NorthWestern Energy Reveals Deal to Acquire Puget Sound Energy’s Interest in Colstrip Plant

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

This no-cost acquisition will enable us to utilize established, dependable, and consistently available infrastructure, ensuring we can meet our customers' energy needs effectively.

NorthWestern Energy is committed to maintaining affordable energy costs, recognizing that many Montanans are on fixed incomes and managing various expenses. The additional 370 megawatt share of the Colstrip Plant offers a cost-effective solution that will benefit our customers starting January 1, 2026. Constructing an equivalent resource, like a natural gas plant, would exceed $700 million and would not be operational for at least five years.

With the addition of the previously announced acquisition of Avista’s 222 megawatts, which follows the same terms and timeline, NorthWestern Energy will hold a 55% stake in the Colstrip Plant. This majority ownership enables NorthWestern Energy to effectively manage investments in the operation and maintenance of the plant, ensuring it remains a reliable and cost-effective source of on-demand, 24/7 power for our Montana customers until comparable, carbon-free energy solutions become commercially viable.

Other states mandate a quicker shift away from coal resources than what is feasible in Montana. This no-cost acquisition enables NorthWestern Energy customers to move towards a cleaner energy future at a pace that suits the needs of Montanans.

The Colstrip Plant serves as a reliable bridge to a cleaner energy future, potentially incorporating new lower- or no-carbon technologies such as gas-fired generation, small modular nuclear reactors, long-duration storage, or other innovations that NorthWestern envisions being developed in the Colstrip area. However, this transition will take time, and the company is committed to maintaining service reliability throughout the process.

Montana Governor Greg Gianforte stated, "This announcement is another important step in ensuring a robust future for energy produced in Montana. By collaborating with our partners, we've upheld our all-of-the-above energy strategy to enhance access to affordable and reliable energy for all Montanans. I appreciate NorthWestern's ongoing investment in our state and the Colstrip community."

Montana currently benefits from significant low-cost wind and solar generation in the company's system, though this generation can be variable. The Colstrip Plant supplies power to NorthWestern Energy’s Montana customers during times when the wind isn’t blowing and the sun isn’t shining, often at costs significantly lower than purchasing energy from the market.

When the sun is shining and the wind is blowing, the company can reduce the power output from the Colstrip Plant.

Montana's energy demand is on the rise, and NorthWestern Energy is in talks with several large customers seeking reliable and consistent energy. The additional portion of the Colstrip Plant will enable the company to reliably serve existing customers well into the future and support economic development and load growth in Montana. It will also help shield current customers from the costs associated with accommodating new large-scale customers.

Puget Sound Energy will remain responsible for its share of the environmental and decommissioning costs related to the plant's eventual closure.