Customers shouldn’t be on the hook for nearly $50 million in cost overruns NorthWestern Energy incurred to build the Yellowstone County Generating Station, according to the Montana Consumer Counsel.

Those “substantial” overruns stem from “unnecessary development risks” NorthWestern Energy took to build the plant, according to briefing from the state’s consumer watchdog in an open rate case before the Montana Public Service Commission.

The plant, built without preapproval from the PSC, was estimated to have cost $320 million in August 2024.

In briefing, the Montana Consumer Counsel argues the PSC should not relieve NorthWestern of “any responsibility” for additional costs related to the plant and associated returns it “seeks to fully recover from ratepayers.”

But the Montana Consumer Co

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