Northwestern Energy Group, Inc. · NASDAQ:NWE

Northwestern Energy — Technical Presentation (November 2025)

102 slides from Northwestern Energy's technical presentation, Nov 10, 2025

1. Slide 1: Northwestern Energy Stakeholder Working Group Meeting #3

   Northwestern Energy Stakeholder Working Group Meeting # 3 2026 MT IRP Planning Cycle November 10th, 2025

2. Slide 2: Agenda

   Thank Agenda you

3. Slide 3: Agenda

   Agenda Introduction/Welcome (30 min) •News Topic Discussion(s) Updated IRP Schedule (45 min) •IRP Progress Towards Draft Release •Stakeholder Working Group Draft Review Timeline •Public Sessions Updates Since last meeting (30 min) •Base Case Updates •NWE Merger Lunch (60 min) PowerSIMM Finalized ARS

4. Slide 4: Introduction

   Thank Introduction you

5. Slide 5: News Topics (Warm up those brains)

   News Topics (Warm up those brains) • October 2025 Publications: • Factors Influencing Recent Trends in Retail Electricity Prices in the United States (2 slides) • China’s primary energy through 2060 (2 slides) • NorthWest Power Conservation Council – 2031 Needs Assessment (2 slides) “Secure Energy e

6. Slide 6: Factors Influencing Recent Trends in Retail Electricity Prices (Slide 1)

   Factors Influencing Recent Trends in Retail Electricity Prices in the United States (Slide 1) https://eta-publications.lbl.gov/sites/default/files/2025-10/full_summary_retail_price_trends_drivers.pdf

7. Slide 7: Factors Influencing Recent Trends in Retail Electricity Prices (Slide 2)

   Factors Influencing Recent Trends in Retail Electricity Prices in the United States (Slide 2) https://eta-publications.lbl.gov/sites/default/files/2025-10/full_summary_retail_price_trends_drivers.pdf

8. Slide 8: China's Primary Energy through 2060

   China’s Primary Energy through 2060 https://www.reuters.com/business/energy/charting-chinas-evolving-primary-energy-mix-through-2060-2025-10-28/ Discussion Items: What is primary energy supply mean? Is China’s energy load reducing in the future?

9. Slide 9: China's Primary Energy through 2060

   China’s Primary Energy through 2060 The Energy Conversion Process https://yaleclimateconnections.org/2022/10/energy-loss-is-single-biggest- component-of-todays-electricity-system/ Solar/Wind/Hydro – Primary Energy – No losses1 1. https://iea.imgix.net/5cccd422-95fb-455f-b20d- 708eac190b99/170901Comm

10. Slide 10: China's Primary Energy through 2060

    China’s Primary Energy through 2060 Based on the previous side: - Why is the primary coal energy being reduced? - Is this graph causing an amplified view of their energy transition? - Is China closing down coal plants? Another Article “The country began building 94.5 gigawatts (GW) of new coal-power

11. Slide 11: Northwest Power and Conservation Council 2031 Needs Assessment

    Northwest Power and Conservation Council 2031 Needs Assessment NWPCC planning authority is focused on Washington, Oregon, Idaho, and Montana, the map includes generation outside the region because Northwest utilities own, contract for, or rely on resources across the broader Western grid. https://ww

12. Slide 12: Northwest Power and Conservation Council 2031 Needs Assessment

    Northwest Power and Conservation Council 2031 Needs Assessment https://www.nwcouncil.org/fs/19637/2025_10_1b.pdf

13. Slide 13: Northwest Power and Conservation Council 2031 Needs Assessment

    Northwest Power and Conservation Council 2031 Needs Assessment https://www.nwcouncil.org/fs/19637/2025_10_1b.pdf

14. Slide 14: https://www.opb.org/article/2025/10/30/renewable-energy-oregon-washington-power-electrical-grid/

    https://www.opb.org/article/2025/10/30/renewable-energy-oregon-washington-power-electrical-grid/

15. Slide 15: Updated IRP Schedule

    Thank you Updated IRP Schedule

16. Slide 16: Timeline – High Level

    Timeline – High Level (see detailed workplan) Modeling Inputs Preliminary Modeling Draft IRP Stakeholder Working File MT Group Modeling Input 2026 IRP with Final Modeling IRP PSC Today Draft Plan Nov. 10 Complete Internal and External Stakeholder Review Dec. 2025 Open period for Public Comment Jan.

17. Slide 17: Stakeholder Working Group Review

    Stakeholder Working Group Review • SWG Members will be given a chance to review and provide comments on the draft IRP prior to release to the public • Timeline: 23-30 December 2025 • Will be sent via LiquidFiles to members

18. Slide 18: Public Sessions

    Public Sessions • NorthWestern is planning to hold 4 public in-person sessions after the release of the draft plan • Timeline for these is end of January/February 2026 • Dates and Locations are still TBD

19. Slide 19: Updates Since Last Meeting

    Thank you Updates Since Last Meeting

20. Slide 20: NWE Merger

    NWE Merger • On October 20, 2025, NorthWestern Energy and Black Hills Corp. submitted a joint application submitted to the Montana Public Service Commission (Docket No. 2025.10.078, available at www.psc.mt.gov) seeking regulatory approval for their proposed merger • The merger is pending. It does no

21. Slide 21: Modeling Update 1: Base Case – Puget Colstrip Shares

    Modeling Update 1: Base Case – Puget Colstrip Shares • Modeling of Puget’s 370MW share: • Removed from the Base Case (no 2026 Resource Adequacy need for Customers) • Added as sensitivity in within the model • What is happening with Puget’s 370MW Share? • Puget’s share will be acquired by a subsidiar

22. Slide 22: Modeling Update 2: Fuel Infrastructure Updates

    Modeling Update 2: Fuel Infrastructure Updates • Fuel infrastructure, i.e. natural gas, and electric interconnection and network upgrade costs are included in the total cost for all candidate resources. Before, these costs were going to be included post-processing. Electric Transmission Related Cost

23. Slide 23: Modeling Update 3: Long Duration Energy Storage

    Modeling Update 3: Long Duration Energy Storage • Long duration energy storage (LDES) • Limited to ~10% of the peak load, or 150 MW (3 units of 50MW with 100-hour duration) • Reason: • The model heavily favored LDES. • Without further reliability and operational analysis, we limited the selection to

24. Slide 24: Modeling Update 4: Overbuilt Constraint

    Modeling Update 4: Overbuilt Constraint • Implemented an 150MW overbuild constraint: • Adds a penalty for builds greater than 150MW of accredited capacity needs. • Modeling impacts: See ARS Results: Scenario A – Base Case slide below. • Why an overbuild constraint? • Overbuild constraints keep the m

25. Slide 25: PowerSIMM Finalized ARS Results

    Thank you PowerSIMM Finalized ARS Results

26. Slide 26: Scenarios for 2026 MT IRP

    Scenarios for 2026 MT IRP A. Base Case – Colstrip retires December 31, 2042. B. Colstrip retires June 30, 2029, according to MATS. C. Colstrip complies with MATS using baghouse on July 1, 2030. Colstrip retires December 31, 2042. D. Colstrip retires December 31, 2031, according to GHG. E. Colstrip r

27. Slide 27: Sensitivities for 2026 MT IRP

    Sensitivities for 2026 MT IRP F. 50% power costs. M. Allow carbon emitting resources after 2035 (PSC request from 2023 IRP) G. 150% power costs. H. 50% natural gas costs. N. Only allow carbon free resources to be selected in ARS I. 150% natural gas costs. J. 150 MW of additional data center load O.

28. Slide 28: Summer Capacity Forecast & Retirements

    Summer Capacity Forecast & Retirements Summer Capacity Forecast Summer Capacity Retirements & PPA Expirations 1,800 188 149 76 69 62 55 1,600 (102)(117)(126)(149) (1) (2) (2) (2) (8) (6) Accredited Capacity (MW) 1,400 (212)(220)(232)(240)(246) (24) (17) (13) (401)(420) (56) Basin Creek 1,200 Powerex

29. Slide 29: Winter Capacity Forecast & Retirements

    Winter Capacity Forecast & Retirements Winter Capacity Forecast Winter Capacity Retirements & PPA Expirations 1,800 93 (33) (40) (45) 1,600 (23) Accredited Capacity (MW) (199)(203)(211)(215)(237) 1,400 (300)(313)(317)(323) (3) (9) (3) (6) (18) (474)(484) (39) 1,200 (59) (100) Powerex Basin Creek Tri

30. Slide 30: Base Case and Main Scenarios

    Thank you Base Case and Main Scenarios

31. Slide 31: ARS Results: Scenario A – Base Case

    ARS Results: Scenario A – Base Case No overbuild constraint With overbuild constraint above 150 MW threshold Candidate Resource Additions Candidate Resource Additions 1,600 1,600 1,400 1,400 Nameplate Capacity (MW) Nameplate Capacity (MW) 1,200 1,200 1,000 1,000 800 320 800 600 150 600 100 400 400 6

32. Slide 32: ARS Results: Scenario B – Colstrip Retires to Comply with MATS

    ARS Results: Scenario B – Colstrip Retires to Comply with MATS Candidate Resource Additions 1,600 1,400 Nameplate Capacity (MW) 1,200 1,000 800 600 50 400 200 200 320 320 100 100 100 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 Wind Wind Hybrid

33. Slide 33: ARS Results: Scenario C – Colstrip Complies with MATS via Baghouse

    ARS Results: Scenario C – Colstrip Complies with MATS via Baghouse • No change from Scenario A, Base Case.

34. Slide 34: ARS Results: Scenario D – Colstrip Retires to Comply with GHG

    ARS Results: Scenario D – Colstrip Retires to Comply with GHG Candidate Resource Additions 1,600 1,400 Nameplate Capacity (MW) 1,200 1,000 800 600 400 640 100 200 300 50 100 100 100 50 50 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 Wind Wind Hy

35. Slide 35: ARS Results: Scenario E – Colstrip Retires in 2035

    ARS Results: Scenario E – Colstrip Retires in 2035 Candidate Resource Additions 1,600 1,400 Nameplate Capacity (MW) 1,200 1,000 800 600 400 100 200 320 320 50 150 200 50 50 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 Wind Wind Hybrid Solar Sola

36. Slide 36: ARS Summary of Base Case and Main Scenarios

    ARS Summary of Base Case and Main Scenarios 2026 MT IRP ARS Results - Base Case vs Scenarios 1490 150 1290 250 1240 1190 100 320 640 250 150 MW 200 640 250 150 50 250 100 320 640 200 300 150 50 50 A Base Case B CSretMATS D CSretGHG E CSret2035 Wind Solar Hybrid Aero CT DF CCCT 150 CCCT 320 SC CT BES

37. Slide 37: Commodity Sensitivities

    Thank you Commodity Sensitivities

38. Slide 38: ARS Results: Sensitivity F – Power Price Forecast Reduced by 50%

    ARS Results: Sensitivity F – Power Price Forecast Reduced by 50% Candidate Resource Additions 1,600 1,400 Nameplate Capacity (MW) 1,200 1,000 800 600 400 640 200 100 108 100 150 50 50 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 Wind Wind Hybrid

39. Slide 39: ARS Results: Sensitivity G – Power Price Forecast Increased by 50%

    ARS Results: Sensitivity G – Power Price Forecast Increased by 50% Candidate Resource Additions 1,600 1,400 Nameplate Capacity (MW) 1,200 1,000 800 600 400 640 200 100 150 50 100 50 100 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 Wind Wind Hybr

40. Slide 40: ARS Results: Sensitivity H – Natural Gas Price Forecast Reduced by 50%

    ARS Results: Sensitivity H – Natural Gas Price Forecast Reduced by 50% Candidate Resource Additions 1,600 1,400 Nameplate Capacity (MW) 1,200 1,000 800 600 400 640 200 100 150 50 100 50 100 50 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 Wind Wi

41. Slide 41: ARS Results: Sensitivity I – Natural Gas Price Forecast Increased by 50%

    ARS Results: Sensitivity I – Natural Gas Price Forecast Increased by 50% Candidate Resource Additions 1,600 1,400 Nameplate Capacity (MW) 1,200 1,000 800 600 400 640 200 100 150 100 108 50 100 50 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 Wind

42. Slide 42: ARS Summary of Commodity Sensitivities

    ARS Summary of Commodity Sensitivities 2026 MT IRP ARS Results - Base Case vs Commodity Sensitivities 1290 1298 1240 1198 1190 640 640 640 640 640 MW 150 150 100 150 150 250 250 250 250 250 150 200 50 150 150 50 108 50 50 108 A Base Case F Power50 G Power150 H NatGas50 I NatGas150 RICE Aero CT DF CC

43. Slide 43: Data Center Sensitivities

    Thank you Data Center Sensitivities

44. Slide 44: ARS Results: Sensitivity J – Add 150 MW of Data Center Load

    ARS Results: Sensitivity J – Add 150 MW of Data Center Load

45. Slide 45: ARS Results: Sensitivity K – Add 650 MW of Data Center Load

    ARS Results: Sensitivity K – Add 650 MW of Data Center Load

46. Slide 46: ARS Results: Sensitivity L – Add 1,160 MW of Data Center Load

    ARS Results: Sensitivity L – Add 1,160 MW of Data Center Load

47. Slide 47: ARS Summary of Data Center Sensitivities

    ARS Summary of Data Center Sensitivities 2026 MT IRP ARS Results - Base Case vs Data Center Sensitivitites 2820 2380 960 960 150 250 MW 1290 1360 150 200 250 640 200 960 960 320 150 250 150 100 50 250 150 200 300 50 50 50 100 A Base Case J DC150 K DC650 L DC1160 Wind Solar Hybrid Aero CT DF CCCT 150

48. Slide 48: Resource Sensitivities

    Thank you Resource Sensitivities

49. Slide 49: ARS Results: Sensitivity M – No Limitation on Carbon Emitting Resources

    ARS Results: Sensitivity M – No Limitation on Carbon Emitting Resources Candidate Resource Additions 1,600 1,400 Nameplate Capacity (MW) 1,200 1,000 800 600 400 50 200 320 320 50 200 150 50 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 Wind Wind

50. Slide 50: ARS Results: Sensitivity N – Carbon Free Candidate Resources Only

    ARS Results: Sensitivity N – Carbon Free Candidate Resources Only Candidate Resource Additions 1,600 1,400 Nameplate Capacity (MW) 1,200 1,000 800 600 400 600 640 200 100 100 50 50 100 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 Wind Wind Hybri

51. Slide 51: ARS Results: Sensitivity O – PSE Colstrip Share is used for Retail Load

    ARS Results: Sensitivity O – PSE Colstrip Share is used for Retail Load

52. Slide 52: ARS Results: Sensitivity P – Avista's Colstrip Shares are not Acquired

    ARS Results: Sensitivity P – Avista’s Colstrip Shares are not Acquired Candidate Resource Additions 1,600 1,400 Nameplate Capacity (MW) 1,200 1,000 800 600 400 320 200 300 150 320 50 100 50 100 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 Wind W

53. Slide 53: ARS Summary of Resource Sensitivities

    ARS Summary of Resource Sensitivities 2026 MT IRP ARS Results - Base Case vs Resource Sensitivities 1640 1640 1390 1290 640 640 320 50 1140 640 250 150 MW 150 150 250 250 250 150 640 320 250 600 600 300 200 150 50 50 50 A Base Case M NoCO2Lim N CO2Free O wPseCS P NoAvaCS Wind Aero CT DF CCCT 150 CCC

54. Slide 54: Other Sensitivities

    Thank you Other Sensitivities

55. Slide 55: ARS Results: Sensitivity Q – Add 300 MW of NPC Capacity

    ARS Results: Sensitivity Q – Add 300 MW of NPC Capacity • No change from Scenario A, Base Case.

56. Slide 56: ARS Results: Sensitivity R – Increase DSM and NEM Forecasts

    ARS Results: Sensitivity R – Increase DSM and NEM Forecasts Forecasted Peak Load Comparison Candidate Resource Additions 1,500 1,600 1,400 1,400 Nameplate Capacity (MW) 1,200 1,300 1,000 800 MW 1,200 600 320 1,100 400 50 100 200 1,000 300 150 108 100 50 100 50 2026 2027 2028 2029 2030 2031 2032 2033

57. Slide 57: ARS Summary of Other Sensitivities

    ARS Summary of Other Sensitivities 2026 MT IRP ARS Results - Base Case vs Other Sensitivities 1328 1290 320 640 100 250 MW 150 150 108 250 100 200 300 50 A Base Case R IncDsmNem Wind Solar Hybrid RICE Aero CT DF CCCT 150 SC CT BESS 4hr BESS 100hr SMR Total

58. Slide 58: PowerSIMM Preliminary PCM Results

    PowerSIMM Thank you Preliminary PCM Results

59. Slide 59: PCM Results: Scenario A – Base Case

    Thank you PCM Results: Scenario A – Base Case

60. Slide 60: Energy production for PCM results of Scenario A – Base Case

    Energy production for PCM results of Scneario A – Base Case. Annual Energy 23 M 20 M 17 M 14 M MWh 11 M 8M 5M 2M (1 M) 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 Hydro Coal Petroleum Coke Natural Gas Solar Hybrid Solar XMSN Wind SMR STCC BESS

61. Slide 61: Capacity Factor for PCM results of Scenario A – Base Case

    Capacity Factor for PCM results of Scenario A – Base Case. Capacity Factor 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 Basin Creek 203606 CELP Heartland 203112 Colstrip Dave Gates Yellowstone Powerex

62. Slide 62: Emissions for PCM results of Scenario A – Base Case

    Emissions for PCM results of Scenario A – Base Case. CO2 Emissions 14 M 12 M 10 M 8M Metric Tons 6M 21% 20% 19% 21% 4M 21% 21% 21% 21% 20% 21% 28% 28% 23% 25% 25% 26% 27% 2M 60% 55% 62% 58% 57% 57% 57% 54% 55% 59% 64% 64% 59% 61% 64% 63% 63% 68% 66% 66% - 2026 2027 2028 2029 2030 2031 2032 2033 2034

63. Slide 63: Transmission volumes for PCM results of Scenario A – Base Case

    Transmission volumes for PCM results of Scenario A – Base Case Transmission Export & Import Volumes 6M 5M 4M MWh 3M 2M 1M - 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 Exports Imports

64. Slide 64: Average transmission usage for PCM results of Scenario A – Base Case

    Average transmission usage for PCM results of Scenario A – Base Case Average of Total Transmission Export & Import Volumes 700 600 500 400 aMW 300 200 100 0 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 aExports aImports

65. Slide 65: Transmission revenues for PCM results of Scenario A – Base Case

    Transmission revenues for PCM results of Scenario A – Base Case. Total Transmission Export Revenues & Import Costs $700 M $600 M $500 M Revenues/Costs ($) $400 M $300 M $200 M $100 M - 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 Export Revenues

66. Slide 66: Total portfolio costs for PCM results of Scenario A – Base Case

    Total portfolio costs for PCM results of Scenario A – Base Case. 20-year NPV Costs ($M) $77 $3,319 Total Import Cost 0% $5,672 Total Production Cost $1,935 Total Candidate Resource RR Total Existing Resource RR $3,092 Total Export Cost Net Total Cost $(2,752) A-BaseCase

67. Slide 67: PCM Summary

    Thank PCM Summaryyou

68. Slide 68: Base Case & Main Scenarios

    Thank you Base Case & Main Scenarios

69. Slide 69: Total energy production of the Base Case and Main Scenarios

    The total energy production of the Base Case and the Main Scenarios relative to the forecasted load. 20-year Total Energy Production and Consumption (MWh) 0% 2% 0% 0% -2% 187 M 190 M 187 M 187 M 184 M - 140 M - 140 M - 140 M - 140 M - 140 M A BaseCase B CSretMATS C BaseCase wCS BagHouse D CSretGHG E

70. Slide 70: CO2 emissions from the Base Case and the Main Scenarios

    CO2 emissions from the Base Case and the Main Scenarios. 20-year Total CO2 Emissions (MT) 0% 0% 100 M 100 M 19 M 19 M -20% 80 M -26% -29% 74 M 71 M 24 M 24 M 25 M 34 M 42 M 21 M 0% 0% 19 M 57 M 57 M 17 M -38% 35 M -63% -78% 21 M 12 M A BaseCase B CSretMATS C BaseCase wCS BagHouse D CSretGHG E CSret2

71. Slide 71: Transmission imports and exports, Base Case and Main Scenarios

    Transmission imports and exports from the Base Case and the Main Scenarios. 20-year Total Portfolio Exports and Import Volumes (MWh) 9% 0% 0% 3% -1% 61 M 56 M 56 M 58 M 55 M 0% 23% 0% 24% 33% -8M - 10 M -8M - 10 M - 11 M A BaseCase B CSretMATS C BaseCase wCS BagHouse D CSretGHG E CSret2035 20-year T

72. Slide 72: PCM results for the Base Case and the Main Scenarios

    PCM results for the Base Case and the Main Scenarios 20-year NPV Total Costs ($) $100 M $434 M $89 M $105 M $77 M $77 M $3,612 M 18% $3,412 M $3,293 M $3,319 M $3,319 M 10% $6,711 M 8% 9% 0% $6,105 M $6,176 M $6,231 M $5,672 M $3,111 M $2,656 M $2,624 M $1,935 M $1,935 M $3,092 M $2,750 M $3,092 M $

73. Slide 73: Remaining book value for candidate resources, Base Case and Main Scenarios

    Remaining book value for candidate resources in the Base Case and the Main Scenarios. 20-year NPV of Candidate Resource Remaining Book Value ($) 0% 0% $2,389 M $2,389 M -34% $1,578 M -49% $1,214 M -66% $803 M A BaseCase B CSretMATS C BaseCase wCS BagHouse D CSretGHG E CSret2035 Total Candidate Resou

74. Slide 74: Base Case & Commodity Sensitivities

    Base Case & Thank you Commodity Sensitivities

75. Slide 75: Total energy production of the Base Case and Commodity Sensitivities

    The total energy production of the Base Case and Commodity Sensitivities relative to the forecasted load. 20-year Total Energy Production and Consumption (MWh) 18% 220 M 9% 0% 205 M 187 M -6% 176 M -19% 152 M - 140 M - 140 M - 140 M - 140 M - 140 M A BaseCase F Power50 G Power150 H NatGas50 I NatGas

76. Slide 76: Carbon emissions from the Base Case and Commodity Sensitivities

    Carbon emissions from the Base Case and Commodity Sensitivities. 20-year Total CO2 Emissions (MT) 14% 114 M 6% 106 M 0% 100 M -6% 29 M 94 M 26 M 19 M 11 M -24% 76 M 4M 24 M 24 M 24 M 27 M 24 M 6% 0% -1% 0% 60 M 57 M -17% 56 M 57 M 47 M A BaseCase F Power50 G Power150 H NatGas50 I NatGas150 20-year C

77. Slide 77: Transmission imports and exports, Base Case and Commodity Sensitivities

    Transmission imports and exports from the Base Case and Commodity Sensitivities. 20-year Total Portfolio Exports and Import Volumes (MWh) 50% 84 M 27% 71 M 0% 56 M -17% 46 M -50% 28 M -62% -30% 0% 21% 88% -3M -6M -8M - 10 M - 16 M A BaseCase F Power50 G Power150 H NatGas50 I NatGas150 20-year Total

78. Slide 78: PCM results for the Base Case and Commodity Sensitivities

    PCM results for the Base Case and Commodity Sensitivities. 20-year NPV Total Costs ($) $34 M $77 M $42 M $101 M $67 M $3,964 M $3,319 M 14% $3,246 M $3,174 M 9% 0% $6,490 M $2,340 M $6,167 M $5,672 M -8% $5,206 M -24% $1,935 M $1,841 M $1,975 M $2,164 M $2,339 M $4,318 M $3,092 M $3,092 M $3,092 M $

79. Slide 79: Remaining book value for candidate resources, Base Case and Commodity Sensitivities

    Remaining book value for candidate resources in the Base Case and Commodity Sensitivities. 20-year NPV of Candidate Resource Remaining Book Value ($) 0% 0% 0% $2,395 M $2,397 M $2,389 M -2% $2,339 M -5% $2,281 M A BaseCase F Power50 G Power150 H NatGas50 I NatGas150 Total Candidate Resource RBV Cost

80. Slide 80: Base Case & Data Center Sensitivities

    Thank you Base Case & Data Center Sensitivities

81. Slide 81: Total energy production of the Base Case and Data Center Sensitivities

    The total energy production of the Base Case and the Data Center Sensitivities relative to the forecasted load. 20-year Total Energy Production and Consumption (MWh) 91% 358 M 52% 284 M 18% 0% 220 M 187 M - 140 M - 140 M - 140 M - 140 M -26 M 18% -101 M -165 M -177 M 72% -241 M 126% -317 M A BaseCas

82. Slide 82: Carbon emissions from the Base Case and Data Center Sensitivities

    Carbon emissions from the Base Case and the Data Center Sensitivities. 20-year Total CO2 Emissions (MT) 96% 196 M 68% 168 M 63 M 39% 139 M 36 M 10 M 0% 27 M 27 M 27 M 100 M 19 M 24 M 81% 86% 87% 103 M 105 M 106 M 0% 57 M A BaseCase J DC150 K DC650 L DC1160 20-year Colstrip Emissions (MT) 20-year CEL

83. Slide 83: Transmission imports and exports, Base Case and Data Center Sensitivities

    Transmission imports and exports from the Base Case and the Data Center Sensitivities. 20-year Total Portfolio Exports and Import Volumes (MWh) 13% 0% 63 M 2% 1% 56 M 57 M 56 M 0% -4% -8M -8M 57% 70% - 13 M - 14 M A BaseCase J DC150 K DC650 L DC1160 20-year Total Exports (MWh) 20-year Total Imports

84. Slide 84: PCM results for the Base Case and Data Center Sensitivities

    PCM results for the Base Case and Data Center Sensitivities. 20-year NPV Total Costs ($) $176 M 135% $13,326 M $133 M $6,200 M 68% $77 M $9,553 M $77 M $4,826 M $3,319 M $3,612 M $6,096 M 0% 3% $5,672 M $5,841 M $3,863 M $1,935 M $1,591 M $3,092 M $3,559 M $3,559 M $3,559 M $(2,752) M $(2,997) M $(2

85. Slide 85: Net total cost per 20-year total load, Data Center Sensitivities

    PCM results for the Base Case and Data Center Sensitivities represented as the 20-year NPV total cost per total 20-year total load. Net Total Cost per 20-year Total Load ($/MWh) 4% $42.05 0% $40.61 -2% $39.70 -13% $35.35 A BaseCase J DC150 K DC650 L DC1160 Net Total Cost per 20-year Total Load ($/MW

86. Slide 86: Remaining book value for candidate resources, Data Center Sensitivities

    Remaining book value for candidate resources in the Base Case and Data Center Sensitivities. 20-year NPV of Candidate Resource Remaining Book Value ($) 67% 69% $3,994 M $4,041 M 33% $3,184 M 0% $2,389 M A BaseCase J DC150 K DC650 L DC1160 Total Candidate Resource RBV Cost NPV

87. Slide 87: Base Case & Resource Sensitivities

    Thank you Base Case & Resource Sensitivities

88. Slide 88: Total energy production of the Base Case and resource sensitivities

    The total energy production of the Base Case and the resource sensitivities relative to the forecasted load. 20-year Total Energy Production and Consumption (MWh) 12% 209 M 4% 0% -1% -1% 195 M 187 M 185 M 186 M - 140 M - 140 M - 140 M - 140 M - 140 M A BaseCase M NoCO2Lim N CO2Free O wPseCS P NoAvaC

89. Slide 89: Carbon emissions from the Base Case and the resource sensitivities

    Carbon emissions from the Base Case and the resource sensitivities. 20-year Total CO2 Emissions (MT) 32% 132 M 6M 4% 26 M 0% 104 M 100 M -4% 96 M 21 M -14% 19 M 12 M 86 M 24 M 27 M 27 M 32 M 75% 100 M 27 M 0% 0% 1% 57 M 57 M 57 M -52% 27 M A BaseCase M NoCO2Lim N CO2Free O wPseCS P NoAvaCS 20-year C

90. Slide 90: Transmission imports and exports, Base Case and resource sensitivities

    Transmission imports and exports from the Base Case and the resource sensitivities. 20-year Total Portfolio Exports and Import Volumes (MWh) 32% 74 M 14% 0% -1% -1% 63 M 56 M 55 M 55 M -45% 0% 16% 12% 0% -5M -8M - 10 M -9M -8M A BaseCase M NoCO2Lim N CO2Free O wPseCS P NoAvaCS 20-year Total Exports

91. Slide 91: PCM results for the Base Case and the resource sensitivities

    PCM results for the Base Case and the resource sensitivities. 20-year NPV Total Costs ($) $75 M $77 M $97 M $89 M $39 M $3,411 M $3,129 M $3,319 M $3,311 M 11% $3,408 M 5% $6,303 M 0% -2% $5,969 M $5,672 M $5,542 M -15% $4,849 M $1,935 M $2,254 M $1,277 M $2,804 M $1,632 M $3,559 M $3,092 M $3,092 M

92. Slide 92: Remaining book value for candidate resources, resource sensitivities

    Remaining book value for candidate resources in the Base Case and the resource sensitivities. 20-year NPV of Candidate Resource Remaining Book Value ($) 20% $2,858 M 9% $2,605 M 0% $2,389 M -26% $1,776 M -56% $1,051 M A BaseCase M NoCO2Lim N CO2Free O wPseCS P NoAvaCS Total Candidate Resource RBV Co

93. Slide 93: Base Case & Other Sensitivities

    Thank you Base Case & Other Sensitivities

94. Slide 94: Total energy production of the Base Case and other sensitivities

    The total energy production of the Base Case and the other sensitivities to the forecasted load. 20-year Total Energy Production and Consumption (MWh) 0% -4% -2% 187 M 183 M 180 M -6% - 140 M - 140 M - 132 M A BaseCase Q AddNPC300 R IncDsmNem 20-year Net Energy Production (MWh) 20-year Total Retail

95. Slide 95: Carbon emissions from the Base Case and the other sensitivities

    Carbon emissions from the Base Case and the other sensitivities. 20-year Total CO2 Emissions (MT) 0% -1% -2% 100 M 99 M 98 M 19 M 15 M 16 M 24 M 27 M 27 M 0% 0% 0% 57 M 57 M 57 M A BaseCase Q AddNPC300 R IncDsmNem 20-year Colstrip Emissions (MT) 20-year CELP & YELP Emissions (MT) 20-year Remaining E

96. Slide 96: Transmission imports and exports, Base Case and other sensitivities

    Transmission imports and exports from the Base Case and the other sensitivities. 20-year Total Portfolio Exports and Import Volumes (MWh) 39% 78 M 0% 4% 56 M 58 M 0% -20% -8M -7M 340% - 37 M A BaseCase Q AddNPC300 R IncDsmNem 20-year Total Exports (MWh) 20-year Total Imports (MWh)

97. Slide 97: Sensitivity Q transmission imports and exports with WECC

    Sensitivity Q transmission imports and exports from and to the WECC interconnection. Average of WECC Transmission Export & Import Volumes 700 600 500 400 aMW 300 200 100 0 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 aNWE-WECC ATC Forecast 20250

98. Slide 98: Sensitivity Q transmission imports and exports with SPP

    Sensitivity Q transmission imports and exports from and to the SPP power market. Average of MISO Transmission Export & Import Volumes 700 600 500 400 aMW 300 200 100 0 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 aMISO Sales 150 MW aMISO Purchas

99. Slide 99: Sensitivity Q transmission imports and exports with MISO

    Sensitivity Q transmission imports and exports from and to the MISO power market. Average of SPP Transmission Export & Import Volumes 700 600 500 400 aMW 300 200 100 0 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 aSPP Sales 150 MW aSPP Purchases

100. Slide 100: PCM results for the Base Case and the other sensitivities

     PCM results for the Base Case and the other sensitivities.

101. Slide 101: Remaining book value for candidate resources, other sensitivities

     Remaining book value for candidate resources in the base case and the other sensitivities. 20-year NPV of Candidate Resource Remaining Book Value ($) 0% 0% $2,389 M $2,389 M -27% $1,733 M A BaseCase Q AddNPC300 R IncDsmNem Total Candidate Resource RBV Cost NPV

102. Slide 102: Thank you – Questions/Comments?

     Thank you Questions/Comments?

NorthWestern Energy Group — Technical Presentation (November 2025) on 6ix