NorthWestern Seeks Regulatory Approval After Boosting Colstrip Ownership to 55% Amid Opposition

NorthWestern Energy has boosted its ownership of the Colstrip coal-fired power plant to approximately 55 percent and has asked state regulators to approve how it will manage the newly acquired capacity and the customer and rate impacts. The company took over additional megawatts previously held by Avista Corp. and Puget Sound Energy, a move announced following transactions completed by January 19, 2026.

The filing seeks regulatory sign-off on allocation of the added power, cost recovery and the distribution of any operational or decommissioning costs tied to the expanded stake. For residents of Lewis and Clark County and Helena ratepayers, the key question is whether the change will translate into higher electricity bills or altered planning for Colstrip’s future. Opponents argue the deals have not received sufficient oversight, pointing to the plant’s complicated ownership web and raising concerns about environmental and economic burdens for Montana customers.

Colstrip has long been a focal point in Montana’s energy conversations because it is a large coal-fired plant with regional implications for emissions and power supply. With NorthWestern now holding a majority position, decisions about maintenance, investments, retirement timetables and potential remediation could shift toward the company’s preferences. That consolidation of control can accelerate decision-making, but it can also concentrate financial and regulatory risk on Montana ratepayers if costs are allocated locally.

Regulatory review will center on how NorthWestern proposes to account for the newly acquired megawatts in rates and long-term planning. Regulators will evaluate whether cost shifts are fair to Montana customers and whether NorthWestern’s plan aligns with state energy policy and reliability needs. Opponents’ complaints about oversight underscore broader policy tensions: should utilities absorb ownership and long-term coal liabilities, or should those risks be shared differently as the region transitions toward lower-carbon generation?

Market implications extend beyond local bills. A majority owner can influence timing of plant retirements, investment in pollution controls, or sales of output into regional markets. Those choices affect not only ratepayers but also the regional supply mix and the pace of Montana’s decarbonization efforts.

For Lewis and Clark County readers, the immediate impact will depend on regulators’ review and any specific rate filings that follow. NorthWestern’s request sets a process in motion that could determine who ultimately pays for Colstrip’s remaining years of operation or closure. The coming regulatory decisions will shape electricity costs, local economic effects tied to the plant, and the community’s role in Montana’s energy transition.