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Regulatory Assets and Liabilities (Tables) | 12 Months Ended
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Dec. 31, 2023
Regulatory Assets and Liabilities Disclosure [Abstract] |
Regulatory Assets | Components of regulatory assets:
(Millions of Dollars) |  | See Note(s) |  | Remaining Amortization Period |  | Dec. 31, 2023 |  | Dec. 31, 2022 (a)
Regulatory Assets |  |  |  |  |  | Current |  | Noncurrent |  | Current |  | Noncurrent
Pension and retiree medical obligations |  | 11 |  | Various |  | $ | 27 |  |  | $ | 1,106 |  |  | $ | 22 |  |  | $ | 1,069 |
Recoverable deferred taxes on AFUDC |  |  |  | Plant lives |  | — |  |  | 332 |  |  | — |  |  | 292 |
Net AROs (b) |  | 1, 12 |  | Various |  | — |  |  | 316 |  |  | — |  |  | 339 |
Excess deferred taxes — TCJA |  | 7 |  | Various |  | 10 |  |  | 198 |  |  | 13 |  |  | 205 |
Depreciation differences |  |  |  | One to 12 years |  | 17 |  |  | 189 |  |  | 17 |  |  | 193 |
Environmental remediation costs |  | 1, 12 |  | Various |  | 15 |  |  | 94 |  |  | 20 |  |  | 92 |
Deferred natural gas, electric, steam energy/fuel costs |  |  |  | One to three years |  | 239 |  |  | 80 |  |  | 581 |  |  | 299 |
Conservation programs (c) |  | 1 |  | One to two years |  | 19 |  |  | 54 |  |  | 16 |  |  | 36 |
Purchased power contract costs |  |  |  | Term of related contract |  | 4 |  |  | 40 |  |  | 10 |  |  | 36 |
PI extended power uprate |  |  |  | 11 years |  | 4 |  |  | 38 |  |  | 4 |  |  | 42 |
Benson biomass PPA termination and asset purchase |  |  |  | Five years |  | 10 |  |  | 36 |  |  | 10 |  |  | 45 |
Sales true-up and revenue decoupling |  |  |  | One to two years |  | 7 |  |  | 33 |  |  | 54 |  |  | — |
State commission adjustments |  |  |  | Plant lives |  | 1 |  |  | 32 |  |  | 1 |  |  | 33 |
Losses on reacquired debt |  |  |  | Term of related debt |  | 2 |  |  | 30 |  |  | 3 |  |  | 32 |
MISO capacity revenue tracker |  |  |  | One to two years |  | 36 |  |  | 26 |  |  | — |  |  | — |
Gas pipeline inspection and remediation costs |  |  |  | One to two years |  | 40 |  |  | 25 |  |  | 42 |  |  | 13 |
Contract valuation adjustments (d) |  | 1, 10 |  | Term of related contract |  | 18 |  |  | 22 |  |  | 28 |  |  | 28 |
Nuclear refueling outage costs |  | 1 |  | One to two years |  | 43 |  |  | 19 |  |  | 30 |  |  | 12 |
Grid modernization costs |  |  |  | One to two years |  | 16 |  |  | 17 |  |  | 14 |  |  | 24 |
Renewable resources and environmental initiatives |  |  |  | One to two years |  | 38 |  |  | 5 |  |  | 50 |  |  | 6 |
Other |  |  |  | Various |  | 65 |  |  | 106 |  |  | 144 |  |  | 75 |
Total regulatory assets |  |  |  |  |  | $ | 611 |  |  | $ | 2,798 |  |  | $ | 1,059 |  |  | $ | 2,871 |
(a)Prior period amounts have been reclassified to conform with current year presentation. (b)The 2022 amount is net of the nuclear decommissioning accruals and gains from decommissioning investments. In 2023, the nuclear decommissioning accruals and gains from decommissioning investments exceeded the expected cost of AROs in NSP-Minnesota and was reclassified to a regulatory liability. (c)Includes costs for conservation programs, as well as incentives allowed in certain jurisdictions. (d)Includes the fair value of certain long-term PPAs used to meet energy capacity requirements and valuation adjustments on natural gas commodity purchases.
Regulatory Liabilities | Components of regulatory liabilities:
(Millions of Dollars) |  | See Note(s) |  | Remaining Amortization Period |  | Dec. 31, 2023 |  | Dec. 31, 2022
Regulatory Liabilities |  |  |  |  |  | Current |  | Noncurrent |  | Current |  | Noncurrent
Deferred income tax adjustments and TCJA refunds (a) |  | 7 |  | Various |  | $ | 7 |  |  | $ | 3,015 |  |  | $ | 9 |  |  | $ | 3,110 |
Plant removal costs |  | 1, 12 |  | Various |  | — |  |  | 1,984 |  |  | — |  |  | 1,819 |
Effects of regulation on employee benefit costs (b) |  |  |  | Various |  | — |  |  | 253 |  |  | — |  |  | 247 |
Renewable resources and environmental initiatives |  |  |  | Various |  | 9 |  |  | 188 |  |  | 6 |  |  | 173 |
Net AROs (c) |  |  |  | Various |  | — |  |  | 90 |  |  | — |  |  | — |
Sales true-up and revenue decoupling |  |  |  | Two years |  | 18 |  |  | 76 |  |  | — |  |  | 77 |
ITC deferrals |  | 1 |  | Various |  | 1 |  |  | 60 |  |  | 1 |  |  | 61 |
LP&L departure payment |  |  |  | Up to 10 years |  | 33 |  |  | 33 |  |  | — |  |  | — |
Formula rates |  |  |  | One to two years |  | 29 |  |  | 18 |  |  | 32 |  |  | 17 |
DOE settlement |  |  |  | One to two years |  | 18 |  |  | 6 |  |  | 12 |  |  | 3 |
Deferred natural gas, electric, steam energy/fuel costs |  |  |  | Less than one year |  | 220 |  |  | — |  |  | 39 |  |  | — |
Contract valuation adjustments (d) |  | 1, 10 |  | Less than one year |  | 56 |  |  | — |  |  | 175 |  |  | 1 |
Conservation programs (e) |  | 1 |  | Less than one year |  | 47 |  |  | — |  |  | 72 |  |  | — |
Other |  |  |  | Various |  | 90 |  |  | 104 |  |  | 72 |  |  | 61 |
Total regulatory liabilities (f) |  |  |  |  |  | $ | 528 |  |  | $ | 5,827 |  |  | $ | 418 |  |  | $ | 5,569 |
(a)Includes the revaluation of recoverable/regulated plant accumulated deferred income taxes and revaluation impact of non-plant accumulated deferred income taxes due to the TCJA. (b)Includes regulatory amortization and certain 2018 TCJA benefits approved by the CPUC to offset the PSCo prepaid pension asset. (c)Includes amounts recorded for future recovery of AROs, less amounts recovered through nuclear decommissioning accruals and gains from decommissioning investments. (d)Includes the fair value of FTR instruments utilized/intended to offset the impacts of transmission system congestion. (e)Includes costs for conservation programs, as well as incentives allowed in certain jurisdictions. (f)Revenue subject to refund of $187 million and $67 million for 2023 and 2022, respectively, is included in other current liabilities.

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