NorthWestern Energy announced late Tuesday afternoon that it will acquire Puget Sound Energy’s 370 megawatts in the Colstrip coal-fired power plant in southeastern Montana.
Washington-based Puget Sound Energy is one of six co-owners. The utility owns a quarter of each of the plant’s two remaining units.
According to a Tuesday news release from NorthWestern, Puget Sound Energy agreed to transfer its share at no cost, effective at the beginning of 2026. Puget Sound Energy says under state law it must stop charging its Washington customers for coal generation by the end of 2025.
Oregon’s Avista Corporation is under similar requirements. Avista is slated to transfer its share in the plant to NorthWestern at the beginning of 2026.
NorthWestern Energy says this agreement, along with its acquisition of Avista’s share, will bring its ownership up to 55 percent. Staffers cite the need for more utility-owned generation available to serve customer needs immediately when they need it.
Environmental groups and advocates for more renewable energy have pushed back against NorthWestern’s interest in remaining in Colstrip. They say customers will ultimately be saddled with the costs.
This is the second time over the last four years NorthWestern has entered an agreement to take on Puget Sound Energy’s ownership in the plant. A deal NorthWestern Energy struck with the utility fell through in 2020.
Puget Sound Energy will keep its obligation for its portion of environmental and decommissioning costs for future closure.
