Income Taxes (Tables)

9 Months Ended

Sep. 30, 2019

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:

	Nine Months Ended Sept. 30,
	2019		2018
Federal statutory rate	21.0	%	21.0	%
State tax (net of federal tax effect)	2.2		2.3
Decreases in tax from:
Plant regulatory differences (a)	(4.7	)	(3.8	)
Wind PTCs	(3.9	)	—
Other tax credits and tax credit and NOL allowances (net)	(0.6	)	(0.7	)
Prior period adjustments	(0.5	)	(1.8	)
Other (net)	(0.5	)	—
Effective income tax rate	13.0	%	17.0	%

^(a)

Regulatory differences for income tax primarily relate to the credit of excess deferred taxes to customers through the average rate assumption method and the timing of regulatory decisions regarding the return of excess deferred taxes. 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 Year(s)	Expiration
2009 - 2013	June 2020
2014 - 2016	September 2020

Reconciliation of Unrecognized Tax Benefits

Unrecognized tax benefits — permanent vs temporary:

(Millions of Dollars)	Sept. 30, 2019		Dec. 31, 2018
Unrecognized tax benefit — Permanent tax positions	$	3.5	$	3.0
Unrecognized tax benefit — Temporary tax positions	1.5		1.5
Total unrecognized tax benefit	$	5.0	$	4.5

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)	Sept. 30, 2019			Dec. 31, 2018
NOL and tax credit carryforwards	$	(4.4	)	$	(3.8	)