Empowering Montana: NorthWestern Energy’s expanded role at the Colstrip Power Plant

Other Colstrip Power Plant owners are leaving because wind and solar energy and battery storage is cheaper.

Out-of-state owners (Avista, Puget Sound Energy) had to exit the Colstrip Power Plant due to Washington state law — not because of cost. Their departure provided NorthWestern Energy the opportunity to secure reliable, affordable, on-demand energy for our customers at no upfront cost, ensuring Montanans’ energy needs are prioritized.

NorthWestern Energy is stuck in the past, relying on fossil fuels.

In 2025 NorthWestern Energy served our Montana customers with a portfolio that was more than 55% carbon-free wind, solar and hydro generation. On-demand generation from the Colstrip Power Plant, which is located in Montana, is available when the wind isn't blowing and the sun isn't shining. Montana customers have depended on unpredictable energy markets for supply, mostly from out of state, to meet peak energy demand for too long. When temperatures plunge and the demand for electricity spikes, market prices can soar -- and supply can be scarce. 

The Colstrip Plant is old, worn out, and unreliable.

Claims that the Colstrip Power Plant is historically undependable are not supported by the facts.

Over the past decade, the Colstrip Plant has been available more than 90 percent of the time when NorthWestern Energy needed its generation to serve Montana customers. This track record demonstrates Colstrip’s ability to provide dependable, on‑demand power.

On Jan. 1, 2026, NorthWestern Energy increased its ownership in the Colstrip Power Plant from 15 percent to 55 percent, securing a majority stake in this critical asset. This increased ownership enables NorthWestern Energy to guide operational decisions and investments with a clear focus on Montana’s energy needs and to prevent the premature closure of a resource that remains essential to keeping the lights on for Montanans reliably and affordably in all weather conditions.

The Colstrip Power Plant is an important part of NorthWestern Energy’s balanced and diverse generation portfolio, which includes wind, solar, hydro, and thermal resources. This diverse mix strengthens grid resilience and helps ensure reliable service for Montana customers during challenging weather conditions at a reasonable cost.

New wind and solar farms will lower Montanans’ energy bills.

Wind and solar generation is low cost, but its construction and land requirements are very expensive. Building enough renewable energy (including the ability to store it) to match the Colstrip Power Plant’s on-demand reliability would cost hundreds of millions of dollars.

Montana’s energy needs can be met with existing generation.

Montana has relied too heavily on out-of-state energy, which can be expensive and unavailable when demand is highest. Owning more of the Colstrip Power Plant means for the first time since Montana's energy industry was deregulated in 1997, NorthWestern Energy's Montana portfolio is resource adequate. There is enough dependable capacity to meet customer needs and required reliability standards. This added generation closes a long-standing capacity gap and strengthens our overall energy mix and service reliability and affordability for our Montana customers.  

NorthWestern Energy’s acquisition of additional shares of the Colstrip Power Plant benefits the company’s shareholders, not Montana customers.

If the Colstrip Power Plant were to close before replacement generation resources are in place, Montanans’ energy service reliability and affordability would be jeopardized. This acquisition, at no cost to customers, ensures Montana has the energy it needs long into the future. 

The Puget Sound Energy share of the Colstrip Power Plant acquired by NorthWestern Energy doesn't benefit Montanans. 

NorthWestern Energy's acquisition of Avista’s share of the Colstrip Power Plant is adequate to serve our Montana customers’ energy demand today. 

Generation from the Puget Sound Energy share of the Colstrip Plant is not needed right now to meet our Montana customers’ energy demand. That’s why we’ve ensured that the costs to operate and maintain this share will not be included in Montana customer rates until it is needed to serve them.

This transaction is specifically structured to protect our Montana customers.

NorthWestern Energy will sell the generation from the Puget Sound Energy share of the Colstrip Power Plant, but Montana customers’ rates will pay for its operation and maintenance costs.

The Montana Public Service Commission requires that the only costs in our customers’ rates are costs for the resources to provide them with energy service. 

The Puget Sound Energy share of the Colstrip Power Plant was acquired by a subsidiary of our parent company, NorthWestern Energy Group, Inc. This means our Montana customers will not pay any costs related to that share unless and until it is needed to serve them.