Document zo9vLL8ZrD9dGvejzmRxO97XB

USCA Case #24-1190 Document #2062093 Filed: 06/27/2024 Page 25 of 123 January 2024 Cold Weather Event - Montana Resource me p ate capacity ft,IWI NWE Mc dana RortIolio Resoune Productiuq Ave , ege Hourly. Price fo, esch cold spell day Thermal ry MMI un~l II Once again during the recent cold spell (1110/24 to 1/16124), energy prices surged when wind and solar weren't providing capacity. And once again, NorthWestern had to be dependent on the market to meet customer needs, with the average price of a megawatt hour over $900 for the last 4 days (13'-16th) of the cold spell. 62. As of December 8, 2023 future prices for heavy load electricity for the months of July, August and September, 2024 are trading at 5130, $180, and $136 per MWh respectively. Further contracted prices have ranged from $200 to $900 per MWh during recent peak events. 'Ile actual cost for purchasing electricity in December 2022 was around $250 per MWh; for the three highest load days (December 21-23), the actual purchase cost averaged about $440/MWh. .1.o provide a simplified illustration of the impact of such a potential difference in cost to serve customers, consider a hypothetical three-day event during which NorthWestern's share of Colstrip would produce about 15,000 MWh. If the difference between the market price and the variable cost of Colstrip is 5400/MWh, the cost of market purchases for the three day period would be about 56 million more than the cost of gencration (5400 x 15,000 MWh = 56 million). Such extra costs of a contracted capacity resource would be passed on to customers. 63. My statements in the preceding paragraphs assume that a capacity contract is even available. However, I stress again that this may not be the case given the recent and planned 24 Sierra Club FOIA 2025-EPA-04883 ED_018388_00000310-00025 SC_EVERSPLIT0006280