Income Taxes (Tables)

3 Months Ended

Mar. 31, 2020

Income Tax Disclosure [Abstract]

Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]

The following table reconciles the difference between the statutory rate and the ETR:

	Three Months Ended March 31,
	2020		2019
Federal statutory rate	21.0	%	21.0	%
State tax (net of federal tax effect)	2.3		2.1
Decreases in tax from:
Wind PTCs	(35.7	)	—
Plant regulatory differences (a)	(6.1	)	(4.6	)
Other tax credits, net of NOL & tax credit allowances	(0.7	)	(0.6	)
Other (net)	(0.7	)	(0.7	)
Effective income tax rate	(19.9	)%	17.2	%

^(a)

Regulatory differences for income tax primarily relate to the credit of excess deferred taxes to customers through the average rate assumption method. Income tax benefits associated with the credit of excess deferred credits are offset by corresponding revenue reductions.

Summary of Statute of Limitations Applicable to Open Tax Years [Table Text Block]

Federal Audits — SPS is a member of the Xcel Energy affiliated group that files a consolidated federal income tax return. Statute of limitations applicable to Xcel Energy’s federal income tax returns expire as follows:

Tax Years	Expiration
2009 - 2013	September 2020
2014 - 2016	June 2021

Reconciliation of Unrecognized Tax Benefits

Unrecognized tax benefits — permanent vs temporary:

(Millions of Dollars)	March 31, 2020		Dec. 31, 2019
Unrecognized tax benefit — Permanent tax positions	$	3.8	$	3.7
Unrecognized tax benefit — Temporary tax positions	1.5		1.5
Total unrecognized tax benefit	$	5.3	$	5.2

Tax Benefits Associated with NOL and Tax Credit Carryforwards

Unrecognized tax benefits were reduced by tax benefits associated with NOL and tax credit carryforwards:

(Millions of Dollars)	March 31, 2020			Dec. 31, 2019
NOL and tax credit carryforwards	$	(4.6	)	$	(4.4	)