Investor Presentaiton

L Appendix 39 Comparison of Installed Capacity Comparison of Installed Capacity (MW) - Dispatchability and Carbon Emitting NorthWestern Energy (Montana) 2019 MW QF Adds Proforma 2021 of Total Percent Dispatchable Non-Carbon 309 309 15.3% 15.3% 0 0 0.0% 0 0.0% 202 10.0% 10.0% 486 24.1% 24.1% 0 0.0% 0 0.0% 17 160 177 8.8% 8.8% 455 391 846 41.9% 41.9% 1,469 551 2,020 100.0% 25.3% 74.7% California MW Percent 2019 of Total Dispatchable Non-Carbon Coal / Coke 91 0.1% 0.1% Oil 351 0.4% 0.4% Nuclear 2,393 3.0% 3.0% Natural Gas 40,382 50.6% 50.6% 202 Hydro 14,039 17.6% 17.6% 486 Biomass 1,308 1.6% Geothermal 2,760 3.5% 3.5% Solar 12,527 15.7% 15.7% Wind 5,973 7.5% 7.5% 79,824 100.0% 54.1% 44.2% California ■ Coal / Coke ■ Oil 54.1% Dispatchable ■ Nuclear ■ Natural Gas ■ Hydro ■ Biomass ■ Geothermal ■ Solar ■Wind North Western (Montana) 25.3% Dispatchable 22.7% Semi- dispatchable 24.1% Semi- dispatchable California is dealing with significant capacity issues DESPITE having a greater amount of dispachable generation and fewer renewables than NorthWestern Energy in Montana (as a percentage of the total). NorthWestern Energy Delivering a Bright Future

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