NorthWestern Energy/Avista Colstrip Agreement
NorthWestern Energy and Avista entered into an agreement to provide NorthWestern Energy’s Montana customers needed on-demand power generation capacity and allow Avista to exit ownership of the Colstrip plant in accordance with the state of Washington laws.
- NorthWestern Energy will acquire Avista’s ownership of Colstrip Units 3 & 4, 222 megawatts, with no purchase price, effective on Jan. 1, 2026.
- Avista will retain its obligation for its portion of environmental and decommissioning costs associated with the future closure of the plant.
- NorthWestern Energy will be responsible for operational costs for the 15% shares of Colstrip Units 3 & 4 when ownership is transferred.
- Avista and NorthWestern Energy will prorate Avista’s share of the cost of certain capital expenses for the Colstrip plant from now through Jan. 1, 2026.

“More resources that can generate power on-demand, 24/7, located in Montana and dedicated to serve Montanans, are needed to meet our responsibility to provide our customers with reliable energy service, keep them safe in all weather conditions and avoid an energy crisis.”
Brian Bird
NorthWestern Energy President and CEO
NorthWestern Energy/Avista Colstrip Agreement
Why are we acquiring Avista's ownership of Colstrip?:
- Acquiring more generation at no purchase price allows NorthWestern Energy to continue to make other necessary investments in our Montana energy system with less impact on customers’ bills.
- It is impossible to identify, permit and build a new resource to meet our Montana customers’ needs that is capable of the same on-demand, 24/7 generation in that timeframe.
- Any new resource would cost about $500 million to build.
- In addressing the need for additional on-demand, 24/7 generation in Montana to avoid an energy crisis, NorthWestern Energy continues to implement our “all-of-the-above” strategy to meet our customers’ energy needs.
Colstrip's role in extreme weather

Colstrip's role in extreme weather
- During frigid temperatures in December 2022, 41% of NorthWestern Energy’s peak Montana energy load was met with market purchases, primarily from out of state, and most at extremely high prices.
- NorthWestern Energy’s Montana natural gas-fired generation facilities, share of the Colstrip plant and hydro generation supplied about half of the power during our customers’ highest energy need.
- Weather conditions, including the extreme cold temperatures, meant NorthWestern Energy’s considerable Montana wind generation resources could not provide much, if any, power.

Had this incremental share of Colstrip and the Yellowstone County Generating Station been available to NorthWestern Energy during the Dec. 21-23, 2022 extreme cold, it would have saved our customers millions of dollars in energy costs procured from out-of-state providers. We have a responsibility to reduce that level of risk to reliable energy service for our Montana customers.
Stakeholder Feedback
Montana Gov. Greg Gianforte
“We want people to invest in Montana who want to be in Montana, and that happened here with NorthWestern Energy. This development will better ensure Colstrip remains in service throughout its full, useful life, and it’s encouraging for Montanans who rely on the reliable, affordable electricity Colstrip generates.”
Montana Rep. Ryan Zinke
“Very positive news about the future of Colstrip. Tens of thousands of Montana households rely on the affordable and reliable power that only Colstrip can provide. Glad to see we can count on Made in Montana energy through the decade.”
Republican leadership of the Montana Legislature
“Colstrip—the power plant, the town, and most importantly the people—are crucial to Montana’s future. Last night’s announcement is the best news coming out of Colstrip in many years. We are excited and encouraged about the future of Colstrip, its people, and Montana energy production.”
- Senate President Jason Ellsworth, President Pro Tempore Ken Bogner, Majority Leader Steve Fitzpatrick, House Speaker Matt Regier, Speaker Pro Tempore Rhonda Knudsen, and Majority Leader Sue Vinton
Montana Rep. Matt Rosendale
“I’m encouraged by the news of NorthWestern’s expanded stake in Colstrip’s power plant. This partnership will provide stability for the town of Colstrip and the state of Montana, while maintaining our commitment to affordable, reliable energy. Not only will it create jobs and lower energy costs for Montanans, but it's a step toward restoring America's energy dominance.”
Todd O'Hair, Montana Chamber of Commerce
"Affordable, reliable electricity is a cornerstone to economic growth. Northwestern Energy's acquisition of a larger share of Colstrip allows us to continue pursuing an 'all of the above' energy strategy while lessening dependence on commercial markets, which drive up rates for all. This announcement is good news for Colstrip, Montana, and the entire business community."
IBEW local 44 and local 1638
David Smith, Montana Contractor’s Association
Darryl James, Montana Infrastructure Coalition
Peggy Trenk, Treasure State Resource Association
A step toward net zero emissions
Our Balanced and Diverse Energy Mix
At NorthWestern Energy, our goal is to provide our customers reliable energy at the lowest long-term cost. We do this through a balanced mix of safe, reliable, affordable and clean energy. Our electric portfolio is built on the carbon-free hydro system, along with wind, coal, gas and solar.
Over time, the natural gas plants and other thermal generation on our system will be used less as new cleaner, cost‑effective resources are available.For more information about the project, please contact: