Investment in Transmission Affiliates (Tables)

12 Months Ended

Dec. 31, 2024

Equity Method Investments and Joint Ventures [Abstract]

Schedule of changes to our investments in ATC and ATC Holdco

The following tables provide a reconciliation of the changes in our investments in ATC and ATC Holdco:

	2024
(in millions)	ATC		ATC Holdco		Total
Balance at January 1	$	1,980.8	$	25.1	$	2,005.9
Add: Earnings from equity method investment	205.4		2.1		207.5
Add: Capital contributions	45.5		—		45.5
Less: Distributions	146.7		3.4		150.1
Add: Other	0.1		—		0.1
Balance at December 31	$	2,085.1	$	23.8	$	2,108.9

	2023
(in millions)	ATC		ATC Holdco		Total
Balance at January 1	$	1,884.6	$	24.6	$	1,909.2
Add: Earnings from equity method investment	175.1		2.4		177.5
Add: Capital contributions	63.7		—		63.7
Less: Distributions	142.6		1.9		144.5
Balance at December 31	$	1,980.8	$	25.1	$	2,005.9

	2022
(in millions)	ATC		ATC Holdco		Total
Balance at January 1	$	1,766.9	$	22.5	$	1,789.4
Add: Earnings from equity method investment	192.6		2.1		194.7
Add: Capital contributions	45.5		—		45.5
Less: Distributions	120.4		—		120.4
Balance at December 31	$	1,884.6	$	24.6	$	1,909.2

Schedule of significant related party transactions with ATC

The following table summarizes our significant related party transactions with ATC during the years ended December 31:

(in millions)	2024		2023		2022
Charges to ATC for services and construction	$	21.6	$	17.4	$	18.9
Charges from ATC for network transmission services	413.3		377.5		363.7
Net payment to ATC related to FERC ROE orders	—		—		(0.1)

Schedule of receivables and payables with ATC

As of December 31, 2024 and 2023, our balance sheets included the following receivables and payables for services provided to or received from ATC:

(in millions)	2024		2023
Accounts receivable for services provided to ATC	$	1.4	$	1.6
Accounts payable for services received from ATC	34.4		49.9
Amounts due from ATC for transmission infrastructure upgrades (1)	54.5		46.1

(1)    The transmission infrastructure upgrades were primarily related to the construction of WE's, WPS's, and UMERC's renewable energy projects.

Schedule of summarized income statement data for ATC

Summarized financial data for ATC is included in the tables below:

	Year Ended December 31
(in millions)	2024		2023		2022
Income statement data
Operating revenues	$	911.3	$	818.9	$	751.2
Operating expenses	442.4		407.6		381.5
Other expense, net	137.7		131.7		123.0
Net income	$	331.2	$	279.6	$	246.7

Schedule of summarized balance sheet data for ATC

(in millions)	December 31, 2024		December 31, 2023
Balance sheet data
Current assets	$	126.6	$	115.2
Noncurrent assets	6,792.6		6,337.0
Total assets	$	6,919.2	$	6,452.2
Current liabilities	$	482.4	$	495.9
Long-term debt	3,083.4		2,736.0
Other noncurrent liabilities	545.0		585.2
Members' equity	2,808.4		2,635.1
Total liabilities and members' equity	$	6,919.2	$	6,452.2