018.2.12 Page 122 of 327 GENERAL RATE CASE M N O P Q ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY ELECTRIC SUPPLY NONPCCAM COMPUTATION OF REQUIRED RETURN AND REVENUE INCREASE 1 Electric Utility Rate Base 2 Rate of Return 3 4 5 Net Operating Income 6 7 Net Operating Income for the Year 8 Ended 12/31/17 Adjusted for Known Changes 9 10 Required Incremental Increase in Net 11 Operating Income 12 13 Add: 14 MPSC Tax 15 Consumer Counsel Tax 16 Incremental Income Taxes 17 18 Required Revenue Increase 19 20 21 MPSC Tax (0.244%) 22 23 Consumer Counsel Tax (0.046%) 24 25 Taxable Income for State Income Tax 26 27 State Income Tax (6.75%) (Unitary Factor = 1.00) 28 29 Taxable Income for Federal Income Tax 30 31 Reduction of Fed.Inc.TaxDue to MCLT Expense 32 Federal Income Tax Expense (21%) 33 34 Required Incremental Increase in Net 35 Operating Income TAXES OTHER CAPITALIZE WORKING INTEREST TOTAL TEST PERIOD THAN INCOME DSM CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT ADJUSTMENT COSTS ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 7.42% 7.42% 7.42% 7.42% 7.42% 7.42% 7.42% 7.42% 7.42% 7.42% 7.42% 0 5,718,179 0 0 0 0 0 1,975,328 300,975 7,978,425 (1,900,286) $0 ($5,718,179) $0 $0 $0 $0 $0 ($1,975,328) ($300,975) ($7,978,425) $1,900,286 0 (18,995) 0 0 0 0 0 (6,562) (1,000) (26,504) 6,311 0 (3,581) 0 0 0 0 0 (1,237) (188) (4,996) 1,190 0 (2,043,967) 0 0 0 0 0 (706,082) (107,584) (2,851,894) 679,258 $0 ($7,784,722) $0 $0 $0 $0 $0 ($2,689,209) ($409,747) ($10,861,819) $2,587,045 0 (18,995) 0 0 0 0 0 (6,562) (1,000) (26,504) 6,311 0 (3,581) 0 0 0 0 0 (1,237) (188) (4,996) 1,190 $0 ($7,762,146) $0 $0 $0 $0 $0 ($2,681,410) ($408,559) (10,830,319) 2,579,544 0 (523,945) 0 0 0 0 0 (180,995) (27,578) (731,047) 174,119 $0 ($7,238,201) $0 $0 $0 $0 $0 ($2,500,415) ($380,981) ($10,099,272) $2,405,425 0 110,028 0 0 0 0 0 38,009 5,791 153,519 (36,566) 0 (1,630,050) 0 0 0 0 0 (563,096) (85,797) (2,274,366) 541,705 $0 ($5,718,179) $0 $0 $0 $0 $0 ($1,975,328) ($300,975) ($7,978,425) $1,900,286

Docket No. D2018.2.12 Page 123 of 327 GENERAL RATE CASE ACTUAL TWELVE MONTHS ENDED 2017 INTERIM NORTHWESTERN ENERGY ELECTRIC SUPPLY NONPCCAM COMPUTATION OF REQUIRED RETURN AND REVENUE INCREASE 1 Electric Utility Rate Base 2 Rate of Return 3 4 5 Net Operating Income 6 7 Net Operating Income for the Year 8 Ended 12/31/17 Adjusted for Known Changes 9 10 Required Incremental Increase in Net 11 Operating Income 12 13 Add: 14 MPSC Tax 15 Consumer Counsel Tax 16 Incremental Income Taxes 17 18 Required Revenue Increase 19 20 21 MPSC Tax (0.244%) 22 23 Consumer Counsel Tax (0.046%) 24 25 Taxable Income for State Income Tax 26 27 State Income Tax (6.75%) (Unitary Factor = 1.00) 28 29 Taxable Income for Federal Income Tax 30 31 Reduction of Fed.Inc.TaxDue to MCLT Expense 32 Federal Income Tax Expense (21%) 33 34 Required Incremental Increase in Net 35 Operating Income INTERIM ADJUSTMENTS INTERIM INTERIM ADJUST TO NONPCCAM MONTANA WORKING INTEREST TOTAL TEST PERIOD ROE FROM DEPRECIATION SUPPLY GENERATION CAPITAL INCOME TAX SYNCHRONIZATION UPDATES & @ PRESENT DOCKET 2009.9.129 ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT ADJUSTMENTS RATES $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 0.20% 7.22% 7.22% 7.22% 7.22% 7.22% 7.22% 7.22% 7.22% 7.22% 7.22% 0 0 545,952 0 0 0 0 0 0 545,952 (1,354,334) $0 $0 ($545,952) $0 $0 $0 $0 $0 $0 ($545,952) $1,354,334 0 0 (1,814) 0 0 0 0 0 0 (1,814) 4,497 0 0 (342) 0 0 0 0 0 0 (342) 848 0 0 (195,150) 0 0 0 0 0 0 (195,150) 484,108 $0 $0 ($743,258) $0 $0 $0 $0 $0 $0 ($743,258) $1,843,787 0 0 (1,814) 0 0 0 0 0 0 (1,814) 4,497 0 0 (342) 0 0 0 0 0 0 (342) 848 $0 $0 ($741,102) $0 $0 $0 $0 $0 $0 (741,102) 1,838,442 0 0 (50,024) 0 0 0 0 0 0 (50,024) 124,095 $0 $0 ($691,078) $0 $0 $0 $0 $0 $0 (691,078) 1,714,347 0 0 10,505 0 0 0 0 0 0 10,505 (26,061) 0 0 (155,631) 0 0 0 0 0 0 (155,631) 386,074 $0 $0 ($545,952) $0 $0 $0 $0 $0 $0 ($545,952) $1,354,334

Docket No. D2018.2.12 Page 124 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 A B C D E F G NorthWestern Energy Electric Transmission & Distribution Utility Derivation of Uniform Percentage Increase Docket No. D2018.2.12 Proposed Interim Revenues Uniform % @ Current Proposed Change Transmission & Distribution Base Rates Change (C)/(E) Rate Without Taxes Total T&D Revenue Requirement without Taxes $ 200,263,409 $ (4,918,420) 2.4560% Rounding Base Rates to Nearest Nickel $ 95,000 Adjusted Uniform Percent Increase $ (4,823,420) 2.4085% Tax Portion of Rates Total T&D Revenue Requirement Taxes $ 63,267,889 $ 34,021,903 53.7744% Adjusted Uniform Percent Increase $ 34,021,903 53.7744% Total T&D Revenue Requirment $ 263,531,298 $ 29,103,483

Docket No. D2018.2.12 Page 125 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 A B C D E NorthWestern Energy Electric Transmission & Distribution Utility Derivation of Proposed Design Rates Docket No. D2018.2.12 Without Tax Rates Interim Transmission & Distribution Rate Without Tax Uniform % Increase Proposed Design Rates Residential: 2.4085% Residential: Service Charge $ 4.10 4.00 Transmission $ 0.007296 $ 0.007120 Distribution $ 0.022712 $ 0.022165 Employee: Service Charge $ 2.46 2.40 Transmission $ 0.004378 $ 0.004273 Distribution $ 0.013627 $ 0.013299 General Service 1: GS 1 Secondary Non Demand: Service Charge $ 5.85 5.70 Transmission $ 0.006353 $ 0.006200 Distribution $ 0.029416 $ 0.028708 GS 1 Secondary Demand: Service Charge $ 7.35 7.20 Energy Distribution $ 0.003924 $ 0.003829 Demand Transmission $ 2.427218 $ 2.368758 Demand Distribution $ 4.947830 $ 4.828660 GS 1 Primary Non Demand: Service Charge $ 6.30 6.15 Transmission $ 0.006645 $ 0.006485 Distribution $ 0.015236 $ 0.014869 GS 1 Primary Demand: Service Charge $ 19.85 19.35 Energy Distribution $ 0.005675 $ 0.005538 Demand Transmission $ 2.950140 $ 2.879085 Demand Distribution $ 3.239425 $ 3.161402 General Service 2: GS 2 Substation: Monthly Cust Charge $ 160.50 156.55 Max Dmd Transmission $ 3.037766 $ 2.964600 Max Dmd Distribution $ 1.196507 $ 1.167689 GS 2 Transmission: Monthly Cust Charge $ 983.70 959.55 Max Dmd Transmission $ 1.710917 $ 1.669709 Max Dmd Distribution $ 0.805511 $ 0.786110

Docket No. D2018.2.12 Page 126 of 327 1 2 3 4 5 6 7 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 A B C D E NorthWestern Energy Electric Transmission & Distribution Utility Derivation of Proposed Design Rates Docket No. D2018.2.12 Without Tax Rates Interim Transmission & Distribution Rate Without Tax Uniform % Increase Proposed Design Rates Irrigation: 2.4085% Irrigation Non Demand: Seasonal Cust Chg $ 43.05 42.00 Energy Transmission $ 0.009257 $ 0.009034 Energy Distribution $ 0.018861 $ 0.018407 Irrigation Demand: Seasonal Cust Chg $ 101.45 98.95 Energy Distribution $ 0.003135 $ 0.003059 Demand Transmission $ 1.588116 $ 1.549866 Demand Distribution $ 5.787516 $ 5.648121 Lighting: Transmission $ 0.002699 $ 0.002634 Distribution $ 0.024141 $ 0.023560 Ownership Charge (monthly): Ownership Chg 200399 $ 2.40 $ 2.34 Ownership Chg 400599 $ 5.12 $ 5.00 Ownership Chg 600799 $ 7.96 $ 7.77 Ownership Chg 800999 $ 9.55 $ 9.32 Ownership Chg 10001199 $ 11.49 $ 11.21 Ownership Chg 12001399 $ 13.94 $ 13.60 Ownership Chg 14001599 $ 17.02 $ 16.61 Ownership Chg 16001799 $ 19.15 $ 18.69 Ownership Chg 18001999 $ 21.58 $ 21.06 Ownership Chg 20002199 $ 23.11 $ 22.55 Ownership Chg 22002399 $ 25.32 $ 24.71 Ownership Chg 24002599 $ 27.51 $ 26.85 Ownership Chg 26002799 $ 29.71 $ 28.99 Ownership Chg 28002999 $ 31.92 $ 31.15 Ownership Chg 30003199 $ 32.29 $ 31.51 Ownership Chg 32003399 $ 32.52 $ 31.74 Ownership Chg 34003599 $ 32.75 $ 31.96 Ownership Chg 36003799 $ 34.63 $ 33.80 Ownership Chg 38003999 $ 36.49 $ 35.61 Ownership Chg 40004199 $ 38.36 $ 37.44 Ownership Chg 42004399 $ 40.24 $ 39.27 Ownership Chg 44004599 $ 42.11 $ 41.10 Ownership Chg 46004799 $ 43.98 $ 42.92 Ownership Chg 48004999 $ 45.85 $ 44.75 Ownership Chg 50005199 $ 47.73 $ 46.58 Ownership Chg 52005399 $ 49.59 $ 48.40 Ownership Chg 54005599 $ 51.47 $ 50.23 Ownership Chg 56005799 $ 53.34 $ 52.06 Ownership Chg 58005999 $ 55.21 $ 53.88 Lighting Misc Charges Operations Charge $ 0.50 $ 0.49 Maintenance Charge $ 0.48 $ 0.47 Billing Charge $ 0.20 $ 0.20

Docket No. D2018.2.12 Page 127 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 A B C D E NorthWestern Energy Electric Tansmission & Distribution Utility Derivation of Proposed Design Rates Docket No. D2018.2.12 Tax Rates Interim Transmission & Distribution Tax Portion of Rates Uniform % Increase Proposed Design Rates Residential: 53.7744% Residential: Service Charge $ $ Transmission $ 0.002329 $ 0.003581 Distribution $ 0.008964 $ 0.013784 Employee: Service Charge $ $ Transmission $ 0.001397 $ 0.002148 Distribution $ 0.005379 $ 0.008272 General Service 1: GS 1 Secondary Non Demand: Service Charge $ $ Transmission $ 0.002027 $ 0.003117 Distribution $ 0.012466 $ 0.019170 GS 1 Secondary Demand: Service Charge $ $ Energy Distribution $ 0.001434 $ 0.002205 Demand Transmission $ 0.774972 $ 1.191708 Demand Distribution $ 1.579767 $ 2.429277 GS 1 Primary Non Demand: Service Charge $ $ Transmission $ 0.002122 $ 0.003263 Distribution $ 0.006463 $ 0.009938 GS 1 Primary Demand: Service Charge $ $ Energy Distribution $ 0.001832 $ 0.002817 Demand Transmission $ 0.941935 $ 1.448455 Demand Distribution $ 1.034300 $ 1.590488 General Service 2: GS 2 Substation: Monthly Cust Charge $ $ Max Dmd Transmission $ 0.969912 $ 1.491476 Max Dmd Distribution $ 0.391069 $ 0.601364 GS 2 Transmission: Monthly Cust Charge $ $ Max Dmd Transmission $ 0.546270 $ 0.840023 Max Dmd Distribution $ 0.349572 $ 0.537552

Docket No. D2018.2.12 Page 128 of 327 1 2 3 4 5 6 7 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 A B C D E NorthWestern Energy Electric Tansmission & Distribution Utility Derivation of Proposed Design Rates Docket No. D2018.2.12 Tax Rates Interim Transmission & Distribution Tax Portion of Rates Uniform % Increase Proposed Design Rates Irrigation: 53.7744% Irrigation Non Demand: Seasonal Cust Chg $ $ Energy Transmission $ 0.002955 $ 0.004544 Energy Distribution $ 0.009425 $ 0.014493 Irrigation Demand: Seasonal Cust Chg $ $ Energy Distribution $ 0.001863 $ 0.002865 Demand Transmission $ 0.507061 $ 0.779730 Demand Distribution $ 1.847866 $ 2.841544 Lighting: Transmission $ 0.000862 $ 0.001326 Distribution $ 0.007709 $ 0.011854 Ownership Charge (monthly): Ownership Chg 200399 $ 0.76 $ 1.17 Ownership Chg 400599 $ 1.64 $ 2.52 Ownership Chg 600799 $ 2.54 $ 3.91 Ownership Chg 800999 $ 3.04 $ 4.67 Ownership Chg 10001199 $ 3.68 $ 5.66 Ownership Chg 12001399 $ 4.44 $ 6.83 Ownership Chg 14001599 $ 5.43 $ 8.35 Ownership Chg 16001799 $ 6.11 $ 9.40 Ownership Chg 18001999 $ 6.87 $ 10.56 Ownership Chg 20002199 $ 7.38 $ 11.35 Ownership Chg 22002399 $ 8.08 $ 12.42 Ownership Chg 24002599 $ 8.76 $ 13.47 Ownership Chg 26002799 $ 9.48 $ 14.58 Ownership Chg 28002999 $ 10.19 $ 15.67 Ownership Chg 30003199 $ 9.69 $ 14.90 Ownership Chg 32003399 $ 9.76 $ 15.01 Ownership Chg 34003599 $ 9.82 $ 15.10 Ownership Chg 36003799 $ 10.40 $ 15.99 Ownership Chg 38003999 $ 10.96 $ 16.85 Ownership Chg 40004199 $ 11.51 $ 17.70 Ownership Chg 42004399 $ 12.08 $ 18.58 Ownership Chg 44004599 $ 12.63 $ 19.42 Ownership Chg 46004799 $ 13.21 $ 20.31 Ownership Chg 48004999 $ 13.76 $ 21.16 Ownership Chg 50005199 $ 14.31 $ 22.01 Ownership Chg 52005399 $ 14.90 $ 22.91 Ownership Chg 54005599 $ 15.46 $ 23.77 Ownership Chg 56005799 $ 16.00 $ 24.60 Ownership Chg 58005999 $ 16.56 $ 25.47 Lighting Misc Charges Operations Charge $ 0.16 $ 0.25 Maintenance Charge $ 0.16 $ 0.25 Billing Charge $ 0.06 $ 0.09

Docket No. D2018.2.12 Page 129 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 A B C D E F G H I J K L NorthWestern Energy Electric Utility 2017 Test Year Billing Determinants and Revenues Transmission & Distribution Proposed Interim Test Period Actual Revenues Revenues Revenues Avg # Market @ Current Avg # Market @ Current @ Proposed Revenue Percent Customer Class Cust (MWh) Base Rates Cust (MWh) Base Rates Interim Rates Change Change Residential Res Non Choice 283,582 2,422,781 $ 114,015,515 283,582 2,373,047 $ 111,961,462 $ 124,314,591 $ 12,353,129 11.03% Emp NonChoice 324 2,780 $ 78,439 324 2,721 $ 76,986 $ 85,490 $ 8,504 11.05% Low Inc NonChoice 11,337 98,097 $ 4,609,292 11,337 96,140 $ 4,528,436 $ 5,029,082 $ 500,646 11.06% Res Choice 3 11 $ 471 3 9 $ 416 $ 452 $ 35 8.47% 295,246 2,523,668 $ 118,703,717 295,246 2,471,917 $ 116,567,300 $ 129,429,614 $ 12,862,315 11.03% General Service 1 GS1 Sec NonDmd NonCh 45,942 277,000 $ 17,147,690 45,942 278,887 $ 17,242,543 $ 19,093,368 $ 1,850,826 10.73% GS1 Sec Dmd NonCh 20,502 2,452,695 $ 88,655,332 20,502 2,471,032 $ 89,449,495 $ 99,407,407 $ 9,957,913 11.13% GS1 Sec NonDmd Choice 157 758 $ 42,779 157 761 $ 42,907 $ 47,189 $ 4,282 9.98% GS1 Sec Dmd Choice 125 64,690 $ 1,471,259 125 64,951 $ 1,462,909 $ 1,630,093 $ 167,184 11.43% GS1 Pri NonDmd NonCh 43 575 $ 20,752 43 577 $ 20,807 $ 23,089 $ 2,282 10.97% GS1 Pri Dmd NonCh 126 337,020 $ 9,000,405 126 338,084 $ 9,032,933 $ 10,042,208 $ 1,009,275 11.17% GS1 Pri NonDmd Choice 1 28 $ 684 1 28 $ 681 $ 765 $ 85 12.47% GS1 Pri Dmd Choice 4 73,289 $ 1,137,649 4 72,879 $ 1,132,231 $ 1,259,369 $ 127,138 11.23% 66,900 3,206,055 $ 117,476,550 66,900 3,227,199 $ 118,384,505 $ 131,503,489 $ 13,118,984 11.08% General Service 2 GS2 Sub NonCh 20 224,010 $ 3,453,734 20 245,968 $ 3,791,837 $ 4,213,522 $ 421,685 11.12% GS2 Sub Choice 32 1,735,183 $ 4,705,849 32 1,882,910 $ 5,109,040 $ 5,684,496 $ 575,456 11.26% GS2 Tran NonCh 19 112,259 $ 1,441,816 19 112,015 $ 1,441,416 $ 1,586,122 $ 144,706 10.04% GS2 Tran Choice 5 248,396 $ 554,268 5 547,649 $ 1,153,796 $ 1,312,124 $ 158,328 13.72% 76 2,319,848 $ 10,155,667 76 2,788,543 $ 11,496,089 $ 12,796,264 $ 1,300,175 11.31% Irrigation Irrig NonDmd NonCh 619 5,408 $ 273,151 619 4,920 $ 253,392 $ 281,491 $ 28,099 11.09% Irrig Dmd NonCh 1,119 101,050 $ 4,614,819 1,119 91,933 $ 4,434,515 $ 4,927,700 $ 493,185 11.12% Irrig Dmd Choice 1 168 $ 11,320 1 150 $ 8,050 $ 8,780 $ 730 9.07% 1,739 106,625 $ 4,899,290 1,739 97,002 $ 4,695,957 $ 5,217,971 $ 522,014 11.12% Lighting Lighting NonCh 3,618 54,853 $ 12,247,611 3,618 54,870 $ 12,248,222 $ 13,479,757 $ 1,231,535 10.05% Lighting Choice 114 4,355 $ 138,711 114 4,371 $ 139,225 $ 154,804 $ 15,579 11.19% 3,732 59,208 $ 12,386,322 3,732 59,241 $ 12,387,447 $ 13,634,561 $ 1,247,114 10.07% Total Rate Schedule 367,693 8,215,404 $ 263,621,545 367,693 8,643,902 $ 263,531,298 $ 292,581,900 $ 29,050,602 11.02% Rounding Difference $ 52,881 Sales for Resale $ 108,861 $ 108,861 $ 108,861 $ Transmission $ 53,168,785 $ 53,346,877 $ 53,346,877 $ Miscellaneous Revenue $ 5,246,850 $ 3,492,605 $ 3,492,605 $ Total T&D Revenue 367,693 8,215,404 $ 322,146,041 367,693 8,643,902 $ 320,479,641 $ 349,530,243 $ 29,103,483 9.08%

Docket No. D2018.2.12 Page 130 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 A B C D E F G H I J K L NorthWestern Energy Electric Utility 2017 Test Year Billing Determinants and Revenues Without Taxes Transmission & Distribution Test Period Actual Revenues Revenues Revenues Avg # Market @ Current Avg # Market @ Current @ Proposed Revenue Percent Customer Class Cust (MWh) Base Rates Cust (MWh) Base Rates Interim Rates Change Change Residential Res Non Choice 283,582 2,422,781 $ 86,655,053 283,582 2,373,047 $ 85,162,643 $ 83,106,631 $ (2,056,012) 2.41% Emp NonChoice 324 2,780 $ 59,603 324 2,721 $ 58,548 $ 57,136 $ (1,411) 2.41% Low Inc NonChoice 11,337 98,097 $ 3,501,479 11,337 96,140 $ 3,442,732 $ 3,359,619 $ (83,113) 2.41% Res Choice 3 11 $ 375 3 9 $ 336 $ 327 $ (8) 2.42% 295,246 2,523,668 $ 90,216,511 295,246 2,471,917 $ 88,664,258 $ 86,523,714 $ (2,140,544) 2.41% General Service 1 GS1 Sec NonDmd NonCh 45,942 277,000 $ 13,133,136 45,942 278,887 $ 13,200,638 $ 12,877,821 $ (322,817) 2.45% GS1 Sec Dmd NonCh 20,502 2,452,695 $ 67,300,437 20,502 2,471,032 $ 67,899,884 $ 66,269,937 $ (1,629,947) 2.40% GS1 Sec NonDmd Choice 157 758 $ 33,326 157 761 $ 33,416 $ 32,595 $ (822) 2.46% GS1 Sec Dmd Choice 125 64,690 $ 1,108,990 125 64,951 $ 1,102,625 $ 1,076,077 $ (26,548) 2.41% GS1 Pri NonDmd NonCh 43 575 $ 15,815 43 577 $ 15,855 $ 15,474 $ (381) 2.40% GS1 Pri Dmd NonCh 126 337,020 $ 6,824,310 126 338,084 $ 6,848,949 $ 6,683,850 $ (165,099) 2.41% GS1 Pri NonDmd Choice 1 28 $ 503 1 28 $ 500 $ 488 $ (12) 2.40% GS1 Pri Dmd Choice 4 73,289 $ 861,438 4 72,879 $ 857,338 $ 836,665 $ (20,673) 2.41% 66,900 3,206,055 $ 89,277,955 66,900 3,227,199 $ 89,959,205 $ 87,792,906 $ (2,166,300) 2.41% General Service 2 GS2 Sub NonCh 20 224,010 $ 2,622,827 20 245,968 $ 2,878,691 $ 2,809,337 $ (69,354) 2.41% GS2 Sub Choice 32 1,735,183 $ 3,561,835 32 1,882,910 $ 3,865,708 $ 3,772,569 $ (93,138) 2.41% GS2 Tran NonCh 19 112,259 $ 1,122,171 19 112,015 $ 1,121,876 $ 1,094,751 $ (27,125) 2.42% GS2 Tran Choice 5 248,396 $ 404,388 5 547,649 $ 822,476 $ 802,639 $ (19,837) 2.41% 76 2,319,848 $ 7,711,221 76 2,788,543 $ 8,688,750 $ 8,479,295 $ (209,455) 2.41% Irrigation Irrig NonDmd NonCh 619 5,408 $ 206,206 619 4,920 $ 192,487 $ 187,836 $ (4,651) 2.42% Irrig Dmd NonCh 1,119 101,050 $ 3,496,982 1,119 91,933 $ 3,366,271 $ 3,284,998 $ (81,273) 2.41% Irrig Dmd Choice 1 168 $ 8,520 1 150 $ 6,053 $ 5,709 $ (344) 5.68% 1,739 106,625 $ 3,711,707 1,739 97,002 $ 3,564,811 $ 3,478,543 $ (86,268) 2.42% Lighting Lighting NonCh 3,618 54,853 $ 9,280,395 3,618 54,870 $ 9,280,858 $ 8,959,193 $ (321,666) 3.47% Lighting Choice 114 4,355 $ 105,137 114 4,371 $ 105,527 $ 102,987 $ (2,540) 2.41% 3,732 59,208 $ 9,385,532 3,732 59,241 $ 9,386,385 $ 9,062,179 $ (324,206) 3.45% Total Rate Schedule 367,693 8,215,404 $ 200,302,925 367,693 8,643,902 $ 200,263,409 $ 195,336,637 $ (4,926,773) 2.46% Rounding Difference $ 8,353 Sales for Resale $ 108,861 $ 108,861 $ 108,861 $ Transmission $ 53,168,785 $ 53,346,877 $ 53,346,877 $ Miscellaneous Revenue $ 5,246,850 $ 3,492,605 $ 3,492,605 $ Total T&D Revenue 367,693 8,215,404 $ 258,827,421 367,693 8,643,902 $ 257,211,752 $ 252,284,979 $ (4,918,420) 1.91%

Docket No. D2018.2.12 Page 131 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 A B C D E F G H I J K L NorthWestern Energy Electric Utility 2017 Test Year Billing Determinants and Revenues Tax Portion Transmission & Distribution Test Period Actual Revenues Revenues Revenues Avg # Market @ Current Avg # Market @ Current @ Proposed Revenue Percent Customer Class Cust (MWh) Base Rates Cust (MWh) Base Rates Interim Rates Change Change Residential Res Non Choice 283,582 2,422,781 $ 27,360,462 283,582 2,373,047 $ 26,798,819 $ 41,207,960 $ 14,409,141 53.77% Emp NonChoice 324 2,780 $ 18,835 324 2,721 $ 18,438 $ 28,354 $ 9,916 53.78% Low Inc NonChoice 11,337 98,097 $ 1,107,813 11,337 96,140 $ 1,085,704 $ 1,669,463 $ 583,759 53.77% Res Choice 3 11 $ 96 3 9 $ 81 $ 124 $ 43 53.77% 295,246 2,523,668 $ 28,487,206 295,246 2,471,917 $ 27,903,042 $ 42,905,901 $ 15,002,859 53.77% General Service 1 GS1 Sec NonDmd NonCh 45,942 277,000 $ 4,014,554 45,942 278,887 $ 4,041,905 $ 6,215,548 $ 2,173,643 53.78% GS1 Sec Dmd NonCh 20,502 2,452,695 $ 21,354,895 20,502 2,471,032 $ 21,549,611 $ 33,137,471 $ 11,587,860 53.77% GS1 Sec NonDmd Choice 157 758 $ 9,452 157 761 $ 9,491 $ 14,594 $ 5,104 53.78% GS1 Sec Dmd Choice 125 64,690 $ 362,269 125 64,951 $ 360,284 $ 554,016 $ 193,732 53.77% GS1 Pri NonDmd NonCh 43 575 $ 4,937 43 577 $ 4,953 $ 7,615 $ 2,663 53.77% GS1 Pri Dmd NonCh 126 337,020 $ 2,176,096 126 338,084 $ 2,183,984 $ 3,358,358 $ 1,174,374 53.77% GS1 Pri NonDmd Choice 1 28 $ 181 1 28 $ 180 $ 277 $ 97 53.77% GS1 Pri Dmd Choice 4 73,289 $ 276,210 4 72,879 $ 274,893 $ 422,704 $ 147,811 53.77% 66,900 3,206,055 $ 28,198,595 66,900 3,227,199 $ 28,425,300 $ 43,710,584 $ 15,285,284 53.77% General Service 2 GS2 Sub NonCh 20 224,010 $ 830,907 20 245,968 $ 913,146 $ 1,404,185 $ 491,039 53.77% GS2 Sub Choice 32 1,735,183 $ 1,144,014 32 1,882,910 $ 1,243,333 $ 1,911,927 $ 668,595 53.77% GS2 Tran NonCh 19 112,259 $ 319,645 19 112,015 $ 319,540 $ 491,371 $ 171,831 53.77% GS2 Tran Choice 5 248,396 $ 149,880 5 547,649 $ 331,320 $ 509,485 $ 178,165 53.77% 76 2,319,848 $ 2,444,447 76 2,788,543 $ 2,807,340 $ 4,316,969 $ 1,509,629 53.77% Irrigation Irrig NonDmd NonCh 619 5,408 $ 66,945 619 4,920 $ 60,905 $ 93,655 $ 32,750 53.77% Irrig Dmd NonCh 1,119 101,050 $ 1,117,837 1,119 91,933 $ 1,068,244 $ 1,642,702 $ 574,458 53.78% Irrig Dmd Choice 1 168 $ 2,800 1 150 $ 1,997 $ 3,071 $ 1,074 53.78% 1,739 106,625 $ 1,187,582 1,739 97,002 $ 1,131,146 $ 1,739,428 $ 608,282 53.78% Lighting Lighting NonCh 3,618 54,853 $ 2,967,216 3,618 54,870 $ 2,967,364 $ 4,520,565 $ 1,553,201 52.34% Lighting Choice 114 4,355 $ 33,574 114 4,371 $ 33,698 $ 51,817 $ 18,119 53.77% 3,732 59,208 $ 3,000,790 3,732 59,241 $ 3,001,062 $ 4,572,382 $ 1,571,320 52.36% Total Rate Schedule 367,693 8,215,404 $ 63,318,619 367,693 8,643,902 $ 63,267,889 $ 97,245,263 $ 33,977,374 53.7040% Rounding Difference $ 44,528 Sales for Resale $ $ $ $ Transmission $ $ $ $ Miscellaneous Revenue $ $ $ $ Total T&D Revenue 367,693 8,215,404 $ 63,318,619 367,693 8,643,902 $ 63,267,889 $ 97,245,263 $ 34,021,902 53.77%

Docket No. D2018.2.12 Page 132 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 A B C D E F G H I J K L M N O NorthWestern Energy Electric Utility 2017 Actual Average # of Customers Customer Class Average Jan17 Feb17 Mar17 Apr17 May17 Jun17 Jul17 Aug17 Sep17 Oct17 Nov17 Dec17 Residential: Res NonCh 283,582 282,482 282,077 281,779 281,373 281,441 281,837 283,505 284,524 285,213 286,053 286,291 286,413 Res Emp NonCh 324 331 330 329 329 326 325 325 324 323 317 313 312 Res Low Inc NonCh 11,337 11,029 11,621 12,138 12,602 12,774 12,606 11,207 10,515 10,283 10,122 10,354 10,792 NonChoice 295,243 293,842 294,028 294,246 294,304 294,541 294,768 295,037 295,363 295,819 296,492 296,958 297,517 Choice 3 4 4 4 3 3 2 2 2 2 2 2 2 Total Residential 295,246 293,846 294,032 294,250 294,307 294,544 294,770 295,039 295,365 295,821 296,494 296,960 297,519 General Service 1: Sec NonDmd NonCh 45,942 45,840 45,802 45,840 45,855 45,740 45,837 45,906 45,960 46,046 46,103 46,113 46,264 Sec Demand NonCh 20,502 20,315 20,383 20,436 20,484 20,414 20,456 20,502 20,530 20,556 20,588 20,635 20,721 GS1 Sec NonChoice 66,444 66,155 66,185 66,276 66,339 66,154 66,293 66,408 66,490 66,602 66,691 66,748 66,985 Sec NonDmd Choice 157 157 157 157 157 157 157 157 157 157 157 157 157 Sec Demand Choice 125 126 127 127 127 124 124 124 123 124 125 126 128 GS1 Sec Choice 282 283 284 284 284 281 281 281 280 281 282 283 285 Pri NonDmd NonCh 43 42 43 43 43 43 43 43 43 43 43 42 42 Pri Demand NonCh 126 123 123 123 125 125 127 126 126 125 129 129 128 GS1 Pri NonChoice 169 165 166 166 168 168 170 169 169 168 172 171 170 Pri NonDmd Choice 1 1 1 1 1 1 1 1 1 1 1 1 1 Pri Demand Choice 4 4 4 4 4 4 4 4 4 4 4 4 4 GS1 Pri Choice 5 5 5 5 5 5 5 5 5 5 5 5 5 Total GS1 66,900 66,608 66,640 66,731 66,796 66,608 66,749 66,863 66,944 67,056 67,150 67,207 67,445 General Service 2: Sub NonChoice 20 20 20 20 20 20 20 19 19 19 19 19 20 Sub Choice 32 32 32 32 32 32 32 32 32 32 32 32 32 Tran NonChoice 19 19 19 19 19 19 19 19 19 19 19 19 19 Tran Choice 5 5 5 5 5 5 5 5 5 5 5 5 5 Total GS2 76 76 76 76 76 76 76 75 75 75 75 75 76 Irrigation: NonDmd NonChoice 619 180 175 161 200 587 1,036 1,167 1,199 1,120 906 424 268 Dmd NonChoice 1,119 61 38 42 77 1,048 2,282 2,507 2,577 2,348 1,954 353 140 NonChoice 1,738 241 213 203 277 1,635 3,318 3,674 3,776 3,468 2,860 777 408 Choice 1 2 2 2 2 2 2 2 Total Irrigation 1,739 241 213 203 277 1,637 3,320 3,676 3,778 3,470 2,862 779 408 Lighting: NonChoice 3,618 3,627 3,627 3,627 3,620 3,617 3,621 3,608 3,603 3,610 3,611 3,615 3,628 Choice 114 112 112 112 112 115 115 115 115 115 115 115 115 Total Lighting 3,732 3,739 3,739 3,739 3,732 3,732 3,736 3,723 3,718 3,725 3,726 3,730 3,743 Total # of Customers 367,693 364,510 364,700 364,999 365,188 366,597 368,651 369,376 369,880 370,147 370,307 368,751 369,191

Docket No. D2018.2.12 Page 133 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 A B C D E F G H I J K L M N O NorthWestern Energy Electric Utility 2017 Actual Energy at the Meter (MWh) Customer Class Total Jan17 Feb17 Mar17 Apr17 May17 Jun17 Jul17 Aug17 Sep17 Oct17 Nov17 Dec17 Residential: Res NonCh 2,422,781 292,173 257,796 212,413 173,895 161,560 158,934 186,528 220,851 187,576 169,183 180,703 221,168 Res Emp NonCh 2,780 350 293 245 205 194 187 217 239 203 194 210 242 Res Low Inc NonCh 98,097 11,722 11,237 9,763 8,283 7,696 7,126 6,820 7,510 6,373 6,104 6,834 8,629 NonChoice 2,523,658 304,245 269,326 222,421 182,382 169,450 166,247 193,565 228,600 194,152 175,480 187,748 230,040 Choice 11 2 2 2 1 0 0 1 1 1 1 0 0 Total Residential 2,523,668 304,247 269,328 222,423 182,383 169,451 166,248 193,565 228,602 194,153 175,481 187,748 230,040 General Service 1: Sec NonDmd NonCh 277,000 32,844 30,399 25,280 20,809 19,042 18,778 20,480 23,430 21,145 19,162 20,765 24,866 Sec Demand NonCh 2,452,695 225,214 217,712 198,807 187,487 183,478 195,439 213,899 232,747 219,749 190,153 187,154 200,858 GS1 Sec NonChoice 2,729,694 258,058 248,111 224,086 208,296 202,520 214,216 234,379 256,177 240,894 209,314 207,918 225,724 Sec NonDmd Choice 758 89 77 67 58 58 51 56 65 56 52 65 63 Sec Demand Choice 64,690 5,396 5,395 4,772 5,086 4,869 5,454 6,163 6,945 6,690 3,796 4,962 5,163 GS1 Sec Choice 65,449 5,486 5,472 4,839 5,144 4,927 5,505 6,220 7,010 6,746 3,848 5,027 5,226 Pri NonDmd NonCh 575 16 24 22 20 44 69 103 85 60 70 38 26 Pri Demand NonCh 337,020 30,791 30,158 27,598 26,483 24,776 25,487 27,013 29,279 29,706 27,880 29,515 28,335 GS1 Pri NonChoice 337,595 30,807 30,182 27,620 26,503 24,820 25,555 27,116 29,364 29,766 27,949 29,553 28,360 Pri NonDmd Choice 28 1 1 1 1 5 6 6 7 (1) Pri Demand Choice 73,289 6,066 6,648 5,901 6,588 5,974 6,253 6,357 5,491 6,139 6,285 5,877 5,711 GS1 Pri Choice 73,317 6,066 6,649 5,902 6,589 5,975 6,253 6,362 5,497 6,139 6,291 5,883 5,711 Total GS1 3,206,055 300,416 290,414 262,447 246,532 238,242 251,530 274,077 298,048 283,544 247,403 248,382 265,021 General Service 2: Sub NonChoice 224,010 20,895 18,903 18,822 20,275 17,186 17,432 16,257 18,119 18,820 17,634 20,080 19,587 Sub Choice 1,735,183 149,660 150,580 134,478 148,593 137,436 121,390 140,676 153,890 153,487 149,669 155,325 139,998 Tran NonChoice 112,259 10,625 9,218 9,510 8,862 8,209 8,330 9,402 9,494 9,797 9,361 9,331 10,120 Tran Choice 248,396 18,537 20,262 18,712 20,821 21,310 22,658 21,996 20,823 21,034 20,700 20,501 21,042 Total GS2 2,319,848 199,717 198,963 181,523 198,551 184,141 169,810 188,330 202,326 203,138 197,365 205,237 190,746 Irrigation: NonDmd NonChoice 5,408 0 5 1 9 146 783 1,211 1,645 1,187 358 50 14 Dmd NonChoice 101,050 18 21 (8) 11 1,609 15,053 25,495 31,128 20,032 7,493 93 105 NonChoice 106,457 18 26 (7) 19 1,755 15,836 26,706 32,773 21,219 7,851 142 119 Choice 168 7 24 32 57 29 13 6 Total Irrigation 106,625 18 26 (7) 19 1,762 15,860 26,738 32,830 21,249 7,864 149 119 Lighting: NonChoice 54,853 4,675 4,652 4,613 4,558 4,533 4,508 4,494 4,509 4,539 4,563 4,594 4,615 Choice 4,355 367 366 365 364 364 362 362 362 363 364 359 358 Total Lighting 59,208 5,042 5,018 4,978 4,922 4,896 4,870 4,856 4,872 4,902 4,927 4,953 4,972 Total Energy 8,215,404 809,440 763,748 671,364 632,407 598,491 608,318 687,567 766,677 706,985 633,039 646,469 690,898

Docket No. D2018.2.12 Page 134 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 A B C D E F G H I J K L M N O NorthWestern Energy Electric Utility 2017 Actual Demand at the Meter (MW) Customer Class Total Jan17 Feb17 Mar17 Apr17 May17 Jun17 Jul17 Aug17 Sep17 Oct17 Nov17 Dec17 General Service 1: Sec Dmd NonChoice 7,575 619 611 601 595 609 646 675 683 676 647 610 603 Sec Dmd Choice 171 13 13 13 14 14 15 17 15 16 15 13 13 Pri Dmd NonChoice 789 67 66 68 65 60 61 62 65 70 67 67 70 Pri Dmd Choice 137 11 11 12 12 12 11 11 11 11 11 11 11 Total GS1 8,672 711 701 694 685 695 734 765 775 773 741 701 698 General Service 2: Sub NonChoice 611 53 48 53 52 51 50 46 50 53 50 52 53 Sub Choice 2,925 220 242 239 244 249 218 250 254 256 255 259 240 Tran NonChoice 357 28 36 35 24 23 29 29 29 27 31 32 33 Tran Choice 429 35 36 36 35 35 35 36 36 36 36 37 36 Total GS2 4,321 336 362 362 356 359 332 361 369 372 370 380 363 Irrigation: NonChoice 395 0 0 0 0 14 71 88 92 75 49 4 0 Choice 1 0 0 0 0 0 0 0 0 0 Total Irrigation 396 0 0 0 0 15 71 88 93 75 49 4 0 Total Demand 13,389 1,047 1,063 1,056 1,041 1,068 1,137 1,214 1,236 1,220 1,160 1,086 1,061

Docket No. D2018.2.12 Page 135 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 A B C D E F G H I J K L M N O NorthWestern Energy Electric Utility 2017 Actual Loads @ Current Rate Revenue (Thousands) Total Rate Schedule Revenue Customer Class Total Jan17 Feb17 Mar17 Apr17 May17 Jun17 Jul17 Aug17 Sep17 Oct17 Nov17 Dec17 Residential Res Non Choice $ 114,016 $ 13,225 $ 11,804 $ 9,928 $ 8,336 $ 7,827 $ 7,720 $ 8,866 $ 10,288 $ 8,916 $ 8,160 $ 8,637 $ 10,309 Emp NonChoice $ 78 $ 9 $ 8 $ 7 $ 6 $ 6 $ 5 $ 6 $ 7 $ 6 $ 6 $ 6 $ 7 Low Inc NonChoice $ 4,609 $ 529 $ 512 $ 453 $ 394 $ 370 $ 346 $ 328 $ 353 $ 305 $ 294 $ 325 $ 401 Res Choice $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 Residential Revenue $ 118,704 $ 13,764 $ 12,324 $ 10,388 $ 8,735 $ 8,202 $ 8,071 $ 9,200 $ 10,648 $ 9,228 $ 8,459 $ 8,968 $ 10,716 General Service 1 GS1 Sec NonDmd NonCh $ 17,148 $ 1,919 $ 1,796 $ 1,539 $ 1,314 $ 1,225 $ 1,212 $ 1,298 $ 1,447 $ 1,332 $ 1,233 $ 1,313 $ 1,520 GS1 Sec Demand NonCh $ 88,655 $ 7,381 $ 7,261 $ 7,062 $ 6,949 $ 7,059 $ 7,487 $ 7,864 $ 8,046 $ 7,903 $ 7,463 $ 7,089 $ 7,093 GS1 Sec NonDmd Choice $ 43 $ 5 $ 4 $ 4 $ 3 $ 3 $ 3 $ 3 $ 4 $ 3 $ 3 $ 4 $ 4 GS1 Sec Demand Choice $ 1,471 $ 114 $ 114 $ 111 $ 117 $ 120 $ 125 $ 144 $ 139 $ 140 $ 119 $ 112 $ 116 GS1 Pri NonDmd NonCh $ 21 $ 1 $ 1 $ 1 $ 1 $ 2 $ 2 $ 3 $ 3 $ 2 $ 2 $ 1 $ 1 GS1 Pri Demand NonCh $ 9,000 $ 782 $ 769 $ 768 $ 729 $ 679 $ 696 $ 711 $ 751 $ 797 $ 761 $ 770 $ 789 GS1 Pri NonDmd Choice $ 1 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ (0) GS1 Pri Demand Choice $ 1,138 $ 94 $ 99 $ 94 $ 99 $ 95 $ 95 $ 96 $ 89 $ 95 $ 96 $ 93 $ 91 GS1 Revenue $ 117,477 $ 10,295 $ 10,043 $ 9,579 $ 9,212 $ 9,182 $ 9,621 $ 10,121 $ 10,478 $ 10,272 $ 9,678 $ 9,382 $ 9,614 General Service 2 GS2 Sub NonCh $ 3,454 $ 302 $ 269 $ 299 $ 295 $ 288 $ 282 $ 261 $ 283 $ 298 $ 280 $ 293 $ 302 GS2 Sub Choice $ 4,706 $ 354 $ 390 $ 385 $ 392 $ 400 $ 351 $ 402 $ 409 $ 411 $ 409 $ 417 $ 386 GS2 Tran NonCh $ 1,442 $ 113 $ 142 $ 137 $ 101 $ 99 $ 119 $ 117 $ 118 $ 112 $ 123 $ 129 $ 131 GS2 Tran Choice $ 554 $ 46 $ 46 $ 46 $ 46 $ 46 $ 46 $ 46 $ 46 $ 46 $ 46 $ 48 $ 47 GS2 Revenue $ 10,156 $ 815 $ 848 $ 866 $ 835 $ 833 $ 798 $ 827 $ 856 $ 868 $ 858 $ 886 $ 866 Irrigation Irrig NonDmd NonCh $ 273 $ 0 $ 0 $ 0 $ 0 $ 58 $ 33 $ 50 $ 67 $ 48 $ 14 $ 2 $ 1 Irrig Demand NonCh $ 4,615 $ 1 $ 1 $ 0 $ 5 $ 405 $ 770 $ 989 $ 1,055 $ 829 $ 516 $ 40 $ 4 Irrig Demand Choice $ 11 $ 0 $ 1 $ $ $ 2 $ 1 $ 1 $ 2 $ 2 $ 1 $ 1 $ Irrigation Revenue $ 4,899 $ 1 $ 1 $ 0 $ 5 $ 465 $ 804 $ 1,040 $ 1,124 $ 878 $ 532 $ 44 $ 4 Lighting Lighting NonCh $ 12,248 $ 1,024 $ 1,024 $ 1,022 $ 1,020 $ 1,019 $ 1,018 $ 1,018 $ 1,018 $ 1,019 $ 1,020 $ 1,021 $ 1,022 Lighting Choice $ 139 $ 12 $ 12 $ 12 $ 12 $ 12 $ 12 $ 12 $ 12 $ 12 $ 12 $ 11 $ 11 Lighting Revenue $ 12,386 $ 1,036 $ 1,035 $ 1,034 $ 1,032 $ 1,031 $ 1,030 $ 1,029 $ 1,030 $ 1,031 $ 1,032 $ 1,033 $ 1,034 Total Rate Schedule $ 263,622 $ 25,911 $ 24,251 $ 21,867 $ 19,819 $ 19,714 $ 20,323 $ 22,216 $ 24,135 $ 22,277 $ 20,560 $ 20,313 $ 22,234

Docket No. D2018.2.12 Page 136 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 A B C D E F G H I J K L M N O NorthWestern Energy Electric Utility 2017 Actual Loads @ Current Rate Revenue (Thousands) Total Rate Schedule Revenue Without Taxes Customer Class Total Jan17 Feb17 Mar17 Apr17 May17 Jun17 Jul17 Aug17 Sep17 Oct17 Nov17 Dec17 Residential Res Non Choice $ 86,655 $ 9,926 $ 8,892 $ 7,529 $ 6,372 $ 6,002 $ 5,925 $ 6,760 $ 7,794 $ 6,798 $ 6,250 $ 6,596 $ 7,811 Emp NonChoice $ 60 $ 7 $ 6 $ 5 $ 5 $ 4 $ 4 $ 5 $ 5 $ 4 $ 4 $ 5 $ 5 Low Inc NonChoice $ 3,501 $ 397 $ 385 $ 343 $ 300 $ 283 $ 266 $ 251 $ 268 $ 233 $ 225 $ 248 $ 303 Res Choice $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 Residential Revenue $ 90,217 $ 10,330 $ 9,283 $ 7,877 $ 6,677 $ 6,290 $ 6,195 $ 7,015 $ 8,067 $ 7,036 $ 6,479 $ 6,848 $ 8,119 General Service 1 GS1 Sec NonDmd NonCh $ 13,133 $ 1,443 $ 1,355 $ 1,172 $ 1,013 $ 949 $ 940 $ 1,001 $ 1,107 $ 1,026 $ 955 $ 1,012 $ 1,160 GS1 Sec Demand NonCh $ 67,300 $ 5,600 $ 5,510 $ 5,362 $ 5,278 $ 5,362 $ 5,685 $ 5,968 $ 6,103 $ 5,997 $ 5,668 $ 5,384 $ 5,385 GS1 Sec NonDmd Choice $ 33 $ 4 $ 3 $ 3 $ 3 $ 3 $ 2 $ 3 $ 3 $ 3 $ 2 $ 3 $ 3 GS1 Sec Demand Choice $ 1,109 $ 86 $ 86 $ 84 $ 88 $ 90 $ 94 $ 109 $ 105 $ 105 $ 90 $ 85 $ 87 GS1 Pri NonDmd NonCh $ 16 $ 1 $ 1 $ 1 $ 1 $ 1 $ 2 $ 3 $ 2 $ 2 $ 2 $ 1 $ 1 GS1 Pri Demand NonCh $ 6,824 $ 593 $ 583 $ 582 $ 552 $ 515 $ 527 $ 539 $ 570 $ 604 $ 577 $ 583 $ 598 GS1 Pri NonDmd Choice $ 1 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ (0) GS1 Pri Demand Choice $ 861 $ 71 $ 75 $ 72 $ 75 $ 72 $ 72 $ 73 $ 67 $ 72 $ 73 $ 70 $ 69 GS1 Revenue $ 89,278 $ 7,797 $ 7,613 $ 7,275 $ 7,010 $ 6,991 $ 7,323 $ 7,695 $ 7,956 $ 7,808 $ 7,367 $ 7,139 $ 7,304 General Service 2 GS2 Sub NonCh $ 2,623 $ 229 $ 204 $ 227 $ 224 $ 219 $ 215 $ 198 $ 215 $ 226 $ 213 $ 223 $ 230 GS2 Sub Choice $ 3,562 $ 268 $ 295 $ 291 $ 297 $ 303 $ 265 $ 304 $ 309 $ 311 $ 310 $ 315 $ 292 GS2 Tran NonCh $ 1,122 $ 88 $ 110 $ 106 $ 80 $ 78 $ 93 $ 91 $ 92 $ 87 $ 96 $ 100 $ 102 GS2 Tran Choice $ 404 $ 33 $ 34 $ 34 $ 33 $ 33 $ 33 $ 34 $ 34 $ 34 $ 34 $ 35 $ 34 GS2 Revenue $ 7,711 $ 619 $ 643 $ 657 $ 634 $ 633 $ 606 $ 628 $ 650 $ 659 $ 652 $ 673 $ 657 Irrigation Irrig NonDmd NonCh $ 206 $ 0 $ 0 $ 0 $ 0 $ 56 $ 23 $ 35 $ 46 $ 33 $ 10 $ 1 $ 0 Irrig Demand NonCh $ 3,497 $ 1 $ 0 $ 0 $ 4 $ 369 $ 575 $ 734 $ 780 $ 615 $ 386 $ 30 $ 3 Irrig Demand Choice $ 9 $ 0 $ 1 $ $ $ 1 $ 1 $ 1 $ 1 $ 1 $ 1 $ 1 $ Irrigation Revenue $ 3,712 $ 1 $ 1 $ 0 $ 4 $ 426 $ 599 $ 770 $ 828 $ 650 $ 397 $ 33 $ 3 Lighting Lighting NonCh $ 9,280 $ 776 $ 776 $ 774 $ 773 $ 772 $ 772 $ 771 $ 772 $ 773 $ 773 $ 774 $ 775 Lighting Choice $ 105 $ 9 $ 9 $ 9 $ 9 $ 9 $ 9 $ 9 $ 9 $ 9 $ 9 $ 9 $ 9 Lighting Revenue $ 9,386 $ 785 $ 784 $ 783 $ 782 $ 781 $ 780 $ 780 $ 780 $ 781 $ 782 $ 783 $ 783 Total Rate Schedule $ 200,303 $ 19,532 $ 18,325 $ 16,594 $ 15,106 $ 15,121 $ 15,503 $ 16,888 $ 18,282 $ 16,934 $ 15,677 $ 15,476 $ 16,867

Docket No. D2018.2.12 Page 137 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 A B C D E F G H I J K L M N O NorthWestern Energy Electric Utility 2017 Actual Loads @ Current Rate Revenue (Thousands) Total Rate Schedule Revenue Tax Portion Customer Class Total Jan17 Feb17 Mar17 Apr17 May17 Jun17 Jul17 Aug17 Sep17 Oct17 Nov17 Dec17 Residential Res Non Choice $ 27,360 $ 3,300 $ 2,911 $ 2,399 $ 1,964 $ 1,825 $ 1,795 $ 2,106 $ 2,494 $ 2,118 $ 1,911 $ 2,041 $ 2,498 Emp NonChoice $ 19 $ 2 $ 2 $ 2 $ 1 $ 1 $ 1 $ 1 $ 2 $ 1 $ 1 $ 1 $ 2 Low Inc NonChoice $ 1,108 $ 132 $ 127 $ 110 $ 94 $ 87 $ 80 $ 77 $ 85 $ 72 $ 69 $ 77 $ 97 Res Choice $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 Residential Revenue $ 28,487 $ 3,434 $ 3,040 $ 2,511 $ 2,059 $ 1,913 $ 1,877 $ 2,185 $ 2,581 $ 2,192 $ 1,981 $ 2,119 $ 2,597 General Service 1 GS1 Sec NonDmd NonCh $ 4,015 $ 476 $ 441 $ 366 $ 302 $ 276 $ 272 $ 297 $ 340 $ 306 $ 278 $ 301 $ 360 GS1 Sec Demand NonCh $ 21,355 $ 1,781 $ 1,751 $ 1,700 $ 1,671 $ 1,697 $ 1,802 $ 1,896 $ 1,943 $ 1,906 $ 1,796 $ 1,705 $ 1,707 GS1 Sec NonDmd Choice $ 9 $ 1 $ 1 $ 1 $ 1 $ 1 $ 1 $ 1 $ 1 $ 1 $ 1 $ 1 $ 1 GS1 Sec Demand Choice $ 362 $ 28 $ 28 $ 27 $ 29 $ 29 $ 31 $ 35 $ 34 $ 35 $ 29 $ 28 $ 28 GS1 Pri NonDmd NonCh $ 5 $ 0 $ 0 $ 0 $ 0 $ 0 $ 1 $ 1 $ 1 $ 1 $ 1 $ 0 $ 0 GS1 Pri Demand NonCh $ 2,176 $ 189 $ 186 $ 186 $ 176 $ 164 $ 168 $ 172 $ 182 $ 193 $ 184 $ 186 $ 191 GS1 Pri NonDmd Choice $ 0 $ $ 0 $ 0 $ 0 $ 0 $ $ 0 $ 0 $ $ 0 $ 0 $ (0) GS1 Pri Demand Choice $ 276 $ 23 $ 24 $ 23 $ 24 $ 23 $ 23 $ 23 $ 22 $ 23 $ 23 $ 23 $ 22 GS1 Revenue $ 28,199 $ 2,498 $ 2,431 $ 2,303 $ 2,203 $ 2,191 $ 2,298 $ 2,425 $ 2,521 $ 2,464 $ 2,311 $ 2,243 $ 2,310 General Service 2 GS2 Sub NonCh $ 831 $ 73 $ 65 $ 72 $ 71 $ 69 $ 68 $ 63 $ 68 $ 72 $ 67 $ 71 $ 73 GS2 Sub Choice $ 1,144 $ 86 $ 95 $ 93 $ 95 $ 97 $ 85 $ 98 $ 99 $ 100 $ 100 $ 101 $ 94 GS2 Tran NonCh $ 320 $ 25 $ 33 $ 31 $ 22 $ 21 $ 26 $ 26 $ 26 $ 24 $ 27 $ 29 $ 29 GS2 Tran Choice $ 150 $ 12 $ 12 $ 13 $ 12 $ 12 $ 12 $ 12 $ 13 $ 13 $ 12 $ 13 $ 13 GS2 Revenue $ 2,444 $ 196 $ 204 $ 209 $ 200 $ 200 $ 192 $ 199 $ 206 $ 209 $ 207 $ 214 $ 209 Irrigation Irrig NonDmd NonCh $ 67 $ 0 $ 0 $ 0 $ 0 $ 2 $ 10 $ 15 $ 20 $ 15 $ 4 $ 1 $ 0 Irrig Demand NonCh $ 1,118 $ 0 $ 0 $ 0 $ 1 $ 37 $ 195 $ 255 $ 275 $ 214 $ 130 $ 10 $ 1 Irrig Demand Choice $ 3 $ 0 $ 0 $ $ $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ Irrigation Revenue $ 1,188 $ 0 $ 0 $ 0 $ 1 $ 39 $ 205 $ 270 $ 296 $ 229 $ 135 $ 11 $ 1 Lighting Lighting NonCh $ 2,967 $ 248 $ 248 $ 248 $ 247 $ 247 $ 247 $ 247 $ 247 $ 247 $ 247 $ 247 $ 248 Lighting Choice $ 34 $ 3 $ 3 $ 3 $ 3 $ 3 $ 3 $ 3 $ 3 $ 3 $ 3 $ 3 $ 3 Lighting Revenue $ 3,001 $ 251 $ 251 $ 250 $ 250 $ 250 $ 250 $ 249 $ 250 $ 250 $ 250 $ 250 $ 250 Total Rate Schedule $ 63,319 $ 6,380 $ 5,926 $ 5,273 $ 4,713 $ 4,592 $ 4,821 $ 5,329 $ 5,854 $ 5,343 $ 4,883 $ 4,837 $ 5,367

Docket No. D2018.2.12 Page 138 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 A B C D E F G H I J K L M N O NorthWestern Energy Electric Utility 2017 Test Year Normalized Average # of Customers Customer Class Average Jan17 Feb17 Mar17 Apr17 May17 Jun17 Jul17 Aug17 Sep17 Oct17 Nov17 Dec17 Residential: Res NonCh 283,582 282,482 282,077 281,779 281,373 281,441 281,837 283,505 284,524 285,213 286,053 286,291 286,413 Res Emp NonCh 324 331 330 329 329 326 325 325 324 323 317 313 312 Res Low Inc NonCh 11,337 11,029 11,621 12,138 12,602 12,774 12,606 11,207 10,515 10,283 10,122 10,354 10,792 NonChoice 295,243 293,842 294,028 294,246 294,304 294,541 294,768 295,037 295,363 295,819 296,492 296,958 297,517 Choice 3 4 4 4 3 3 2 2 2 2 2 2 2 Total Residential 295,246 293,846 294,032 294,250 294,307 294,544 294,770 295,039 295,365 295,821 296,494 296,960 297,519 General Service 1: Sec NonDmd NonCh 45,942 45,840 45,802 45,840 45,855 45,740 45,837 45,906 45,960 46,046 46,103 46,113 46,264 Sec Demand NonCh 20,502 20,315 20,383 20,436 20,484 20,414 20,456 20,502 20,530 20,556 20,588 20,635 20,721 GS1 Sec NonChoice 66,444 66,155 66,185 66,276 66,339 66,154 66,293 66,408 66,490 66,602 66,691 66,748 66,985 Sec NonDmd Choice 157 157 157 157 157 157 157 157 157 157 157 157 157 Sec Demand Choice 125 126 127 127 127 124 124 124 123 124 125 126 128 GS1 Sec Choice 282 283 284 284 284 281 281 281 280 281 282 283 285 Pri NonDmd NonCh 43 42 43 43 43 43 43 43 43 43 43 42 42 Pri Demand NonCh 126 123 123 123 125 125 127 126 126 125 129 129 128 GS1 Pri NonChoice 169 165 166 166 168 168 170 169 169 168 172 171 170 Pri NonDmd Choice 1 1 1 1 1 1 1 1 1 1 1 1 1 Pri Demand Choice 4 4 4 4 4 4 4 4 4 4 4 4 4 GS1 Pri Choice 5 5 5 5 5 5 5 5 5 5 5 5 5 Total GS1 66,900 66,608 66,640 66,731 66,796 66,608 66,749 66,863 66,944 67,056 67,150 67,207 67,445 General Service 2: Sub NonChoice 20 20 20 20 20 20 20 19 19 19 19 19 20 Sub Choice 32 32 32 32 32 32 32 32 32 32 32 32 32 Tran NonChoice 19 19 19 19 19 19 19 19 19 19 19 19 19 Tran Choice 5 5 5 5 5 5 5 5 5 5 5 5 5 Total GS2 76 76 76 76 76 76 76 75 75 75 75 75 76 Irrigation: NonDmd NonChoice 619 180 175 161 200 587 1,036 1,167 1,199 1,120 906 424 268 Dmd NonChoice 1,119 61 38 42 77 1,048 2,282 2,507 2,577 2,348 1,954 353 140 NonChoice 1,738 241 213 203 277 1,635 3,318 3,674 3,776 3,468 2,860 777 408 Choice 1 2 2 2 2 2 2 2 Total Irrigation 1,739 241 213 203 277 1,637 3,320 3,676 3,778 3,470 2,862 779 408 Lighting: NonChoice 3,618 3,627 3,627 3,627 3,620 3,617 3,621 3,608 3,603 3,610 3,611 3,615 3,628 Choice 114 112 112 112 112 115 115 115 115 115 115 115 115 Total Lighting 3,732 3,739 3,739 3,739 3,732 3,732 3,736 3,723 3,718 3,725 3,726 3,730 3,743 Total # of Customers 367,693 364,510 364,700 364,999 365,188 366,597 368,651 369,376 369,880 370,147 370,307 368,751 369,191

Docket No. D2018.2.12 Page 139 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 A B C D E F G H I J K L M N O NorthWestern Energy Electric Utility 2017 Test Year Normalized Energy at the Meter (MWh) Customer Class Total Jan17 Feb17 Mar17 Apr17 May17 Jun17 Jul17 Aug17 Sep17 Oct17 Nov17 Dec17 Residential: Res NonCh 2,373,047 255,232 229,775 205,069 184,137 166,034 163,753 185,514 201,519 181,643 171,044 193,293 236,034 Res Emp NonCh 2,721 293 264 236 213 192 189 212 230 207 195 221 270 Res Low Inc NonCh 96,140 10,232 10,009 9,418 8,765 7,904 7,338 6,780 6,851 6,170 6,167 7,305 9,203 NonChoice 2,471,908 265,756 240,048 214,724 193,114 174,130 171,279 192,505 208,600 188,020 177,405 200,819 245,507 Choice 9 1 2 1 1 1 1 1 1 1 1 Total Residential 2,471,917 265,757 240,050 214,725 193,115 174,130 171,280 192,506 208,601 188,021 177,406 200,819 245,507 General Service 1: Sec NonDmd NonCh 278,887 24,789 23,467 22,633 22,101 21,591 22,402 24,172 25,571 23,995 22,214 22,263 23,688 Sec Demand NonCh 2,471,032 219,642 207,930 200,538 195,824 191,303 198,488 214,172 226,565 212,605 196,824 197,256 209,886 GS1 Sec NonChoice 2,749,919 244,431 231,397 223,171 217,925 212,894 220,890 238,344 252,135 236,600 219,038 219,519 233,574 Sec NonDmd Choice 761 63 60 59 59 60 64 71 75 69 62 60 61 Sec Demand Choice 64,951 5,384 5,108 5,004 5,044 5,091 5,467 6,038 6,376 5,880 5,315 5,079 5,165 GS1 Sec Choice 65,712 5,447 5,168 5,062 5,103 5,150 5,531 6,109 6,451 5,949 5,377 5,139 5,225 Pri NonDmd NonCh 577 52 50 47 45 43 45 48 50 50 49 49 50 Pri Demand NonCh 338,084 30,260 29,055 27,742 26,492 25,370 26,151 27,953 29,533 29,043 28,688 28,674 29,123 GS1 Pri NonChoice 338,661 30,312 29,104 27,789 26,537 25,413 26,196 28,000 29,583 29,093 28,737 28,723 29,173 Pri NonDmd Choice 28 2 2 2 2 2 2 2 2 2 2 2 2 Pri Demand Choice 72,879 6,115 6,273 6,243 6,280 6,112 6,305 5,927 5,816 6,213 6,083 5,830 5,683 GS1 Pri Choice 72,907 6,117 6,275 6,246 6,282 6,114 6,307 5,929 5,818 6,215 6,085 5,832 5,685 Total GS1 3,227,199 286,307 271,945 262,268 255,848 249,572 258,924 278,382 293,987 277,857 259,238 259,213 273,658 General Service 2: Sub NonChoice 245,968 21,555 21,173 22,306 20,037 18,906 17,484 18,839 20,916 19,483 20,209 21,676 23,386 Sub Choice 1,882,910 166,015 149,529 162,565 151,119 134,991 154,204 167,464 164,986 161,665 164,830 148,225 157,316 Tran NonChoice 112,015 10,328 9,214 9,262 8,267 8,360 8,934 9,738 9,992 9,403 9,111 9,996 9,410 Tran Choice 547,649 45,260 41,291 45,786 45,502 47,656 46,188 45,822 46,033 44,892 45,499 45,267 48,453 Total GS2 2,788,543 243,158 221,207 239,918 224,925 209,913 226,810 241,863 241,927 235,444 239,649 225,164 238,566 Irrigation: NonDmd NonChoice 4,920 2 2 1 9 205 813 1,440 1,425 795 210 17 1 Dmd NonChoice 91,933 29 30 24 173 3,826 15,199 26,910 26,622 14,860 3,916 317 27 NonChoice 96,852 30 32 25 183 4,031 16,012 28,350 28,046 15,656 4,126 334 28 Choice 150 0 0 0 6 25 44 43 24 6 1 0 Total Irrigation 97,002 30 32 25 183 4,037 16,037 28,394 28,090 15,680 4,132 334 28 Lighting: NonChoice 54,870 4,572 4,572 4,572 4,572 4,572 4,572 4,572 4,572 4,572 4,572 4,572 4,572 Choice 4,371 364 364 364 364 364 364 364 364 364 364 364 364 Total Lighting 59,241 4,937 4,937 4,937 4,937 4,937 4,937 4,937 4,937 4,937 4,937 4,937 4,937 Total Energy 8,643,902 800,189 738,170 721,873 679,007 642,589 677,987 746,082 777,541 721,939 685,361 690,468 762,695

Docket No. D2018.2.12 Page 140 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 A B C D E F G H I J K L M N O NorthWestern Energy Electric Utility 2017 Test Year Normalized Demand at the Meter (MW) Customer Class Total Jan17 Feb17 Mar17 Apr17 May17 Jun17 Jul17 Aug17 Sep17 Oct17 Nov17 Dec17 General Service 1: Sec Dmd NonChoice 7,647 604 584 606 622 635 657 676 665 654 670 643 630 Sec Dmd Choice 169 14 13 13 13 13 14 16 17 15 14 13 13 Pri Dmd NonChoice 792 66 64 69 65 62 63 64 65 68 69 65 72 Pri Dmd Choice 137 11 11 12 11 12 11 11 12 12 11 11 11 Total GS1 8,744 695 671 700 711 722 746 767 759 749 764 733 727 General Service 2: Sub NonChoice 671 55 53 63 52 56 50 53 58 55 57 56 64 Sub Choice 3,179 244 241 289 248 245 276 298 272 270 280 247 270 Tran NonChoice 357 27 36 34 23 24 32 30 30 26 30 35 31 Tran Choice 948 86 72 88 77 79 72 74 79 76 78 82 84 Total GS2 5,155 412 403 473 400 403 430 455 440 427 445 420 448 Irrigation: NonChoice 381 0 0 (0) 8 34 72 93 79 56 26 14 Choice 1 0 0 0 0 0 0 0 Total Irrigation 382 0 0 (0) 8 34 72 93 79 56 26 14 Total Demand 14,281 1,108 1,074 1,173 1,119 1,159 1,247 1,315 1,278 1,232 1,235 1,166 1,175

Docket No. D2018.2.12 Page 141 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 A B C D E F G H I J K L M N O NorthWestern Energy Electric Utility 2017 Normalized Loads @ Proposed Rate Revenue (Thousands) Total Rate Schedule Customer Class Total Jan17 Feb17 Mar17 Apr17 May17 Jun17 Jul17 Aug17 Sep17 Oct17 Nov17 12/1/20017 Residential Res Non Choice $ 124,315 $ 13,036 $ 11,847 $ 10,694 $ 9,715 $ 8,871 $ 8,766 $ 9,788 $ 10,539 $ 9,615 $ 9,123 $ 10,162 $ 12,157 Emp NonChoice $ 85 $ 9 $ 8 $ 7 $ 7 $ 6 $ 6 $ 7 $ 7 $ 7 $ 6 $ 7 $ 8 Low Inc NonChoice $ 5,029 $ 521 $ 513 $ 488 $ 459 $ 420 $ 393 $ 361 $ 362 $ 329 $ 328 $ 382 $ 472 Res Choice $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 Residential Revenue $ 129,430 $ 13,567 $ 12,369 $ 11,189 $ 10,182 $ 9,297 $ 9,165 $ 10,156 $ 10,908 $ 9,950 $ 9,458 $ 10,551 $ 12,637 General Service 1 GS1 Sec NonDmd NonCh $ 19,093 $ 1,679 $ 1,603 $ 1,556 $ 1,525 $ 1,496 $ 1,543 $ 1,644 $ 1,724 $ 1,635 $ 1,533 $ 1,536 $ 1,619 GS1 Sec Demand NonCh $ 99,407 $ 8,005 $ 7,716 $ 7,914 $ 8,060 $ 8,174 $ 8,451 $ 8,755 $ 8,713 $ 8,506 $ 8,582 $ 8,298 $ 8,233 GS1 Sec NonDmd Choice $ 47 $ 4 $ 4 $ 4 $ 4 $ 4 $ 4 $ 4 $ 4 $ 4 $ 4 $ 4 $ 4 GS1 Sec Demand Choice $ 1,630 $ 135 $ 128 $ 126 $ 127 $ 128 $ 137 $ 151 $ 160 $ 147 $ 133 $ 128 $ 130 GS1 Pri NonDmd NonCh $ 23 $ 2 $ 2 $ 2 $ 2 $ 2 $ 2 $ 2 $ 2 $ 2 $ 2 $ 2 $ 2 GS1 Pri Demand NonCh $ 10,042 $ 854 $ 823 $ 858 $ 810 $ 773 $ 793 $ 818 $ 843 $ 866 $ 870 $ 831 $ 901 GS1 Pri NonDmd Choice $ 1 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 GS1 Pri Demand Choice $ 1,259 $ 106 $ 104 $ 111 $ 105 $ 108 $ 107 $ 100 $ 104 $ 107 $ 104 $ 102 $ 101 GS1 Revenue $ 131,503 $ 10,785 $ 10,380 $ 10,570 $ 10,633 $ 10,684 $ 11,037 $ 11,475 $ 11,551 $ 11,267 $ 11,229 $ 10,901 $ 10,989 General Service 2 GS2 Sub NonCh $ 4,214 $ 346 $ 334 $ 393 $ 324 $ 352 $ 315 $ 336 $ 363 $ 343 $ 356 $ 351 $ 400 GS2 Sub Choice $ 5,684 $ 436 $ 431 $ 516 $ 443 $ 438 $ 494 $ 531 $ 487 $ 482 $ 501 $ 443 $ 482 GS2 Tran NonCh $ 1,586 $ 121 $ 157 $ 148 $ 105 $ 110 $ 139 $ 133 $ 135 $ 119 $ 132 $ 151 $ 136 GS2 Tran Choice $ 1,312 $ 119 $ 101 $ 121 $ 107 $ 109 $ 100 $ 103 $ 110 $ 106 $ 108 $ 113 $ 116 GS2 Revenue $ 12,796 $ 1,023 $ 1,023 $ 1,177 $ 980 $ 1,009 $ 1,048 $ 1,103 $ 1,095 $ 1,049 $ 1,098 $ 1,058 $ 1,134 Irrigation Irrig NonDmd NonCh $ 281 $ 0 $ 0 $ 0 $ 0 $ 60 $ 39 $ 68 $ 66 $ 37 $ 10 $ 1 $ 0 Irrig Demand NonCh $ 4,928 $ 2 $ 1 $ (1) $ 87 $ 645 $ 868 $ 1,168 $ 1,014 $ 689 $ 301 $ 153 $ 0 Irrig Demand Choice $ 9 $ 0 $ 0 $ $ 0 $ 2 $ 2 $ 2 $ 1 $ 1 $ 1 $ 0 $ 0 Irrigation Revenue $ 5,218 $ 2 $ 1 $ (1) $ 88 $ 707 $ 908 $ 1,238 $ 1,082 $ 728 $ 312 $ 154 $ 0 Lighting Lighting NonCh $ 13,480 $ 1,123 $ 1,123 $ 1,123 $ 1,123 $ 1,123 $ 1,123 $ 1,123 $ 1,123 $ 1,123 $ 1,123 $ 1,123 $ 1,123 Lighting Choice $ 155 $ 13 $ 13 $ 13 $ 13 $ 13 $ 13 $ 13 $ 13 $ 13 $ 13 $ 13 $ 13 Lighting Revenue $ 13,635 $ 1,136 $ 1,136 $ 1,136 $ 1,136 $ 1,136 $ 1,136 $ 1,136 $ 1,136 $ 1,136 $ 1,136 $ 1,136 $ 1,136 Total Rate Schedule $ 292,582 $ 26,513 $ 24,910 $ 24,072 $ 23,019 $ 22,833 $ 23,294 $ 25,108 $ 25,772 $ 24,131 $ 23,233 $ 23,801 $ 25,897

Docket No. D2018.2.12 Page 142 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 A B C D E F G H I J K L M N O NorthWestern Energy Electric Utility 2017 Normalized Loads @ Proposed Rate Revenue (Thousands) Total Rate Schedule Without Taxes Customer Class Total Jan17 Feb17 Mar17 Apr17 May17 Jun17 Jul17 Aug17 Sep17 Oct17 Nov17 12/1/20017 Residential Res Non Choice $ 83,107 $ 8,604 $ 7,857 $ 7,133 $ 6,518 $ 5,988 $ 5,923 $ 6,567 $ 7,040 $ 6,460 $ 6,153 $ 6,806 $ 8,058 Emp NonChoice $ 57 $ 6 $ 5 $ 5 $ 5 $ 4 $ 4 $ 5 $ 5 $ 4 $ 4 $ 5 $ 5 Low Inc NonChoice $ 3,360 $ 344 $ 340 $ 324 $ 307 $ 283 $ 265 $ 243 $ 243 $ 222 $ 221 $ 255 $ 313 Res Choice $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 Residential Revenue $ 86,524 $ 8,954 $ 8,202 $ 7,462 $ 6,830 $ 6,275 $ 6,192 $ 6,815 $ 7,287 $ 6,687 $ 6,379 $ 7,066 $ 8,376 General Service 1 GS1 Sec NonDmd NonCh $ 12,878 $ 1,127 $ 1,080 $ 1,051 $ 1,033 $ 1,014 $ 1,043 $ 1,105 $ 1,155 $ 1,100 $ 1,038 $ 1,040 $ 1,091 GS1 Sec Demand NonCh $ 66,270 $ 5,334 $ 5,144 $ 5,277 $ 5,376 $ 5,452 $ 5,635 $ 5,834 $ 5,804 $ 5,669 $ 5,723 $ 5,534 $ 5,488 GS1 Sec NonDmd Choice $ 33 $ 3 $ 3 $ 3 $ 3 $ 3 $ 3 $ 3 $ 3 $ 3 $ 3 $ 3 $ 3 GS1 Sec Demand Choice $ 1,076 $ 89 $ 85 $ 83 $ 84 $ 84 $ 91 $ 100 $ 105 $ 97 $ 88 $ 84 $ 86 GS1 Pri NonDmd NonCh $ 15 $ 1 $ 1 $ 1 $ 1 $ 1 $ 1 $ 1 $ 1 $ 1 $ 1 $ 1 $ 1 GS1 Pri Demand NonCh $ 6,684 $ 568 $ 548 $ 571 $ 539 $ 515 $ 528 $ 545 $ 561 $ 577 $ 579 $ 553 $ 600 GS1 Pri NonDmd Choice $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 GS1 Pri Demand Choice $ 837 $ 70 $ 69 $ 74 $ 70 $ 72 $ 71 $ 66 $ 69 $ 71 $ 69 $ 68 $ 67 GS1 Revenue $ 87,793 $ 7,192 $ 6,930 $ 7,060 $ 7,105 $ 7,141 $ 7,372 $ 7,655 $ 7,699 $ 7,518 $ 7,501 $ 7,283 $ 7,336 General Service 2 GS2 Sub NonCh $ 2,809 $ 231 $ 223 $ 262 $ 216 $ 235 $ 210 $ 224 $ 242 $ 229 $ 238 $ 234 $ 267 GS2 Sub Choice $ 3,773 $ 290 $ 286 $ 342 $ 294 $ 291 $ 328 $ 352 $ 323 $ 320 $ 332 $ 294 $ 320 GS2 Tran NonCh $ 1,095 $ 84 $ 107 $ 101 $ 74 $ 77 $ 96 $ 92 $ 93 $ 83 $ 91 $ 103 $ 93 GS2 Tran Choice $ 803 $ 73 $ 62 $ 74 $ 66 $ 67 $ 61 $ 63 $ 67 $ 65 $ 66 $ 69 $ 71 GS2 Revenue $ 8,479 $ 678 $ 678 $ 779 $ 650 $ 669 $ 695 $ 731 $ 725 $ 696 $ 727 $ 700 $ 751 Irrigation Irrig NonDmd NonCh $ 188 $ 0 $ 0 $ 0 $ 0 $ 56 $ 23 $ 41 $ 39 $ 22 $ 6 $ 0 $ 0 Irrig Demand NonCh $ 3,285 $ 1 $ 1 $ (1) $ 58 $ 511 $ 565 $ 754 $ 652 $ 445 $ 197 $ 102 $ 0 Irrig Demand Choice $ 6 $ 0 $ 0 $ $ 0 $ 1 $ 1 $ 1 $ 1 $ 1 $ 1 $ 0 $ 0 Irrigation Revenue $ 3,479 $ 1 $ 1 $ (1) $ 58 $ 568 $ 589 $ 796 $ 692 $ 468 $ 203 $ 102 $ 0 Lighting Lighting NonCh $ 8,959 $ 747 $ 747 $ 747 $ 747 $ 747 $ 747 $ 747 $ 747 $ 747 $ 747 $ 747 $ 747 Lighting Choice $ 103 $ 9 $ 9 $ 9 $ 9 $ 9 $ 9 $ 9 $ 9 $ 9 $ 9 $ 9 $ 9 Lighting Revenue $ 9,062 $ 755 $ 755 $ 755 $ 755 $ 755 $ 755 $ 755 $ 755 $ 755 $ 755 $ 755 $ 755 Total Rate Schedule $ 195,337 $ 17,580 $ 16,566 $ 16,056 $ 15,398 $ 15,408 $ 15,604 $ 16,752 $ 17,158 $ 16,124 $ 15,566 $ 15,907 $ 17,218

Docket No. D2018.2.12 Page 143 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 A B C D E F G H I J K L M N O NorthWestern Energy Electric Utility 2017 Normalized Loads @ Proposed Rate Revenue (Thousands) Total Rate Schedule Tax Portion Customer Class Total Jan17 Feb17 Mar17 Apr17 May17 Jun17 Jul17 Aug17 Sep17 Oct17 Nov17 12/1/20017 Residential Res Non Choice $ 41,208 $ 4,432 $ 3,990 $ 3,561 $ 3,198 $ 2,883 $ 2,844 $ 3,221 $ 3,499 $ 3,154 $ 2,970 $ 3,357 $ 4,099 Emp NonChoice $ 28 $ 3 $ 3 $ 2 $ 2 $ 2 $ 2 $ 2 $ 2 $ 2 $ 2 $ 2 $ 3 Low Inc NonChoice $ 1,669 $ 178 $ 174 $ 164 $ 152 $ 137 $ 127 $ 118 $ 119 $ 107 $ 107 $ 127 $ 160 Res Choice $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ $ Residential Revenue $ 42,906 $ 4,613 $ 4,167 $ 3,727 $ 3,352 $ 3,022 $ 2,973 $ 3,341 $ 3,621 $ 3,264 $ 3,079 $ 3,486 $ 4,261 General Service 1 GS1 Sec NonDmd NonCh $ 6,216 $ 552 $ 523 $ 504 $ 493 $ 481 $ 499 $ 539 $ 570 $ 535 $ 495 $ 496 $ 528 GS1 Sec Demand NonCh $ 33,137 $ 2,671 $ 2,572 $ 2,637 $ 2,685 $ 2,722 $ 2,816 $ 2,921 $ 2,909 $ 2,837 $ 2,859 $ 2,764 $ 2,745 GS1 Sec NonDmd Choice $ 15 $ 1 $ 1 $ 1 $ 1 $ 1 $ 1 $ 1 $ 1 $ 1 $ 1 $ 1 $ 1 GS1 Sec Demand Choice $ 554 $ 46 $ 44 $ 43 $ 43 $ 43 $ 47 $ 52 $ 54 $ 50 $ 45 $ 43 $ 44 GS1 Pri NonDmd NonCh $ 8 $ 1 $ 1 $ 1 $ 1 $ 1 $ 1 $ 1 $ 1 $ 1 $ 1 $ 1 $ 1 GS1 Pri Demand NonCh $ 3,358 $ 286 $ 275 $ 287 $ 271 $ 259 $ 265 $ 274 $ 282 $ 290 $ 291 $ 278 $ 301 GS1 Pri NonDmd Choice $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 GS1 Pri Demand Choice $ 423 $ 35 $ 35 $ 37 $ 35 $ 36 $ 36 $ 34 $ 35 $ 36 $ 35 $ 34 $ 34 GS1 Revenue $ 43,711 $ 3,593 $ 3,451 $ 3,510 $ 3,528 $ 3,543 $ 3,665 $ 3,820 $ 3,852 $ 3,749 $ 3,728 $ 3,618 $ 3,654 General Service 2 GS2 Sub NonCh $ 1,404 $ 115 $ 111 $ 131 $ 108 $ 117 $ 105 $ 112 $ 121 $ 114 $ 119 $ 117 $ 134 GS2 Sub Choice $ 1,912 $ 147 $ 145 $ 174 $ 149 $ 147 $ 166 $ 179 $ 164 $ 162 $ 169 $ 149 $ 162 GS2 Tran NonCh $ 491 $ 37 $ 50 $ 46 $ 31 $ 33 $ 44 $ 41 $ 42 $ 36 $ 41 $ 48 $ 42 GS2 Tran Choice $ 509 $ 46 $ 39 $ 47 $ 42 $ 42 $ 39 $ 40 $ 43 $ 41 $ 42 $ 44 $ 45 GS2 Revenue $ 4,317 $ 345 $ 345 $ 398 $ 330 $ 340 $ 353 $ 372 $ 369 $ 354 $ 370 $ 358 $ 383 Irrigation Irrig NonDmd NonCh $ 94 $ 0 $ 0 $ 0 $ 0 $ 4 $ 15 $ 27 $ 27 $ 15 $ 4 $ 0 $ 0 Irrig Demand NonCh $ 1,643 $ 1 $ 0 $ (0) $ 29 $ 134 $ 303 $ 414 $ 362 $ 244 $ 104 $ 52 $ 0 Irrig Demand Choice $ 3 $ 0 $ 0 $ $ 0 $ 1 $ 1 $ 1 $ 1 $ 0 $ 0 $ 0 $ 0 Irrigation Revenue $ 1,739 $ 1 $ 0 $ (0) $ 30 $ 139 $ 319 $ 442 $ 390 $ 259 $ 109 $ 52 $ 0 Lighting Lighting NonCh $ 4,521 $ 377 $ 377 $ 377 $ 377 $ 377 $ 377 $ 377 $ 377 $ 377 $ 377 $ 377 $ 377 Lighting Choice $ 52 $ 4 $ 4 $ 4 $ 4 $ 4 $ 4 $ 4 $ 4 $ 4 $ 4 $ 4 $ 4 Lighting Revenue $ 4,572 $ 381 $ 381 $ 381 $ 381 $ 381 $ 381 $ 381 $ 381 $ 381 $ 381 $ 381 $ 381 Total Rate Schedule $ 97,245 $ 8,933 $ 8,344 $ 8,016 $ 7,621 $ 7,425 $ 7,691 $ 8,356 $ 8,613 $ 8,007 $ 7,667 $ 7,894 $ 8,679

Docket No. D2018.2.12 Page 144 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 A B C D E F G NorthWestern Energy Electric Generation Derivation of Uniform Percentage Increase Docket No. D2018.2.12 Proposed Interim Revenues Uniform % @ Current Proposed Change Generation Base Rates Change (C)/(E) Rate Without Taxes Total Generation Revenue Requirement without Taxes $ 239,352,293 $ (20,951,218) 8.7533% Adjusted Uniform Percent Increase $ (20,951,218) 8.7533% Tax Portion of Rates Total Generation Revenue Requirement Taxes $ 21,863,914 $ 5,694,691 26.0461% Adjusted Uniform Percent Increase $ 5,694,691 26.0461% Total $ 261,216,206 $ (15,256,527)

Docket No. D2018.2.12 Page 145 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 A B C D E NorthWestern Energy Electric Generation Derivation of Proposed Design Rates Docket No. D2018.2.12 Generation Rate Without Tax Uniform % Increase Interim Proposed Design Rates Residential: 8.7533% Residential: CU4 Fixed $ 0.012229 $ 0.011159 DGGS Fixed $ 0.004278 $ 0.003904 Spion Kop Fixed $ 0.001796 $ 0.001639 Hydro Fixed $ 0.021283 $ 0.019420 Employee: CU4 Fixed $ 0.007337 $ 0.006695 DGGS Fixed $ 0.002567 $ 0.002342 Spion Kop Fixed $ 0.001078 $ 0.000984 Hydro Fixed $ 0.012770 $ 0.011652 General Service 1: GS 1 Secondary Non Demand: CU4 Fixed $ 0.012229 $ 0.011159 DGGS Fixed $ 0.004278 $ 0.003904 Spion Kop Fixed $ 0.001796 $ 0.001639 Hydro Fixed $ 0.021283 $ 0.019420 GS 1 Secondary Demand: CU4 Fixed $ 0.012229 $ 0.011159 DGGS Fixed $ 0.004278 $ 0.003904 Spion Kop Fixed $ 0.001796 $ 0.001639 Hydro Fixed $ 0.021283 $ 0.019420 GS 1 Primary Non Demand: CU4 Fixed $ 0.011894 $ 0.010853 DGGS Fixed $ 0.004161 $ 0.003797 Spion Kop Fixed $ 0.001747 $ 0.001594 Hydro Fixed $ 0.020700 $ 0.018888 GS 1 Primary Demand: CU4 Fixed $ 0.011894 $ 0.010853 DGGS Fixed $ 0.004161 $ 0.003797 Spion Kop Fixed $ 0.001747 $ 0.001594 Hydro Fixed $ 0.020700 $ 0.018888 General Service 2: GS 2 Substation: CU4 Fixed $ 0.011791 $ 0.010759 DGGS Fixed $ 0.004126 $ 0.003765 Spion Kop Fixed $ 0.001732 $ 0.001580 Hydro Fixed $ 0.020523 $ 0.018727 GS 2 Transmission: CU4 Fixed $ 0.011720 $ 0.010694 DGGS Fixed $ 0.004101 $ 0.003742 Spion Kop Fixed $ 0.001721 $ 0.001570 Hydro Fixed $ 0.020398 $ 0.018613

Docket No. D2018.2.12 Page 146 of 327 1 2 3 4 5 6 7 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 A B C D E NorthWestern Energy Electric Generation Derivation of Proposed Design Rates Docket No. D2018.2.12 Generation Rate Without Tax Uniform % Increase Interim Proposed Design Rates Irrigation: 8.7533% Irrigation Non Demand: CU4 Fixed $ 0.012229 $ 0.011159 DGGS Fixed $ 0.004278 $ 0.003904 Spion Kop Fixed $ 0.001796 $ 0.001639 Hydro Fixed $ 0.021283 $ 0.019420 Irrigation Demand: CU4 Fixed $ 0.012229 $ 0.011159 DGGS Fixed $ 0.004278 $ 0.003904 Spion Kop Fixed $ 0.001796 $ 0.001639 Hydro Fixed $ 0.021283 $ 0.019420 Lighting: CU4 Fixed $ 0.012229 $ 0.011159 DGGS Fixed $ 0.004278 $ 0.003904 Spion Kop Fixed $ 0.001796 $ 0.001639 Hydro Fixed $ 0.021283 $ 0.019420

Docket No. D2018.2.12 Page 147 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 A B C D E NorthWestern Energy Electric Generation Derivation of Proposed Design Rates Docket No. D2018.2.12 Generation Tax Portion of Rate Uniform % Increase Interim Proposed Design Rates Residential: 26.0461% Residential: CU4 Fixed $ 0.000505 $ 0.000637 DGGS Fixed $ 0.000517 $ 0.000652 Spion Kop Fixed $ 0.000054 $ 0.000068 Hydro Fixed $ 0.002540 $ 0.003202 Employee: CU4 Fixed $ 0.000303 $ 0.000382 DGGS Fixed $ 0.000310 $ 0.000391 Spion Kop Fixed $ 0.000032 $ 0.000040 Hydro Fixed $ 0.001524 $ 0.001921 General Service 1: GS 1 Secondary Non Demand: CU4 Fixed $ 0.000505 $ 0.000637 DGGS Fixed $ 0.000517 $ 0.000652 Spion Kop Fixed $ 0.000054 $ 0.000068 Hydro Fixed $ 0.002540 $ 0.003202 GS 1 Secondary Demand: CU4 Fixed $ 0.000505 $ 0.000637 DGGS Fixed $ 0.000517 $ 0.000652 Spion Kop Fixed $ 0.000054 $ 0.000068 Hydro Fixed $ 0.002540 $ 0.003202 GS 1 Primary Non Demand: CU4 Fixed $ 0.000491 $ 0.000619 DGGS Fixed $ 0.000503 $ 0.000634 Spion Kop Fixed $ 0.000053 $ 0.000067 Hydro Fixed $ 0.002471 $ 0.003115 GS 1 Primary Demand: CU4 Fixed $ 0.000491 $ 0.000619 DGGS Fixed $ 0.000503 $ 0.000634 Spion Kop Fixed $ 0.000053 $ 0.000067 Hydro Fixed $ 0.002471 $ 0.003115 General Service 2: GS 2 Substation: CU4 Fixed $ 0.000487 $ 0.000614 DGGS Fixed $ 0.000498 $ 0.000628 Spion Kop Fixed $ 0.000052 $ 0.000066 Hydro Fixed $ 0.002449 $ 0.003087 GS 2 Transmission: CU4 Fixed $ 0.000484 $ 0.000610 DGGS Fixed $ 0.000495 $ 0.000624 Spion Kop Fixed $ 0.000052 $ 0.000066 Hydro Fixed $ 0.002435 $ 0.003069

Docket No. D2018.2.12 Page 148 of 327 1 2 3 4 5 6 7 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 A B C D E NorthWestern Energy Electric Generation Derivation of Proposed Design Rates Docket No. D2018.2.12 Generation Tax Portion of Rate Uniform % Increase Interim Proposed Design Rates Irrigation: 26.0461% Irrigation Non Demand: CU4 Fixed $ 0.000505 $ 0.000637 DGGS Fixed $ 0.000517 $ 0.000652 Spion Kop Fixed $ 0.000054 $ 0.000068 Hydro Fixed $ 0.002540 $ 0.003202 Irrigation Demand: CU4 Fixed $ 0.000505 $ 0.000637 DGGS Fixed $ 0.000517 $ 0.000652 Spion Kop Fixed $ 0.000054 $ 0.000068 Hydro Fixed $ 0.002540 $ 0.003202 Lighting: CU4 Fixed $ 0.000505 $ 0.000637 DGGS Fixed $ 0.000517 $ 0.000652 Spion Kop Fixed $ 0.000054 $ 0.000068 Hydro Fixed $ 0.002540 $ 0.003202

Docket No. D2018.2.12 Page 149 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 A B C D E F G H I J K L NorthWestern Energy Supply 2017 Test Year Billing Determinants and Revenues Generation Proposed Interim Test Period Actual Revenues Revenues Revenues Avg # Market @ Current Avg # Market @ Current @ Proposed Revenue Percent Customer Class Cust (MWh) Base Rates Cust (MWh) Base Rates Interim Rates Change Change Residential Res Non Choice 283,582 2,422,781 $ 104,668,970 283,582 2,373,047 $ 102,520,373 $ 96,537,922 $ (5,982,451) 5.84% Emp NonChoice 324 2,780 $ 72,053 324 2,721 $ 70,533 $ 66,414 $ (4,120) 5.84% Low Inc NonChoice 11,337 98,097 $ 4,237,998 11,337 96,140 $ 4,153,421 $ 3,911,053 $ (242,368) 5.84% 295,243 2,523,658 $ 108,979,021 295,243 2,471,908 $ 106,744,327 $ 100,515,388 $ (6,228,939) 5.84% General Service 1 GS1 Sec NonDmd NonCh 45,942 277,000 $ 11,966,933 45,942 278,887 $ 12,048,463 $ 11,345,389 $ (703,073) 5.84% GS1 Sec Dmd NonCh 20,502 2,452,695 $ 105,961,317 20,502 2,471,032 $ 106,753,541 $ 100,524,069 $ (6,229,473) 5.84% GS1 Pri NonDmd NonCh 43 575 $ 24,164 43 577 $ 24,241 $ 22,825 $ (1,415) 5.84% GS1 Pri Dmd NonCh 126 337,020 $ 14,161,575 126 338,084 $ 14,206,297 $ 13,376,976 $ (829,320) 5.84% 66,613 3,067,289 $ 132,113,989 66,613 3,088,580 $ 133,032,541 $ 125,269,260 $ (7,763,282) 5.84% General Service 2 GS2 Sub NonCh 20 224,010 $ 9,331,794 20 245,968 $ 10,246,541 $ 9,648,346 $ (598,195) 5.84% GS2 Tran NonCh 19 112,259 $ 4,648,213 19 112,015 $ 4,638,102 $ 4,367,250 $ (270,853) 5.84% 39 336,269 $ 13,980,007 39 357,983 $ 14,884,643 $ 14,015,596 $ (869,047) 5.84% Irrigation Irrig NonDmd NonCh 619 5,408 $ 233,616 619 4,920 $ 212,538 $ 200,136 $ (12,402) 5.84% Irrig Dmd NonCh 1,119 101,050 $ 4,365,545 1,119 91,933 $ 3,971,672 $ 3,739,910 $ (231,762) 5.84% 1,738 106,457 $ 4,599,160 1,738 96,852 $ 4,184,210 $ 3,940,046 $ (244,164) 5.84% Lighting Lighting NonCh 3,618 54,853 $ 2,369,739 3,618 54,870 $ 2,370,485 $ 2,232,158 $ (138,327) 5.84% 3,618 54,853 $ 2,369,739 3,618 54,870 $ 2,370,485 $ 2,232,158 $ (138,327) 5.84% Total Rate Schedule 367,251 6,088,525 $ 262,041,916 367,251 6,070,193 $ 261,216,206 $ 245,972,448 $ (15,243,759) 5.8357% Rounding Difference $ (12,768) Sales for Resale $ $ $ $ Transmission $ 1,551,608 $ 1,547,144 $ 1,547,144 $ Miscellaneous Revenue $ (3,796) $ $ $ Total Generation Revenue 367,251 6,088,525 $ 263,589,728 367,251 6,070,193 $ 262,763,351 $ 247,519,592 $ (15,256,527) 5.81%

Docket No. D2018.2.12 Page 150 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 A B C D E F G H I J K L NorthWestern Energy Supply 2017 Test Year Billing Determinants and Revenues Without Taxes Generation Proposed Interim Test Period Actual Revenues Revenues Revenues Avg # Market @ Current Avg # Market @ Current @ Proposed Revenue Percent Customer Class Cust (MWh) Base Rates Cust (MWh) Base Rates Interim Rates Change Change Residential Res Non Choice 283,582 2,422,781 $ 95,908,195 283,582 2,373,047 $ 93,939,436 $ 85,719,201 $ (8,220,235) 8.75% Emp NonChoice 324 2,780 $ 66,024 324 2,721 $ 64,631 $ 58,974 $ (5,657) 8.75% Low Inc NonChoice 11,337 98,097 $ 3,883,279 11,337 96,140 $ 3,805,780 $ 3,472,753 $ (333,027) 8.75% 295,243 2,523,658 $ 99,857,497 295,243 2,471,908 $ 97,809,847 $ 89,250,928 $ (8,558,919) 8.75% General Service 1 GS1 Sec NonDmd NonCh 45,942 277,000 $ 10,965,303 45,942 278,887 $ 11,040,008 $ 10,073,945 $ (966,063) 8.75% GS1 Sec Dmd NonCh 20,502 2,452,695 $ 97,092,373 20,502 2,471,032 $ 97,818,288 $ 89,258,632 $ (8,559,656) 8.75% GS1 Pri NonDmd NonCh 43 575 $ 22,141 43 577 $ 22,211 $ 20,267 $ (1,944) 8.75% GS1 Pri Dmd NonCh 126 337,020 $ 12,975,939 126 338,084 $ 13,016,917 $ 11,877,573 $ (1,139,344) 8.75% 66,613 3,067,289 $ 121,055,756 66,613 3,088,580 $ 121,897,424 $ 111,230,417 $ (10,667,007) 8.75% General Service 2 GS2 Sub NonCh 20 224,010 $ 8,550,896 20 245,968 $ 9,389,096 $ 8,567,316 $ (821,780) 8.75% GS2 Tran NonCh 19 112,259 $ 4,259,122 19 112,015 $ 4,249,858 $ 3,877,855 $ (372,003) 8.75% 39 336,269 $ 12,810,018 39 357,983 $ 13,638,953 $ 12,445,171 $ (1,193,782) 8.75% Irrigation Irrig NonDmd NonCh 619 5,408 $ 214,062 619 4,920 $ 194,749 $ 177,707 $ (17,042) 8.75% Irrig Dmd NonCh 1,119 101,050 $ 4,000,149 1,119 91,933 $ 3,639,244 $ 3,320,789 $ (318,455) 8.75% 1,738 106,457 $ 4,214,211 1,738 96,852 $ 3,833,992 $ 3,498,496 $ (335,496) 8.75% Lighting Lighting NonCh 3,618 54,853 $ 2,171,392 3,618 54,870 $ 2,172,076 $ 1,982,007 $ (190,069) 8.75% 3,618 54,853 $ 2,171,392 3,618 54,870 $ 2,172,076 $ 1,982,007 $ (190,069) 8.75% Total Rate Schedule 367,251 6,088,525 $ 240,108,875 367,251 6,070,193 $ 239,352,293 $ 218,407,019 $ (20,945,274) 8.7508% Rounding Difference $ (5,944) Sales for Resale $ $ $ $ Transmission $ 1,551,608 $ 1,547,144 $ 1,547,144 $ Miscellaneous Revenue $ (3,796) $ $ $ Total Generation Revenue 367,251 6,088,525 $ 241,656,687 367,251 6,070,193 $ 240,899,437 $ 219,954,163 $ (20,951,218) 8.70%

Docket No. D2018.2.12 Page 151 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 A B C D E F G H I J K L NorthWestern Energy Supply 2017 Test Year Billing Determinants and Revenues Tax Portion Generation Proposed Interim Test Period Actual Revenues Revenues Revenues Avg # Market @ Current Avg # Market @ Current @ Proposed Revenue Percent Customer Class Cust (MWh) Base Rates Cust (MWh) Base Rates Interim Rates Change Change Residential Res Non Choice 283,582 2,422,781 $ 8,760,775 283,582 2,373,047 $ 8,580,938 $ 10,818,721 $ 2,237,783 26.08% Emp NonChoice 324 2,780 $ 6,029 324 2,721 $ 5,902 $ 7,439 $ 1,537 26.05% Low Inc NonChoice 11,337 98,097 $ 354,720 11,337 96,140 $ 347,641 $ 438,300 $ 90,660 26.08% 295,243 2,523,658 $ 9,121,524 295,243 2,471,908 $ 8,934,480 $ 11,264,461 $ 2,329,980 26.08% General Service 1 GS1 Sec NonDmd NonCh 45,942 277,000 $ 1,001,630 45,942 278,887 $ 1,008,454 $ 1,271,444 $ 262,990 26.08% GS1 Sec Dmd NonCh 20,502 2,452,695 $ 8,868,944 20,502 2,471,032 $ 8,935,253 $ 11,265,437 $ 2,330,184 26.08% GS1 Pri NonDmd NonCh 43 575 $ 2,023 43 577 $ 2,029 $ 2,558 $ 529 26.07% GS1 Pri Dmd NonCh 126 337,020 $ 1,185,636 126 338,084 $ 1,189,380 $ 1,499,403 $ 310,023 26.07% 66,613 3,067,289 $ 11,058,233 66,613 3,088,580 $ 11,135,117 $ 14,038,843 $ 2,903,726 26.08% General Service 2 GS2 Sub NonCh 20 224,010 $ 780,898 20 245,968 $ 857,445 $ 1,081,030 $ 223,585 26.08% GS2 Tran NonCh 19 112,259 $ 389,091 19 112,015 $ 388,245 $ 489,395 $ 101,150 26.05% 39 336,269 $ 1,169,989 39 357,983 $ 1,245,690 $ 1,570,424 $ 324,735 26.07% Irrigation Irrig NonDmd NonCh 619 5,408 $ 19,554 619 4,920 $ 17,789 $ 22,429 $ 4,639 26.08% Irrig Dmd NonCh 1,119 101,050 $ 365,395 1,119 91,933 $ 332,428 $ 419,121 $ 86,692 26.08% 1,738 106,457 $ 384,949 1,738 96,852 $ 350,218 $ 441,549 $ 91,332 26.08% Lighting Lighting NonCh 3,618 54,853 $ 198,347 3,618 54,870 $ 198,409 $ 250,151 $ 51,742 26.08% 3,618 54,853 $ 198,347 3,618 54,870 $ 198,409 $ 250,151 $ 51,742 26.08% Total Rate Schedule 367,251 6,088,525 $ 21,933,041 367,251 6,070,193 $ 21,863,914 $ 27,565,429 $ 5,701,515 26.0773% Rounding Difference $ (6,824) Sales for Resale $ $ $ $ Transmission $ $ $ $ Miscellaneous Revenue $ $ $ $ Total Generation Revenue 367,251 6,088,525 $ 21,933,041 367,251 6,070,193 $ 21,863,914 $ 27,565,429 $ 5,694,691 26.05%

Docket No. D2018.2.12 Page 152 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 A B C D E F G H I J K L M N O NorthWestern Energy Electric Utility 2017 Actual Average # of Customers Customer Class Average Jan17 Feb17 Mar17 Apr17 May17 Jun17 Jul17 Aug17 Sep17 Oct17 Nov17 Dec17 Residential: Res NonCh 283,582 282,482 282,077 281,779 281,373 281,441 281,837 283,505 284,524 285,213 286,053 286,291 286,413 Res Emp NonCh 324 331 330 329 329 326 325 325 324 323 317 313 312 Res Low Inc NonCh 11,337 11,029 11,621 12,138 12,602 12,774 12,606 11,207 10,515 10,283 10,122 10,354 10,792 NonChoice 295,243 293,842 294,028 294,246 294,304 294,541 294,768 295,037 295,363 295,819 296,492 296,958 297,517 Choice 3 4 4 4 3 3 2 2 2 2 2 2 2 Total Residential 295,246 293,846 294,032 294,250 294,307 294,544 294,770 295,039 295,365 295,821 296,494 296,960 297,519 General Service 1: Sec NonDmd NonCh 45,942 45,840 45,802 45,840 45,855 45,740 45,837 45,906 45,960 46,046 46,103 46,113 46,264 Sec Demand NonCh 20,502 20,315 20,383 20,436 20,484 20,414 20,456 20,502 20,530 20,556 20,588 20,635 20,721 GS1 Sec NonChoice 66,444 66,155 66,185 66,276 66,339 66,154 66,293 66,408 66,490 66,602 66,691 66,748 66,985 Sec NonDmd Choice 157 157 157 157 157 157 157 157 157 157 157 157 157 Sec Demand Choice 125 126 127 127 127 124 124 124 123 124 125 126 128 GS1 Sec Choice 282 283 284 284 284 281 281 281 280 281 282 283 285 Pri NonDmd NonCh 43 42 43 43 43 43 43 43 43 43 43 42 42 Pri Demand NonCh 126 123 123 123 125 125 127 126 126 125 129 129 128 GS1 Pri NonChoice 169 165 166 166 168 168 170 169 169 168 172 171 170 Pri NonDmd Choice 1 1 1 1 1 1 1 1 1 1 1 1 1 Pri Demand Choice 4 4 4 4 4 4 4 4 4 4 4 4 4 GS1 Pri Choice 5 5 5 5 5 5 5 5 5 5 5 5 5 Total GS1 66,900 66,608 66,640 66,731 66,796 66,608 66,749 66,863 66,944 67,056 67,150 67,207 67,445 General Service 2: Sub NonChoice 20 20 20 20 20 20 20 19 19 19 19 19 20 Sub Choice 32 32 32 32 32 32 32 32 32 32 32 32 32 Tran NonChoice 19 19 19 19 19 19 19 19 19 19 19 19 19 Tran Choice 5 5 5 5 5 5 5 5 5 5 5 5 5 Total GS2 76 76 76 76 76 76 76 75 75 75 75 75 76 Irrigation: NonDmd NonChoice 619 180 175 161 200 587 1,036 1,167 1,199 1,120 906 424 268 Dmd NonChoice 1,119 61 38 42 77 1,048 2,282 2,507 2,577 2,348 1,954 353 140 NonChoice 1,738 241 213 203 277 1,635 3,318 3,674 3,776 3,468 2,860 777 408 Choice 1 2 2 2 2 2 2 2 Total Irrigation 1,739 241 213 203 277 1,637 3,320 3,676 3,778 3,470 2,862 779 408 Lighting: NonChoice 3,618 3,627 3,627 3,627 3,620 3,617 3,621 3,608 3,603 3,610 3,611 3,615 3,628 Choice 114 112 112 112 112 115 115 115 115 115 115 115 115 Total Lighting 3,732 3,739 3,739 3,739 3,732 3,732 3,736 3,723 3,718 3,725 3,726 3,730 3,743 Total # of Customers 367,693 364,510 364,700 364,999 365,188 366,597 368,651 369,376 369,880 370,147 370,307 368,751 369,191

Docket No. D2018.2.12 Page 153 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 A B C D E F G H I J K L M N O NorthWestern Energy Electric Utility 2017 Actual Energy at the Meter (MWh) Customer Class Total Jan17 Feb17 Mar17 Apr17 May17 Jun17 Jul17 Aug17 Sep17 Oct17 Nov17 Dec17 Residential: Res NonCh 2,422,781 292,173 257,796 212,413 173,895 161,560 158,934 186,528 220,851 187,576 169,183 180,703 221,168 Res Emp NonCh 2,780 350 293 245 205 194 187 217 239 203 194 210 242 Res Low Inc NonCh 98,097 11,722 11,237 9,763 8,283 7,696 7,126 6,820 7,510 6,373 6,104 6,834 8,629 NonChoice 2,523,658 304,245 269,326 222,421 182,382 169,450 166,247 193,565 228,600 194,152 175,480 187,748 230,040 Choice 11 2 2 2 1 0 0 1 1 1 1 0 0 Total Residential 2,523,668 304,247 269,328 222,423 182,383 169,451 166,248 193,565 228,602 194,153 175,481 187,748 230,040 General Service 1: Sec NonDmd NonCh 277,000 32,844 30,399 25,280 20,809 19,042 18,778 20,480 23,430 21,145 19,162 20,765 24,866 Sec Demand NonCh 2,452,695 225,214 217,712 198,807 187,487 183,478 195,439 213,899 232,747 219,749 190,153 187,154 200,858 GS1 Sec NonChoice 2,729,694 258,058 248,111 224,086 208,296 202,520 214,216 234,379 256,177 240,894 209,314 207,918 225,724 Sec NonDmd Choice 758 89 77 67 58 58 51 56 65 56 52 65 63 Sec Demand Choice 64,690 5,396 5,395 4,772 5,086 4,869 5,454 6,163 6,945 6,690 3,796 4,962 5,163 GS1 Sec Choice 65,449 5,486 5,472 4,839 5,144 4,927 5,505 6,220 7,010 6,746 3,848 5,027 5,226 Pri NonDmd NonCh 575 16 24 22 20 44 69 103 85 60 70 38 26 Pri Demand NonCh 337,020 30,791 30,158 27,598 26,483 24,776 25,487 27,013 29,279 29,706 27,880 29,515 28,335 GS1 Pri NonChoice 337,595 30,807 30,182 27,620 26,503 24,820 25,555 27,116 29,364 29,766 27,949 29,553 28,360 Pri NonDmd Choice 28 1 1 1 1 5 6 6 7 (1) Pri Demand Choice 73,289 6,066 6,648 5,901 6,588 5,974 6,253 6,357 5,491 6,139 6,285 5,877 5,711 GS1 Pri Choice 73,317 6,066 6,649 5,902 6,589 5,975 6,253 6,362 5,497 6,139 6,291 5,883 5,711 Total GS1 3,206,055 300,416 290,414 262,447 246,532 238,242 251,530 274,077 298,048 283,544 247,403 248,382 265,021 General Service 2: Sub NonChoice 224,010 20,895 18,903 18,822 20,275 17,186 17,432 16,257 18,119 18,820 17,634 20,080 19,587 Sub Choice 1,735,183 149,660 150,580 134,478 148,593 137,436 121,390 140,676 153,890 153,487 149,669 155,325 139,998 Tran NonChoice 112,259 10,625 9,218 9,510 8,862 8,209 8,330 9,402 9,494 9,797 9,361 9,331 10,120 Tran Choice 248,396 18,537 20,262 18,712 20,821 21,310 22,658 21,996 20,823 21,034 20,700 20,501 21,042 Total GS2 2,319,848 199,717 198,963 181,523 198,551 184,141 169,810 188,330 202,326 203,138 197,365 205,237 190,746 Irrigation: NonDmd NonChoice 5,408 0 5 1 9 146 783 1,211 1,645 1,187 358 50 14 Dmd NonChoice 101,050 18 21 (8) 11 1,609 15,053 25,495 31,128 20,032 7,493 93 105 NonChoice 106,457 18 26 (7) 19 1,755 15,836 26,706 32,773 21,219 7,851 142 119 Choice 168 7 24 32 57 29 13 6 Total Irrigation 106,625 18 26 (7) 19 1,762 15,860 26,738 32,830 21,249 7,864 149 119 Lighting: NonChoice 54,853 4,675 4,652 4,613 4,558 4,533 4,508 4,494 4,509 4,539 4,563 4,594 4,615 Choice 4,355 367 366 365 364 364 362 362 362 363 364 359 358 Total Lighting 59,208 5,042 5,018 4,978 4,922 4,896 4,870 4,856 4,872 4,902 4,927 4,953 4,972 Total Energy 8,215,404 809,440 763,748 671,364 632,407 598,491 608,318 687,567 766,677 706,985 633,039 646,469 690,898

Docket No. D2018.2.12 Page 154 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 A B C D E F G H I J K L M N O NorthWestern Energy Supply 2017 Actual Loads @ Current Rate Revenue (Thousands) Total Rate Schedule Revenue Customer Class Total Jan17 Feb17 Mar17 Apr17 May17 Jun17 Jul17 Aug17 Sep17 Oct17 Nov17 Dec17 Residential Res Non Choice $ 104,669 $ 12,622 $ 11,137 $ 9,177 $ 7,513 $ 6,980 $ 6,866 $ 8,058 $ 9,541 $ 8,104 $ 7,309 $ 7,807 $ 9,555 Emp NonChoice $ 72 $ 9 $ 8 $ 6 $ 5 $ 5 $ 5 $ 6 $ 6 $ 5 $ 5 $ 5 $ 6 Low Inc NonChoice $ 4,238 $ 506 $ 485 $ 422 $ 358 $ 332 $ 308 $ 295 $ 324 $ 275 $ 264 $ 295 $ 373 Residential Revenue $ 108,979 $ 13,138 $ 11,630 $ 9,605 $ 7,876 $ 7,317 $ 7,179 $ 8,359 $ 9,872 $ 8,384 $ 7,578 $ 8,107 $ 9,934 (0) General Service 1 GS1 Sec NonDmd NonCh $ 11,967 $ 1,419 $ 1,313 $ 1,092 $ 899 $ 823 $ 811 $ 885 $ 1,012 $ 914 $ 828 $ 897 $ 1,074 GS1 Sec Demand NonCh $ 105,961 $ 9,730 $ 9,406 $ 8,589 $ 8,100 $ 7,927 $ 8,443 $ 9,241 $ 10,055 $ 9,494 $ 8,215 $ 8,085 $ 8,677 GS1 Pri NonDmd NonCh $ 24 $ 1 $ 1 $ 1 $ 1 $ 2 $ 3 $ 4 $ 4 $ 3 $ 3 $ 2 $ 1 GS1 Pri Demand NonCh $ 14,162 $ 1,294 $ 1,267 $ 1,160 $ 1,113 $ 1,041 $ 1,071 $ 1,135 $ 1,230 $ 1,248 $ 1,172 $ 1,240 $ 1,191 GS1 Revenue $ 132,114 $ 12,443 $ 11,987 $ 10,842 $ 10,112 $ 9,792 $ 10,328 $ 11,265 $ 12,301 $ 11,658 $ 10,217 $ 10,224 $ 10,943 (0) General Service 2 GS2 Sub NonCh $ 9,332 $ 870 $ 787 $ 784 $ 845 $ 716 $ 726 $ 677 $ 755 $ 784 $ 735 $ 836 $ 816 GS2 Tran NonCh $ 4,648 $ 440 $ 382 $ 394 $ 367 $ 340 $ 345 $ 389 $ 393 $ 406 $ 388 $ 386 $ 419 GS2 Revenue $ 13,980 $ 1,310 $ 1,169 $ 1,178 $ 1,212 $ 1,056 $ 1,071 $ 1,067 $ 1,148 $ 1,190 $ 1,122 $ 1,223 $ 1,235 Irrigation Irrig NonDmd NonCh $ 234 $ 0 $ 0 $ 0 $ 0 $ 6 $ 34 $ 52 $ 71 $ 51 $ 15 $ 2 $ 1 Irrig Demand NonCh $ 4,366 $ 1 $ 1 $ (0) $ 0 $ 70 $ 650 $ 1,101 $ 1,345 $ 865 $ 324 $ 4 $ 5 Irrigation Revenue $ 4,599 $ 1 $ 1 $ (0) $ 1 $ 76 $ 684 $ 1,154 $ 1,416 $ 917 $ 339 $ 6 $ 5 Lighting Lighting NonCh $ 2,370 $ 202 $ 201 $ 199 $ 197 $ 196 $ 195 $ 194 $ 195 $ 196 $ 197 $ 198 $ 199 Lighting Revenue $ 2,370 $ 202 $ 201 $ 199 $ 197 $ 196 $ 195 $ 194 $ 195 $ 196 $ 197 $ 198 $ 199 Total Rate Schedule $ 262,042 $ 27,094 $ 24,989 $ 21,823 $ 19,397 $ 18,437 $ 19,457 $ 22,038 $ 24,932 $ 22,345 $ 19,454 $ 19,759 $ 22,317

Docket No. D2018.2.12 Page 155 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 A B C D E F G H I J K L M N O NorthWestern Energy Supply 2017 Actual Loads @ Current Rate Revenue (Thousands) Total Rate Schedule Revenue Without Taxes Customer Class Total Jan17 Feb17 Mar17 Apr17 May17 Jun17 Jul17 Aug17 Sep17 Oct17 Nov17 Dec17 Residential Res Non Choice $ 95,908 $ 11,566 $ 10,205 $ 8,409 $ 6,884 $ 6,396 $ 6,292 $ 7,384 $ 8,743 $ 7,425 $ 6,697 $ 7,153 $ 8,755 Emp NonChoice $ 66 $ 8 $ 7 $ 6 $ 5 $ 5 $ 4 $ 5 $ 6 $ 5 $ 5 $ 5 $ 6 Low Inc NonChoice $ 3,883 $ 464 $ 445 $ 386 $ 328 $ 305 $ 282 $ 270 $ 297 $ 252 $ 242 $ 271 $ 342 Residential Revenue $ 99,857 $ 12,038 $ 10,657 $ 8,801 $ 7,217 $ 6,705 $ 6,578 $ 7,659 $ 9,046 $ 7,682 $ 6,943 $ 7,429 $ 9,103 General Service 1 GS1 Sec NonDmd NonCh $ 10,965 $ 1,300 $ 1,203 $ 1,001 $ 824 $ 754 $ 743 $ 811 $ 928 $ 837 $ 759 $ 822 $ 984 GS1 Sec Demand NonCh $ 97,092 $ 8,915 $ 8,618 $ 7,870 $ 7,422 $ 7,263 $ 7,737 $ 8,467 $ 9,214 $ 8,699 $ 7,527 $ 7,409 $ 7,951 GS1 Pri NonDmd NonCh $ 22 $ 1 $ 1 $ 1 $ 1 $ 2 $ 3 $ 4 $ 3 $ 2 $ 3 $ 1 $ 1 GS1 Pri Demand NonCh $ 12,976 $ 1,186 $ 1,161 $ 1,063 $ 1,020 $ 954 $ 981 $ 1,040 $ 1,127 $ 1,144 $ 1,073 $ 1,136 $ 1,091 GS1 Revenue $ 121,056 $ 11,402 $ 10,984 $ 9,934 $ 9,266 $ 8,973 $ 9,464 $ 10,322 $ 11,272 $ 10,682 $ 9,362 $ 9,369 $ 10,027 General Service 2 GS2 Sub NonCh $ 8,551 $ 798 $ 722 $ 718 $ 774 $ 656 $ 665 $ 621 $ 692 $ 718 $ 673 $ 766 $ 748 GS2 Tran NonCh $ 4,259 $ 403 $ 350 $ 361 $ 336 $ 311 $ 316 $ 357 $ 360 $ 372 $ 355 $ 354 $ 384 GS2 Revenue $ 12,810 $ 1,201 $ 1,071 $ 1,079 $ 1,110 $ 967 $ 981 $ 977 $ 1,052 $ 1,090 $ 1,028 $ 1,121 $ 1,132 Irrigation Irrig NonDmd NonCh $ 214 $ 0 $ 0 $ 0 $ 0 $ 6 $ 31 $ 48 $ 65 $ 47 $ 14 $ 2 $ 1 Irrig Demand NonCh $ 4,000 $ 1 $ 1 $ (0) $ 0 $ 64 $ 596 $ 1,009 $ 1,232 $ 793 $ 297 $ 4 $ 4 Irrigation Revenue $ 4,214 $ 1 $ 1 $ (0) $ 1 $ 69 $ 627 $ 1,057 $ 1,297 $ 840 $ 311 $ 6 $ 5 Lighting Lighting NonCh $ 2,171 $ 185 $ 184 $ 183 $ 180 $ 179 $ 178 $ 178 $ 179 $ 180 $ 181 $ 182 $ 183 Lighting Revenue $ 2,171 $ 185 $ 184 $ 183 $ 180 $ 179 $ 178 $ 178 $ 179 $ 180 $ 181 $ 182 $ 183 Total Rate Schedule $ 240,109 $ 24,826 $ 22,897 $ 19,997 $ 17,774 $ 16,894 $ 17,829 $ 20,194 $ 22,845 $ 20,474 $ 17,825 $ 18,105 $ 20,449

Docket No. D2018.2.12 Page 156 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 A B C D E F G H I J K L M N O NorthWestern Energy Supply 2017 Actual Loads @ Current Rate Revenue (Thousands) Total Rate Schedule Revenue Tax Portion Customer Class Total Jan17 Feb17 Mar17 Apr17 May17 Jun17 Jul17 Aug17 Sep17 Oct17 Nov17 Dec17 Residential Res Non Choice $ 8,761 $ 1,056 $ 932 $ 768 $ 629 $ 584 $ 575 $ 674 $ 799 $ 678 $ 612 $ 653 $ 800 Emp NonChoice $ 6 $ 1 $ 1 $ 1 $ 0 $ 0 $ 0 $ 0 $ 1 $ 0 $ 0 $ 0 $ 1 Low Inc NonChoice $ 355 $ 42 $ 41 $ 35 $ 30 $ 28 $ 26 $ 25 $ 27 $ 23 $ 22 $ 25 $ 31 Residential Revenue $ 9,122 $ 1,100 $ 973 $ 804 $ 659 $ 612 $ 601 $ 700 $ 826 $ 702 $ 634 $ 679 $ 831 General Service 1 GS1 Sec NonDmd NonCh $ 1,002 $ 119 $ 110 $ 91 $ 75 $ 69 $ 68 $ 74 $ 85 $ 76 $ 69 $ 75 $ 90 GS1 Sec Demand NonCh $ 8,869 $ 814 $ 787 $ 719 $ 678 $ 663 $ 707 $ 773 $ 842 $ 795 $ 688 $ 677 $ 726 GS1 Pri NonDmd NonCh $ 2 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 GS1 Pri Demand NonCh $ 1,186 $ 108 $ 106 $ 97 $ 93 $ 87 $ 90 $ 95 $ 103 $ 105 $ 98 $ 104 $ 100 GS1 Revenue $ 11,058 $ 1,042 $ 1,003 $ 907 $ 846 $ 820 $ 865 $ 943 $ 1,030 $ 976 $ 855 $ 856 $ 916 General Service 2 GS2 Sub NonCh $ 781 $ 73 $ 66 $ 66 $ 71 $ 60 $ 61 $ 57 $ 63 $ 66 $ 61 $ 70 $ 68 GS2 Tran NonCh $ 389 $ 37 $ 32 $ 33 $ 31 $ 28 $ 29 $ 33 $ 33 $ 34 $ 32 $ 32 $ 35 GS2 Revenue $ 1,170 $ 110 $ 98 $ 99 $ 101 $ 88 $ 90 $ 89 $ 96 $ 100 $ 94 $ 102 $ 103 Irrigation Irrig NonDmd NonCh $ 20 $ 0 $ 0 $ 0 $ 0 $ 1 $ 3 $ 4 $ 6 $ 4 $ 1 $ 0 $ 0 Irrig Demand NonCh $ 365 $ 0 $ 0 $ (0) $ 0 $ 6 $ 54 $ 92 $ 113 $ 72 $ 27 $ 0 $ 0 Irrigation Revenue $ 385 $ 0 $ 0 $ (0) $ 0 $ 6 $ 57 $ 97 $ 119 $ 77 $ 28 $ 1 $ 0 Lighting Lighting NonCh $ 198 $ 17 $ 17 $ 17 $ 16 $ 16 $ 16 $ 16 $ 16 $ 16 $ 17 $ 17 $ 17 Lighting Revenue $ 198 $ 17 $ 17 $ 17 $ 16 $ 16 $ 16 $ 16 $ 16 $ 16 $ 17 $ 17 $ 17 Total Rate Schedule $ 21,933 $ 2,268 $ 2,092 $ 1,827 $ 1,624 $ 1,543 $ 1,629 $ 1,845 $ 2,087 $ 1,870 $ 1,628 $ 1,654 $ 1,868

Docket No. D2018.2.12 Page 157 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 A B C D E F G H I J K L M N O NorthWestern Energy Electric Utility 2017 Test Year Normalized Energy at the Meter (MWh) Customer Class Total Jan17 Feb17 Mar17 Apr17 May17 Jun17 Jul17 Aug17 Sep17 Oct17 Nov17 Dec17 Residential: Res NonCh 2,373,047 255,232 229,775 205,069 184,137 166,034 163,753 185,514 201,519 181,643 171,044 193,293 236,034 Res Emp NonCh 2,721 293 264 236 213 192 189 212 230 207 195 221 270 Res Low Inc NonCh 96,140 10,232 10,009 9,418 8,765 7,904 7,338 6,780 6,851 6,170 6,167 7,305 9,203 NonChoice 2,471,908 265,756 240,048 214,724 193,114 174,130 171,279 192,505 208,600 188,020 177,405 200,819 245,507 Choice 9 1 2 1 1 1 1 1 1 1 1 Total Residential 2,471,917 265,757 240,050 214,725 193,115 174,130 171,280 192,506 208,601 188,021 177,406 200,819 245,507 General Service 1: Sec NonDmd NonCh 278,887 24,789 23,467 22,633 22,101 21,591 22,402 24,172 25,571 23,995 22,214 22,263 23,688 Sec Demand NonCh 2,471,032 219,642 207,930 200,538 195,824 191,303 198,488 214,172 226,565 212,605 196,824 197,256 209,886 GS1 Sec NonChoice 2,749,919 244,431 231,397 223,171 217,925 212,894 220,890 238,344 252,135 236,600 219,038 219,519 233,574 Sec NonDmd Choice 761 63 60 59 59 60 64 71 75 69 62 60 61 Sec Demand Choice 64,951 5,384 5,108 5,004 5,044 5,091 5,467 6,038 6,376 5,880 5,315 5,079 5,165 GS1 Sec Choice 65,712 5,447 5,168 5,062 5,103 5,150 5,531 6,109 6,451 5,949 5,377 5,139 5,225 Pri NonDmd NonCh 577 52 50 47 45 43 45 48 50 50 49 49 50 Pri Demand NonCh 338,084 30,260 29,055 27,742 26,492 25,370 26,151 27,953 29,533 29,043 28,688 28,674 29,123 GS1 Pri NonChoice 338,661 30,312 29,104 27,789 26,537 25,413 26,196 28,000 29,583 29,093 28,737 28,723 29,173 Pri NonDmd Choice 28 2 2 2 2 2 2 2 2 2 2 2 2 Pri Demand Choice 72,879 6,115 6,273 6,243 6,280 6,112 6,305 5,927 5,816 6,213 6,083 5,830 5,683 GS1 Pri Choice 72,907 6,117 6,275 6,246 6,282 6,114 6,307 5,929 5,818 6,215 6,085 5,832 5,685 Total GS1 3,227,199 286,307 271,945 262,268 255,848 249,572 258,924 278,382 293,987 277,857 259,238 259,213 273,658 General Service 2: Sub NonChoice 245,968 21,555 21,173 22,306 20,037 18,906 17,484 18,839 20,916 19,483 20,209 21,676 23,386 Sub Choice 1,882,910 166,015 149,529 162,565 151,119 134,991 154,204 167,464 164,986 161,665 164,830 148,225 157,316 Tran NonChoice 112,015 10,328 9,214 9,262 8,267 8,360 8,934 9,738 9,992 9,403 9,111 9,996 9,410 Tran Choice 547,649 45,260 41,291 45,786 45,502 47,656 46,188 45,822 46,033 44,892 45,499 45,267 48,453 Total GS2 2,788,543 243,158 221,207 239,918 224,925 209,913 226,810 241,863 241,927 235,444 239,649 225,164 238,566 Irrigation: NonDmd NonChoice 4,920 2 2 1 9 205 813 1,440 1,425 795 210 17 1 Dmd NonChoice 91,933 29 30 24 173 3,826 15,199 26,910 26,622 14,860 3,916 317 27 NonChoice 96,852 30 32 25 183 4,031 16,012 28,350 28,046 15,656 4,126 334 28 Choice 150 0 0 0 6 25 44 43 24 6 1 0 Total Irrigation 97,002 30 32 25 183 4,037 16,037 28,394 28,090 15,680 4,132 334 28 Lighting: NonChoice 54,870 4,572 4,572 4,572 4,572 4,572 4,572 4,572 4,572 4,572 4,572 4,572 4,572 Choice 4,371 364 364 364 364 364 364 364 364 364 364 364 364 Total Lighting 59,241 4,937 4,937 4,937 4,937 4,937 4,937 4,937 4,937 4,937 4,937 4,937 4,937 Total Energy 8,643,902 800,189 738,170 721,873 679,007 642,589 677,987 746,082 777,541 721,939 685,361 690,468 762,695

Docket No. D2018.2.12 Page 158 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 A B C D E F G H I J K L M N O NorthWestern Energy Generation 2017 Normalized Loads @ Proposed Rate Revenue (Thousands) Total Rate Schedule Customer Class Total Jan17 Feb17 Mar17 Apr17 May17 Jun17 Jul17 Aug17 Sep17 Oct17 Nov17 12/1/20017 Residential Res Non Choice $ 96,538 $ 10,383 $ 9,347 $ 8,342 $ 7,491 $ 6,754 $ 6,662 $ 7,547 $ 8,198 $ 7,389 $ 6,958 $ 7,863 $ 9,602 Emp NonChoice $ 66 $ 7 $ 6 $ 6 $ 5 $ 5 $ 5 $ 5 $ 6 $ 5 $ 5 $ 5 $ 7 Low Inc NonChoice $ 3,911 $ 416 $ 407 $ 383 $ 357 $ 322 $ 299 $ 276 $ 279 $ 251 $ 251 $ 297 $ 374 Residential Revenue $ 100,515 $ 10,806 $ 9,761 $ 8,731 $ 7,853 $ 7,081 $ 6,965 $ 7,828 $ 8,482 $ 7,645 $ 7,214 $ 8,166 $ 9,983 0 General Service 1 GS1 Sec NonDmd NonCh $ 11,345 $ 1,008 $ 955 $ 921 $ 899 $ 878 $ 911 $ 983 $ 1,040 $ 976 $ 904 $ 906 $ 964 GS1 Sec Demand NonCh $ 100,524 $ 8,935 $ 8,459 $ 8,158 $ 7,966 $ 7,782 $ 8,075 $ 8,713 $ 9,217 $ 8,649 $ 8,007 $ 8,025 $ 8,538 GS1 Pri NonDmd NonCh $ 23 $ 2 $ 2 $ 2 $ 2 $ 2 $ 2 $ 2 $ 2 $ 2 $ 2 $ 2 $ 2 GS1 Pri Demand NonCh $ 13,377 $ 1,197 $ 1,150 $ 1,098 $ 1,048 $ 1,004 $ 1,035 $ 1,106 $ 1,169 $ 1,149 $ 1,135 $ 1,135 $ 1,152 GS1 Revenue $ 125,269 $ 11,143 $ 10,565 $ 10,178 $ 9,915 $ 9,666 $ 10,022 $ 10,804 $ 11,428 $ 10,776 $ 10,048 $ 10,067 $ 10,656 General Service 2 GS2 Sub NonCh $ 9,648 $ 846 $ 831 $ 875 $ 786 $ 742 $ 686 $ 739 $ 820 $ 764 $ 793 $ 850 $ 917 GS2 Tran NonCh $ 4,367 $ 403 $ 359 $ 361 $ 322 $ 326 $ 348 $ 380 $ 390 $ 367 $ 355 $ 390 $ 367 GS2 Revenue $ 14,016 $ 1,248 $ 1,190 $ 1,236 $ 1,108 $ 1,068 $ 1,034 $ 1,119 $ 1,210 $ 1,131 $ 1,148 $ 1,240 $ 1,284 Irrigation Irrig NonDmd NonCh $ 200 $ 0 $ 0 $ 0 $ 0 $ 8 $ 33 $ 59 $ 58 $ 32 $ 9 $ 1 $ 0 Irrig Demand NonCh $ 3,740 $ 1 $ 1 $ 1 $ 7 $ 156 $ 618 $ 1,095 $ 1,083 $ 605 $ 159 $ 13 $ 1 Irrigation Revenue $ 3,940 $ 1 $ 1 $ 1 $ 7 $ 164 $ 651 $ 1,153 $ 1,141 $ 637 $ 168 $ 14 $ 1 Lighting Lighting NonCh $ 2,232 $ 186 $ 186 $ 186 $ 186 $ 186 $ 186 $ 186 $ 186 $ 186 $ 186 $ 186 $ 186 Lighting Revenue $ 2,232 $ 186 $ 186 $ 186 $ 186 $ 186 $ 186 $ 186 $ 186 $ 186 $ 186 $ 186 $ 186 0 Total Rate Schedule $ 245,972 $ 23,385 $ 21,703 $ 20,333 $ 19,070 $ 18,164 $ 18,859 $ 21,090 $ 22,447 $ 20,375 $ 18,763 $ 19,672 $ 22,111

Docket No. D2018.2.12 Page 159 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 A B C D E F G H I J K L M N O NorthWestern Energy Generation 2017 Normalized Loads @ Proposed Rate Revenue (Thousands) Total Rate Schedule Without Taxes Customer Class Total Jan17 Feb17 Mar17 Apr17 May17 Jun17 Jul17 Aug17 Sep17 Oct17 Nov17 12/1/20017 Residential Res Non Choice $ 85,719 $ 9,219 $ 8,300 $ 7,408 $ 6,651 $ 5,997 $ 5,915 $ 6,701 $ 7,279 $ 6,561 $ 6,178 $ 6,982 $ 8,526 Emp NonChoice $ 59 $ 6 $ 6 $ 5 $ 5 $ 4 $ 4 $ 5 $ 5 $ 4 $ 4 $ 5 $ 6 Low Inc NonChoice $ 3,473 $ 370 $ 362 $ 340 $ 317 $ 286 $ 265 $ 245 $ 247 $ 223 $ 223 $ 264 $ 332 Residential Revenue $ 89,251 $ 9,595 $ 8,667 $ 7,753 $ 6,973 $ 6,287 $ 6,184 $ 6,951 $ 7,532 $ 6,789 $ 6,405 $ 7,251 $ 8,864 General Service 1 GS1 Sec NonDmd NonCh $ 10,074 $ 895 $ 848 $ 818 $ 798 $ 780 $ 809 $ 873 $ 924 $ 867 $ 802 $ 804 $ 856 GS1 Sec Demand NonCh $ 89,259 $ 7,934 $ 7,511 $ 7,244 $ 7,074 $ 6,910 $ 7,170 $ 7,736 $ 8,184 $ 7,680 $ 7,110 $ 7,125 $ 7,581 GS1 Pri NonDmd NonCh $ 20 $ 2 $ 2 $ 2 $ 2 $ 2 $ 2 $ 2 $ 2 $ 2 $ 2 $ 2 $ 2 GS1 Pri Demand NonCh $ 11,878 $ 1,063 $ 1,021 $ 975 $ 931 $ 891 $ 919 $ 982 $ 1,038 $ 1,020 $ 1,008 $ 1,007 $ 1,023 GS1 Revenue $ 111,230 $ 9,894 $ 9,381 $ 9,038 $ 8,804 $ 8,583 $ 8,899 $ 9,593 $ 10,147 $ 9,569 $ 8,922 $ 8,939 $ 9,462 General Service 2 GS2 Sub NonCh $ 8,567 $ 751 $ 737 $ 777 $ 698 $ 659 $ 609 $ 656 $ 729 $ 679 $ 704 $ 755 $ 815 GS2 Tran NonCh $ 3,878 $ 358 $ 319 $ 321 $ 286 $ 289 $ 309 $ 337 $ 346 $ 326 $ 315 $ 346 $ 326 GS2 Revenue $ 12,445 $ 1,108 $ 1,056 $ 1,098 $ 984 $ 948 $ 918 $ 993 $ 1,074 $ 1,004 $ 1,019 $ 1,101 $ 1,140 Irrigation Irrig NonDmd NonCh $ 178 $ 0 $ 0 $ 0 $ 0 $ 7 $ 29 $ 52 $ 51 $ 29 $ 8 $ 1 $ 0 Irrig Demand NonCh $ 3,321 $ 1 $ 1 $ 1 $ 6 $ 138 $ 549 $ 972 $ 962 $ 537 $ 141 $ 11 $ 1 Irrigation Revenue $ 3,498 $ 1 $ 1 $ 1 $ 7 $ 146 $ 578 $ 1,024 $ 1,013 $ 566 $ 149 $ 12 $ 1 Lighting Lighting NonCh $ 1,982 $ 165 $ 165 $ 165 $ 165 $ 165 $ 165 $ 165 $ 165 $ 165 $ 165 $ 165 $ 165 Lighting Revenue $ 1,982 $ 165 $ 165 $ 165 $ 165 $ 165 $ 165 $ 165 $ 165 $ 165 $ 165 $ 165 $ 165 Total Rate Schedule $ 218,407 $ 20,764 $ 19,271 $ 18,054 $ 16,933 $ 16,129 $ 16,745 $ 18,726 $ 19,931 $ 18,092 $ 16,661 $ 17,468 $ 19,633

Docket No. D2018.2.12 Page 160 of 327 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 A B C D E F G H I J K L M N O NorthWestern Energy Generation 2017 Normalized Loads @ Proposed Rate Revenue (Thousands) Total Rate Schedule Tax Portion Customer Class Total Jan17 Feb17 Mar17 Apr17 May17 Jun17 Jul17 Aug17 Sep17 Oct17 Nov17 12/1/20017 Residential Res Non Choice $ 10,819 $ 1,164 $ 1,048 $ 935 $ 839 $ 757 $ 747 $ 846 $ 919 $ 828 $ 780 $ 881 $ 1,076 Emp NonChoice $ 7 $ 1 $ 1 $ 1 $ 1 $ 1 $ 1 $ 1 $ 1 $ 1 $ 1 $ 1 $ 1 Low Inc NonChoice $ 438 $ 47 $ 46 $ 43 $ 40 $ 36 $ 33 $ 31 $ 31 $ 28 $ 28 $ 33 $ 42 Residential Revenue $ 11,264 $ 1,211 $ 1,094 $ 978 $ 880 $ 794 $ 781 $ 877 $ 951 $ 857 $ 808 $ 915 $ 1,119 General Service 1 GS1 Sec NonDmd NonCh $ 1,271 $ 113 $ 107 $ 103 $ 101 $ 98 $ 102 $ 110 $ 117 $ 109 $ 101 $ 101 $ 108 GS1 Sec Demand NonCh $ 11,265 $ 1,001 $ 948 $ 914 $ 893 $ 872 $ 905 $ 976 $ 1,033 $ 969 $ 897 $ 899 $ 957 GS1 Pri NonDmd NonCh $ 3 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 GS1 Pri Demand NonCh $ 1,499 $ 134 $ 129 $ 123 $ 117 $ 113 $ 116 $ 124 $ 131 $ 129 $ 127 $ 127 $ 129 GS1 Revenue $ 14,039 $ 1,249 $ 1,184 $ 1,141 $ 1,111 $ 1,083 $ 1,123 $ 1,211 $ 1,281 $ 1,208 $ 1,126 $ 1,128 $ 1,194 General Service 2 GS2 Sub NonCh $ 1,081 $ 95 $ 93 $ 98 $ 88 $ 83 $ 77 $ 83 $ 92 $ 86 $ 89 $ 95 $ 103 GS2 Tran NonCh $ 489 $ 45 $ 40 $ 40 $ 36 $ 37 $ 39 $ 43 $ 44 $ 41 $ 40 $ 44 $ 41 GS2 Revenue $ 1,570 $ 140 $ 133 $ 138 $ 124 $ 120 $ 116 $ 125 $ 136 $ 127 $ 129 $ 139 $ 144 Irrigation Irrig NonDmd NonCh $ 22 $ 0 $ 0 $ 0 $ 0 $ 1 $ 4 $ 7 $ 6 $ 4 $ 1 $ 0 $ 0 Irrig Demand NonCh $ 419 $ 0 $ 0 $ 0 $ 1 $ 17 $ 69 $ 123 $ 121 $ 68 $ 18 $ 1 $ 0 Irrigation Revenue $ 442 $ 0 $ 0 $ 0 $ 1 $ 18 $ 73 $ 129 $ 128 $ 71 $ 19 $ 2 $ 0 Lighting Lighting NonCh $ 250 $ 21 $ 21 $ 21 $ 21 $ 21 $ 21 $ 21 $ 21 $ 21 $ 21 $ 21 $ 21 Lighting Revenue $ 250 $ 21 $ 21 $ 21 $ 21 $ 21 $ 21 $ 21 $ 21 $ 21 $ 21 $ 21 $ 21 Total Rate Schedule $ 27,565 $ 2,621 $ 2,432 $ 2,279 $ 2,137 $ 2,036 $ 2,113 $ 2,363 $ 2,516 $ 2,283 $ 2,103 $ 2,205 $ 2,478

Docket No. D2018.2.12 Page 161 of 327 NORTHWESTERN ENERGY MONTANA ELECTRIC 13 MONTH INTERIM RATE BASE INTERIM (A) (B) (C) (D) (E) (F) (G) (H) (I) (J) (K) (L) (M) (N) (O) (P) T & D T & D T & D INTERIM T & D INTERIM T & D INTERIM GENERATION GENERATION HYDRO GEN INTERIM GEN INTERIM GEN INTERIM TWO DOT INTERIM STIPULATION & TEST PERIOD 13 MONTH AVG NORMALIZING REMOVE DEPR REMOVE EDIT ADJ WORKING 13 MONTH AVG NORMALIZING ACQ. ADJ. REMOVE DEPR REMOVE EDIT ADJ WORKING NORMALIZED REMOVE MARKET CREDIT DEFERRED 12/31/17 RATE BASE 12/31/17 ADJUSTMENTS STUDY ADJ AMORTIZATION CAPITAL RATE BASE 12/31/17 ADJUSTMENTS RECLASS STUDY ADJ AMORTIZATION CAPITAL RATE BASE TWO DOT PLANT ADJ TAXES ADJUSTED 1 UTILITY PLANT IN SERVICE 2 Electric 2,134,245,306 (46,852) 1,233,719,820 (302,945) 20,854,278 (20,854,278) (19,070,666) 3,348,544,663 3 Common Allocated 62,447,532 27,488,968 (5,296,490) 84,640,009 4 Plant Acquisition Adjustment 350,704,330 99,948,519 911,707 (911,707) 450,652,849 5 TOTAL UTILITY PLANT IN SERVICE 2,196,692,838 (46,852) 1,611,913,118 (302,945) 99,948,519 21,765,985 (21,765,985) (24,367,156) 3,883,837,522 6 7 ACCUMULATED DEPRECIATION 8 Electric 1,022,259,184 (759,166) 759,166 150,695,461 961,433 99,948,519 (1,288,177) 4,110,382 (4,110,382) 1,272,576,420 9 Common Allocated 14,702,100 (37,161) 37,161 6,577,099 (16,070) 16,070 21,279,199 10 Hydro Acquisition Adjustment 18,460,544 18,460,544 11 TOTAL ACCUMULATED DEPRECIATION 1,036,961,284 (796,328) 796,328 175,733,104 945,363 99,948,519 (1,272,107) 4,110,382 (4,110,382) 1,312,316,163 12 13 TOTAL NET PLANT 1,159,731,554 749,476 (796,328) 1,436,180,013 (1,248,308) 1,272,107 17,655,603 (17,655,603) (24,367,156) 2,571,521,358 14 15 16 Cost of Refinancing Debt 12,049,669 12,049,669 17 Regulatory Liability (TCJA) (16,246,177) (20,250,780) (36,496,957) 18 MPSC / MCC Taxes 3,226,710 3,226,710 19 20 21 LESS: CUSTOMER CONTRIBUTED CAPITAL 22 Accumulated Deferred Income Taxes 23 See Below for Details 60,303,567 (920,151) 65,632,901 11,167,232 121,633 (121,633) 2,211,698 138,395,246 24 Personal Injury & Property Damage 4,249,957 4,249,957 25 Customer Advances for Construction 33,868,784 33,868,784 26 TOTAL CUSTOMER CONTRIBUTED CAPITAL 98,422,307 (920,151) 65,632,901 11,167,232 121,633 (121,633) 2,211,698 176,513,987 27 28 29 PLUS: WORKING CAPITAL 30 Gross Cash Requirements (56,676,796) 4,081,815 820,905 (28,450,955) 1,436,665 337,826 (78,450,538) 31 Materials and Supplies 14,555,886 2,678,952 17,234,838 32 Fuels 1,961,881 1,961,881 33 TOTAL WORKING CAPITAL (42,120,910) 4,081,815 820,905 (23,810,122) 1,436,665 337,826 (59,253,820) 34 35 TOTAL ELECTRIC UTILITY RATE BASE 1,018,218,539 4,831,291 (796,328) 920,151 820,905 1,326,486,210 188,356 1,272,107 (11,167,232) 337,826 17,533,971 (17,533,971) (24,367,156) (2,211,698) 2,314,532,973 36 37 38 39 Accumulated Deferred Income Taxes 40 Deferred Revenue (3,238,201) (1,160,865) (4,399,066) 41 Accrued Incentive Compensation (1,603,773) (574,938) (2,178,711) 42 Injury & damages (1,171,249) (419,882) (1,591,131) 43 Cost of Refinancing Debt (369,765) 57,499 (312,266) 44 Property Taxes (774,852) (212,577) (987,429) 45 FAS 106 & FAS 112 Post Retirement Benefit (11,854,918) (4,249,876) (16,104,794) 46 MPSC/MCC Taxes 187,196 57,565 244,761 47 Accelerated Depreciation 100,644,797 (920,151) 115,092,691 11,167,232 1,124,234 (1,124,234) (7,675,194) 218,309,375 48 Customer Advances for Construction (10,953,981) (10,953,981) 49 Environmental Reserve (1,059,939) (379,978) (1,439,917) 50 Net Operating Loss (9,501,749) (42,576,738) (1,002,601) 1,002,601 9,886,892 (42,191,595) 51 52 Total Deferred Income Taxes 60,303,567 (920,151) 65,632,901 11,167,232 121,633 (121,633) 2,211,698 138,395,246

Docket No. D2018.2.12 Page 162 of 327 NORTHWESTERN ENERGY MONTANA ELECTRIC UTILITY CALCULATION OF INTERIM CASH WORKING CAPITAL INTERIM 12 MONTH ENDED NET LAG CASH LINE No. EXPENSES DAYS WORKING CAPITAL 1 ELECTRIC DELIVERY O & M COSTS 168,631,221 2 PROPERTY TAXES 132,710,926 3 STATE INCOME TAXES 0 4 FEDERAL INCOME TAXES 0 5 SUBTOTAL 301,342,147 85.65 70,712,205 6 RATE BASE w/o CWC 2,417,964,180 7 WEIGHTED COST OF DEBT 2.16% 8 INTEREST EXPENSE IN RETURN 52,228,026 54.08 7,738,333 9 TOTAL CASH WORKING REQUIREMENT 78,450,538 10 WORKING CASH 2017 ACTUAL (79,609,270) 11 CASH WORKING CAPITAL ADJUSTMENT 1,158,732

Docket No. D2018.2.12 Page 163 of 327 NORTHWESTERN ENERGY MONTANA ELECTRIC UTILITY TRANSMISSION & DISTRIBUTION CALCULATION OF INTERIM CASH WORKING CAPITAL INTERIM 12 MONTH ENDED NET LAG CASH LINE No. EXPENSES DAYS WORKING CAPITAL 1 ELECTRIC DELIVERY O & M COSTS 103,325,644 2 PROPERTY TAXES 102,648,373 3 STATE INCOME TAXES 0 4 FEDERAL INCOME TAXES 0 5 SUBTOTAL 205,974,017 85.65 48,333,355 6 RATE BASE w/o CWC 1,075,107,193 7 WEIGHTED COST OF DEBT 2.16% 8 INTEREST EXPENSE IN RETURN 23,222,315 54.08 3,440,720 9 TOTAL CASH WORKING REQUIREMENT 51,774,075 10 WORKING CASH 2017 ACTUAL 52,594,980 11 CASH WORKING CAPITAL ADJUSTMENT 820,905

Docket No. D2018.2.12 Page 164 of 327 NORTHWESTERN ENERGY MONTANA ELECTRIC UTILITY COLSTRIP UNIT 4 CALCULATION OF INTERIM CASH WORKING CAPITAL INTERIM 12 MONTH ENDED NET LAG CASH LINE No. EXPENSES DAYS WORKING CAPITAL 1 ELECTRIC DELIVERY O & M COSTS 19,987,659 2 PROPERTY TAXES 4,225,091 3 STATE INCOME TAXES 0 4 FEDERAL INCOME TAXES 0 5 SUBTOTAL 24,212,750 85.65 5,681,704 6 RATE BASE w/o CWC 307,831,504 7 WEIGHTED COST OF DEBT 2.16% 8 INTEREST EXPENSE IN RETURN 6,649,160 54.08 985,169 9 TOTAL CASH WORKING REQUIREMENT 6,666,873 10 WORKING CASH 2017 ACTUAL 6,675,917 11 CASH WORKING CAPITAL ADJUSTMENT 9,044

Docket No. D2018.2.12 Page 165 of 327 NORTHWESTERN ENERGY MONTANA ELECTRIC UTILITY DAVE GATES GENERATING STATION CALCULATION OF INTERIM CASH WORKING CAPITAL INTERIM 12 MONTH ENDED NET LAG CASH LINE No. EXPENSES DAYS WORKING CAPITAL 1 ELECTRIC DELIVERY O & M COSTS 6,219,585 2 PROPERTY TAXES 4,638,965 3 STATE INCOME TAXES 0 4 FEDERAL INCOME TAXES 0 5 SUBTOTAL 10,858,550 85.65 2,548,041 6 RATE BASE w/o CWC 174,625,564 7 WEIGHTED COST OF DEBT 2.16% 8 INTEREST EXPENSE IN RETURN 3,771,912 54.08 558,863 9 TOTAL CASH WORKING REQUIREMENT 3,106,904 10 WORKING CASH 2017 ACTUAL 3,103,444 11 CASH WORKING CAPITAL ADJUSTMENT 3,460

Docket No. D2018.2.12 Page 166 of 327 NORTHWESTERN ENERGY MONTANA ELECTRIC UTILITY SPION KOP CALCULATION OF INTERIM CASH WORKING CAPITAL INTERIM 12 MONTH ENDED NET LAG CASH LINE No. EXPENSES DAYS WORKING CAPITAL 1 ELECTRIC DELIVERY O & M COSTS 2,225,425 2 PROPERTY TAXES 433,959 3 STATE INCOME TAXES 0 4 FEDERAL INCOME TAXES 0 5 SUBTOTAL 2,659,384 85.65 624,044 6 RATE BASE w/o CWC 57,507,767 7 WEIGHTED COST OF DEBT 2.16% 8 INTEREST EXPENSE IN RETURN 1,242,168 54.08 184,045 9 TOTAL CASH WORKING REQUIREMENT 808,090 10 WORKING CASH 2017 ACTUAL 810,686 11 CASH WORKING CAPITAL ADJUSTMENT 2,596

Docket No. D2018.2.12 Page 167 of 327 NORTHWESTERN ENERGY MONTANA ELECTRIC UTILITY HYDRO CALCULATION OF INTERIM CASH WORKING CAPITAL INTERIM 12 MONTH ENDED NET LAG CASH LINE No. EXPENSES DAYS WORKING CAPITAL 1 ELECTRIC DELIVERY O & M COSTS 36,872,907 2 PROPERTY TAXES 20,764,538 3 STATE INCOME TAXES 0 4 FEDERAL INCOME TAXES 0 5 SUBTOTAL 57,637,446 85.65 13,525,061 6 RATE BASE w/o CWC 802,892,153 7 WEIGHTED COST OF DEBT 2.16% 8 INTEREST EXPENSE IN RETURN 17,342,471 54.08 2,569,536 9 TOTAL CASH WORKING REQUIREMENT 16,094,597 10 WORKING CASH 2017 ACTUAL 16,424,243 11 CASH WORKING CAPITAL ADJUSTMENT 329,646

Pictorial Exhibits Interim

NorthWestern Energy Statement O Interim Docket No. D2018.2.12 Page 168 of 327 Return, 27% SUMMARY OF REVENUE REQUIREMENTS INTERIM Misc Revenues, 1% Cost of Electricity, 6% Total O&M, 27% Income Taxes, 2% Taxes Other Than Income, 21% Regulatory Amortizations, 0% Depreciation, 18% Revenue Requirement Interim Cost of Electricity 6% $38,841,627 Total O&M 27% $168,631,221 Depreciation 18% $114,572,630 Regulatory Amortizations 0% $1,827,814 Taxes Other Than Income 21% $132,751,088 Income Taxes 2% $14,762,777 Return 27% $168,200,046 Misc Revenues 1% $5,039,749 Total $630,891,826