Montana regulators find NorthWestern Energy’s long-term power plan deficient
Montana regulators found NorthWestern Energy’s 20-year electricity plan deficient and gave the utility until September 18, 2026, to submit revisions or request an extension.
The Montana Public Service Commission’s action could shape later debates over reliability, generation, transmission, data-center demand and whether customers should pay for future investments. It does not approve or reject a specific power plant, set electric rates or select a final resource mix.
What regulators found
Commissioners voted 3-1 to require NorthWestern to address problems identified in an independent review by GDS Associates, according to Montana Free Press. Billings-based Commissioner Brad Molnar was suspended and was not participating in the decision.
State regulators and the GDS review identified five areas in which the filing did not provide information the commission expected. The concerns included inadequate testing of different future scenarios, insufficient explanation and documentation of the utility’s modeling, questions about whether the analysis could be reproduced and evaluated, gaps in the explanation for proposed new resources and limited information about demand-response programs that can compensate customers for reducing electricity use.
Those gaps matter because an incomplete plan can make it harder to assess whether the utility is preparing for future demand at a reasonable cost. PSC officials warned that weak analysis could increase the risk of overbuilding facilities, which could raise rates, or underpreparing for demand and creating reliability problems.
What an integrated resource plan does
An integrated resource plan, or IRP, is a long-term study of projected electricity demand and the resources that could meet it. NorthWestern describes the process as an evaluation of future scenarios involving reliability, affordability and risk, along with existing generation, transmission, fuel systems, energy efficiency and possible resources such as natural gas, renewable energy and storage.
The plan looks ahead 20 years. It is a planning document, not a construction order or final investment decision. NorthWestern’s explanation says an IRP does not approve or build specific projects, set electric rates or lock the utility into one path.
Why the review could matter to ratepayers
The PSC’s review is not a rate case. Under Montana’s process, the commission reviews whether the filing contains required information and may return it for additional work. The review itself does not immediately change what customers pay.
But the commission’s concerns could become relevant if NorthWestern later asks regulators to recover the cost of a particular project through customer rates. The PSC has said it can consider whether costs were prudent when reviewing a future cost-recovery request.
That distinction matters because projections in a draft IRP are not the same as approved investments. NorthWestern has not received authorization through this proceeding to build a particular plant or transmission project.
Data-center demand remains uncertain
The GDS review also raised questions about the effect of possible data-center growth on future electricity demand. NorthWestern has entered agreements related to serving data centers that have not been made public, according to Montana Free Press.
Public commenters have raised concerns that large new loads could lead to generation and transmission costs being spread among existing customers. Those concerns are part of the public debate, but the available records do not establish that data centers are shifting costs to Montana ratepayers or that they caused current bill increases.
NorthWestern spokesperson Jo Dee Black said additional analysis should improve understanding of costs, reliability risks and long-term tradeoffs. The company says its planning process is intended to evaluate how to meet customer needs reliably, safely and affordably.
Separate investigation into August bill spikes
The IRP review is separate from an investigation into unexpectedly high August bills. The PSC says hundreds of NorthWestern customers have contacted its consumer affairs unit about increases on their billing statements.
The agency is working with NorthWestern to investigate the issue. Customers who saw a spike can email pschelp@mt.gov and provide the account holder’s name, service address, front and back copies of the bill and any other relevant records.
The PSC says staff will contact NorthWestern about individual cases and include submitted documentation in the broader investigation. The agency has not said that the bill increases were caused by NorthWestern’s long-term power plan.
What happens next
NorthWestern must submit revisions by September 18, 2026, or ask for additional time. The PSC will then review the response and determine whether further information is needed.
For Montana residents, the next significant questions are whether the revised filing provides clearer scenario testing, more transparent and reproducible modeling, and stronger treatment of demand response. Later proceedings involving specific investments or cost recovery could determine whether particular projects and expenses are reasonable for customers to fund.
Sources
- Montana Public Service Commission: NorthWestern Energy long-term power plan review
- Montana Free Press: NorthWestern Energy’s power plan found deficient by independent review
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