Effective Jan. 1, 2026, NorthWestern Energy will acquire, at no cost, Puget Sound Energy’s 370 megawatt share of the Colstrip Plant.

The acquisition will allow NWE to leverage existing infrastructure that is “well established, dependable, reliable and consistently available when our customers need energy the most”.

An equivalent resource would cost more than $700 million to build and would not be available to serve customers for at least 5 years. Including the previously announced acquisition of Avista’s 222 megawatts, that are under the same terms and timeline, NorthWestern Energy will own 55% of the Colstrip Plant.

Puget Sound Energy is a Washington-based utility.

“We are working hard to keep energy costs affordable knowing that many Montanans live on fixed incomes and are managing other life expenses,” states the company’s press release, “This 370 megawatt additional share of the Colstrip Plant presents an affordable opportunity that benefits our customers.” An equivalent resource, such as a natural gas plant, would cost more than $700 million to build and would not be available to serve customers for at least 5 years.

“Today’s announcement is yet another step in securing a strong future for Montana-made energy,” Montana Governor Greg Gianforte said. “Working with our partners, we’ve defended our all-of-the-above energy strategy to increase access to affordable, reliable energy for all Montana consumers. I thank NorthWestern for their continued investment in our state and in the community of Colstrip.”

Majority ownership allows NorthWestern Energy to effectively guide investments in operation and maintenance of the Colstrip Plant, ensuring the plant continues to provide on-demand, 24/7 cost-effective generation for our Montana customers until viable, equivalent, carbon-free energy resources are commercially available.

Montana has considerable low cost wind and solar generation on its system today, but that generation is variable. The Colstrip Plant’s generation provides power for Montana customers when the wind isn’t blowing and the sun isn’t shining at costs that are typically much less than the cost of purchasing energy on the market.

When the sun is shining and the wind is blowing, the amount of power being generated by the Colstrip Plant can be lowered.

Montana’s energy demand is growing. “We are in discussions with several large customers seeking dependable, established and consistent energy. This additional portion of the Colstrip Plant will not only allow us to reliably serve our current customers into the future, but it will also allow us to support economic development and load growth in Montana while helping to insulate existing customers from costs associated with serving new large load customers,” said the press release.

Puget Sound Energy will retain its obligation for its portion of environmental and decommissioning costs associated with the future closure of the plant.

“Other states require a transition away from coal resources at a pace faster than is feasible in Montana. This no-cost acquisition allows our customers to transition to a cleaner energy future at a pace that works for Montanans,” states the press release.

The Colstrip Plant is seen as a “dependable” bridge to a cleaner energy future, which could ultimately include new lower- or no-carbon emitting resources such as gas-fired generation, small modular nuclear reactors, long-duration storage or other technologies, which we believe could be located in the Colstrip area. Such changes will, however, take time and “we will not sacrifice service reliability during the transition.”

This announcement follows an announcement a week ago, from NorthWestern Energy, about a $39 million deal to purchase Energy West Montana, a natural gas provider headquartered in Great Falls. The acquisition is expected to be completed in the first quarter of 2025. It must be approved by the Montana Public Service Commission.