Related Party Transactions

12 Months Ended

Dec. 31, 2017

Xcel Energy Services Inc. provides management, administrative and other services for the subsidiaries of Xcel Energy Inc., including NSP-Wisconsin. The services are provided and billed to each subsidiary in accordance with service agreements executed by each subsidiary. NSP-Wisconsin uses services provided by Xcel Energy Services Inc. whenever possible. Costs are charged directly to the subsidiary and are allocated if they cannot be directly assigned.

The electric production and transmission costs of the entire NSP System are shared by NSP-Minnesota and NSP-Wisconsin. The Interchange Agreement provides for the sharing of all costs of generation and transmission facilities of the system, including capital costs.

The table below contains significant affiliate transactions among the companies and related parties including billings under the Interchange Agreement for the years ended Dec. 31:



(Thousands of Dollars)	2017		2016		2015
Operating revenues:
Electric	$	177,234	$	170,483	$	163,255
Operating expenses:
Purchased power	421,609		413,615		419,028
Transmission expense	68,613		61,920		54,070
Natural gas purchased for resale	47		41		45
Other operating expenses — paid to Xcel Energy Services Inc.	92,715		106,454		93,890
Interest expense	7		4		2

Accounts receivable and payable with affiliates at Dec. 31 were:



	2017				2016
(Thousands of Dollars)	Accounts Receivable		Accounts Payable		Accounts Receivable		Accounts Payable
NSP-Minnesota	$	—	$	17,825	$	—	$	18,567
PSCo	—		61		—		974
SPS	—		7		333		—
Other subsidiaries of Xcel Energy Inc.	3,391		11,735		—		9,496
	$	3,391	$	29,628	$	333	$	29,037