v3.26.1
Regulatory matters (Tables)
 6 Months Ended
Jun. 30, 2026
Regulatory Assets and Liabilities Disclosure [Abstract]  
Schedule of Regulatory Assets
The following table summarizes the individual components of unamortized regulatory assets and liabilities:
Estimated
Recovery or Refund
Period as of
June 30, 2026
*June 30, 2026June 30, 2025December 31, 2025
(In thousands)
Regulatory assets:
Current:
Environmental compliance programs
Up to 1 year
$95,915 $63,245 $78,784 
Conservation programs
Up to 1 year
33,426 21,541 29,148 
Decoupling mechanisms
Up to 1 year
23,272 7,974 17,091 
Cost recovery mechanisms
Up to 1 year
18,376 6,389 13,460 
Natural gas costs recoverable through rate adjustments
Up to 1 year
11,334 36,567 22,897 
Electric fuel and purchased power deferral
Up to 1 year
2,043 2,050 6,902 
Other
Up to 1 year
8,428 3,978 11,297 
192,794 141,744 179,579 
Noncurrent:
Pension and postretirement benefits**135,222 142,064 135,222 
Cost recovery mechanisms
Up to 23 years
58,977 70,533 63,328 
Plant costs/asset retirement obligationsOver plant lives48,088 46,684 48,352 
Manufactured gas plant site remediation-28,042 27,212 28,411 
Taxes recoverable from customersOver plant lives12,101 12,220 12,250 
Covid-19 deferred costs
Up to 2 years
3,590 3,886 3,761 
Long-term debt refinancing costs
Up to 37 years
1,500 1,718 1,799 
Other
Up to 13 years
8,345 4,985 4,095 
295,865 309,302 297,218 
Total regulatory assets$488,659 $451,046 $476,797 
Estimated
Recovery or Refund
Period as of
June 30, 2026
*June 30, 2026June 30, 2025December 31, 2025
(In thousands)
Regulatory liabilities:
Current:
Environmental compliance programs
Up to 1 year
$100,186 $72,520 $89,306 
Natural gas costs refundable through rate adjustments
Up to 1 year
34,598 44,377 47,130 
Electric fuel and purchased power deferral
Up to 1 year
10,465 934 — 
Margin sharing
Up to 1 year
4,065 3,410 3,946 
Taxes refundable to customers
Up to 1 year
2,313 2,197 2,301 
Provision for rate refund
Up to 1 year
1,353 4,254 1,780 
Conservation programs
Up to 1 year
851 1,996 733 
Other
Up to 1 year
3,120 4,566 3,388 
156,951 134,254 148,584 
Noncurrent:
Plant removal and decommissioning costsOver plant lives230,673 225,142 224,313 
Taxes refundable to customersOver plant lives171,179 180,212 176,665 
Cost recovery mechanisms
Up to 16 years
46,098 35,794 41,323 
Accumulated deferred investment tax creditOver plant lives22,831 19,814 22,663 
Pension and postretirement benefits**4,776 4,862 4,776 
Other
Up to 12 years
2,848 2,344 2,589 
478,405 468,168 472,329 
Total regulatory liabilities$635,356 $602,422 $620,913 
Net regulatory position$(146,697)$(151,376)$(144,116)
*Estimated recovery or refund period for amounts currently being recovered or refunded in rates to customers.
**Recovered as expense is incurred or cash contributions are made.
Schedule of Regulatory Liabilities
The following table summarizes the individual components of unamortized regulatory assets and liabilities:
Estimated
Recovery or Refund
Period as of
June 30, 2026
*June 30, 2026June 30, 2025December 31, 2025
(In thousands)
Regulatory assets:
Current:
Environmental compliance programs
Up to 1 year
$95,915 $63,245 $78,784 
Conservation programs
Up to 1 year
33,426 21,541 29,148 
Decoupling mechanisms
Up to 1 year
23,272 7,974 17,091 
Cost recovery mechanisms
Up to 1 year
18,376 6,389 13,460 
Natural gas costs recoverable through rate adjustments
Up to 1 year
11,334 36,567 22,897 
Electric fuel and purchased power deferral
Up to 1 year
2,043 2,050 6,902 
Other
Up to 1 year
8,428 3,978 11,297 
192,794 141,744 179,579 
Noncurrent:
Pension and postretirement benefits**135,222 142,064 135,222 
Cost recovery mechanisms
Up to 23 years
58,977 70,533 63,328 
Plant costs/asset retirement obligationsOver plant lives48,088 46,684 48,352 
Manufactured gas plant site remediation-28,042 27,212 28,411 
Taxes recoverable from customersOver plant lives12,101 12,220 12,250 
Covid-19 deferred costs
Up to 2 years
3,590 3,886 3,761 
Long-term debt refinancing costs
Up to 37 years
1,500 1,718 1,799 
Other
Up to 13 years
8,345 4,985 4,095 
295,865 309,302 297,218 
Total regulatory assets$488,659 $451,046 $476,797 
Estimated
Recovery or Refund
Period as of
June 30, 2026
*June 30, 2026June 30, 2025December 31, 2025
(In thousands)
Regulatory liabilities:
Current:
Environmental compliance programs
Up to 1 year
$100,186 $72,520 $89,306 
Natural gas costs refundable through rate adjustments
Up to 1 year
34,598 44,377 47,130 
Electric fuel and purchased power deferral
Up to 1 year
10,465 934 — 
Margin sharing
Up to 1 year
4,065 3,410 3,946 
Taxes refundable to customers
Up to 1 year
2,313 2,197 2,301 
Provision for rate refund
Up to 1 year
1,353 4,254 1,780 
Conservation programs
Up to 1 year
851 1,996 733 
Other
Up to 1 year
3,120 4,566 3,388 
156,951 134,254 148,584 
Noncurrent:
Plant removal and decommissioning costsOver plant lives230,673 225,142 224,313 
Taxes refundable to customersOver plant lives171,179 180,212 176,665 
Cost recovery mechanisms
Up to 16 years
46,098 35,794 41,323 
Accumulated deferred investment tax creditOver plant lives22,831 19,814 22,663 
Pension and postretirement benefits**4,776 4,862 4,776 
Other
Up to 12 years
2,848 2,344 2,589 
478,405 468,168 472,329 
Total regulatory liabilities$635,356 $602,422 $620,913 
Net regulatory position$(146,697)$(151,376)$(144,116)
*Estimated recovery or refund period for amounts currently being recovered or refunded in rates to customers.
**Recovered as expense is incurred or cash contributions are made.
Schedule of Regulatory Proceedings
The following tables summarize the Company's significant regulatory proceedings and cases by jurisdiction:
SegmentStateFiling DateAnnual Revenue Increase (%) *
Annual Revenue Increase
(In millions) *
ROE*StatusKey Drivers and Additional Information
General Rate Cases Pending
ElectricMontanaSeptember 30, 202515.0 %$10.0 9.65 %
•Settlement filed
•Interim rate increase of $10.4M or 16.2% effective April 1, 2026
•Investments, including Badger Wind Farm
•Corresponding depreciation on those investments
•Increased operation and maintenance expense
Natural Gas DistributionOregonNovember 25, 202511.8 %$12.2 9.50 %
•Settlement filed
•Requested rates to be effective October 31, 2026
•Rate base growth
•Growth in operations and maintenance expense
•Growth in depreciation expense associated with new investments in rate base
Natural Gas DistributionWashingtonMay 29, 2026
Rate Year 1

4.9%
Rate Year 2

3.4%
Rate Year 1

$25.1
Rate Year 2

$18.1
10.50 %
•Pending
•Multi-year rate case
•Infrastructure investments necessary to provide safe and reliable service
•Higher operating costs and depreciation tied to system improvements
Pipeline
FERC
May 29, 202613.5 %$31.0 14.59 %
•Pending
•Rates to be effective December 1, 2026
•Increase in proposed depreciation rates represent 30% of the annual revenue increase
ElectricNorth DakotaJune 30, 202614.5 %$34.5 10.80 %
•Pending
•Requested interim rate increase of $26.3M or 11.0% effective September 1, 2026
•Increase in operations and maintenance expense
•Investments made across the system since the last filing
•Higher depreciation expense related to infrastructure investments
General Rate Cases Finalized
Natural Gas DistributionWashingtonMarch 29, 2024
Rate Year 1

7.9%



Rate Year 2

2.6%
Rate Year 1

$29.8



Rate Year 2

$10.8
9.50 %
Approved February 24, 2025
Final rates effective March 5, 2025
$3.7M revenue reduction effective June 1, 2025**

Final rates effective March 1, 2026
Filed for a $2.1M revenue reduction effective June 1, 2026**
•Multi-year rate case
•Infrastructure investments necessary to provide safe and reliable service
•Higher operating costs due to inflation
•$3.7M revenue reduction was driven by forecasted plant that was not placed in service by December 31, 2024
•$2.1M revenue reduction was driven by forecasted plant that was not placed in service by December 31, 2025
ElectricWyomingJune 30, 202518.6 %$5.8 9.70 %
Approved
Final rates effective April 1, 2026
•Increases in operation and maintenance expense
•Investments made since the last rate case
•Corresponding depreciation on those infrastructure investments
•Withdrew the requested Reliability and Safety Rider
*Annual revenue increase, percent increase and ROE for general rate cases pending and general rate cases finalized, reflects the final approved amount or the amount reflected in the most recent settlement agreement, if applicable.
**Reflects a reduction to revenues resulting from a provisional plant review. The adjustment applies retroactively to the original rate effective date. As a result, the Company is required to refund customers for amounts over collected during the retroactive period.
SegmentStateFiling Date
Annual Revenue Increase
(In millions)
StatusKey Drivers and Additional Information
Other Filings
Natural Gas DistributionWyomingAugust 15, 2025N/ARequest denied May 19, 2026
System Safety and Integrity Rider
•Would allow Montana-Dakota to recover costs and expenses associated with a pipeline replacement program
ElectricMontanaSeptember 30, 2025N/AWithdrawn as part of rate case settlement agreement
Systems Management Cost Adjustment Mechanism
•Recovery of transmission and wildfire related costs
ElectricSouth DakotaOctober 31, 2025$1.1 Approved
Rates effective July 1, 2026
Infrastructure Rider
•Allows annual adjustments for recent projected capital costs and related expenses for projects determined to be recoverable
•Update includes Badger Wind Farm