v3.26.1
Environmental Matters (Tables)
 6 Months Ended
Jun. 30, 2026
Environmental Remediation Obligations [Abstract]  
Schedule of Environmental Loss Contingencies by Site
The following table summarizes information regarding liabilities related to environmental sites, which are recorded in other current liabilities and other noncurrent liabilities in NW Natural's balance sheet:
Current LiabilitiesNon-Current Liabilities
June 30,December 31,June 30,December 31,
In thousands202620252025202620252025
Portland Harbor site:
Gasco Sediments$10,982 $10,034 $13,950 $42,286 $43,776 $43,247 
Other Portland Harbor3,211 3,327 3,669 11,493 11,043 12,770 
Gasco Upland site18,748 18,390 25,643 274,547 62,666 61,782 
Front Street site510 831 486 294 279 292 
Oregon Steel Mills— — — 179 179 179 
Total$33,451 $32,582 $43,748 $328,799 $117,943 $118,270 
Schedule of Regulatory Assets
Amounts deferred as regulatory assets and liabilities for NW Holdings and NW Natural were as follows:
Regulatory Assets
June 30,December 31,
In thousands202620252025
Current:
NW Natural:
Unrealized loss on derivatives(1)
$36,508 $25,977 $63,578 
Gas costs19,240 5,973 6,284 
Environmental costs(2)
12,690 11,447 12,148 
Decoupling(3)
42,164 9,313 11,631 
Pension balancing(4)
7,131 7,131 7,131 
Income taxes2,208 2,208 2,208 
Washington Climate Commitment Act compliance7,754 7,874 7,482 
Security and systems improvements1,270 2,018 1,771 
Industrial demand side management(5)
12,181 13,612 10,539 
Weather Adjusted Rate Mechanism15,099 8,708 9,932 
Other(6)
11,197 8,929 10,431 
Total current - NW Natural167,442 103,190 143,135 
SiEnergy331 699 410 
NWN Water319 25 200 
Total current - NW Holdings$168,092 $103,914 $143,745 
Non-current:
NW Natural:
Unrealized loss on derivatives(1)
$17,541 $7,908 $14,039 
Pension balancing(4)
12,004 18,169 15,647 
Income taxes9,289 8,993 9,148 
Pension and other postretirement benefit liabilities91,539 106,705 96,008 
Environmental costs(2)
386,293 160,120 180,063 
Gas costs4,983 1,360 9,434 
Decoupling(3)
11,069 1,534 8,891 
Washington Climate Commitment Act compliance48,228 32,851 33,085 
Security and systems improvements8,085 8,369 8,234 
Industrial demand side management(5)
2,604 1,906 9,334 
Weather Adjusted Rate Mechanism3,424 1,332 6,062 
Other(6)
38,129 21,289 29,902 
Total non-current - NW Natural633,188 370,536 419,847 
SiEnergy HB 4384 depreciation deferral(7)
4,675 — 2,095 
SiEnergy other1,636 995 1,412 
NWN Water1,157 1,137 840 
Total non-current - NW Holdings$640,656 $372,668 $424,194 
(1)Unrealized gains or losses on derivatives are non-cash items and therefore do not earn a rate of return or a carrying charge. These amounts are recoverable through NW Natural rates as part of the annual Purchased Gas Adjustment (PGA) mechanism when realized at settlement.
(2)Refer to the Environmental Cost Deferral and Recovery table in Note 17 for a description of environmental costs.
(3)This deferral represents the margin adjustment resulting from differences between actual and expected volumes. 
(4)Balance represents deferred net periodic benefit costs as approved by the OPUC.
(5)Energy efficiency program for industrial sales customers in Oregon to provide assistance with reducing their gas usage.
(6)Balances consist of deferrals and amortizations under approved regulatory mechanisms and typically earn a rate of return or carrying charge.
(7)HB 4384 became effective on June 20, 2025. The Company began deferring depreciation costs on July 1, 2025.
The following table presents information regarding the total regulatory asset deferred:
June 30,December 31,
In thousands202620252025
Deferred costs and interest (1)
$79,609 $69,335 $71,954 
Accrued site liabilities (2)
362,225 150,488 161,993 
Insurance proceeds and interest(42,851)(48,257)(41,736)
Total regulatory asset deferral(1)
$398,983 $171,566 $192,211 
Current regulatory assets(3)
$12,690 $11,447 $12,148 
Long-term regulatory assets(3)
386,293 160,120 180,063 
(1)    Includes pre-review and post-review deferred costs, amounts currently in amortization, and interest, net of amounts collected from customers.
(2)    Excludes 3.3% of the Front Street site liability as the OPUC only allows recovery of 96.7% of costs for those sites allocable to Oregon, including those that historically served only Oregon customers. Amounts excluded from regulatory assets were immaterial at June 30, 2026, June 30, 2025, and December 31, 2025.
(3)    Environmental costs relate to specific sites approved for regulatory deferral by the OPUC and WUTC. In Oregon, NW Natural earns a carrying charge on cash amounts paid, whereas amounts accrued but not yet paid do not earn a carrying charge until expended. It also accrues a carrying charge on insurance proceeds for amounts owed to customers. In Washington, neither the cash paid for insurance proceeds received accrue a carrying charge. Current environmental costs represent remediation costs management expects to collect from customers in the next 12 months. Amounts included in this estimate are still subject to a prudence and earnings test review by the OPUC and do not include the $5 million tariff rider. The amounts allocable to Oregon are recoverable through NW Natural rates, subject to an earnings test.