Myths or Facts? Understand The Facts Behind the Colstrip Power Plant
You've Heard the Myths
Get the facts about this important piece of Montana’s energy future.
NorthWestern Energy is responsible for providing reliable, affordable energy service to Montana communities 24 hours a day, seven days a week. By securing majority ownership in the Colstrip Power Plant, we are taking an important step to keep energy dependable and costs reasonable for Montana families and businesses—especially during harsh weather when energy demand is high.
This expanded ownership will secure the future of this vital resource for Montana and ensure that the Colstrip Power Plant can continue to serve a vital need for our state.
Myth:
Other Colstrip Power Plant owners are leaving because wind and solar energy and battery storage is cheaper.
Fact:
Out-of-state owners (Avista, Puget Sound Energy) must exit the Colstrip Power Plant due to Washington state law — not because of cost. Their departure gives NorthWestern Energy the chance to secure reliable, affordable, on-demand energy for our customers at no acquisition (or upfront) cost, increasing ownership to 55% and ensuring Montanans’ energy needs are prioritized.
Myth:
NorthWestern Energy is stuck in the past, relying on fossil fuels.
Fact:
NorthWestern Energy’s Montana portfolio is among the cleanest in the U.S., with more than 58% wind, solar, and hydro generation. The Colstrip Power Plant provides on demand generation in all weather, including when the wind isn’t blowing and the sun isn’t shining.
Myth:
The Colstrip Plant is old, worn out, and unreliable.
Fact:
In the last decade, the Colstrip Power Plant has been available more than 90% of the time when NorthWestern Energy needed its generation for our Montana customers. It provides dependable, on-demand power in all weather conditions.
Myth:
New wind and solar farms will lower Montanans’ energy bills.
Fact:
Wind and solar generation has low operating costs, but its construction and land requirements are very expensive. Building enough renewable energy generation and the ability to store it to match the Colstrip Power Plant’s on-demand reliability would cost at least hundreds of millions of dollars.
Myth:
Montana’s energy needs can be met with existing generation.
Fact:
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 that Montana has reliable, affordable power—especially when demand is high and the weather is extreme. This protects our customers from price spikes and supply shortages.
Myth:
NorthWestern Energy’s acquisition of additional shares of the Colstrip Power Plant benefits the company’s shareholders, not Montana customers.
Fact:
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, ensures Montana has the energy it needs and safeguards Montana’s energy future.
Myth:
Setting up a subsidiary for the Puget Sound Energy share of the Colstrip Power Plant by NorthWestern Energy is a violation of Montana law.
Fact:
NorthWestern Energy is acquiring Avista’s share of the Colstrip Power Plant, which 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 and fully complies with state law and regulatory requirements.
Myth:
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.
Fact:
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 is being acquired by a subsidiary of our parent company, NorthWestern Energy Group, Inc. This means our Montana customers will not pay for costs related to that share unless and until it is needed to serve them.
Myth:
It’s unprecedented for a regulated utility and an unregulated subsidiary of a holding company to own the same asset.
Fact:
Colstrip’s Montana ownership structure has included both regulated and unregulated shares at the direction of the Montana PSC.
Reliability First, Opportunity Ahead
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Reliability First, Opportunity Ahead
Our priority is reliable, affordable energy for Montana families and businesses. We’re working collaboratively with stakeholders on a plan that supports economic development while protecting the interests of all Montanans. Together, we are building an energy strategy that strengthens our communities and secures long-term prosperity.
Reliability First, Opportunity Ahead
Date: Dec 5, 2025
TYPE: News
By Brian Bird, President & CEO, NorthWestern Energy
On Jan. 1, NorthWestern Energy will take a decisive step to secure our state’s energy future. Our ownership in Montana’s Colstrip Plant will increase from 15% to 55%. We are guided by a singular responsibility -- to meet our obligation to provide reliable, cost-effective energy service for our customers.
This plan has been in the works for three years.
Today NorthWestern Energy owns 222 megawatts of the Colstrip Plant, on-demand generation that keeps the lights on, cost effectively, for Montana families and businesses in all weather conditions. The Colstrip Plant is a critical piece of the portfolio of generation resources serving our Montana customers – a portfolio with more than 58% wind, solar and hydro generation today.
In early 2023, NorthWestern Energy announced plans to acquire an additional share of the Colstrip Plant from Washington-based Avista, to provide our Montana customers with a more balanced mix of energy resources.
In July 2024, we announced plans to acquire another share of the Colstrip Plant from Washington-based Puget Sound Energy.
Washington state law requires Avista and Puget Sound Energy to exit the Colstrip Plant on Dec. 31. In Montana, the plant’s on-demand generation remains essential to keeping the lights on and homes warm in our state at reasonable rates.
With 55% majority ownership, we can protect this critical resource from premature closure driven by out-of-state interests. We will guide operational investments so the plant continues to deliver cost-effective, around-the-clock energy for Montana communities.
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.
For decades, energy service providers in Montana owned power generation facilities to supply electricity to their customers. In 1997, the state deregulated the energy generation industry, ending that long-standing policy. However, deregulation failed and resulted in higher energy costs for Montanans. In response, lawmakers changed state law in 2007 to allow energy service providers to once again own power generation facilities and serve their customers directly.
Over the last 18 years, NorthWestern Energy has added nearly 1,100 megawatts of power generation to serve our Montana customers. More than half of this comes from renewable wind and hydro generation.
When the wind isn’t blowing and the sun isn’t shining, Colstrip is there. This acquisition strengthens our generation portfolio and reinforces a stable energy backbone for Montana.
The added capacity from Avista’s and Puget Sound Energy’s shares of Colstrip come at no purchase price, avoiding the enormous expense of building or buying a similar resource.
This is responsible progress.
We’re committed to a cleaner energy future, but you don’t tear down one bridge until another is built. The Colstrip Plant will keep the lights on in Montana in all weather conditions as we safely and cost-effectively transition to new carbon-free technologies.
This acquisition also opens the door to new opportunities.
Montana is attracting interest from the data center industry. With expanded generation capacity, NorthWestern Energy is positioned to support that economic opportunity in Montana while existing customers are protected.
Generation from the Puget Sound Energy share of the Colstrip Plant isn’t needed in the near term to serve our Montana customers’ energy demand –the cost of operations and maintenance of this share will not be included in customer rates. However, acquiring the Puget Sound Energy share means we gain majority ownership of the plant and the flexibility to serve future energy growth in Montana.
Our priority is reliable, affordable energy for Montana families and businesses. We’re working collaboratively with stakeholders on a plan that supports economic development while protecting the interests of all Montanans. Together, we are building an energy strategy that strengthens our communities and secures long-term prosperity.
This is more than an energy transaction. It’s a promise to Montana. By securing the Colstrip Plant’s capacity today, we’re safeguarding reliability during the harshest weather—and creating space for tomorrow’s opportunities.
Reliability comes first. And with this acquisition, Montana can move forward with confidence -- toward an energy future that is both secure and prosperous.