The Colstrip Power Plant, photographed in August 2019. Credit: Photo by Eric Dietrich/MTFP

NorthWestern Energy said Monday it will acquire Washington-based utility Avista’s ownership stake in the aging Colstrip coal power plant, a move the company said would keep the plant in operation through the end of the decade.

NorthWestern, Montana’s dominant power utility, has been trying for several years to expand its stake in Colstrip, which is owned in part by Washington- and Oregon-based companies that have been planning a 2025 exit in the face of their states’ climate action targets.

John Hines, NorthWestern’s vice president of energy supply and government affairs, announced the acquisition Monday evening at a legislative reception organized by the company and others on behalf of the community of Colstrip, the southeast Montana town where the plant is a major employer. 

“We have entered into an agreement with Avista where we’re going to be acquiring all their shares, output in units three and four,” Hines said to cheers from a crowd of lawmakers, lobbyists, state officials and others who filled the ballroom of Helena’s Great Northern Hotel.

The agreement, Hines said, was signed this week and will bring NorthWestern’s stake in Colstrip to a total of 444 megawatts as of Jan. 1, 2026.

Hines added that the transaction doesn’t require immediate action by the Montana Public Service Commission, the state’s utility regulation board, or action by the Legislature in order to move forward.

“This provides a mechanism for units three and four to stay open through the rest of this decade, which is absolutely critical for the community, for the state, and allowing us to have sufficient, adequate power in Montana,” Hines said.

Avista will retain its existing environmental obligations instead of transferring them to NorthWestern and, by extension, to NorthWestern ratepayers, Hines said. According to NorthWestern, Avista will also retain its ownership stake in high-capacity transmission lines that transport power out of Colstrip. 

“The purchase price is zero. Our customer’s rates will not go up because of this transaction,” Hines said.

In a subsequent emailed release about the purchase, NorthWestern said it will be picking up the operating costs associated with the Avista shares starting in 2026. The company said the two utilities have worked out an arrangement in which Avista’s share of “certain capital expenses” will be prorated in the interim. 

The Montana Environmental Information Center, which has long called for the plant’s closure, on Tuesday called NorthWestern’s plan environmentally and economically irresponsible.

MEIC Policy and Legislative Affairs Director Anne Hedges said in an interview that NorthWestern is investing in “last-century’s energy system” while other utility companies invest in storage technology that can even out the peaks and troughs associated with renewable wind and solar generators. She added that the acquisition could leave NorthWestern customers on the hook for plant repairs that can cost tens of millions of dollars.

“With climate change, this is the Olympics and these guys are swimming backward,” she said of NorthWestern. “This is nuts.”

At Monday’s event, NorthWestern’s newly appointed President and CEO Brian Bird acknowledged that “I may be the only CEO in the utility industry adding coal to his portfolio” — a line that won applause from the crowd. 

In a later phone conversation with MTFP, Hines spoke to that dynamic, saying that the gas plant NorthWestern is building in Laurel and the doubled ownership stake of Colstrip will give the company more time to evaluate non-carbon-emitting resources. He said the company still intends to be carbon-free by 2050.

The doubled Colstrip stake, Bird said, provides NorthWestern with a reliable and affordable power supply. NorthWestern’s existing 222 megawatt share in Colstrip, he said, saved the company and its customers $10 million in power purchases from other providers during last month’s holiday cold snap.

“From a reliability standpoint, this incremental 222 megawatts and the 175 megawatt gas plant we’re building near Laurel moves us from a deficit from a resource adequacy standpoint to a point where we can actually serve our customers long-term,” Bird said.

Hedges said she believes NorthWestern is misrepresenting its generation capacity shortage in order to justify its ownership of additional capital assets, which are more profitable for regulated utilities than buying power from other companies. In filings it submitted to the Western Resource Adequacy Program, a collective that aims to help utilities and other entities meet their power capacity needs, NorthWestern indicated it has more generation capacity in its renewable energy assets than it has listed in rate case filings to state utility regulators, she said. 

Executives from Avista, Colstrip co-owner PacifiCorp, coal mining company Westmoreland and Talen Energy, which co-owns and operates the coal plant and also recently negotiated an increased share of units three and four, lauded the deal in remarks at Monday’s event — as did Gov. Greg Gianforte.

“This is a good deal for Montana and a good deal for Colstrip,” Gianforte, a Republican, told the crowd. “It means we’re going to have reliable, affordable energy for all Montanans. If we didn’t have this power going forward, this decade and beyond, our grid would no longer be stable.”

Avista CEO Dennis Vermillion said his company, which also owns the Noxon Rapids Dam on the Clark Fork in western Montana, remains committed to doing business in Montana.

Holding onto eastern Montana transmission lines will let Avista explore “less reliable,” non-coal energy generation, Vermillion said. 

“We’ll be going for renewables. Yay renewables,” Vermillion said, joking that the line might have earned him a standing ovation in a different state.

Other Colstrip co-owners have entered into agreements for more than 700 megawatts of power from a wind farm in eastern Montana that will tie into the 500-kilovolt transmission lines leading out of Colstrip.

Talen CEO Alex Hernandez said NorthWestern’s acquisition and his company’s effort to expand its ownership stake in the remaining Colstrip units “align the ownership of the plant with the parties that are committed to the long-term future of Montana.”

“We are here for the long-run. We are not transitioning. We are here until Colstrip serves its useful life. We are here until the very end,” Hernandez said.

Talen negotiated its own deal with Puget Sound Energy last year to acquire its 25% stake in units three and four. That means that by 2026, companies with Montana operations will have a majority stake in both operational Colstrip units for the first time since they came online in the mid-1980s.

Colstrip’s co-owners have frequently been at odds over the plant’s future, with its implications for climate and the regional economy. Bird said NorthWestern’s additional share will put the remaining owners on track to determine the plant’s future outside of a formal mediation process, which is one avenue NorthWestern has explored to garner more clarity about the plant’s eventual closure. 

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Eric DietrichDeputy Editor

Eric came to journalism in a roundabout way after studying engineering at Montana State University in Bozeman (credit, or blame, for his career direction rests with the campus's student newspaper, the Exponent). He has worked as a professional journalist in Montana since 2013, with stints at the Great Falls Tribune, Bozeman Daily Chronicle, and Solutions Journalism Network before joining the Montana Free Press newsroom in Helena full time in 2019.

Amanda EggertEnvironmental Reporter

Amanda Eggert studied print journalism at the University of Montana. Prior to becoming a full-time journalist, Amanda spent four years working with the Forest Service as a wildland firefighter. After leaving the Forest Service in 2014, Amanda worked for Outside magazine as an editorial fellow before joining Outlaw Partners’ staff to lead coverage for Explore Big Sky newspaper and contribute writing and editing to Explore Yellowstone and Mountain Outlaw magazines. Prior to joining Montana Free Press’ staff in 2021 Amanda was a freelance writer, researcher and interviewer. In addition to writing...