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Income Taxes (Tables)
 12 Months Ended
Dec. 31, 2025
Income Tax Disclosure [Abstract]  
Summary of Statute of Limitations Applicable to Open Tax Years
Tax YearExpiration
2022September 2026
Tax Benefits Associated with NOL and Tax Credit Carryforwards
Unrecognized tax benefits were reduced by tax benefits associated with tax credit carryforwards:
(Millions of Dollars)Dec. 31, 2025Dec. 31, 2024
Tax credit carryforwards$(4)$(4)
Interest Payable related to Unrecognized Tax Benefits
Interest payable related to unrecognized tax benefits:
(Millions of Dollars)202520242023
Payable for interest related to unrecognized tax benefits at Jan. 1$— $— $— 
Interest expense related to unrecognized tax benefits(1)— — 
Payable for interest related to unrecognized tax benefits at Dec. 31$(1)$— $— 
NOL and Tax Credit Carryforwards NOL amounts represent the tax loss that is carried forward and tax credits represent the deferred tax asset. NOL and tax credit carryforwards as of Dec. 31 were as follows:
(Millions of Dollars)20252024
Federal tax credit carryforwards$295 $292 
State NOL carryforwards1 2 
Schedule of Effective Income Tax Rate Reconciliation
Total income tax expense from operations differs from the amount computed by applying the statutory federal income tax rate to income before income tax expense.
Effective income tax reconciliation for years ended Dec. 31:
(Millions of Dollars)202520242023
Income before income taxes (domestic)$355 $337 $339 
Federal statutory rate impact75 71 71 
(Decreases) increases in tax from:
Tax credits
PTCs (a)
(115)(115)(114)
Other(1)(1)(2)
Regulatory adjustments (b)
Plant related excess deferred taxes(14)(14)(12)
AFUDC equity(7)(4)(1)
Adjustments to tax reform implementation10 — — 
Other3 1 2 
State income taxes, net of federal tax effect (c)
11 5 9 
Other(2)— 2 
Income tax benefit$(40)$(57)$(45)
202520242023
Federal statutory rate21.0 %21.0 %21.0 %
(Decreases) increases in tax from:
Tax credits
PTCs (a)
(32.6)(34.3)(33.5)
Other(0.3)(0.4)(0.5)
Regulatory adjustments (b)
Plant related excess deferred taxes(3.9)(4.2)(3.4)
AFUDC equity(1.8)(1.0)(0.4)
Adjustments to tax reform implementation2.7 — — 
Other0.8 0.4 0.7 
State income taxes, net of federal tax effect (c)
3.2 1.5 2.6 
Other(0.4)0.1 0.2 
Effective income tax rate(11.3)%(16.9)%(13.3)%
(a)Wind PTCs (net of transfer discounts) are generally credited to customers (reduction to revenue) and do not materially impact earnings.
(b)Regulatory adjustments primarily relate to the credit of plant related excess deferred taxes to customers for tax rate increases as well as the capitalization of AFUDC equity for book purposes only. Income tax benefits associated with the credit of excess deferred taxes are offset by corresponding revenue reductions.
(c)State and local income taxes are primarily made up of the following jurisdictions: Texas
Schedule of Components of Income Tax Expense (Benefit)
Components of income tax expense for years ended Dec. 31:
(Millions of Dollars)202520242023
Current federal tax expense$30 $42 $76 
Current state tax expense9 4 12 
Current change in unrecognized tax expense2 — — 
Deferred federal tax benefit(86)(105)(132)
Deferred state tax expense (benefit)5 2 (1)
Deferred change in unrecognized tax expense— — — 
Total income tax benefit$(40)$(57)$(45)
Components of deferred income tax expense as of Dec. 31:
(Millions of Dollars)202520242023
Deferred tax expense (benefit) excluding items below
$48 $143 $(117)
Adjustments to deferred income taxes for tax credit cash transfers(114)(226)— 
Amortization and adjustments to deferred income taxes on income tax regulatory assets and liabilities(14)(19)(16)
Tax expense allocated to other comprehensive income and other(1)(1)— 
Deferred tax expense (benefit)$(81)$(103)$(133)
Schedule of Deferred Tax Assets and Liabilities
Components of the net deferred tax liability as of Dec. 31:
(Millions of Dollars)20252024
Deferred tax liabilities:
Differences between book and tax bases of property$1,139 $1,089 
Operating lease assets76 83 
Regulatory assets38 53 
Pension expense33 33 
Other2 2 
Total deferred tax liabilities$1,288 $1,260 
Deferred tax assets:
Tax credit carryforward$295 $292 
Regulatory liabilities81 90 
Operating lease liabilities76 83 
Other employee benefits6 5 
Deferred fuel costs3 10 
Other14 15 
Total deferred tax assets475 495 
Net deferred tax liability$813 $765 
Cash received (paid) for income taxes for the years ended Dec. 31:
(Millions of Dollars)202520242023
Cash received (paid) for income taxes: federal, net (a)
$102 $164 $(69)
Cash received (paid) for income taxes: state
New Mexico— (3)(10)
Other(2)(2)(1)
Total$100 $159 $(80)
(a)Includes proceeds from tax credit transfers.
State Summary of Statute of Limitations Applicable to Open Tax Years SPS is a member of the Xcel Energy affiliated group that files consolidated state tax returns based on income in its major operating jurisdictions and various other state income-based tax returns. As of Dec. 31, 2025, SPS’ earliest open tax years (subject to examination by state taxing authorities in its major operating jurisdictions) were as follows:
StateTax Year(s)Expiration
Texas2020June 2028
Texas2021June 2029
Texas2022August 2027
Texas2023November 2028
Schedule of Unrecognized Tax Benefits Roll Forward
Unrecognized tax benefits — permanent vs temporary:
(Millions of Dollars)Dec. 31, 2025Dec. 31, 2024
Unrecognized tax benefit — Permanent tax positions$7 $5 
Unrecognized tax benefit — Temporary tax positions— — 
Total unrecognized tax benefit$7 $5 
Changes in unrecognized tax benefits:
(Millions of Dollars)202520242023
Balance at Jan. 1$5 $5 $9 
Additions based on tax positions related to the current year— 1 1 
Additions for tax positions of prior years2 — — 
Reductions for tax positions of prior years— (1)(5)
Balance at Dec. 31$7 $5 $5