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Regulatory matters
 6 Months Ended
Jun. 30, 2025
Regulated Operations [Abstract]  
Regulatory matters Regulatory matters
The Company regularly reviews the need for electric and natural gas rate changes in each of the jurisdictions in which service is provided. The Company files for rate adjustments to seek recovery of operating costs and capital investments, as well as reasonable returns as allowed by regulators. Certain regulatory proceedings and cases may also contain recurring mechanisms that can have an annual true-up. Examples of these recurring mechanisms include: infrastructure riders, transmission trackers, renewable resource cost adjustment riders, as well as weather normalization and decoupling mechanisms. The following paragraphs summarize the Company's significant open regulatory proceedings and cases by jurisdiction including updates to those reported in the 2024 Annual Report and should be read in conjunction with previous filings. The Company is unable to predict the ultimate outcome of these matters, the timing of final decisions of the various regulators and courts, or the effect on the Company's results of operations, financial position or cash flows.
IPUC
On May 30, 2025, Intermountain filed a request with the IPUC for a natural gas general rate increase of approximately $26.5 million annually or 8.6 percent above current rates. The requested increase is primarily to recover increased operating expenses and costs associated with plant additions, as well as revenues necessary to produce a fair rate of return to enable continued safe and reliable service. The IPUC has up to seven months to issue a decision on the request, which is currently pending.
NDPSC
On July 15, 2025, Montana-Dakota filed an annual update to its transmission cost adjustment rider with the NDPSC requesting to recover revenues of approximately $6.3 million, which includes a true-up of the prior period adjustment, resulting in an increase of approximately $7.2 million over current rates. Included in this filing is capital investment in transmission projects and the associated revenue of approximately $8.6 million. This matter is pending before the NDPSC.
MTPSC
On July 15, 2024, Montana-Dakota filed a request with the MTPSC for a natural gas general rate increase of approximately $9.4 million annually or 11.1 percent above current rates. The requested increase is primarily to recover investments in system upgrades and pipeline replacement projects enhancing the reliability, safety and integrity of the natural gas system, as well as increased costs to operate and maintain that system. On October 15, 2024, the MTPSC denied Montana-Dakota's request for an interim rate increase of approximately $8.0 million annually or 10.2 percent above current rates. On October 25, 2024, Montana-Dakota filed a motion for reconsideration of the interim rate increase. On January 14, 2025, the MTPSC approved an interim increase of approximately $7.7 million with interim rates effective on and after February 1, 2025. On April 3, 2025, an all-party settlement agreement was filed reflecting an annual revenue increase of $7.3 million or 8.6 percent overall. This matter is pending before the MTPSC.
WUTC
On March 29, 2024, Cascade filed a request with the WUTC for a multi-year natural gas general rate increase of $43.8 million or 11.6 percent effective March 1, 2025 and $11.7 million or 2.8 percent to be effective March 1, 2026. Multi-year filings are now required by Washington law that went into effect on January 1, 2022. The requested increase is primarily to recover infrastructure investments necessary to provide safe and reliable service and higher operating costs due to inflation. On December 11, 2024, a multi-party settlement agreement was filed reflecting rate increases of $29.8 million or 7.9 percent to be effective March 1, 2025, and $10.8 million or 2.6 percent to be effective March 1, 2026. On February 24, 2025, the WUTC approved the multi-party settlement agreement with year one rates effective on and after March 5, 2025. On April 30, 2025, Cascade filed a revision to decrease revenues by $3.7 million or 0.5 percent effective June 1, 2025. The reduction was driven by forecasted plant that was not placed in service by December 31, 2024. On May 22, 2025, the WUTC allowed this revision to become effective on or after June 1, 2025.
WYPSC
On October 31, 2024, Montana-Dakota filed a request with the WYPSC for a natural gas general rate increase of approximately $2.6 million annually or 14.0 percent above current rates. The requested increase is primarily to recover investments in system upgrades and pipeline replacement projects enhancing the reliability, safety and integrity of the natural gas system, as well as increased costs to operate and maintain that system. On May 9, 2025, an all-party settlement agreement was filed reflecting an annual revenue increase of $2.1 million or 11.7 percent. On June 24, 2025, the WYPSC approved the settlement with rates effective on and after August 1, 2025.

On June 30, 2025, Montana-Dakota filed a request with the WYPSC for an electric general rate increase of approximately $7.5 million annually or 24.4 percent above current rates. The requested increase is primarily to recover increases in operation and maintenance expenses, investments made since the last rate case, and the corresponding depreciation on those infrastructure investments. This matter is pending before the WYPSC.