MGE Energy (MGEE) 10-Q 6 Nov 24 2024 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2024	Oct. 30, 2024
Document And Entity Information [Line Items]
Entity Registrant Name	MGE Energy, Inc.
Entity Central Index Key	0001161728
Document Type	10-Q
Document Period End Date	Sep. 30, 2024
Amendment Flag	false
Trading Symbol	MGEE
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		36,207,529
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Shell Company	false
Security Exchange Name	NASDAQ
Security 12(b) Title	Common Stock, $1 Par Value Per Share
Entity Tax Identification Number	39-2040501
Securities Act File Number	000-49965
Entity Incorporation, State or Country Code	WI
Entity Address, Address Line One	133 South Blair Street
Entity Address, City or Town	Madison
Entity Address, State or Province	WI
Entity Address, Postal Zip Code	53788
City Area Code	608
Local Phone Number	252-7000
Document Transition Report	false
Entity Interactive Data Current	Yes
Document Quarterly Report	true
MGE [Member]
Document And Entity Information [Line Items]
Entity Registrant Name	Madison Gas and Electric Company
Entity Central Index Key	0000061339
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		17,347,894
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Shell Company	false
Entity Tax Identification Number	39-0444025
Securities Act File Number	000-1125
Entity Incorporation, State or Country Code	WI
Entity Address, Address Line One	133 South Blair Street
Entity Address, City or Town	Madison
Entity Address, State or Province	WI
Entity Address, Postal Zip Code	53788
City Area Code	608
Local Phone Number	252-7000
Document Transition Report	false
Entity Interactive Data Current	Yes
Document Quarterly Report	true

Consolidated Statements of Inco

Consolidated Statements of Income (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Operating Revenues:
Electric revenues	$ 148,004	$ 139,104	$ 384,768	$ 378,102
Gas revenue	20,476	21,424	120,761	147,677
Total Operating Revenues	168,480	160,528	505,529	525,779
Operating Expenses:
Fuel for electric generation	17,252	19,712	41,193	47,118
Purchased power	8,127	7,021	26,419	28,252
Cost of gas sold	4,628	5,160	52,798	80,296
Other operations and maintenance	57,129	53,997	167,833	156,004
Depreciation and amortization	27,104	25,241	80,636	74,971
Other general taxes	6,100	5,605	18,030	16,922
Total Operating Expenses	120,340	116,736	386,909	403,563
Operating Income	48,140	43,792	118,620	122,216
Other income, net	4,839	10,549	12,576	20,841
Interest expense, net	(8,396)	(7,654)	(24,725)	(22,901)
Income before income taxes	44,583	46,687	106,471	120,156
Income tax provision	(3,644)	(8,830)	(7,924)	(22,540)
Net Income Including Noncontrolling Interest	40,939	37,857	98,547	97,616
Net Income	$ 40,939	$ 37,857	$ 98,547	$ 97,616
Earnings per share of Common Stock - Basic	$ 1.13	$ 1.05	$ 2.72	$ 2.7
Earnings per share of Common Stock - Diluted	1.13	1.05	2.72	2.7
Dividends per share of common stock	$ 0.45	$ 0.428	$ 1.305	$ 1.243
Weighted Average Shares Outstanding - Basic	36,181	36,163	36,176	36,163
Weighted Average Shares Outstanding - Diluted	36,211	36,189	36,202	36,185
MGE [Member]
Operating Revenues:
Electric revenues	$ 148,004	$ 139,104	$ 384,768	$ 378,102
Gas revenue	20,476	21,424	120,761	147,677
Total Operating Revenues	168,480	160,528	505,529	525,779
Operating Expenses:
Fuel for electric generation	17,252	19,712	41,193	47,118
Purchased power	8,127	7,021	26,419	28,252
Cost of gas sold	4,628	5,160	52,798	80,296
Other operations and maintenance	56,937	53,847	167,098	155,251
Depreciation and amortization	27,104	25,241	80,636	74,971
Other general taxes	6,100	5,605	18,030	16,922
Total Operating Expenses	120,148	116,586	386,174	402,810
Operating Income	48,332	43,942	119,355	122,969
Other income, net	2,025	7,824	4,267	13,985
Interest expense, net	(8,527)	(7,721)	(25,036)	(23,056)
Income before income taxes	41,830	44,045	98,586	113,898
Income tax provision	(2,720)	(8,093)	(5,522)	(20,696)
Net Income Including Noncontrolling Interest	39,110	35,952	93,064	93,202
Less Net Income Attributable to Noncontrolling Interest, net of tax	(5,777)	(5,487)	(17,140)	(16,382)
Net Income	$ 33,333	$ 30,465	$ 75,924	$ 76,820

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Operating Activities:
Net Income	$ 98,547	$ 97,616
Items not affecting cash:
Depreciation and amortization	80,636	74,971
Deferred income taxes	170	16,326
Provision for doubtful receivables	6,600	1,323
Employee benefit plan cost (credit)	424	(2,976)
Equity earnings in investments	(8,427)	(7,930)
Other items	1,247	(2,502)
Changes in working capital items:
Current assets	27,544	33,976
Accounts payable	(11,699)	(16,586)
Deferred income taxes	7,146	0
Other current liabilities	2,120	(3,714)
Dividends from investments	6,414	6,305
Cash contributions to pension and other postretirement plans	(5,511)	(5,290)
Other noncurrent items, net	4,625	2,519
Cash Provided by Operating Activities	209,836	194,038
Investing Activities:
Capital expenditures	(164,064)	(150,298)
Capital contributions to investments	(4,348)	(5,986)
Other	801	(206)
Cash Used for Investing Activities	(167,611)	(156,490)
Financing Activities:
Issuance of common stock, net	2,591	0
Cash dividends paid on common stock	(47,210)	(44,933)
Repayments of long-term debt	(3,847)	(53,048)
Issuance of long-term debt	0	109,300
Proceeds from (repayments of) short-term debt	10,500	(48,500)
Other	(879)	(2,128)
Cash Used for Financing Activities	(38,845)	(39,309)
Change in cash, cash equivalents, and restricted cash	3,380	(1,761)
Cash, cash equivalents, and restricted cash at beginning of period	15,026	17,968
Cash, cash equivalents, and restricted cash at end of period	18,406	16,207
Significant noncash investing activities:
Accrued capital expenditures	9,194	17,716
MGE [Member]
Operating Activities:
Net Income	93,064	93,202
Items not affecting cash:
Depreciation and amortization	80,636	74,971
Deferred income taxes	387	15,218
Provision for doubtful receivables	6,600	1,323
Employee benefit plan cost (credit)	424	(2,976)
Other items	1,911	(2,604)
Changes in working capital items:
Current assets	27,668	33,076
Accounts payable	(11,697)	(16,583)
Deferred income taxes	7,146	0
Other current liabilities	2,904	(1,809)
Cash contributions to pension and other postretirement plans	(5,511)	(5,290)
Other noncurrent items, net	3,171	1,840
Cash Provided by Operating Activities	206,703	190,368
Investing Activities:
Capital expenditures	(164,064)	(150,298)
Other	(1,447)	(1,338)
Cash Used for Investing Activities	(165,511)	(151,636)
Financing Activities:
Cash dividends paid to parent by MGE	(31,000)	(30,000)
Distributions to parent from noncontrolling interest	(16,000)	(17,250)
Repayments of long-term debt	(3,847)	(53,048)
Issuance of long-term debt	0	109,300
Proceeds from (repayments of) short-term debt	10,500	(48,500)
Other	(879)	(2,128)
Cash Used for Financing Activities	(41,226)	(41,626)
Change in cash, cash equivalents, and restricted cash	(34)	(2,894)
Cash, cash equivalents, and restricted cash at beginning of period	6,705	10,500
Cash, cash equivalents, and restricted cash at end of period	6,671	7,606
Significant noncash investing activities:
Accrued capital expenditures	$ 9,194	$ 17,716

Consolidated Balance Sheets (Un

Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Current Assets:
Cash and cash equivalents	$ 14,875	$ 11,140
Accounts receivable, less reserves	44,626	46,734
Other accounts receivables, less reserves	14,744	15,618
Unbilled revenues	25,925	33,181
Materials and supplies, at average cost	34,993	33,385
Fuel for electric generation, at average cost	11,295	13,423
Stored natural gas, at average cost	23,126	25,840
Prepaid taxes	13,674	22,310
Regulatory assets - current	12,291	20,979
Other current assets	14,776	15,587
Total Current Assets	210,325	238,197
Regulatory assets	66,186	81,589
Pension benefit asset	101,584	93,896
Other deferred assets and other	22,273	20,741
Property, Plant, and Equipment:
Property, plant, and equipment, net	2,077,104	2,018,121
Construction work in progress	155,448	110,091
Total Property, Plant, and Equipment	2,232,552	2,128,212
Investments	116,405	112,823
Total Assets	2,749,325	2,675,458
Current Liabilities:
Long-term debt due within one year	5,250	5,146
Short-term debt	48,500	38,000
Accounts payable	45,710	65,451
Accrued interest and taxes	10,479	9,372
Accrued payroll related items	14,739	15,888
Regulatory liabilities - current	16,465	15,296
Other current liabilities	8,462	8,003
Total Current Liabilities	149,605	157,156
Other Credits:
Deferred income taxes	299,728	279,029
Investment tax credit - deferred	45,464	46,892
Regulatory liabilities	151,657	162,316
Accrued pension and other postretirement benefits	56,363	55,058
Asset retirement obligations	72,226	54,430
Other deferred liabilities and other	63,749	61,682
Total Other Credits	689,187	659,407
Capitalization:
Common shareholders equity	1,195,265	1,140,073
Long-term debt	715,268	718,822
Total Capitalization	1,910,533	1,858,895
Commitments and contingencies (see Footnote 8)
Total Liabilities and Capitalization	2,749,325	2,675,458
MGE [Member]
Current Assets:
Cash and cash equivalents	3,140	2,819
Accounts receivable, less reserves	44,626	46,734
Other accounts receivables, less reserves	14,740	15,616
Unbilled revenues	25,925	33,181
Materials and supplies, at average cost	34,993	33,385
Fuel for electric generation, at average cost	11,295	13,423
Stored natural gas, at average cost	23,126	25,840
Prepaid taxes	13,614	22,338
Regulatory assets - current	12,291	20,979
Other current assets	15,243	16,088
Total Current Assets	198,993	230,403
Regulatory assets	66,186	81,589
Pension benefit asset	101,584	93,896
Other deferred assets and other	21,777	20,780
Property, Plant, and Equipment:
Property, plant, and equipment, net	2,077,132	2,018,149
Construction work in progress	155,448	110,091
Total Property, Plant, and Equipment	2,232,580	2,128,240
Investments	0	60
Total Assets	2,621,120	2,554,968
Current Liabilities:
Long-term debt due within one year	5,250	5,146
Short-term debt	48,500	38,000
Accounts payable	45,695	65,434
Accrued interest and taxes	9,685	9,325
Accrued payroll related items	14,739	15,888
Regulatory liabilities - current	16,465	15,296
Other current liabilities	8,495	6,502
Total Current Liabilities	148,829	155,591
Other Credits:
Deferred income taxes	265,549	244,634
Investment tax credit - deferred	45,464	46,892
Regulatory liabilities	151,657	162,316
Accrued pension and other postretirement benefits	56,363	55,058
Asset retirement obligations	72,226	54,430
Other deferred liabilities and other	66,444	63,969
Total Other Credits	657,703	627,299
Capitalization:
Common shareholders equity	948,649	903,725
Noncontrolling interest	150,671	149,531
Total Equity	1,099,320	1,053,256
Long-term debt	715,268	718,822
Total Capitalization	1,814,588	1,772,078
Commitments and contingencies (see Footnote 8)
Total Liabilities and Capitalization	$ 2,621,120	$ 2,554,968

Consolidated Balance Sheets (_2

Consolidated Balance Sheets (Unaudited) (Parentheticals) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Receivables, Net
Reserve for uncollectible accounts receivable	$ 5,565	$ 6,537
Reserve for uncollectible other accounts receivable	1,976	1,561
MGE [Member]
Receivables, Net
Reserve for uncollectible accounts receivable	5,565	6,537
Reserve for uncollectible other accounts receivable	$ 1,976	$ 1,561

MGE Energy Inc Consolidated Sta

MGE Energy Inc Consolidated Statements of Common Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]
Beginning balance, shares at Dec. 31, 2022		36,163,000
Beginning balance, value at Dec. 31, 2022	$ 1,081,674	$ 36,163	$ 395,657	$ 649,854	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss)	97,616			97,616
Common stock dividends declared	(44,933)			(44,933)
Issuance of common stock, net	0
Equity-based compensation plans and other	896		896
Ending balance, shares at Sep. 30, 2023		36,163,000
Ending balance, value at Sep. 30, 2023	1,135,253	$ 36,163	396,553	702,537	0
Beginning balance, shares at Jun. 30, 2023		36,163,000
Beginning balance, value at Jun. 30, 2023	1,112,584	$ 36,163	396,281	680,140	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss)	37,857			37,857
Common stock dividends declared	(15,460)			(15,460)
Equity-based compensation plans and other	272		272
Ending balance, shares at Sep. 30, 2023		36,163,000
Ending balance, value at Sep. 30, 2023	1,135,253	$ 36,163	396,553	702,537	0
Beginning balance, shares at Dec. 31, 2023		36,163,000
Beginning balance, value at Dec. 31, 2023	1,140,073	$ 36,163	396,750	707,160	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss)	98,547			98,547
Common stock dividends declared	$ (47,210)			(47,210)
Stock Issued During Period, Shares, Dividend Reinvestment Plan	29,176	29,000
Stock Issued During Period, Value, Dividend Reinvestment Plan	$ 2,591	$ 29	2,562
Equity-based compensation plans and other - Shares		13,000
Issuance of common stock, net	2,591
Equity-based compensation plans and other	1,264	$ 13	1,251
Ending balance, shares at Sep. 30, 2024		36,205,000
Ending balance, value at Sep. 30, 2024	1,195,265	$ 36,205	400,563	758,497	0
Beginning balance, shares at Jun. 30, 2024		36,176,000
Beginning balance, value at Jun. 30, 2024	1,167,628	$ 36,176	397,614	733,838	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss)	40,939			40,939
Common stock dividends declared	$ (16,280)			(16,280)
Stock Issued During Period, Shares, Dividend Reinvestment Plan	29,176	29,000
Stock Issued During Period, Value, Dividend Reinvestment Plan	$ 2,591	$ 29	2,562
Issuance of common stock, net	2,600
Equity-based compensation plans and other	387		387
Ending balance, shares at Sep. 30, 2024		36,205,000
Ending balance, value at Sep. 30, 2024	$ 1,195,265	$ 36,205	$ 400,563	$ 758,497	$ 0

Consolidated Statements of Comm

Consolidated Statements of Common Equity (Unaudited) (Parentheticals) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Dividends per share of common stock	$ 0.45	$ 0.428	$ 1.305	$ 1.243

Madison Gas and Electric Compan

Madison Gas and Electric Company Consolidated Statements of Common Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	MGE [Member]	Common Stock [Member]	Common Stock [Member] MGE [Member]	Additional Paid-in Capital [Member] MGE [Member]	Retained Earnings [Member] MGE [Member]	Accumulated Other Comprehensive Income/(Loss) [Member] MGE [Member]	Noncontrolling Interest [Member] MGE [Member]
Beginning balance, shares at Dec. 31, 2022			36,163	17,348
Beginning balance, value at Dec. 31, 2022		$ 1,002,386		$ 17,348	$ 252,917	$ 583,958	$ 0	$ 148,163
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	$ 97,616	93,202				76,820		16,382
Cash dividends paid to parent by MGE		(30,000)				(30,000)
Distributions to parent from noncontrolling interest		(17,250)						(17,250)
Ending balance, shares at Sep. 30, 2023			36,163	17,348
Ending balance, value at Sep. 30, 2023		1,048,338		$ 17,348	252,917	630,778	0	147,295
Beginning balance, shares at Jun. 30, 2023			36,163	17,348
Beginning balance, value at Jun. 30, 2023		1,028,386		$ 17,348	252,917	609,313	0	148,808
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	37,857	35,952				30,465		5,487
Cash dividends paid to parent by MGE		(9,000)				(9,000)
Distributions to parent from noncontrolling interest		(7,000)						(7,000)
Ending balance, shares at Sep. 30, 2023			36,163	17,348
Ending balance, value at Sep. 30, 2023		1,048,338		$ 17,348	252,917	630,778	0	147,295
Beginning balance, shares at Dec. 31, 2023			36,163	17,348
Beginning balance, value at Dec. 31, 2023		1,053,256		$ 17,348	252,917	633,460	0	149,531
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	98,547	93,064				75,924		17,140
Cash dividends paid to parent by MGE		(31,000)				(31,000)
Distributions to parent from noncontrolling interest		(16,000)						(16,000)
Ending balance, shares at Sep. 30, 2024			36,205	17,348
Ending balance, value at Sep. 30, 2024		1,099,320		$ 17,348	252,917	678,384	0	150,671
Beginning balance, shares at Jun. 30, 2024			36,176	17,348
Beginning balance, value at Jun. 30, 2024		1,073,210		$ 17,348	252,917	652,051	0	150,894
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	$ 40,939	39,110				33,333		5,777
Cash dividends paid to parent by MGE		(7,000)				(7,000)
Distributions to parent from noncontrolling interest		(6,000)						(6,000)
Ending balance, shares at Sep. 30, 2024			36,205	17,348
Ending balance, value at Sep. 30, 2024		$ 1,099,320		$ 17,348	$ 252,917	$ 678,384	$ 0	$ 150,671

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Summary of Significant Accounting Principles	Summary of Significa nt Accounting Policies – MGE Energy and MGE. a. Basis of Presentation. This report is a combined report of MGE Energy and MGE. References in this report to "MGE Energy" are to MGE Energy, Inc. and its subsidiaries. References in this report to "MGE" are to Madison Gas and Electric Company. MGE Power Elm Road and MGE Power West Campus own electric generating assets and lease those assets to MGE. Both entities are variable interest entities (VIE) under applicable authoritative accounting guidance. MGE is considered the primary beneficiary of these entities as a result of contractual agreements. As a result, MGE has consolidated MGE Power Elm Road and MGE Power West Campus. See Footnote 3 of Notes to Consolidated Financial Statements under Item 8, Financial Statements and Supplementary Data, of MGE Energy's and MGE's 2023 Annual Report on Form 10-K (the 2023 Annual Report on Form 10-K ). The accompanying consolidated financial statements as of September 30, 2024, and during the three and nine months ended, are unaudited but include all adjustments that MGE Energy and MGE management consider necessary for a fair statement of their respective financial statements. All adjustments are of a normal, recurring nature except as otherwise disclosed. The year-end consolidated balance sheet information was derived from the audited balance sheet appearing in the 2023 Annual Report on Form 10-K but does not include all disclosures required by accounting principles generally accepted in the United States of America. These notes should be read in conjunction with the financial statements and the notes on pages 59 through 107 of the 2023 Annual Report on Form 10-K . b. Cash, Cash Equivalents, and Restricted Cash. The following table presents the components of total cash, cash equivalents, and restricted cash on the consolidated balance sheets. MGE Energy MGE September 30, December 31, September 30, December 31, (In thousands) 2024 2023 2024 2023 Cash and cash equivalents $ 14,875 $ 11,140 $ 3,140 $ 2,819 Restricted cash 639 858 639 858 Receivable - margin account 2,892 3,028 2,892 3,028 Cash, cash equivalents, and restricted cash $ 18,406 $ 15,026 $ 6,671 $ 6,705 Cash Equivalents All highly liquid investments purchased with an original maturity of three months or less are considered to be cash equivalents. Restricted Cash MGE has certain cash accounts that are restricted to uses other than current operations and designated for a specific purpose. MGE's restricted cash accounts include cash held by trustees for certain employee benefits and cash deposits held by third parties. These are included in "Other current assets" on the consolidated balance sheets. Receivable – Margin Account Cash amounts held by counterparties as margin collateral for certain financial transactions are recorded as Receivable – margin account in "Other current assets" on the consolidated balance sheets. The costs being hedged are fuel for electric generation, purchased power, and cost of gas sold. c. Property, Plant, and Equipment. Columbia. An asset that will be retired in the near future and substantially in advance of its previously expected retirement date is subject to abandonment accounting. In the second quarter of 2021, the operator of Columbia received approval from Midcontinent Independent System Operator (MISO) to retire Columbia Units 1 and 2. Final timing and retirement dates continue to be evaluated and depend upon operational, regulatory, capacity needs and availability, and other factors impacting one or more of the Columbia co-owners. As of September 30, 2024, early retirement of Columbia Unit 1 and 2 was probable. Our ownership share of Columbia assets was classified as plant to be retired within "Property, plant, and equipment, net" on the consolidated balance sheets. Assets for Columbia Unit 1 and Unit 2 are currently included in rate base, and MGE continues to depreciate them on a straight-line basis using the composite depreciation rates approved by the Public Service Commission of Wisconsin (PSCW) that include retirement dates of 2029 for both Units. If it becomes probable that regulators will disallow full recovery or a return on the remaining net book value of a generating unit that is either abandoned or probable of being abandoned, an impairment loss would be required. An impairment loss would be recorded to the extent that the remaining net book value of the generating unit exceeds the present value of the amount expected to be recovered from ratepayers. No impairment was recorded as of September 30, 2024 .

New Accounting Standards

New Accounting Standards	9 Months Ended
	Sep. 30, 2024
Accounting Standards Update and Change in Accounting Principle [Abstract]
New Accounting Pronouncements	New Ac counti ng Standards - MGE Energy and MGE. In November 2023, the Financial Accounting Standards Board modified authoritative guidance within the codification's Segment Reporting topic, which enhanced the disclosure requirements for significant segment expenses and other segment items. The authoritative guidance will become effective for fiscal years beginning after December 15, 2023, and for interim periods within fiscal years beginning after December 15, 2024. MGE will adopt the standard as of the effective date. The adoption of this standard will not have a material impact on MGE Energy's and MGE's financial statements. In December 2023, the Financial Accounting Standards Board issued authoritative guidance within the codification's Income Taxes topic, which expanded the disclosure requirements over effective tax rate reconciliations and income taxes paid. For public business entities, the authoritative guidance will become effective for fiscal years beginning after December 15, 2024. MGE will adopt the standard as of the effective date. The adoption of this standard will not have a material impact on MGE Energy's and MGE's financial statements.

Investment in ATC and ATC Holdc

Investment in ATC and ATC Holdco	9 Months Ended
	Sep. 30, 2024
Equity Method Investments and Joint Ventures [Abstract]
Investment in ATC and ATC Holdco	Investme nt in ATC and ATC Holdco - MGE Energy and MGE. ATC owns and operates electric transmission facilities primarily in Wisconsin. MGE received an interest in ATC when it, like other Wisconsin electric utilities, contributed its electric transmission facilities to ATC as required by Wisconsin law. That interest is presently held by MGE Transco, a subsidiary of MGE Energy. ATC Holdco was formed by several members of ATC, including MGE Energy, to pursue electric transmission development and investments outside of Wisconsin. The ownership interest in ATC Holdco is held by MGEE Transco, a subsidiary of MGE Energy. MGE Transco and MGEE Transco have accounted for their investments in ATC and ATC Holdco, respectively, under the equity method of accounting. Equity earnings from investments are recorded as "Other income" on the consolidated statements of income of MGE Energy. MGE Transco recorded the following amounts related to its investment in ATC: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2024 2023 2024 2023 Equity earnings from investment in ATC $ 2,868 $ 2,662 $ 8,338 $ 7,844 Dividends received from ATC 2,176 2,057 6,414 6,305 Capital contributions to ATC 894 1,075 2,679 3,033 ATC's summarized financial data is as follows: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2024 2023 2024 2023 Operating revenues $ 221,434 $ 206,197 $ 651,584 $ 610,399 Operating expenses ( 110,043 ) ( 102,819 ) ( 324,082 ) ( 303,412 ) Other income, net 355 701 898 1,657 Interest expense, net ( 36,838 ) ( 33,555 ) ( 108,296 ) ( 99,969 ) Earnings before members' income taxes $ 74,908 $ 70,524 $ 220,104 $ 208,675 MGE receives transmission and other related services from ATC. During the three and nine months ended September 30, 2024, MGE recorded $ 9.1 million and $ 27.3 million, respectively, for transmission service compared to $ 8.5 million and $ 25.4 million for comparable periods in 2023. MGE also provides a variety of operational, maintenance, and project management work for ATC, which is reimbursed by ATC. As of September 30, 2024, and December 31, 2023, MGE had a receivable due from ATC of $ 2.2 million and $ 5.3 million, respectively. The receivable is primarily related to transmission interconnection activities at Badger Hollow and Paris solar generation sites. MGE will be reimbursed for these costs after the new generation assets are placed into service.

Taxes

Taxes	9 Months Ended
	Sep. 30, 2024
Income Tax Disclosure [Abstract]
Taxes	Taxes - MGE E nergy and MGE. Effective Tax Rate. The consolidated income tax provision differs from the amount computed by applying the statutory federal income tax rate to income before income taxes, as follows: MGE Energy MGE Three Months Ended September 30, 2024 2023 2024 2023 Statutory federal income tax rate 21.0 % 21.0 % 21.0 % 21.0 % State income taxes, net of federal benefit 6.2 6.2 6.2 6.2 Amortized investment tax credits ( 2.0 ) ( 0.6 ) ( 2.2 ) ( 0.6 ) Credit for electricity from renewable energy ( 10.7 ) ( 4.9 ) ( 11.6 ) ( 5.2 ) AFUDC equity, net ( 0.6 ) ( 0.9 ) ( 0.6 ) ( 1.0 ) Amortization of utility excess deferred tax - tax reform (a) ( 5.7 ) ( 1.4 ) ( 6.2 ) ( 1.5 ) Other, net, individually insignificant — ( 0.5 ) ( 0.1 ) ( 0.5 ) Effective income tax rate 8.2 % 18.9 % 6.5 % 18.4 % MGE Energy MGE Nine Months Ended September 30, 2024 2023 2024 2023 Statutory federal income tax rate 21.0 % 21.0 % 21.0 % 21.0 % State income taxes, net of federal benefit 6.2 6.3 6.2 6.3 Amortized investment tax credits ( 2.2 ) ( 0.7 ) ( 2.4 ) ( 0.7 ) Credit for electricity from renewable energy ( 10.8 ) ( 5.4 ) ( 11.7 ) ( 5.7 ) AFUDC equity, net ( 0.6 ) ( 0.6 ) ( 0.7 ) ( 0.7 ) Amortization of utility excess deferred tax - tax reform (a) ( 6.1 ) ( 1.6 ) ( 6.7 ) ( 1.7 ) Other, net, individually insignificant ( 0.1 ) ( 0.2 ) ( 0.1 ) ( 0.3 ) Effective income tax rate 7.4 % 18.8 % 5.6 % 18.2 % (a) Included are impacts of the Tax Cut and Jobs Act of 2017 for the regulated utility for excess deferred taxes recognized using a normalization method of accounting in recognition of IRS rules that restrict the rate at which the excess deferred taxes may be returned to utility customers. For both the three months ended September 30, 2024 and 2023, MGE recognized $ 0.9 million. For the nine months ended September 30, 2024 and 2023, MGE recognized $ 2.6 million and $ 2.7 million, respectively. For the three and nine months ended September 30, 2024, MGE recognized $ 1.0 million and $ 3.1 million, respectively, of deferred taxes not restricted by IRS normalization rules, compared to a net collection from customers of $ 0.3 million and $ 1.0 milli on for the three and nine months ended September 30, 2023 . The Inflation Reduction Act of 2022 allows the transfer of certain tax credits to third parties in exchange for cash. In September 2024, MGE sold transfer eligible tax credits generated in 2023 to a third party for $ 7.1 million. MGE elects to account for the transferred tax credits under the scope of ASC 740. The sale of tax credits is presented in the operating activities section of the consolidated statements of cash flows consistent with the presentation of cash taxes paid. MGE also plans to sell eligible credits generated in 2024. MGE includes any expected proceeds from the transfer of tax credits in the evaluation of realizability of deferred tax assets related to tax credits and records a valuation allowance for the difference between the tax value of the credits and the expected proceeds. The PSCW approved the deferral by MGE of any differential between tax credit transfer proceeds and the tax value of credits reflected in rates to its next rate case filing.

Pension and Other Postretiremen

Pension and Other Postretirement Plans	9 Months Ended
	Sep. 30, 2024
Retirement Benefits [Abstract]
Pension and Other Postretirement Plans	Pensi on and Other Postretirement Plans - MGE Energy and MGE. MGE maintains qualified and nonqualified pension plans, health care, and life insurance benefits and defined contribution 401(k) benefit plans for its employees and retirees. The components of net periodic benefit cost, other than the service cost component, are recorded in " Other income, net " on the consolidated statements of income. The service cost component is recorded in "Other operations and maintenance" on the consolidated statements of income. MGE has regulatory treatment and recognizes regulatory assets or liabilities for timing differences between when net periodic benefit costs are recovered and when costs are recognized. The following table presents the components of net periodic benefit costs recognized. Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2024 2023 2024 2023 Pension Benefits Components of net periodic benefit cost: Service cost $ 769 $ 723 $ 2,308 $ 2,169 Interest cost 4,280 4,330 12,839 12,989 Expected return on assets ( 7,149 ) ( 6,312 ) ( 21,448 ) ( 18,936 ) Amortization of: Actuarial loss 215 440 644 1,320 Net periodic benefit (credit) cost $ ( 1,885 ) $ ( 819 ) $ ( 5,657 ) $ ( 2,458 ) Postretirement Benefits (a) Components of net periodic benefit cost: Service cost $ 214 $ 195 $ 642 $ 585 Interest cost 778 827 2,354 2,481 Expected return on assets ( 675 ) ( 649 ) ( 2,059 ) ( 1,946 ) Settlement cost 288 — 288 — Amortization of: Transition obligation 1 1 2 2 Prior service credit ( 234 ) — ( 242 ) — Actuarial loss (gain) 774 ( 48 ) 568 ( 143 ) Net periodic benefit cost $ 1,146 $ 326 $ 1,553 $ 979 (a) In August 2024, MGE entered into an agreement to transfer the mortality and investment risk, as well as the administration of, its employer-paid life insurance plan to a third party. MGE accounted for the settlement under the scope of ASC 715. As approved by the PSCW, MGE is allowed to defer differences between actual employee benefit plan costs and costs reflected in current rates. The deferred costs may be recovered or refunded in MGE's next rate filing. During the three and nine months ended September 30, 2024, MGE recovered $ 0.5 million and $ 3.1 million, respectively, of pension and other postretirement costs previously deferred. During the three and nine months ended September 30, 2023, MGE deferred $ 1.6 million and $ 2.4 million, respectively, of pension and other postretirement costs. These costs have not been reflected in the table above.

Equity and Financing Arrangemen

Equity and Financing Arrangements	9 Months Ended
	Sep. 30, 2024
Equity and Financing Arrangements Disclosure [Abstract]
Equity and Financing Arrangements	Equity and Fi nancing Arrangements - MGE Energy. a. Common Stock. MGE Energy sells shares of its common stock through its Direct Stock Purchase and Dividend Reinvestment Plan (the Stock Plan). Those shares may be newly issued shares or shares that are purchased in the open market by an independent agent for participants in the Stock Plan. Sales of newly issued shares under the Stock Plan are covered by a shelf registration statement that MGE Energy filed with the SEC. During the three and nine months ended September 30, 2024, MGE Energy issued approximately 29,176 shares of common stock. The net proceeds from these issuances were approximately $ 2.6 million, which were used for general corporate purposes. b. Dilutive Shares Calculation. As of September 30, 2024, 26,302 shares were included in the calculation of diluted earnings per share related to nonvested equity awards. See Footnote 7 for additional information on share-based compensation awards. c. Long-Term Debt Issuance - MGE Energy and MGE. On October 31, 2024, MGE entered into a private placement Note Purchase Agreement in which it committed to issue $ 25 million of 5.30 % senior unsecured notes due 2039 and $ 25 million of 5.59 % senior unsecured notes due 2054. Funding is expected to occur on December 4, 2024. The proceeds of the senior notes will be used to assist with capital expenditures and other corporate obligations. The covenants of these senior notes are substantially consistent with MGE's existing senior unsecured notes.

Share-Based Compensation

Share-Based Compensation	9 Months Ended
	Sep. 30, 2024
Share-Based Payment Arrangement [Abstract]
Share-Based Compensation	Share-Based C ompensation - MGE Energy and MGE. During the three and nine months ended September 30, 2024 , MGE recorded $ 1.2 million and $ 3.1 million, respectively, in compensation expense related to share-based compensation awards compared to $ 0.1 million and $ 1.8 million for the comparable periods in 2023. In the first quarter of 2024, cash payments of $ 2.5 million and 12,518 shares were distributed related to awards that were granted in 2021 under the 2021 Incentive Plan and cash-based awards granted in 2019 under the 2006 Performance Unit Plan. In March 2024, MGE granted 16,414 performance units and 29,733 restricted stock units under the 2021 Incentive Plan to eligible employees and non-employee directors. MGE recognizes share-based compensation expense on a straight-line basis over the requisite service period. Awards classified as equity awards are measured based on their grant-date fair value. Awards classified as liability awards are recorded at fair value each reporting period. The performance units can be paid out in either cash, shares of common stock, or a combination of cash and stock and are classified as a liability award. The restricted stock units will be paid out in shares of common stock, and therefore are classified as equity awards.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2024
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitmen ts and Contingencies - MGE Energy and MGE. a. Environmental. In February 2021, MGE and the other co-owners of Columbia announced plans to retire Units 1 and 2 at that facility. Effects of the environmental compliance requirements discussed below will depend upon the final Columbia retirement dates, applicable regulations at that time, and required compliance dates. MGE Energy and MGE are subject to frequently changing local, state, and federal regulations concerning air quality, water quality, land use, threatened and endangered species, hazardous materials handling, and solid waste disposal. These regulations affect the manner in which operations are conducted, the costs of operations, as well as capital and operating expenditures. Several of these environmental rules are subject to legal challenges, reconsideration and/or other uncertainties. Regulatory initiatives, proposed rules, and court challenges to adopted rules could have a material effect on capital expenditures and operating costs. Management believes compliance costs will be recovered in future rates based on previous treatment of environmental compliance projects. These initiatives, proposed rules, and court challenges include: • The United States Environmental Protection Agency's (EPA) promulgated water Effluent Limitations Guidelines (ELG) and standards for steam electric power plants that focus on the reduction of metals and other pollutants in wastewater from new and existing power plants. With the closure of the wet pond system in 2023 (as described in further detail in the CCR section below), Columbia complies with ELG requirements. With the installation of additional wastewater treatment equipment completed in 2023, the Elm Road Units comply with ELG requirements. In May 2024, the EPA finalized the ELG rule that further regulates the wastewater discharges associated with coal-fired power plants. The rule focuses on wastewater discharges from flue gas desulfurization and bottom ash transport water. The rule includes a reduction in requirements for plants that have already installed pollution controls based on previous versions of the rule, and for plants that will be retiring or switching to natural gas by certain dates. The operator of the Elm Road Units believes that pollution prevention installed under previous versions of the rule and the planned fuel switching will qualify the Elm Road Units for the reduced requirements. MGE and the operator of the Elm Road Units currently are evaluating operational options for Elm Road with the requirements of the final rule. • The EPA's cooling water intake rule requires cooling water intake structures at electric power plants to meet best technology available (BTA) standards to reduce the mortality from entrainment (drawing aquatic life into a plant's cooling system) and impingement (trapping aquatic life on screens). Blount received its most recent Wisconsin Pollutant Discharge Elimination System (WPDES) permit from the Wisconsin Department of Natural Resources (WDNR) in October 2023. Blount's latest WPDES permit assumes that the plant meets BTA standards for entrainment for the duration of this permit, which expires in 2028. The WDNR included a requirement to conduct an impingement study in the latest permit that needs to be completed by the end of 2027. Once the WDNR determines the impingement requirements at Blount, MGE will be able to determine any compliance costs of meeting Blount's permit requirements. Intakes at Columbia are subject to this rule. The Columbia operator's most recent permit required that studies of intake structures be submitted to the WDNR by November 2023 to help determine BTA. Columbia's permit renewal application is due in 2024 and in November 2023 the Columbia operator timely submitted its renewal application to the WDNR. BTA improvements required by the renewal permit will be coordinated with the owners' plan to retire both units by June of 2026. MGE will continue to work with Columbia's operator to evaluate regulatory requirements in light of the planned retirement. MGE does not expect this rule to have a material effect on Columbia. • Greenhouse Gas (GHG) new source performance standards and emission guidelines established under the Clean Air Act for states to use in developing plans to control GHG emissions from fossil fuel-fired electric generating units, including existing and proposed regulations governing existing, new, or modified fossil-fuel generating units. In May 2024, the EPA published its final performance standards and emission guidelines under section 111(b) of the Clean Air Act for carbon dioxide emissions from new combustion turbines and existing fossil-fuel fired boilers used to produce electricity. The final rule grants some emissions flexibility for existing coal-fired units that retire and/or fuel switch by certain dates. For existing natural gas boiler units, the final rule establishes a process where states must submit plans to the EPA for establishing standards. States will have two years from the publication date of these rules to submit plans to the EPA for review and approval. The EPA has indicated that it is separately developing performance standards and emission guidelines for GHG emissions from existing natural gas-fired combustion turbines. Our preliminary evaluation of the final ruling shows that MGE meets the requirements for our gas-fired boilers at Blount. Furthermore, MGE will meet the requirements for our coal-fired units at Columbia through planned unit retirements and the Elm Road Units through its transition to natural gas. MGE will monitor for upcoming rulemaking planned for gas-fired combustion turbines. • The EPA's rule to regulate ambient levels of ozone through the 2015 Ozone National Ambient Air Quality Standards (NAAQS). The Elm Road Units are located in Milwaukee County, Wisconsin, a nonattainment area for the 2015 Ozone NAAQS. At this time, the operator of the Elm Road Units does not expect that the 2015 Ozone NAAQS or the Milwaukee County nonattainment designation will have a material effect on the Units. • The EPA's rule to regulate Fine Particulate Matter (PM2.5). In March 2024, the EPA published a final rule to lower the average annual PM2.5 NAAQS from 12 ug/m3 to 9 ug/m3 effective May 2024. The new annual PM2.5 NAAQS could impact Milwaukee County, where our Elm Road units are located, if the county is determined to be in nonattainment. A nonattainment designation would require the State of Wisconsin to develop a plan to get into attainment, which would likely include additional limitations for new and modified plants in the county. With the planned transition of the Elm Road Units to natural gas, there is a low probability for the need of additional emission limitations. However, we will not know the impact of this rule until PM data from 2023 and 2024 is evaluated and approved, the EPA determines the attainment status of Wisconsin counties, and the State of Wisconsin develops an attainment implementation plan. MGE will continue to follow the rule's developments. • Rules regulating nitrogen oxide (NO x ) and sulfur dioxide (SO 2 ) emissions, including the Cross State Air Pollution Rule (CSAPR) and Clean Air Visibility Rule. The EPA's CSAPR and its progeny are a suite of interstate air pollution transport rules designed to reduce ozone and PM2.5 ambient air levels in areas that the EPA has determined as being significantly impacted by pollution from upwind states. This is accomplished through a reduction in NO x and SO 2 from qualifying fossil-fuel fired power plants and industrial boilers in upwind "contributing" states. NO x and SO 2 contribute to fine particulate pollution and NO x contributes to ozone formation in downwind areas. Reductions are generally achieved through a cap-and-trade system. Individual plants can meet their caps through reducing emissions and/or buying allowances on the market. In March 2023 (published June 2023), the EPA finalized its Federal Implementation Plan to address state obligations under the Clean Air Act "good neighbor" provisions for the 2015 Ozone NAAQS (FIP Rule). The FIP Rule impacts 23 states, including Wisconsin. For Wisconsin, the FIP Rule includes revisions to the current obligations for fossil-fuel power generation, which includes Blount, Columbia, the Elm Road Units, WCCF, West Riverside, and West Marinette. Emissions budgets can be met with planned retirements, fuel switching, and immediately available measures, including consistently operating emissions controls already installed at power plants. In 2026, additional obligations would go into effect, including a further reduction in emissions budgets. Wisconsin would need to submit a State Implementation Plan to meet its obligations or accept the EPA's FIP Rule. Legal challenges to the FIP Rule are pending in the United States Court of Appeals for the District of Columbia. In June 2024, the Supreme Court of the United States granted a request to stay the FIP Rule pending judicial review by the U.S. Court of Appeals for the District of Columbia on the merits of petitioner's challenges to implementation of the rule. Based on our current evaluation, if the FIP Rule were to go into effect, the 2026 additional emission reductions may impact the Elm Road Units and additional upgrades may be needed to comply, however, we will not know the final impact until final decisions are issued in the pending litigation. • The EPA's Coal Combustion Residuals (CCR) Rule. The CCR rule regulates the disposal of solid waste coal ash and defines what ash use activities would be considered generally exempt beneficial reuse of coal ash. The CCR rule also regulates landfills, ash ponds, and other surface impoundments used for coal combustion residuals by regulating their design, location, monitoring, and operation. The CCR rule requires owners and operators of coal-fired power plants to stop transporting CCR and non-CCR wastewater to unlined surface impoundments. At Columbia, the coal combustion residuals system completed in 2023 replaced the unlined surface impoundment, and Columbia complies with this rule. In May 2024, the EPA published its final CCR Legacy Rule. The CCR Legacy Rule applies to previous closed disposal sites. In June 2024, MGE recorded $ 23.7 million asset retirement obligation for its estimated share of the legal liability associated with the effect of the CCR Legacy Rule for remediation and groundwater compliance monitoring. Actual costs of compliance may be different than the amount recorded due to potential changes in compliance strategies that will be used, as well as other potential changes in cost estimate. b. Legal Matters. MGE is involved in various legal matters that are being defended and handled in the normal course of business. MGE accrues for costs that are probable of being incurred and subject to reasonable estimation. The accrued amount for these matters is not material to the financial statements. MGE does not expect the resolution of these matters to have a material adverse effect on its consolidated results of operations, financial condition, or cash flows. Several environmental groups filed petitions against the PSCW challenging the fixed customer charge set in MGE's 2022/2023 rate settlement, 2023 electric limited reopener, and 2024/2025 rate order. MGE has intervened in the petitions in cooperation with the PSCW. See Footnote 9.a. for more information regarding this matter. c. Purchase Contracts. MGE Energy and MGE have entered into various commodity supply, transportation, and storage contracts to meet their obligations to deliver electricity and natural gas to customers. Management expects to recover these costs in future customer rates. The following table shows future commitments related to purchase contracts as of September 30, 2024: (In thousands) 2024 2025 2026 2027 2028 Thereafter Coal (a) $ 10,902 $ 19,894 $ 3,751 $ — $ — $ — Natural gas (b) 18,695 39,937 15,492 2,546 2,546 11,224 $ 29,597 $ 59,831 $ 19,243 $ 2,546 $ 2,546 $ 11,224 (a) Total coal commitments for MGE's share of the Columbia and Elm Road Units, including transportation. Fuel procurement for MGE's jointly owned Columbia and Elm Road Units is handled by WPL and WEPCO, respectively, who are the operators of those facilities. (b) MGE's natural gas transportation and storage contracts require fixed monthly payments for firm supply pipeline transportation and storage capacity. The pricing components of the fixed monthly payments for the transportation and storage contracts are approved by FERC but may be subject to change. MGE's natural gas supply commitments include market-based pricing.

Rate Matters

Rate Matters	9 Months Ended
	Sep. 30, 2024
Regulated Operations [Abstract]
Rate Matters	Rate Mat ters - MGE Energy and MGE. a. Rate Proceedings. Rate increase Return on Common Equity Common Equity Component of Regulatory Capital Structure Effective Date Approved 2022/2023 settlement Gas 0.96 % 9.8 % 55.6 % 1/1/2023 Approved limited 2023 reopener (a) Electric 9.01 % 9.8 % 55.6 % 1/1/2023 Approved 2024/2025 rate proceeding (b)(c) Electric 1.54 % 9.7 % 56.1 % 1/1/2024 Gas 2.44 % 9.7 % 56.1 % 1/1/2024 Electric (d) 4.17 % 9.7 % 56.1 % 1/1/2025 Gas 1.32 % 9.7 % 56.1 % 1/1/2025 (a) The electric rate increase was driven by generation assets including our investments in Badger Hollow II (solar), Paris (solar and battery), Red Barn Wind Farm (wind), and West Riverside (natural gas). In addition, the reopener request included an increase in fuel costs and the recovery of deferred 2021 fuel costs. The reopener also revised the depreciation schedule for Columbia Unit 2 and shared equipment to 2029 to align with the depreciation schedule for Unit 1. (b) The electric increase was driven by an increase in rate base including our investments made in West Riverside, local solar, continued investment in grid modernization, as well as higher costs for transmission, pension and OPEB, and uncollectible costs (including costs previously deferred from prior years). This increase in electric costs is offset by a decrease in fuel costs and benefit from lower tax expense (including impacts from the Inflation Reduction Act). MGE filed an updated 2025 fuel forecast with the PSCW in 2024, which will impact rates in 2025, based on any variance between the forecast submitted as part of the rates and updated forecast. In addition, the PSCW authorized MGE to defer a recovery of and a return on costs associated for any change in the in service date for Paris and force majeure costs for Badger Hollow II and Paris that were not reflected in this rate filing. The PSCW also approved deferral of any differential in PTC tax credits reflected in rates and actual credits produced. These deferrals will be reflected in MGE's next rate case filing. The gas rate increases were also driven by our investment made in grid modernization and higher pension and OPEB and uncollectible costs (including costs previously deferred from prior years). This increase in gas costs is offset by a tax benefit related to excess deferred taxes. Included in the gas residential rate is a reduction in the customer fixed charge. (c) The 2024/2025 rate order includes an earnings sharing mechanism, under which, if MGE earns above the authorized Return on Equity (ROE) in the rate order: (i) the utility will retain 100.0% of earnings for the first 15 basis points above the authorized ROE; (ii) 50.0% of the next 60 basis points will be required to be deferred and returned to customers; and (iii) 100.0% of any remaining excess earnings will be required to be refunded to customers. The earnings calculation excludes fuel rules adjustments. See "Fuel Rules" below. (d) MGE filed a 2025 Fuel Cost Plan with the PSCW in June 2024. The plan would lower the 2025 increase in electric rates to 2.47 % to reflect lower expected fuel costs. MGE expects a final decision from the PSCW on the Fuel Cost Plan by the end of 2024. Sierra Club and Vote Solar have filed petitions with the Dane County Circuit Court seeking review of the PSCW decisions approving MGE's electric and gas 2022/2023 rate settlement, 2023 electric limited reopener, and 2024/2025 rate order. The PSCW is named as the responding party; MGE is not named as a party. The Petitions challenge the amount of customer fixed charge that does not vary with usage. The requested relief is unclear. The revenue requirement approved by the PSCW in the settlement, limited reopener, and 2024/2025 rate order have not been challenged. The PSCW is expected to vigorously defend its approval of the rate case settlement, limited reopener, and the 2024/2025 rate order. MGE has intervened in the proceedings to further defend the PSCW's decision. The Dane County Circuit Court affirmed the PSCW's decision to approve the 2022/2023 rate settlement, and Sierra Club and Vote Solar appealed that decision to the Wisconsin Court of Appeals. On August 6, 2024, the Wisconsin Court of Appeals denied Sierra Club and Vote Solar's appeal and affirmed the PSCW's approval of the 2022/2023 rate settlement. Sierra Club and Vote Solar have petitioned the Wisconsin Supreme Court for review of the Court of Appeals decision. The PSCW and MGE both filed responses asking the Wisconsin Supreme Court to deny the petition. All parties are awaiting the Wisconsin Supreme Court's decision on the petition. The petitions challenging the 2023 electric limited reopener and the 2024/2025 rate order remain stayed pending further proceedings. b. Fu el Rules. Fuel rules require Wisconsin utilities to defer electric fuel-related costs that fall outside a symmetrical cost tolerance band around the amount approved for a utility in its annual fuel proceedings. Any over- or under-recovery of the actual costs is determined in the following year and is then reflected in future billings to electric retail customers. The fuel rules bandwidth is set at plus or minus 2 % in 2024 and 2023. The electric fuel-related costs are subject to an excess revenues test. Excess revenues are defined as revenues in the year in question that provide MGE with a greater return on common equity than authorized by the PSCW in MGE's latest rate order. The recovery of under-collected electric fuel-related costs would be reduced by the amount that exceeds the excess revenue test. These costs are subject to the PSCW's annual review of fuel costs completed in the year following the deferral. The following table summarizes deferred electric fuel-related costs: Fuel Costs (Savings) ( in millions ) Refund or Recovery Period 2021 $ 3.3 (a) January 2023 through December 2023 2022 $ 8.8 (a) October 2023 through September 2024 2023 ($ 7.2 ) (a) October 2024 through December 2024 (a) There was no change to the refund or recovery in the fuel rules proceedings from the amount MGE deferred .

Derivative and Hedging Instrume

Derivative and Hedging Instruments	9 Months Ended
	Sep. 30, 2024
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative and Hedging Instruments	Derivati ve and Hedging Instruments - MGE Energy and MGE. a. Purpose. As part of its regular operations, MGE enters into contracts, including options, swaps, futures, forwards, and other contractual commitments, to manage its exposure to commodity prices. To the extent that these contracts are derivatives, MGE assesses whether or not the normal purchases or normal sales exclusion applies. For contracts to which this exclusion cannot be applied, the derivatives are recognized in the consolidated balance sheets at fair value. MGE's financial commodity derivative activities are conducted in accordance with its electric and gas risk management program, which is approved by the PSCW and limits the volume MGE can hedge with specific risk management strategies. The maximum length of time over which cash flows related to energy commodities can be hedged is four years . If the derivative qualifies for regulatory deferral, the derivatives are marked to fair value and are offset with a corresponding regulatory asset or liability depending on whether the derivative is in a net loss or net gain position, respectively. The deferred gain or loss is recognized in earnings in the delivery month applicable to the instrument. Gains and losses related to hedges qualifying for regulatory treatment are refundable or recoverable in gas rates through the Purchased Gas Adjustment (PGA) or in electric rates as a component of the fuel rules mechanism. b. Notional Amounts. The gross notional volume of open derivatives is as follows: September 30, 2024 December 31, 2023 Commodity derivative contracts 269,120 MWh 392,000 MWh Commodity derivative contracts 7,900,000 Dth 7,180,000 Dth FTRs 3,276 MW 1,824 MW c. Financial Statement Presentation. MGE purchases and sells exchange-traded and over-the-counter options, swaps, and future contracts. These arrangements are primarily entered into to help stabilize the price risk associated with gas or power purchases. These transactions are employed by both MGE's gas and electric segments. Additionally, as a result of the firm transmission agreements that MGE holds on electricity transmission paths in the MISO market, MGE holds financial transmission rights (FTRs). An FTR is a financial instrument that entitles the holder to a stream of revenues or charges based on the differences in hourly day-ahead energy prices between two points on the transmission grid. The fair values of these instruments are offset with a corresponding regulatory asset/liability depending on whether the instruments are in a net loss/gain position. Depending on the nature of the instrument, the gain or loss associated with these transactions will be reflected as cost of gas sold, fuel for electric generation, or purchased power expense in the delivery month applicable to the instrument. As of September 30, 2024, and December 31, 2023, the cost basis of exchange traded derivatives and FTRs exceeded their fair value by $ 1.5 million and $ 5.2 million, respectively. The following table summarizes the fair value of the derivative instruments on the consolidated balance sheets. All derivative instruments in this table are presented on a gross basis and are calculated prior to the netting of instruments with the same counterparty under a master netting agreement as well as the netting of collateral. For financial statement purposes, instruments are netted with the same counterparty under a master netting agreement as well as the netting of collateral. Derivative Derivative (In thousands) Assets Liabilities Balance Sheet Location September 30, 2024 Commodity derivative contracts (a) $ 891 $ 2,199 Other current liabilities Commodity derivative contracts (a) 84 261 Other deferred liabilities and other FTRs — 17 Other current liabilities December 31, 2023 Commodity derivative contracts (a) $ 263 $ 4,942 Other current liabilities Commodity derivative contracts (a) 156 882 Other deferred liabilities and other FTRs 179 — Other current assets (a) As of September 30, 2024, and December 31, 2023, collateral of $ 1.5 million and $ 5.4 million, respectively, was posted against and netted with derivative liability positions on the consolidated balance sheets. The fair value of the derivative liability disclosed in this table has not been reduced for the collateral posted. The following table shows the effect of netting arrangements for recognized derivative assets and liabilities that are subject to a master netting arrangement or similar arrangement on the consolidated balance sheets. Offsetting of Derivative Assets and Liabilities (In thousands) Gross Amounts Gross Amounts Offset in Balance Sheets Collateral Posted Against Derivative Positions Net Amount Presented in Balance Sheets September 30, 2024 Assets Commodity derivative contracts $ 975 $ ( 975 ) $ — $ — Liabilities FTRs 17 — ( 17 ) — Commodity derivative contracts 2,460 ( 975 ) ( 1,485 ) — December 31, 2023 Assets Commodity derivative contracts $ 419 $ ( 419 ) $ — $ — FTRs 179 — — 179 Liabilities Commodity derivative contracts 5,824 ( 419 ) ( 5,405 ) — The following tables summarize the unrealized and realized gains/losses related to the derivative instruments on the consolidated balance sheets and the consolidated statements of income. 2024 2023 (In thousands) Current and Long-Term Regulatory Asset (Liability) Other Current Assets Current and Long-Term Regulatory Asset (Liability) Other Current Assets Three Months Ended September 30: Balance as of July 1, $ 1,946 $ 527 $ 5,017 $ 1,074 Unrealized loss 1,768 — 1,100 — Realized (loss) gain reclassified to a deferred account ( 639 ) 639 ( 1,676 ) 1,676 Realized loss reclassified to income statement ( 1,573 ) ( 707 ) ( 1,893 ) ( 2,155 ) Balance as of September 30, $ 1,502 $ 459 $ 2,548 $ 595 Nine Months Ended September 30: Balance as of January 1, $ 5,226 $ 1,569 $ 5,094 $ 2,747 Unrealized loss 4,666 — 15,495 — Realized (loss) gain reclassified to a deferred account ( 3,333 ) 3,333 ( 10,581 ) 10,581 Realized loss reclassified to income statement ( 5,057 ) ( 4,443 ) ( 7,460 ) ( 12,733 ) Balance as of September 30, $ 1,502 $ 459 $ 2,548 $ 595 Realized Losses (Gains) 2024 2023 (In thousands) Fuel for Electric Generation/ Purchased Power Cost of Gas Sold Fuel for Electric Generation/ Purchased Power Cost of Gas Sold Three Months Ended September 30: Commodity derivative contracts $ 1,969 $ — $ 4,179 $ — FTRs 311 — ( 131 ) — Nine Months Ended September 30: Commodity derivative contracts $ 5,723 $ 3,265 $ 14,566 $ 6,451 FTRs 512 — ( 824 ) — MGE's commodity derivative contracts and FTRs are subject to regulatory deferral. These derivatives are marked to fair value and are offset with a corresponding regulatory asset or liability. Realized gains and losses are deferred on the consolidated balance sheets and are recognized in earnings in the delivery month applicable to the instrument. As a result of the treatment described above, there are no unrealized gains or losses that flow through earnings. Certain counterparties extend MGE a credit limit. If MGE exceeds these limits, the counterparties may require collateral to be posted. As of September 30, 2024, and December 31, 2023 , no counterparties were in a net liability position. Nonperformance of counterparties to the non-exchange traded derivatives could expose MGE to credit loss. However, MGE enters into transactions only with companies that meet or exceed strict credit guidelines, and it monitors these counterparties on an ongoing basis to mitigate nonperformance risk in its portfolio. As of September 30, 2024 , no counterparties had defaulted.

Fair Value of Financial Instrum

Fair Value of Financial Instruments	9 Months Ended
	Sep. 30, 2024
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	Fair Value of Fin ancial Instruments - MGE Energy and MGE. Fair value is defined as the price that would be received to sell an asset or would be paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants at the measurement date. The accounting standard clarifies that fair value should be based on the assumptions market participants would use when pricing the asset or liability including assumptions about risk. The standard also establishes a three-level fair value hierarchy based upon the observability of the assumptions used and requires the use of observable market data when available. The levels are: Level 1 - Pricing inputs are quoted prices within active markets for identical assets or liabilities. Level 2 - Pricing inputs are quoted prices within active markets for similar assets or liabilities; quoted prices for identical or similar instruments in markets that are not active; and model-derived valuations that are correlated with or otherwise verifiable by observable market data. Level 3 - Pricing inputs are unobservable and reflect management's best estimate of what market participants would use in pricing the asset or liability. a. Fair Value of Financial Assets and Liabilities Recorded at the Carrying Amount. The carrying amount of cash, cash equivalents, and outstanding commercial paper approximates fair market value due to the short maturity of those investments and obligations. The estimated fair market value of long-term debt is based on quoted market prices for similar financial instruments. Since long-term debt is not traded in an active market, it is classified as Level 2. The estimated fair market value of financial instruments are as follows: September 30, 2024 December 31, 2023 (In thousands) Carrying Amount Fair Value Carrying Amount Fair Value Long-term debt (a) $ 724,699 $ 682,359 $ 728,546 $ 675,922 (a) Includes long-term debt due within one year. Excludes debt issuance costs and unamortized discount of $ 4.2 million and $ 4.6 million as of September 30, 2024, and December 31, 2023 , respectively. b. Recurring Fair Value Measurements. The following table presents the balances of assets and liabilities measured at fair value on a recurring basis. Fair Value as of September 30, 2024 (In thousands) Total Level 1 Level 2 Level 3 MGE Energy Assets: Derivatives, net (b) $ 975 $ 920 $ — $ 55 Exchange-traded investments — — — — Total Assets $ 975 $ 920 $ — $ 55 Liabilities: Derivatives, net (b) $ 2,477 $ 1,290 $ — $ 1,187 Deferred compensation 6,108 — 6,108 — Total Liabilities $ 8,585 $ 1,290 $ 6,108 $ 1,187 MGE Assets: Derivatives, net (b) $ 975 $ 920 $ — $ 55 Exchange-traded investments — — — — Total Assets $ 975 $ 920 $ — $ 55 Liabilities: Derivatives, net (b) $ 2,477 $ 1,290 $ — $ 1,187 Deferred compensation 6,108 — 6,108 — Total Liabilities $ 8,585 $ 1,290 $ 6,108 $ 1,187 Fair Value as of December 31, 2023 (In thousands) Total Level 1 Level 2 Level 3 MGE Energy Assets: Derivatives, net (b) $ 598 $ 352 $ — $ 246 Exchange-traded investments 2,034 2,034 — — Total Assets $ 2,632 $ 2,386 $ — $ 246 Liabilities: Derivatives, net (b) $ 5,824 $ 2,974 $ — $ 2,850 Deferred compensation 5,246 — 5,246 — Total Liabilities $ 11,070 $ 2,974 $ 5,246 $ 2,850 MGE Assets: Derivatives, net (b) $ 598 $ 352 $ — $ 246 Exchange-traded investments 60 60 — — Total Assets $ 658 $ 412 $ — $ 246 Liabilities: Derivatives, net (b) $ 5,824 $ 2,974 $ — $ 2,850 Deferred compensation 5,246 — 5,246 — Total Liabilities $ 11,070 $ 2,974 $ 5,246 $ 2,850 (b) As of September 30, 2024, and December 31, 2023, collateral of $ 1.5 million and $ 5.4 million, respectively, was posted against and netted with derivative liability positions on the consolidated balance sheets. The fair value of the derivative liability disclosed in this table has not been reduced for the collateral posted. E xchange-traded Investments. Investments include exchange-traded investment securities valued using quoted prices on active exchanges and are therefore classified as Level 1. Deferred Compensation. The deferred compensation plans allow participants to defer certain cash compensation into notional investment accounts. These amounts are included within "Other deferred liabilities and other" in the consolidated balance sheets. The value of certain deferred compensation obligations is based on the market value of the participants' notional investment accounts. The underlying notional investments are comprised primarily of equities, mutual funds, and fixed income securities that are based on directly and indirectly observable market prices. Since the deferred compensation obligations themselves are not exchanged in an active market, they are classified as Level 2. The value of legacy deferred compensation obligations is based on notional investments that earn interest based upon the semiannual rate of U.S. Treasury Bills having a 26 -week maturity increased by 1 % compounded monthly with a minimum annual rate of 7 %, compounded monthly. The notional investments are based upon observable market data, however, since the deferred compensation obligations themselves are not exchanged in an active market, they are classified as Level 2. Derivatives. Derivatives include exchange-traded derivative contracts, over-the-counter transactions and FTRs. Most exchange-traded derivative contracts are valued based on unadjusted quoted prices in active markets and are therefore classified as Level 1. A small number of exchange-traded derivative contracts are valued using quoted market pricing in markets with insufficient volumes and are therefore considered unobservable and classified as Level 3. Transactions done with an over-the-counter party are on inactive markets and are therefore classified as Level 3. These transactions are valued based on quoted prices from markets with similar exchange-traded transactions. FTRs are priced based upon monthly auction results for identical or similar instruments in a closed market with limited data available and are therefore classified as Level 3. The following table summarizes the changes in Level 3 commodity derivative assets and liabilities measured at fair value on a recurring basis. Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2024 2023 2024 2023 Beginning balance $ ( 1,432 ) $ ( 2,892 ) $ ( 2,604 ) $ ( 866 ) Realized and unrealized gains (losses): Included in regulatory assets 300 1,768 1,472 ( 258 ) Included in earnings ( 1,572 ) ( 2,016 ) ( 5,174 ) ( 7,590 ) Settlements 1,572 2,016 5,174 7,590 Balance as of September 30, $ ( 1,132 ) $ ( 1,124 ) $ ( 1,132 ) $ ( 1,124 ) The following table presents total realized and unrealized gains (losses) included in income for Level 3 assets and liabilities measured at fair value on a recurring basis (c) . Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2024 2023 2024 2023 Purchased power expense $ ( 1,572 ) $ ( 2,016 ) $ ( 5,174 ) $ ( 7,590 ) (c) MGE's exchange-traded derivative contracts, over-the-counter party transactions, and FTRs are subject to regulatory deferral. These derivatives are therefore marked to fair value and are offset in the financial statements with a corresponding regulatory asset or liability.

Joint Plant Ownership

Joint Plant Ownership	9 Months Ended
	Sep. 30, 2024
Public Utilities, Property, Plant and Equipment [Abstract]
Jointly Owned Electric Utility Plant	Joint Plant Constr uction Project Ownership - MGE Energy and MGE MGE has ownership interests in generation projects with other co-owners, some of which are under construction, as shown in the following table. Incurred costs are reflected in "Property, plant, and equipment, net" or "Construction work in progress" on the consolidated balance sheets. Project Ownership Interest Source Share of Share of Estimated (a) Costs incurred as (a) Estimated Date of Paris (b) 10 % Solar/Battery 20 MW/ 11 MW $ 61 million (d) $ 48.6 million 2024 Solar Darien (c) 10 % Solar/Battery 25 MW/ 7.5 MW $ 63 million (d) $ 41.9 million 2025 Solar Koshkonong (e) 10 % Solar/Battery 30 MW/ 16.5 MW $ 104 million (d) $ 6.6 million 2026 Solar West Riverside 3.5 % Natural Gas 25 MW $ 25 million $ 25.2 million (f) (a) Excluding AFUDC. (b) Paris Solar-Battery Park is located in the Town of Paris in Kenosha County, Wisconsin. (c) Darien Solar Energy Center is located in Walworth and Rock Counties in southern Wisconsin. (d) Estimated costs are expected to exceed PSCW previously approved Certificate of Authority (CA) levels. Notifications are provided to the PSCW when costs increase above CA levels. MGE has and will continue to request recovery of the updates in its rate case proceedings. (e) Koshkonong Solar Energy Center is located in the Towns of Christiana and Deerfield in Dane County, Wisconsin. (f) In June 2024, MGE purchased an additional ownership interest in West Riverside, a natural gas-fired facility located in Beloit, WI, from WPL, operator and co-owner of the plant. West Riverside was placed in-service in 2020. MGE's interest in West Riverside increased to 6.9 %. MGE received specific approval to recover 100 % AFUDC on Paris, Darien, and Koshkonong. During the three and nine months ended September 30, 2024, MGE recognized $ 1.9 million and $ 4.7 million, respectively, after tax, in AFUDC for these projects compared to $ 0.8 million and $ 1.9 million for the comparable periods in 2023 .

Revenue

Revenue	9 Months Ended
	Sep. 30, 2024
Revenue from Contract with Customer [Abstract]
Revenue from Contract with Customer	Reven ue - MGE Energy and MGE. Revenues disaggregated by revenue source were as follows: Three Months Ended Nine Months Ended (In thousands) September 30, September 30, Electric revenues 2024 2023 2024 2023 Residential $ 52,834 $ 50,008 $ 134,296 $ 131,552 Commercial 73,517 70,795 197,541 193,760 Industrial 3,459 3,715 10,314 10,578 Other-retail/municipal 11,346 10,991 31,439 30,853 Total retail 141,156 135,509 373,590 366,743 Sales to the market 5,799 3,305 8,394 9,617 Other 835 77 2,314 1,267 Total electric revenues 147,790 138,891 384,298 377,627 Gas revenues Residential 13,069 13,719 72,057 86,131 Commercial/Industrial 5,892 6,016 43,292 55,726 Total retail 18,961 19,735 115,349 141,857 Gas transportation 1,417 1,587 5,003 5,354 Other 98 102 409 466 Total gas revenues 20,476 21,424 120,761 147,677 Non-regulated energy revenues 214 213 470 475 Total Operating Revenue $ 168,480 $ 160,528 $ 505,529 $ 525,779

Segment Information

Segment Information	9 Months Ended
	Sep. 30, 2024
Segment Reporting [Abstract]
Segment Information	Segment Infor mation - MGE Energy and MGE. MGE Energy operates in the following business segments: electric utility, gas utility, nonregulated energy, transmission investment, and all other. See the 2023 Annual Report on Form 10-K for additional discussion of each of these segments. (In thousands) Electric Gas Non-Regulated Energy Transmission Investment All Others Consolidation/ Consolidated Total Three Months Ended September 30, 2024 Operating revenues $ 147,790 $ 20,476 $ 214 $ — $ — $ — $ 168,480 Interdepartmental revenues ( 44 ) 4,207 11,052 — — ( 15,215 ) — Total operating revenues 147,746 24,683 11,266 — — ( 15,215 ) 168,480 Equity in earnings of investments — — — 2,901 — — 2,901 Net income (loss) 35,035 ( 2,026 ) 6,101 2,112 ( 283 ) — 40,939 Three Months Ended September 30, 2023 Operating revenues $ 138,891 $ 21,424 $ 213 $ — $ — $ — $ 160,528 Interdepartmental revenues 512 3,547 10,398 — — ( 14,457 ) — Total operating revenues 139,403 24,971 10,611 — — ( 14,457 ) 160,528 Equity in earnings of investments — — — 2,690 — — 2,690 Net income (loss) 31,126 ( 801 ) 5,627 1,957 ( 52 ) — 37,857 Nine Months Ended September 30, 2024 Operating revenues $ 384,298 $ 120,761 $ 470 $ — $ — $ — $ 505,529 Interdepartmental revenues ( 154 ) 11,591 32,825 — — ( 44,262 ) — Total operating revenues 384,144 132,352 33,295 — — ( 44,262 ) 505,529 Equity in earnings of investments — — — 8,427 — — 8,427 Net income (loss) 66,458 8,638 17,968 6,130 ( 647 ) — 98,547 Nine Months Ended September 30, 2023 Operating revenues $ 377,627 $ 147,677 $ 475 $ — $ — $ — $ 525,779 Interdepartmental revenues 653 12,978 31,143 — — ( 44,774 ) — Total operating revenues 378,280 160,655 31,618 — — ( 44,774 ) 525,779 Equity in earnings of investments — — — 7,930 — — 7,930 Net income (loss) 65,996 10,539 16,667 5,770 ( 1,356 ) — 97,616 (In thousands) Electric Gas Non-Regulated Energy Consolidation/ Consolidated Total Three Months Ended September 30, 2024 Operating revenues $ 147,790 $ 20,476 $ 214 $ — $ 168,480 Interdepartmental revenues ( 44 ) 4,207 11,052 ( 15,215 ) — Total operating revenues 147,746 24,683 11,266 ( 15,215 ) 168,480 Net income attributable to MGE 35,035 ( 2,026 ) 6,101 ( 5,777 ) 33,333 Three Months Ended September 30, 2023 Operating revenues $ 138,891 $ 21,424 $ 213 $ — $ 160,528 Interdepartmental revenues 512 3,547 10,398 ( 14,457 ) — Total operating revenues 139,403 24,971 10,611 ( 14,457 ) 160,528 Net income attributable to MGE 31,126 ( 801 ) 5,627 ( 5,487 ) 30,465 Nine Months Ended September 30, 2024 Operating revenues $ 384,298 $ 120,761 $ 470 $ — $ 505,529 Interdepartmental revenues ( 154 ) 11,591 32,825 ( 44,262 ) — Total operating revenues 384,144 132,352 33,295 ( 44,262 ) 505,529 Net income attributable to MGE 66,458 8,638 17,968 ( 17,140 ) 75,924 Nine Months Ended September 30, 2023 Operating revenues $ 377,627 $ 147,677 $ 475 $ — $ 525,779 Interdepartmental revenues 653 12,978 31,143 ( 44,774 ) — Total operating revenues 378,280 160,655 31,618 ( 44,774 ) 525,779 Net income attributable to MGE 65,996 10,539 16,667 ( 16,382 ) 76,820

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Pay vs Performance Disclosure
Net Income (Loss)	$ 40,939	$ 37,857	$ 98,547	$ 97,616

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended
	Sep. 30, 2024
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

Significant Accounting Policies

Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2024
Accounting Policies [Abstract]
Variable Interest Entities	MGE Power Elm Road and MGE Power West Campus own electric generating assets and lease those assets to MGE. Both entities are variable interest entities (VIE) under applicable authoritative accounting guidance. MGE is considered the primary beneficiary of these entities as a result of contractual agreements. As a result, MGE has consolidated MGE Power Elm Road and MGE Power West Campus.
Cash and Cash Equivalents	Cash Equivalents All highly liquid investments purchased with an original maturity of three months or less are considered to be cash equivalents.
Restricted Cash	Restricted Cash MGE has certain cash accounts that are restricted to uses other than current operations and designated for a specific purpose. MGE's restricted cash accounts include cash held by trustees for certain employee benefits and cash deposits held by third parties. These are included in "Other current assets" on the consolidated balance sheets.
Receivable Margin Account	Receivable – Margin Account Cash amounts held by counterparties as margin collateral for certain financial transactions are recorded as Receivable – margin account in "Other current assets" on the consolidated balance sheets. The costs being hedged are fuel for electric generation, purchased power, and cost of gas sold.
New Accounting Pronouncement Disclosure	In November 2023, the Financial Accounting Standards Board modified authoritative guidance within the codification's Segment Reporting topic, which enhanced the disclosure requirements for significant segment expenses and other segment items. The authoritative guidance will become effective for fiscal years beginning after December 15, 2023, and for interim periods within fiscal years beginning after December 15, 2024. MGE will adopt the standard as of the effective date. The adoption of this standard will not have a material impact on MGE Energy's and MGE's financial statements. In December 2023, the Financial Accounting Standards Board issued authoritative guidance within the codification's Income Taxes topic, which expanded the disclosure requirements over effective tax rate reconciliations and income taxes paid. For public business entities, the authoritative guidance will become effective for fiscal years beginning after December 15, 2024. MGE will adopt the standard as of the effective date. The adoption of this standard will not have a material impact on MGE Energy's and MGE's financial statements.
Investments - ATC and ATC Holdco	MGE Transco and MGEE Transco have accounted for their investments in ATC and ATC Holdco, respectively, under the equity method of accounting.
Pension and Other Postretirement Benefit Plan Assets	MGE maintains qualified and nonqualified pension plans, health care, and life insurance benefits and defined contribution 401(k) benefit plans for its employees and retirees. The components of net periodic benefit cost, other than the service cost component, are recorded in " Other income, net " on the consolidated statements of income. The service cost component is recorded in "Other operations and maintenance" on the consolidated statements of income. MGE has regulatory treatment and recognizes regulatory assets or liabilities for timing differences between when net periodic benefit costs are recovered and when costs are recognized.
Common Stock	MGE Energy sells shares of its common stock through its Direct Stock Purchase and Dividend Reinvestment Plan (the Stock Plan). Those shares may be newly issued shares or shares that are purchased in the open market by an independent agent for participants in the Stock Plan. Sales of newly issued shares under the Stock Plan are covered by a shelf registration statement that MGE Energy filed with the SEC.
Wisconsin Fuel Rules	Fuel rules require Wisconsin utilities to defer electric fuel-related costs that fall outside a symmetrical cost tolerance band around the amount approved for a utility in its annual fuel proceedings. Any over- or under-recovery of the actual costs is determined in the following year and is then reflected in future billings to electric retail customers. The fuel rules bandwidth is set at plus or minus 2 % in 2024 and 2023. The electric fuel-related costs are subject to an excess revenues test. Excess revenues are defined as revenues in the year in question that provide MGE with a greater return on common equity than authorized by the PSCW in MGE's latest rate order. The recovery of under-collected electric fuel-related costs would be reduced by the amount that exceeds the excess revenue test. These costs are subject to the PSCW's annual review of fuel costs completed in the year following the deferral.
Derivative Hedging	As part of its regular operations, MGE enters into contracts, including options, swaps, futures, forwards, and other contractual commitments, to manage its exposure to commodity prices. To the extent that these contracts are derivatives, MGE assesses whether or not the normal purchases or normal sales exclusion applies. For contracts to which this exclusion cannot be applied, the derivatives are recognized in the consolidated balance sheets at fair value. MGE's financial commodity derivative activities are conducted in accordance with its electric and gas risk management program, which is approved by the PSCW and limits the volume MGE can hedge with specific risk management strategies. The maximum length of time over which cash flows related to energy commodities can be hedged is four years . If the derivative qualifies for regulatory deferral, the derivatives are marked to fair value and are offset with a corresponding regulatory asset or liability depending on whether the derivative is in a net loss or net gain position, respectively. The deferred gain or loss is recognized in earnings in the delivery month applicable to the instrument. Gains and losses related to hedges qualifying for regulatory treatment are refundable or recoverable in gas rates through the Purchased Gas Adjustment (PGA) or in electric rates as a component of the fuel rules mechanism.
Derivative Netting	All derivative instruments in this table are presented on a gross basis and are calculated prior to the netting of instruments with the same counterparty under a master netting agreement as well as the netting of collateral. For financial statement purposes, instruments are netted with the same counterparty under a master netting agreement as well as the netting of collateral.
Recurring Fair Value Measurements	Fair value is defined as the price that would be received to sell an asset or would be paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants at the measurement date. The accounting standard clarifies that fair value should be based on the assumptions market participants would use when pricing the asset or liability including assumptions about risk. The standard also establishes a three-level fair value hierarchy based upon the observability of the assumptions used and requires the use of observable market data when available. The levels are: Level 1 - Pricing inputs are quoted prices within active markets for identical assets or liabilities. Level 2 - Pricing inputs are quoted prices within active markets for similar assets or liabilities; quoted prices for identical or similar instruments in markets that are not active; and model-derived valuations that are correlated with or otherwise verifiable by observable market data. Level 3 - Pricing inputs are unobservable and reflect management's best estimate of what market participants would use in pricing the asset or liability. a. Fair Value of Financial Assets and Liabilities Recorded at the Carrying Amount. The carrying amount of cash, cash equivalents, and outstanding commercial paper approximates fair market value due to the short maturity of those investments and obligations. The estimated fair market value of long-term debt is based on quoted market prices for similar financial instruments. Since long-term debt is not traded in an active market, it is classified as Level 2. Investments include exchange-traded investment securities valued using quoted prices on active exchanges and are therefore classified as Level 1. Deferred Compensation. The deferred compensation plans allow participants to defer certain cash compensation into notional investment accounts. These amounts are included within "Other deferred liabilities and other" in the consolidated balance sheets. The value of certain deferred compensation obligations is based on the market value of the participants' notional investment accounts. The underlying notional investments are comprised primarily of equities, mutual funds, and fixed income securities that are based on directly and indirectly observable market prices. Since the deferred compensation obligations themselves are not exchanged in an active market, they are classified as Level 2. The value of legacy deferred compensation obligations is based on notional investments that earn interest based upon the semiannual rate of U.S. Treasury Bills having a 26 -week maturity increased by 1 % compounded monthly with a minimum annual rate of 7 %, compounded monthly. The notional investments are based upon observable market data, however, since the deferred compensation obligations themselves are not exchanged in an active market, they are classified as Level 2. Derivatives. Derivatives include exchange-traded derivative contracts, over-the-counter transactions and FTRs. Most exchange-traded derivative contracts are valued based on unadjusted quoted prices in active markets and are therefore classified as Level 1. A small number of exchange-traded derivative contracts are valued using quoted market pricing in markets with insufficient volumes and are therefore considered unobservable and classified as Level 3. Transactions done with an over-the-counter party are on inactive markets and are therefore classified as Level 3. These transactions are valued based on quoted prices from markets with similar exchange-traded transactions. FTRs are priced based upon monthly auction results for identical or similar instruments in a closed market with limited data available and are therefore classified as Level 3.

Summary of Significant Accoun_2

Summary of Significant Accounting Principles (Tables)	9 Months Ended
	Sep. 30, 2024
Cash, Cash Equivalents, And Restricted Cash [Abstract]
Cash, Cash Equivalents, and Restricted Cash	The following table presents the components of total cash, cash equivalents, and restricted cash on the consolidated balance sheets. MGE Energy MGE September 30, December 31, September 30, December 31, (In thousands) 2024 2023 2024 2023 Cash and cash equivalents $ 14,875 $ 11,140 $ 3,140 $ 2,819 Restricted cash 639 858 639 858 Receivable - margin account 2,892 3,028 2,892 3,028 Cash, cash equivalents, and restricted cash $ 18,406 $ 15,026 $ 6,671 $ 6,705

Investment in ATC and ATC Hol_2

Investment in ATC and ATC Holdco (Tables)	9 Months Ended
	Sep. 30, 2024
Equity Method Investments and Joint Ventures [Abstract]
Equity Method Investments Financial Data	MGE Transco recorded the following amounts related to its investment in ATC: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2024 2023 2024 2023 Equity earnings from investment in ATC $ 2,868 $ 2,662 $ 8,338 $ 7,844 Dividends received from ATC 2,176 2,057 6,414 6,305 Capital contributions to ATC 894 1,075 2,679 3,033 ATC's summarized financial data is as follows: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2024 2023 2024 2023 Operating revenues $ 221,434 $ 206,197 $ 651,584 $ 610,399 Operating expenses ( 110,043 ) ( 102,819 ) ( 324,082 ) ( 303,412 ) Other income, net 355 701 898 1,657 Interest expense, net ( 36,838 ) ( 33,555 ) ( 108,296 ) ( 99,969 ) Earnings before members' income taxes $ 74,908 $ 70,524 $ 220,104 $ 208,675

Taxes (Tables)

Taxes (Tables)	9 Months Ended
	Sep. 30, 2024
Income Tax Disclosure [Abstract]
Effective Tax Rate Reconciliation	The consolidated income tax provision differs from the amount computed by applying the statutory federal income tax rate to income before income taxes, as follows: MGE Energy MGE Three Months Ended September 30, 2024 2023 2024 2023 Statutory federal income tax rate 21.0 % 21.0 % 21.0 % 21.0 % State income taxes, net of federal benefit 6.2 6.2 6.2 6.2 Amortized investment tax credits ( 2.0 ) ( 0.6 ) ( 2.2 ) ( 0.6 ) Credit for electricity from renewable energy ( 10.7 ) ( 4.9 ) ( 11.6 ) ( 5.2 ) AFUDC equity, net ( 0.6 ) ( 0.9 ) ( 0.6 ) ( 1.0 ) Amortization of utility excess deferred tax - tax reform (a) ( 5.7 ) ( 1.4 ) ( 6.2 ) ( 1.5 ) Other, net, individually insignificant — ( 0.5 ) ( 0.1 ) ( 0.5 ) Effective income tax rate 8.2 % 18.9 % 6.5 % 18.4 % MGE Energy MGE Nine Months Ended September 30, 2024 2023 2024 2023 Statutory federal income tax rate 21.0 % 21.0 % 21.0 % 21.0 % State income taxes, net of federal benefit 6.2 6.3 6.2 6.3 Amortized investment tax credits ( 2.2 ) ( 0.7 ) ( 2.4 ) ( 0.7 ) Credit for electricity from renewable energy ( 10.8 ) ( 5.4 ) ( 11.7 ) ( 5.7 ) AFUDC equity, net ( 0.6 ) ( 0.6 ) ( 0.7 ) ( 0.7 ) Amortization of utility excess deferred tax - tax reform (a) ( 6.1 ) ( 1.6 ) ( 6.7 ) ( 1.7 ) Other, net, individually insignificant ( 0.1 ) ( 0.2 ) ( 0.1 ) ( 0.3 ) Effective income tax rate 7.4 % 18.8 % 5.6 % 18.2 % (a) Included are impacts of the Tax Cut and Jobs Act of 2017 for the regulated utility for excess deferred taxes recognized using a normalization method of accounting in recognition of IRS rules that restrict the rate at which the excess deferred taxes may be returned to utility customers. For both the three months ended September 30, 2024 and 2023, MGE recognized $ 0.9 million. For the nine months ended September 30, 2024 and 2023, MGE recognized $ 2.6 million and $ 2.7 million, respectively. For the three and nine months ended September 30, 2024, MGE recognized $ 1.0 million and $ 3.1 million, respectively, of deferred taxes not restricted by IRS normalization rules, compared to a net collection from customers of $ 0.3 million and $ 1.0 milli on for the three and nine months ended September 30, 2023 .

Pension and Other Postretirem_2

Pension and Other Postretirement Plans (Tables)	9 Months Ended
	Sep. 30, 2024
Retirement Benefits [Abstract]
Schedule of Net Periodic Benefit Costs	The following table presents the components of net periodic benefit costs recognized. Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2024 2023 2024 2023 Pension Benefits Components of net periodic benefit cost: Service cost $ 769 $ 723 $ 2,308 $ 2,169 Interest cost 4,280 4,330 12,839 12,989 Expected return on assets ( 7,149 ) ( 6,312 ) ( 21,448 ) ( 18,936 ) Amortization of: Actuarial loss 215 440 644 1,320 Net periodic benefit (credit) cost $ ( 1,885 ) $ ( 819 ) $ ( 5,657 ) $ ( 2,458 ) Postretirement Benefits (a) Components of net periodic benefit cost: Service cost $ 214 $ 195 $ 642 $ 585 Interest cost 778 827 2,354 2,481 Expected return on assets ( 675 ) ( 649 ) ( 2,059 ) ( 1,946 ) Settlement cost 288 — 288 — Amortization of: Transition obligation 1 1 2 2 Prior service credit ( 234 ) — ( 242 ) — Actuarial loss (gain) 774 ( 48 ) 568 ( 143 ) Net periodic benefit cost $ 1,146 $ 326 $ 1,553 $ 979 (a) In August 2024, MGE entered into an agreement to transfer the mortality and investment risk, as well as the administration of, its employer-paid life insurance plan to a third party. MGE accounted for the settlement under the scope of ASC 715.

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2024
Commitments and Contingencies Disclosure [Abstract]
Contractual Obligation, Fiscal Year Maturity Schedule	The following table shows future commitments related to purchase contracts as of September 30, 2024: (In thousands) 2024 2025 2026 2027 2028 Thereafter Coal (a) $ 10,902 $ 19,894 $ 3,751 $ — $ — $ — Natural gas (b) 18,695 39,937 15,492 2,546 2,546 11,224 $ 29,597 $ 59,831 $ 19,243 $ 2,546 $ 2,546 $ 11,224 (a) Total coal commitments for MGE's share of the Columbia and Elm Road Units, including transportation. Fuel procurement for MGE's jointly owned Columbia and Elm Road Units is handled by WPL and WEPCO, respectively, who are the operators of those facilities. (b) MGE's natural gas transportation and storage contracts require fixed monthly payments for firm supply pipeline transportation and storage capacity. The pricing components of the fixed monthly payments for the transportation and storage contracts are approved by FERC but may be subject to change. MGE's natural gas supply commitments include market-based pricing.

Rate Matters (Tables)

Rate Matters (Tables)	9 Months Ended
	Sep. 30, 2024
Regulated Operations [Abstract]
Rate Proceedings	Rate increase Return on Common Equity Common Equity Component of Regulatory Capital Structure Effective Date Approved 2022/2023 settlement Gas 0.96 % 9.8 % 55.6 % 1/1/2023 Approved limited 2023 reopener (a) Electric 9.01 % 9.8 % 55.6 % 1/1/2023 Approved 2024/2025 rate proceeding (b)(c) Electric 1.54 % 9.7 % 56.1 % 1/1/2024 Gas 2.44 % 9.7 % 56.1 % 1/1/2024 Electric (d) 4.17 % 9.7 % 56.1 % 1/1/2025 Gas 1.32 % 9.7 % 56.1 % 1/1/2025 (a) The electric rate increase was driven by generation assets including our investments in Badger Hollow II (solar), Paris (solar and battery), Red Barn Wind Farm (wind), and West Riverside (natural gas). In addition, the reopener request included an increase in fuel costs and the recovery of deferred 2021 fuel costs. The reopener also revised the depreciation schedule for Columbia Unit 2 and shared equipment to 2029 to align with the depreciation schedule for Unit 1. (b) The electric increase was driven by an increase in rate base including our investments made in West Riverside, local solar, continued investment in grid modernization, as well as higher costs for transmission, pension and OPEB, and uncollectible costs (including costs previously deferred from prior years). This increase in electric costs is offset by a decrease in fuel costs and benefit from lower tax expense (including impacts from the Inflation Reduction Act). MGE filed an updated 2025 fuel forecast with the PSCW in 2024, which will impact rates in 2025, based on any variance between the forecast submitted as part of the rates and updated forecast. In addition, the PSCW authorized MGE to defer a recovery of and a return on costs associated for any change in the in service date for Paris and force majeure costs for Badger Hollow II and Paris that were not reflected in this rate filing. The PSCW also approved deferral of any differential in PTC tax credits reflected in rates and actual credits produced. These deferrals will be reflected in MGE's next rate case filing. The gas rate increases were also driven by our investment made in grid modernization and higher pension and OPEB and uncollectible costs (including costs previously deferred from prior years). This increase in gas costs is offset by a tax benefit related to excess deferred taxes. Included in the gas residential rate is a reduction in the customer fixed charge. (c) The 2024/2025 rate order includes an earnings sharing mechanism, under which, if MGE earns above the authorized Return on Equity (ROE) in the rate order: (i) the utility will retain 100.0% of earnings for the first 15 basis points above the authorized ROE; (ii) 50.0% of the next 60 basis points will be required to be deferred and returned to customers; and (iii) 100.0% of any remaining excess earnings will be required to be refunded to customers. The earnings calculation excludes fuel rules adjustments. See "Fuel Rules" below. (d) MGE filed a 2025 Fuel Cost Plan with the PSCW in June 2024. The plan would lower the 2025 increase in electric rates to 2.47 % to reflect lower expected fuel costs. MGE expects a final decision from the PSCW on the Fuel Cost Plan by the end of 2024.
Deferred Fuel Rules	The following table summarizes deferred electric fuel-related costs: Fuel Costs (Savings) ( in millions ) Refund or Recovery Period 2021 $ 3.3 (a) January 2023 through December 2023 2022 $ 8.8 (a) October 2023 through September 2024 2023 ($ 7.2 ) (a) October 2024 through December 2024 (a) There was no change to the refund or recovery in the fuel rules proceedings from the amount MGE deferred .

Derivative and Hedging Instru_2

Derivative and Hedging Instruments (Tables)	9 Months Ended
	Sep. 30, 2024
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Gross Notional Volume of Open Derivatives	The gross notional volume of open derivatives is as follows: September 30, 2024 December 31, 2023 Commodity derivative contracts 269,120 MWh 392,000 MWh Commodity derivative contracts 7,900,000 Dth 7,180,000 Dth FTRs 3,276 MW 1,824 MW
Fair Value of Derivative Instruments on the Balance Sheet	The following table summarizes the fair value of the derivative instruments on the consolidated balance sheets. All derivative instruments in this table are presented on a gross basis and are calculated prior to the netting of instruments with the same counterparty under a master netting agreement as well as the netting of collateral. For financial statement purposes, instruments are netted with the same counterparty under a master netting agreement as well as the netting of collateral. Derivative Derivative (In thousands) Assets Liabilities Balance Sheet Location September 30, 2024 Commodity derivative contracts (a) $ 891 $ 2,199 Other current liabilities Commodity derivative contracts (a) 84 261 Other deferred liabilities and other FTRs — 17 Other current liabilities December 31, 2023 Commodity derivative contracts (a) $ 263 $ 4,942 Other current liabilities Commodity derivative contracts (a) 156 882 Other deferred liabilities and other FTRs 179 — Other current assets (a) As of September 30, 2024, and December 31, 2023, collateral of $ 1.5 million and $ 5.4 million, respectively, was posted against and netted with derivative liability positions on the consolidated balance sheets. The fair value of the derivative liability disclosed in this table has not been reduced for the collateral posted.
Offsetting Assets	The following table shows the effect of netting arrangements for recognized derivative assets and liabilities that are subject to a master netting arrangement or similar arrangement on the consolidated balance sheets. Offsetting of Derivative Assets and Liabilities (In thousands) Gross Amounts Gross Amounts Offset in Balance Sheets Collateral Posted Against Derivative Positions Net Amount Presented in Balance Sheets September 30, 2024 Assets Commodity derivative contracts $ 975 $ ( 975 ) $ — $ — Liabilities FTRs 17 — ( 17 ) — Commodity derivative contracts 2,460 ( 975 ) ( 1,485 ) — December 31, 2023 Assets Commodity derivative contracts $ 419 $ ( 419 ) $ — $ — FTRs 179 — — 179 Liabilities Commodity derivative contracts 5,824 ( 419 ) ( 5,405 ) —
Offsetting Liabilities	The following table shows the effect of netting arrangements for recognized derivative assets and liabilities that are subject to a master netting arrangement or similar arrangement on the consolidated balance sheets. Offsetting of Derivative Assets and Liabilities (In thousands) Gross Amounts Gross Amounts Offset in Balance Sheets Collateral Posted Against Derivative Positions Net Amount Presented in Balance Sheets September 30, 2024 Assets Commodity derivative contracts $ 975 $ ( 975 ) $ — $ — Liabilities FTRs 17 — ( 17 ) — Commodity derivative contracts 2,460 ( 975 ) ( 1,485 ) — December 31, 2023 Assets Commodity derivative contracts $ 419 $ ( 419 ) $ — $ — FTRs 179 — — 179 Liabilities Commodity derivative contracts 5,824 ( 419 ) ( 5,405 ) —
Derivative Gains and Losses in Balance Sheet	The following tables summarize the unrealized and realized gains/losses related to the derivative instruments on the consolidated balance sheets and the consolidated statements of income. 2024 2023 (In thousands) Current and Long-Term Regulatory Asset (Liability) Other Current Assets Current and Long-Term Regulatory Asset (Liability) Other Current Assets Three Months Ended September 30: Balance as of July 1, $ 1,946 $ 527 $ 5,017 $ 1,074 Unrealized loss 1,768 — 1,100 — Realized (loss) gain reclassified to a deferred account ( 639 ) 639 ( 1,676 ) 1,676 Realized loss reclassified to income statement ( 1,573 ) ( 707 ) ( 1,893 ) ( 2,155 ) Balance as of September 30, $ 1,502 $ 459 $ 2,548 $ 595 Nine Months Ended September 30: Balance as of January 1, $ 5,226 $ 1,569 $ 5,094 $ 2,747 Unrealized loss 4,666 — 15,495 — Realized (loss) gain reclassified to a deferred account ( 3,333 ) 3,333 ( 10,581 ) 10,581 Realized loss reclassified to income statement ( 5,057 ) ( 4,443 ) ( 7,460 ) ( 12,733 ) Balance as of September 30, $ 1,502 $ 459 $ 2,548 $ 595
Derivative Gains and Losses in Income Statement	Realized Losses (Gains) 2024 2023 (In thousands) Fuel for Electric Generation/ Purchased Power Cost of Gas Sold Fuel for Electric Generation/ Purchased Power Cost of Gas Sold Three Months Ended September 30: Commodity derivative contracts $ 1,969 $ — $ 4,179 $ — FTRs 311 — ( 131 ) — Nine Months Ended September 30: Commodity derivative contracts $ 5,723 $ 3,265 $ 14,566 $ 6,451 FTRs 512 — ( 824 ) —

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2024
Fair Value Disclosures [Abstract]
Estimated Fair Market Value of Financial Instruments	The estimated fair market value of financial instruments are as follows: September 30, 2024 December 31, 2023 (In thousands) Carrying Amount Fair Value Carrying Amount Fair Value Long-term debt (a) $ 724,699 $ 682,359 $ 728,546 $ 675,922 (a) Includes long-term debt due within one year. Excludes debt issuance costs and unamortized discount of $ 4.2 million and $ 4.6 million as of September 30, 2024, and December 31, 2023 , respectively.
Assets and Liabilities Measured at Fair Value on a Recurring Basis	The following table presents the balances of assets and liabilities measured at fair value on a recurring basis. Fair Value as of September 30, 2024 (In thousands) Total Level 1 Level 2 Level 3 MGE Energy Assets: Derivatives, net (b) $ 975 $ 920 $ — $ 55 Exchange-traded investments — — — — Total Assets $ 975 $ 920 $ — $ 55 Liabilities: Derivatives, net (b) $ 2,477 $ 1,290 $ — $ 1,187 Deferred compensation 6,108 — 6,108 — Total Liabilities $ 8,585 $ 1,290 $ 6,108 $ 1,187 MGE Assets: Derivatives, net (b) $ 975 $ 920 $ — $ 55 Exchange-traded investments — — — — Total Assets $ 975 $ 920 $ — $ 55 Liabilities: Derivatives, net (b) $ 2,477 $ 1,290 $ — $ 1,187 Deferred compensation 6,108 — 6,108 — Total Liabilities $ 8,585 $ 1,290 $ 6,108 $ 1,187 Fair Value as of December 31, 2023 (In thousands) Total Level 1 Level 2 Level 3 MGE Energy Assets: Derivatives, net (b) $ 598 $ 352 $ — $ 246 Exchange-traded investments 2,034 2,034 — — Total Assets $ 2,632 $ 2,386 $ — $ 246 Liabilities: Derivatives, net (b) $ 5,824 $ 2,974 $ — $ 2,850 Deferred compensation 5,246 — 5,246 — Total Liabilities $ 11,070 $ 2,974 $ 5,246 $ 2,850 MGE Assets: Derivatives, net (b) $ 598 $ 352 $ — $ 246 Exchange-traded investments 60 60 — — Total Assets $ 658 $ 412 $ — $ 246 Liabilities: Derivatives, net (b) $ 5,824 $ 2,974 $ — $ 2,850 Deferred compensation 5,246 — 5,246 — Total Liabilities $ 11,070 $ 2,974 $ 5,246 $ 2,850 (b) As of September 30, 2024, and December 31, 2023, collateral of $ 1.5 million and $ 5.4 million, respectively, was posted against and netted with derivative liability positions on the consolidated balance sheets. The fair value of the derivative liability disclosed in this table has not been reduced for the collateral posted.
Changes in Level 3 Assets and Liabilities Measured at Fair Value on a Recurring Basis	The following table summarizes the changes in Level 3 commodity derivative assets and liabilities measured at fair value on a recurring basis. Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2024 2023 2024 2023 Beginning balance $ ( 1,432 ) $ ( 2,892 ) $ ( 2,604 ) $ ( 866 ) Realized and unrealized gains (losses): Included in regulatory assets 300 1,768 1,472 ( 258 ) Included in earnings ( 1,572 ) ( 2,016 ) ( 5,174 ) ( 7,590 ) Settlements 1,572 2,016 5,174 7,590 Balance as of September 30, $ ( 1,132 ) $ ( 1,124 ) $ ( 1,132 ) $ ( 1,124 )
Gains and Losses Included in Income for Level 3 Assets and Liabilities Measured at Fair Value on a Recurring Basis	The following table presents total realized and unrealized gains (losses) included in income for Level 3 assets and liabilities measured at fair value on a recurring basis (c) . Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2024 2023 2024 2023 Purchased power expense $ ( 1,572 ) $ ( 2,016 ) $ ( 5,174 ) $ ( 7,590 ) (c) MGE's exchange-traded derivative contracts, over-the-counter party transactions, and FTRs are subject to regulatory deferral. These derivatives are therefore marked to fair value and are offset in the financial statements with a corresponding regulatory asset or liability.

Joint Plant (Tables)

Joint Plant (Tables)	9 Months Ended
	Sep. 30, 2024
Public Utilities, Property, Plant and Equipment [Abstract]
Schedule of Jointly Owned Utility Plants	MGE has ownership interests in generation projects with other co-owners, some of which are under construction, as shown in the following table. Incurred costs are reflected in "Property, plant, and equipment, net" or "Construction work in progress" on the consolidated balance sheets. Project Ownership Interest Source Share of Share of Estimated (a) Costs incurred as (a) Estimated Date of Paris (b) 10 % Solar/Battery 20 MW/ 11 MW $ 61 million (d) $ 48.6 million 2024 Solar Darien (c) 10 % Solar/Battery 25 MW/ 7.5 MW $ 63 million (d) $ 41.9 million 2025 Solar Koshkonong (e) 10 % Solar/Battery 30 MW/ 16.5 MW $ 104 million (d) $ 6.6 million 2026 Solar West Riverside 3.5 % Natural Gas 25 MW $ 25 million $ 25.2 million (f) (a) Excluding AFUDC. (b) Paris Solar-Battery Park is located in the Town of Paris in Kenosha County, Wisconsin. (c) Darien Solar Energy Center is located in Walworth and Rock Counties in southern Wisconsin. (d) Estimated costs are expected to exceed PSCW previously approved Certificate of Authority (CA) levels. Notifications are provided to the PSCW when costs increase above CA levels. MGE has and will continue to request recovery of the updates in its rate case proceedings. (e) Koshkonong Solar Energy Center is located in the Towns of Christiana and Deerfield in Dane County, Wisconsin. (f) In June 2024, MGE purchased an additional ownership interest in West Riverside, a natural gas-fired facility located in Beloit, WI, from WPL, operator and co-owner of the plant. West Riverside was placed in-service in 2020. MGE's interest in West Riverside increased to 6.9 %.

Revenue (Tables)

Revenue (Tables)	9 Months Ended
	Sep. 30, 2024
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	Revenues disaggregated by revenue source were as follows: Three Months Ended Nine Months Ended (In thousands) September 30, September 30, Electric revenues 2024 2023 2024 2023 Residential $ 52,834 $ 50,008 $ 134,296 $ 131,552 Commercial 73,517 70,795 197,541 193,760 Industrial 3,459 3,715 10,314 10,578 Other-retail/municipal 11,346 10,991 31,439 30,853 Total retail 141,156 135,509 373,590 366,743 Sales to the market 5,799 3,305 8,394 9,617 Other 835 77 2,314 1,267 Total electric revenues 147,790 138,891 384,298 377,627 Gas revenues Residential 13,069 13,719 72,057 86,131 Commercial/Industrial 5,892 6,016 43,292 55,726 Total retail 18,961 19,735 115,349 141,857 Gas transportation 1,417 1,587 5,003 5,354 Other 98 102 409 466 Total gas revenues 20,476 21,424 120,761 147,677 Non-regulated energy revenues 214 213 470 475 Total Operating Revenue $ 168,480 $ 160,528 $ 505,529 $ 525,779

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2024
Segment Reporting [Abstract]
Segment Information	MGE Energy operates in the following business segments: electric utility, gas utility, nonregulated energy, transmission investment, and all other. See the 2023 Annual Report on Form 10-K for additional discussion of each of these segments. (In thousands) Electric Gas Non-Regulated Energy Transmission Investment All Others Consolidation/ Consolidated Total Three Months Ended September 30, 2024 Operating revenues $ 147,790 $ 20,476 $ 214 $ — $ — $ — $ 168,480 Interdepartmental revenues ( 44 ) 4,207 11,052 — — ( 15,215 ) — Total operating revenues 147,746 24,683 11,266 — — ( 15,215 ) 168,480 Equity in earnings of investments — — — 2,901 — — 2,901 Net income (loss) 35,035 ( 2,026 ) 6,101 2,112 ( 283 ) — 40,939 Three Months Ended September 30, 2023 Operating revenues $ 138,891 $ 21,424 $ 213 $ — $ — $ — $ 160,528 Interdepartmental revenues 512 3,547 10,398 — — ( 14,457 ) — Total operating revenues 139,403 24,971 10,611 — — ( 14,457 ) 160,528 Equity in earnings of investments — — — 2,690 — — 2,690 Net income (loss) 31,126 ( 801 ) 5,627 1,957 ( 52 ) — 37,857 Nine Months Ended September 30, 2024 Operating revenues $ 384,298 $ 120,761 $ 470 $ — $ — $ — $ 505,529 Interdepartmental revenues ( 154 ) 11,591 32,825 — — ( 44,262 ) — Total operating revenues 384,144 132,352 33,295 — — ( 44,262 ) 505,529 Equity in earnings of investments — — — 8,427 — — 8,427 Net income (loss) 66,458 8,638 17,968 6,130 ( 647 ) — 98,547 Nine Months Ended September 30, 2023 Operating revenues $ 377,627 $ 147,677 $ 475 $ — $ — $ — $ 525,779 Interdepartmental revenues 653 12,978 31,143 — — ( 44,774 ) — Total operating revenues 378,280 160,655 31,618 — — ( 44,774 ) 525,779 Equity in earnings of investments — — — 7,930 — — 7,930 Net income (loss) 65,996 10,539 16,667 5,770 ( 1,356 ) — 97,616 (In thousands) Electric Gas Non-Regulated Energy Consolidation/ Consolidated Total Three Months Ended September 30, 2024 Operating revenues $ 147,790 $ 20,476 $ 214 $ — $ 168,480 Interdepartmental revenues ( 44 ) 4,207 11,052 ( 15,215 ) — Total operating revenues 147,746 24,683 11,266 ( 15,215 ) 168,480 Net income attributable to MGE 35,035 ( 2,026 ) 6,101 ( 5,777 ) 33,333 Three Months Ended September 30, 2023 Operating revenues $ 138,891 $ 21,424 $ 213 $ — $ 160,528 Interdepartmental revenues 512 3,547 10,398 ( 14,457 ) — Total operating revenues 139,403 24,971 10,611 ( 14,457 ) 160,528 Net income attributable to MGE 31,126 ( 801 ) 5,627 ( 5,487 ) 30,465 Nine Months Ended September 30, 2024 Operating revenues $ 384,298 $ 120,761 $ 470 $ — $ 505,529 Interdepartmental revenues ( 154 ) 11,591 32,825 ( 44,262 ) — Total operating revenues 384,144 132,352 33,295 ( 44,262 ) 505,529 Net income attributable to MGE 66,458 8,638 17,968 ( 17,140 ) 75,924 Nine Months Ended September 30, 2023 Operating revenues $ 377,627 $ 147,677 $ 475 $ — $ 525,779 Interdepartmental revenues 653 12,978 31,143 ( 44,774 ) — Total operating revenues 378,280 160,655 31,618 ( 44,774 ) 525,779 Net income attributable to MGE 65,996 10,539 16,667 ( 16,382 ) 76,820

Summary of Significant Accoun_3

Summary of Significant Accounting Principles (Details-1) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023	Sep. 30, 2023	Dec. 31, 2022
Cash Cash Equivalents And Restricted Cash [Line Items]
Cash and cash equivalents	$ 14,875	$ 11,140
Restricted cash	639	858
Receivable - margin account	2,892	3,028
Cash, cash equivalents, and restricted cash	18,406	15,026	$ 16,207	$ 17,968
MGE [Member]
Cash Cash Equivalents And Restricted Cash [Line Items]
Cash and cash equivalents	3,140	2,819
Restricted cash	639	858
Receivable - margin account	2,892	3,028
Cash, cash equivalents, and restricted cash	$ 6,671	$ 6,705	$ 7,606	$ 10,500

Summary of Significant Accoun_4

Summary of Significant Accounting Principles (Details-2) $ in Millions	9 Months Ended
	Sep. 30, 2024 USD ($)
Columbia Units [Member]
Impairment of Long-Lived Assets
Impairment of long-lived assets	$ 0

Investment in ATC and ATC Hol_3

Investment in ATC and ATC Holdco (Details-1) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Schedule of Equity Method Investments [Line Items]
Equity earnings from investment			$ 8,427	$ 7,930
Dividends from investments			6,414	6,305
Capital contributions to investments			4,348	5,986
MGE Transco [Member] | ATC [Member]
Schedule of Equity Method Investments [Line Items]
Equity earnings from investment	$ 2,868	$ 2,662	8,338	7,844
Dividends from investments	2,176	2,057	6,414	6,305
Capital contributions to investments	$ 894	$ 1,075	$ 2,679	$ 3,033

Investment in ATC and ATC Hol_4

Investment in ATC and ATC Holdco (Details-2) - ATC [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Schedule of Equity Method Investments [Line Items]
Operating revenues	$ 221,434	$ 206,197	$ 651,584	$ 610,399
Operating expenses	(110,043)	(102,819)	(324,082)	(303,412)
Other income, net	355	701	898	1,657
Interest expense, net	(36,838)	(33,555)	(108,296)	(99,969)
Earnings before members' income taxes	$ 74,908	$ 70,524	$ 220,104	$ 208,675

Investment in ATC and ATC Hol_5

Investment in ATC and ATC Holdco (Details-3) - ATC [Member] - Affiliated Entity [Member] - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Receivables [Abstract]
Other Receivables	$ 2.2		$ 2.2		$ 5.3
Operating Costs and Expenses [Abstract]
Operating Costs and Expenses, Total	$ 9.1	$ 8.5	$ 27.3	$ 25.4

Taxes (Details)

Taxes (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Statutory federal income tax rate		21%	21%	21%	21%
State income taxes, net of federal benefit		6.20%	6.20%	6.20%	6.30%
Amortized investment tax credits		(2.00%)	(0.60%)	(2.20%)	(0.70%)
Credit for electricity from renewable energy		(10.70%)	(4.90%)	(10.80%)	(5.40%)
AFUDC equity, net		(0.60%)	(0.90%)	(0.60%)	(0.60%)
Amortization of utility excess deferred tax - tax reform	[1]	(5.70%)	(1.40%)	(6.10%)	(1.60%)
Other, net, individually insignificant		0%	(0.50%)	(0.10%)	(0.20%)
Effective income tax rate		8.20%	18.90%	7.40%	18.80%
Excess Deferred Taxes, Tax Cuts And Jobs Act [Member]
Effects Of The Tax Cuts And Jobs Act [Abstract]
Excess deferred tax - Income statement effect		$ 0.9	$ 0.9	$ 2.6	$ 2.7
Return of unprotected excess deferred taxes		$ 1		$ 3.1
Deficient Deferred Taxes, Tax Cuts And Jobs Act [Member]
Effects Of The Tax Cuts And Jobs Act [Abstract]
Collection of unprotected deficient deferred taxes			$ 0.3		$ 1
MGE [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Statutory federal income tax rate		21%	21%	21%	21%
State income taxes, net of federal benefit		6.20%	6.20%	6.20%	6.30%
Amortized investment tax credits		(2.20%)	(0.60%)	(2.40%)	(0.70%)
Credit for electricity from renewable energy		(11.60%)	(5.20%)	(11.70%)	(5.70%)
AFUDC equity, net		(0.60%)	(1.00%)	(0.70%)	(0.70%)
Amortization of utility excess deferred tax - tax reform	[1]	(6.20%)	(1.50%)	(6.70%)	(1.70%)
Other, net, individually insignificant		(0.10%)	(0.50%)	(0.10%)	(0.30%)
Effective income tax rate		6.50%	18.40%	5.60%	18.20%
Indemnification Agreement [Member] | Renewable Tax Credits Transferred [Member]
Effects of The Inflation Reduction Act [Abstract]
Guarantor Obligations, Liquidation Proceeds, Monetary Amount				$ 7.1
[1] Included are impacts of the Tax Cut and Jobs Act of 2017 for the regulated utility for excess deferred taxes recognized using a normalization method of accounting in recognition of IRS rules that restrict the rate at which the excess deferred taxes may be returned to utility customers. For both the three months ended September 30, 2024 and 2023, MGE recognized $ 0.9 million. For the nine months ended September 30, 2024 and 2023, MGE recognized $ 2.6 million and $ 2.7 million, respectively. For the three and nine months ended September 30, 2024, MGE recognized $ 1.0 million and $ 3.1 million, respectively, of deferred taxes not restricted by IRS normalization rules, compared to a net collection from customers of $ 0.3 million and $ 1.0 milli on for the three and nine months ended September 30, 2023 .

Pension and Other Postretirem_3

Pension and Other Postretirement Plans (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Defined Benefit Plan Deferred Pension And Other Postretirement Benefit Plan Costs Recovered [Abstract]
Deferred (recognized) pension and OPEB costs	$ (500)	$ 1,600	$ (3,100)	$ 2,400
Amortization of:
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Amortization of Prior Service Cost (Credit), Statement of Income or Comprehensive Income [Extensible Enumeration]			Nonoperating Income (Expense)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Interest Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]			Nonoperating Income (Expense)
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Expected Return (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]			Nonoperating Income (Expense)
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Amortization of Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]			Nonoperating Income (Expense)
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Amortization of Transition Asset (Obligation), Statement of Income or Comprehensive Income [Extensible Enumeration]			Nonoperating Income (Expense)
Pension Benefits [Member]
Components of net periodic benefit cost:
Service cost	769	723	$ 2,308	2,169
Interest cost	4,280	4,330	12,839	12,989
Expected return on assets	(7,149)	(6,312)	(21,448)	(18,936)
Amortization of:
Actuarial (gain) loss	215	440	644	1,320
Net periodic benefit (credit) cost	(1,885)	(819)	(5,657)	(2,458)
Postretirement Benefits [Member]
Components of net periodic benefit cost:
Service cost	214	195	642	585
Interest cost	778	827	2,354	2,481
Expected return on assets	(675)	(649)	(2,059)	(1,946)
Settlement cost	(288)	0	(288)	0
Amortization of:
Transition obligation	1	1	2	2
Prior service credit	(234)	0	(242)	0
Actuarial (gain) loss	774	(48)	568	(143)
Net periodic benefit (credit) cost	$ 1,146	$ 326	$ 1,553	$ 979

Equity and Financing Arrangem_2

Equity and Financing Arrangements (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2024	Sep. 30, 2023	Oct. 31, 2024
Common Stock [Abstract]
Stock Issued During Period, Shares, Dividend Reinvestment Plan	29,176	29,176
Issuance of common stock, net	$ 2,600	$ 2,591	$ 0
Dilutive Shares Calculation [Abstract]
Shares included in diluted earnings per share		26,302
Debt issuance, 5.30% due 2039 | Subsequent Event [Member] | Other Long-Term Debt [Member]
Debt Instrument [Line Items]
Face amount				$ 25,000
Interest rate				5.30%
Debt issuance, 5.59% due 2054 | Subsequent Event [Member] | Other Long-Term Debt [Member]
Debt Instrument [Line Items]
Face amount				$ 25,000
Interest rate				5.59%

Share Based Compensation (Detai

Share Based Compensation (Details) - USD ($) $ in Millions		3 Months Ended			9 Months Ended
	Mar. 01, 2024	Sep. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Compensation expense		$ 1.2		$ 0.1	$ 3.1	$ 1.8
2021 Long Term Incentive Plan [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Equity-based compensation plans and other - Shares			12,518
2021 Long Term Incentive Plan [Member] | Performance Shares [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period	16,414
2021 Long Term Incentive Plan [Member] | Restricted Units [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period	29,733
2006 Performance Unit Plan and 2021 Long Term Incentive Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Cash payments distributed related to awards previously granted and now payable			$ 2.5

Commitments and Contingencies_2

Commitments and Contingencies (Details-1) $ in Millions	Jun. 30, 2024 USD ($)
Columbia Environmental Project, CCR [Member]
Public Utilities, General Disclosures [Line Items]
Asset Retirement Obligation	$ 23.7

Commitments and Contingencies_3

Commitments and Contingencies (Details-2) $ in Thousands	Sep. 30, 2024 USD ($)
Operating expense purchase contracts [Abstract]
Purchase obligation, 2024	$ 29,597
Purchase obligation, 2025	59,831
Purchase obligation, 2026	19,243
Purchase obligation, 2027	2,546
Purchase obligation, 2028	2,546
Purchase obligation, Thereafter	11,224
Coal [Member]
Operating expense purchase contracts [Abstract]
Purchase obligation, 2024	10,902	[1]
Purchase obligation, 2025	19,894	[1]
Purchase obligation, 2026	3,751	[1]
Purchase obligation, 2027	0	[1]
Purchase obligation, 2028	0	[1]
Purchase obligation, Thereafter	0	[1]
Natural Gas [Member]
Operating expense purchase contracts [Abstract]
Purchase obligation, 2024	18,695	[2]
Purchase obligation, 2025	39,937	[2]
Purchase obligation, 2026	15,492	[2]
Purchase obligation, 2027	2,546	[2]
Purchase obligation, 2028	2,546	[2]
Purchase obligation, Thereafter	$ 11,224	[2]
[1] Total coal commitments for MGE's share of the Columbia and Elm Road Units, including transportation. Fuel procurement for MGE's jointly owned Columbia and Elm Road Units is handled by WPL and WEPCO, respectively, who are the operators of those facilities. MGE's natural gas transportation and storage contracts require fixed monthly payments for firm supply pipeline transportation and storage capacity. The pricing components of the fixed monthly payments for the transportation and storage contracts are approved by FERC but may be subject to change. MGE's natural gas supply commitments include market-based pricing.

Rate Matters (Details)

Rate Matters (Details) - USD ($) $ in Millions		9 Months Ended		12 Months Ended
		Sep. 30, 2024		Dec. 31, 2025	Dec. 31, 2023		Dec. 31, 2022	Dec. 31, 2021
Fuel Rules [Abstract]
Deferred fuel rules monitored costs	[1]				$ 7.2		$ (8.8)	$ (3.3)
Electric Rate Proceeding [Member] | PSCW [Member] | MGE [Member]
Rate Proceedings [Abstract]
Authorized rate increase (decrease), percentage		1.54%	[2],[3]		9.01%	[4]
Authorized return on equity, percentage		9.70%			9.80%
Approved equity capital structure, percentage		56.10%			55.60%
Fuel Rules [Abstract]
Fuel rules, bandwidth		2%			2%
Electric Rate Proceeding [Member] | PSCW [Member] | Rate Matters For Future Periods [Member] | MGE [Member]
Rate Proceedings [Abstract]
Proposed rate increase (decrease), percentage				2.47%
Authorized rate increase (decrease), percentage	[2],[3],[5]			4.17%
Authorized return on equity, percentage				9.70%
Approved equity capital structure, percentage				56.10%
Gas Rate Proceeding [Member] | PSCW [Member] | MGE [Member]
Rate Proceedings [Abstract]
Authorized rate increase (decrease), percentage		2.44%	[2],[3]		0.96%
Authorized return on equity, percentage		9.70%			9.80%
Approved equity capital structure, percentage		56.10%			55.60%
Gas Rate Proceeding [Member] | PSCW [Member] | Rate Matters For Future Periods [Member] | MGE [Member]
Rate Proceedings [Abstract]
Authorized rate increase (decrease), percentage	[2],[3]			1.32%
Authorized return on equity, percentage				9.70%
Approved equity capital structure, percentage				56.10%
[1] There was no change to the refund or recovery in the fuel rules proceedings from the amount MGE deferred . 2024/2025 rate order includes an earnings sharing mechanism, under which, if MGE earns above the authorized Return on Equity (ROE) in the rate order: (i) the utility will retain 100.0% of earnings for the first 15 basis points above the authorized ROE; (ii) 50.0% of the next 60 basis points will be required to be deferred and returned to customers; and (iii) 100.0% of any remaining excess earnings will be required to be refunded to customers. The earnings calculation excludes fuel rules adjustments. See "Fuel Rules" below. The electric increase was driven by an increase in rate base including our investments made in West Riverside, local solar, continued investment in grid modernization, as well as higher costs for transmission, pension and OPEB, and uncollectible costs (including costs previously deferred from prior years). This increase in electric costs is offset by a decrease in fuel costs and benefit from lower tax expense (including impacts from the Inflation Reduction Act). MGE filed an updated 2025 fuel forecast with the PSCW in 2024, which will impact rates in 2025, based on any variance between the forecast submitted as part of the rates and updated forecast. In addition, the PSCW authorized MGE to defer a recovery of and a return on costs associated for any change in the in service date for Paris and force majeure costs for Badger Hollow II and Paris that were not reflected in this rate filing. The PSCW also approved deferral of any differential in PTC tax credits reflected in rates and actual credits produced. These deferrals will be reflected in MGE's next rate case filing. The gas rate increases were also driven by our investment made in grid modernization and higher pension and OPEB and uncollectible costs (including costs previously deferred from prior years). This increase in gas costs is offset by a tax benefit related to excess deferred taxes. Included in the gas residential rate is a reduction in the customer fixed charge. The electric rate increase was driven by generation assets including our investments in Badger Hollow II (solar), Paris (solar and battery), Red Barn Wind Farm (wind), and West Riverside (natural gas). In addition, the reopener request included an increase in fuel costs and the recovery of deferred 2021 fuel costs. The reopener also revised the depreciation schedule for Columbia Unit 2 and shared equipment to 2029 to align with the depreciation schedule for Unit 1. MGE filed a 2025 Fuel Cost Plan with the PSCW in June 2024. The plan would lower the 2025 increase in electric rates to 2.47 % to reflect lower expected fuel costs. MGE expects a final decision from the PSCW on the Fuel Cost Plan by the end of 2024.

Derivative and Hedging Instru_3

Derivative and Hedging Instruments (Details-1) $ in Thousands		9 Months Ended	12 Months Ended
		Sep. 30, 2024 USD ($) Dth1 MWh MW	Dec. 31, 2023 USD ($) Dth1 MWh MW
Derivative fair values [Abstract]
Derivative, right to reclaim collateral		$ 1,500	$ 5,400
Commodity Contracts And Financial Transimission Rights [Member]
Derivative fair values [Abstract]
Derivative, Fair Value, Net		$ (1,500)	$ (5,200)
Commodity Contract [Member]
Gross Notional Volume of Open Derivatives [Abstract]
Notional amount, energy measures (in MWh) | MWh		269,120	392,000
Notional amount, decatherm measure (in Dth) | Dth1		7,900,000	7,180,000
Derivative fair values [Abstract]
Derivative Asset, Fair Value, Gross Asset		$ 975	$ 419
Derivative Liability, Fair Value, Gross Liability		2,460	5,824
Collateral posted against derivative positions		0	0
Derivative, right to reclaim collateral		1,485	5,405
Commodity Contract [Member] | Other Current Liabilities [Member]
Derivative fair values [Abstract]
Derivative Asset, Fair Value, Gross Asset	[1]	891	263
Derivative Liability, Fair Value, Gross Liability	[1]	2,199	4,942
Commodity Contract [Member] | Other Deferred Liabilities and Other [Member]
Derivative fair values [Abstract]
Derivative Asset, Fair Value, Gross Asset	[1]	84	156
Derivative Liability, Fair Value, Gross Liability	[1]	261	882
Commodity Contract [Member] | Cash Flow Hedging [Member]
Derivative fair values [Abstract]
Derivative, right to reclaim collateral		$ 1,500	$ 5,400
Energy Related Commodity Contract [Member] | Cash Flow Hedging [Member]
Derivatives, Fair Value [Line Items]
Maximum term of derivative hedging contract		4 years
Financial Transmission Rights [Member]
Gross Notional Volume of Open Derivatives [Abstract]
Notional amount, power measure (in MW) | MW		3,276	1,824
Derivative fair values [Abstract]
Derivative Asset, Fair Value, Gross Asset			$ 179
Derivative Liability, Fair Value, Gross Liability		$ 17
Collateral posted against derivative positions			0
Derivative, right to reclaim collateral		17
Financial Transmission Rights [Member] | Other Current Assets/Liabilities
Derivative fair values [Abstract]
Derivative Asset, Fair Value, Gross Asset		0	179
Derivative Liability, Fair Value, Gross Liability		$ 17	$ 0
[1] As of September 30, 2024, and December 31, 2023, collateral of $ 1.5 million and $ 5.4 million, respectively, was posted against and netted with derivative liability positions on the consolidated balance sheets. The fair value of the derivative liability disclosed in this table has not been reduced for the collateral posted.

Derivative and Hedging Instru_4

Derivative and Hedging Instruments (Details-2) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Commodity Contract [Member]
Offsetting Assets [Line Items]
Derivative Asset, Fair Value, Gross Asset	$ 975	$ 419
Gross amounts offset in balance sheet	(975)	(419)
Collateral posted against derivative positions	0	0
Net amount presented in balance sheet	$ 0	0
Financial Transmission Rights [Member]
Offsetting Assets [Line Items]
Derivative Asset, Fair Value, Gross Asset		179
Gross amounts offset in balance sheet		0
Collateral posted against derivative positions		0
Net amount presented in balance sheet		$ 179

Derivative and Hedging Instru_5

Derivative and Hedging Instruments (Details-3) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Offsetting Liabilities [Line Items]
Collateral posted against derivative positions	$ (1,500)	$ (5,400)
Commodity Contract [Member]
Offsetting Liabilities [Line Items]
Derivative Liability, Fair Value, Gross Liability	2,460	5,824
Gross amounts offset in balance sheet	(975)	(419)
Collateral posted against derivative positions	(1,485)	(5,405)
Net amount presented in balance sheet	0	$ 0
Financial Transmission Rights [Member]
Offsetting Liabilities [Line Items]
Derivative Liability, Fair Value, Gross Liability	17
Gross amounts offset in balance sheet	0
Collateral posted against derivative positions	(17)
Net amount presented in balance sheet	$ 0

Derivative and Hedging Instru_6

Derivative and Hedging Instruments (Details-4) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Derivative Unrealized Realized Gains Losses On Balance Sheet [Line Items]
Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Utilities Operating Expense, Purchased Power, Utilities Operating Expense, Cost of Gas Sold	Utilities Operating Expense, Purchased Power, Utilities Operating Expense, Cost of Gas Sold	Utilities Operating Expense, Purchased Power, Utilities Operating Expense, Cost of Gas Sold	Utilities Operating Expense, Purchased Power, Utilities Operating Expense, Cost of Gas Sold
Current and Long-Term Regulatory Asset (Liability)
Change In Derivative Fair Value [Roll Forward]
Beginning balance,	$ 1,946	$ 5,017	$ 5,226	$ 5,094
Unrealized loss (gain)	1,768	1,100	4,666	15,495
Realized (loss) gain reclassified to a deferred account	(639)	(1,676)	(3,333)	(10,581)
Realized (loss) gain reclassified to income statement	(1,573)	(1,893)	(5,057)	(7,460)
Ending balance,	1,502	2,548	1,502	2,548
Other Current Assets
Change In Derivative Fair Value [Roll Forward]
Beginning balance,	527	1,074	1,569	2,747
Unrealized loss (gain)	0	0	0	0
Realized (loss) gain reclassified to a deferred account	639	1,676	3,333	10,581
Realized (loss) gain reclassified to income statement	(707)	(2,155)	(4,443)	(12,733)
Ending balance,	$ 459	$ 595	$ 459	$ 595

Derivative and Hedging Instru_7

Derivative and Hedging Instruments (Details-5) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024 USD ($) Counterparty	Sep. 30, 2023 USD ($)	Sep. 30, 2024 USD ($) Counterparty	Sep. 30, 2023 USD ($)	Dec. 31, 2023 USD ($)
Counterparties in net liability position or default [Abstract]
Derivative, net liability position of counterparties	$ 0		$ 0		$ 0
Number of counterparties in default | Counterparty	0		0
Commodity Contract [Member] | Fuel For Electric Generation Purchased Power [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Realized losses (gains) on income statement	$ 1,969	$ 4,179	$ 5,723	$ 14,566
Commodity Contract [Member] | Cost Of Gas Sold Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Realized losses (gains) on income statement	0	0	3,265	6,451
Financial Transmission Rights [Member] | Fuel For Electric Generation Purchased Power [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Realized losses (gains) on income statement	311	(131)	512	(824)
Financial Transmission Rights [Member] | Cost Of Gas Sold Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Realized losses (gains) on income statement	$ 0	$ 0	$ 0	$ 0

Fair Value of Financial Instr_3

Fair Value of Financial Instruments (Details-1) - USD ($) $ in Thousands		Sep. 30, 2024	Dec. 31, 2023
Liabilities:
Unamortized discount and debt issuance costs, net		$ 4,200	$ 4,600
Carrying Amount [Member]
Liabilities:
Long-term debt	[1]	724,699	728,546
Fair Value [Member]
Liabilities:
Long-term debt	[1]	$ 682,359	$ 675,922
[1] Includes long-term debt due within one year. Excludes debt issuance costs and unamortized discount of $ 4.2 million and $ 4.6 million as of September 30, 2024, and December 31, 2023 , respectively.

Fair Value of Financial Instr_4

Fair Value of Financial Instruments (Details-2) - USD ($) $ in Thousands		Sep. 30, 2024	Dec. 31, 2023
Liabilities:
Derivative, right to reclaim collateral		$ 1,500	$ 5,400
Recurring [Member]
Assets:
Derivative assets, net	[1]	975	598
Exchange-traded investments		0	2,034
Total Assets		975	2,632
Liabilities:
Derivative liabilities, net	[1]	2,477	5,824
Deferred compensation		6,108	5,246
Total liabilities		8,585	11,070
Recurring [Member] | Level 1 [Member]
Assets:
Derivative assets, net	[1]	920	352
Exchange-traded investments		0	2,034
Total Assets		920	2,386
Liabilities:
Derivative liabilities, net	[1]	1,290	2,974
Deferred compensation		0	0
Total liabilities		1,290	2,974
Recurring [Member] | Level 2 [Member]
Assets:
Derivative assets, net	[1]	0	0
Exchange-traded investments		0	0
Total Assets		0	0
Liabilities:
Derivative liabilities, net	[1]	0	0
Deferred compensation		6,108	5,246
Total liabilities		6,108	5,246
Recurring [Member] | Level 3 [Member]
Assets:
Derivative assets, net	[1]	55	246
Exchange-traded investments		0	0
Total Assets		55	246
Liabilities:
Derivative liabilities, net	[1]	1,187	2,850
Deferred compensation		0	0
Total liabilities		1,187	2,850
MGE [Member] | Recurring [Member]
Assets:
Derivative assets, net	[1]	975	598
Exchange-traded investments		0	60
Total Assets		975	658
Liabilities:
Derivative liabilities, net	[1]	2,477	5,824
Deferred compensation		6,108	5,246
Total liabilities		8,585	11,070
MGE [Member] | Recurring [Member] | Level 1 [Member]
Assets:
Derivative assets, net	[1]	920	352
Exchange-traded investments		0	60
Total Assets		920	412
Liabilities:
Derivative liabilities, net	[1]	1,290	2,974
Deferred compensation		0	0
Total liabilities		1,290	2,974
MGE [Member] | Recurring [Member] | Level 2 [Member]
Assets:
Derivative assets, net	[1]	0	0
Exchange-traded investments		0	0
Total Assets		0	0
Liabilities:
Derivative liabilities, net	[1]	0	0
Deferred compensation		6,108	5,246
Total liabilities		6,108	5,246
MGE [Member] | Recurring [Member] | Level 3 [Member]
Assets:
Derivative assets, net	[1]	55	246
Exchange-traded investments		0	0
Total Assets		55	246
Liabilities:
Derivative liabilities, net	[1]	1,187	2,850
Deferred compensation		0	0
Total liabilities		$ 1,187	$ 2,850
[1] As of September 30, 2024, and December 31, 2023, collateral of $ 1.5 million and $ 5.4 million, respectively, was posted against and netted with derivative liability positions on the consolidated balance sheets. The fair value of the derivative liability disclosed in this table has not been reduced for the collateral posted.

Fair Value of Financial Instr_5

Fair Value of Financial Instruments (Details-3)	9 Months Ended
	Sep. 30, 2024
Deferred compensation plan [Abstract]
Investment interest calculation, investment maturity period (26 weeks)	182 days
Investment interest calculation, monthly compounding rate	1%
Investment interest calculation, minimum annual rate compounded monthly	7%

Fair Value of Financial Instr_6

Fair Value of Financial Instruments (Details-4) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance,		$ (1,432)	$ (2,892)	$ (2,604)	$ (866)
Realized and unrealized gains (losses):
Included in regulatory assets		300	1,768	1,472	(258)
Included in earnings	[1]	(1,572)	(2,016)	(5,174)	(7,590)
Settlements		1,572	2,016	5,174	7,590
Ending balance,		$ (1,132)	$ (1,124)	$ (1,132)	$ (1,124)
[1] MGE's exchange-traded derivative contracts, over-the-counter party transactions, and FTRs are subject to regulatory deferral. These derivatives are therefore marked to fair value and are offset in the financial statements with a corresponding regulatory asset or liability.

Fair Value of Financial Instr_7

Fair Value of Financial Instruments (Details-5) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Included in earnings	[1]	$ (1,572)	$ (2,016)	$ (5,174)	$ (7,590)
Fair Value, Net Derivative Asset (Liability), Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]		Utilities Operating Expense, Purchased Power	Utilities Operating Expense, Purchased Power	Utilities Operating Expense, Purchased Power	Utilities Operating Expense, Purchased Power
[1] MGE's exchange-traded derivative contracts, over-the-counter party transactions, and FTRs are subject to regulatory deferral. These derivatives are therefore marked to fair value and are offset in the financial statements with a corresponding regulatory asset or liability.

Joint Plant Ownership (Details)

Joint Plant Ownership (Details) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2024 USD ($) MW	Sep. 30, 2023 USD ($)	Sep. 30, 2024 USD ($) MW	Sep. 30, 2023 USD ($)	Dec. 31, 2023 USD ($)
Jointly Owned Utility Plant Interests [Line Items]
Property, plant, and equipment, net		$ 2,077,104		$ 2,077,104		$ 2,018,121
MGE [Member]
Jointly Owned Utility Plant Interests [Line Items]
Property, plant, and equipment, net		2,077,132		2,077,132		$ 2,018,149
Paris Units [Member]
Jointly Owned Utility Plant Interests [Line Items]
Projected renewable project costs	[1],[2],[3]	61,000		61,000
Public Utilities, Property, Plant and Equipment, Construction Work in Progress	[2],[3]	$ 48,600		$ 48,600
Paris Units [Member] | Public Service Commission of Wisconsin [Member]
Allowance for Funds Used During Construction
Authorized AFUDC rate - Signficiant projects (100%)				100%
Paris Units [Member] | MGE [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, ownership interest	[3]	10%		10%
Paris Units [Member] | Solar | MGE [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, plant capacity (in MW) | MW	[3]	20		20
Paris Units [Member] | Battery storage | MGE [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, plant capacity (in MW) | MW	[3]	11		11
Darien Units [Member]
Jointly Owned Utility Plant Interests [Line Items]
Projected renewable project costs	[1],[2],[4]	$ 63,000		$ 63,000
Public Utilities, Property, Plant and Equipment, Construction Work in Progress	[2],[4]	$ 41,900		$ 41,900
Darien Units [Member] | Public Service Commission of Wisconsin [Member]
Allowance for Funds Used During Construction
Authorized AFUDC rate - Signficiant projects (100%)				100%
Darien Units [Member] | MGE [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, ownership interest	[4]	10%		10%
Darien Units [Member] | Solar | MGE [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, plant capacity (in MW) | MW	[4]	25		25
Darien Units [Member] | Battery storage | MGE [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, plant capacity (in MW) | MW	[4]	7.5		7.5
Koshkonong Units [Member]
Jointly Owned Utility Plant Interests [Line Items]
Projected renewable project costs	[1],[2],[5]	$ 104,000		$ 104,000
Public Utilities, Property, Plant and Equipment, Construction Work in Progress	[2],[5]	$ 6,600		$ 6,600
Koshkonong Units [Member] | Public Service Commission of Wisconsin [Member]
Allowance for Funds Used During Construction
Authorized AFUDC rate - Signficiant projects (100%)				100%
Koshkonong Units [Member] | MGE [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, ownership interest	[5]	10%		10%
Koshkonong Units [Member] | Solar | MGE [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, plant capacity (in MW) | MW	[5]	30		30
Koshkonong Units [Member] | Battery storage | MGE [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, plant capacity (in MW) | MW	[5]	16.5		16.5
West Riverside Energy Center [Member] | MGE [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, ownership interest		6.90%		6.90%
West Riverside Energy Center II [Member]
Jointly Owned Utility Plant Interests [Line Items]
Projected renewable project costs	[2]	$ 25,000		$ 25,000
Public Utilities, Property, Plant and Equipment, Construction Work in Progress	[2]	$ 25,200		$ 25,200
West Riverside Energy Center II [Member] | MGE [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, ownership interest		3.50%		3.50%
West Riverside Energy Center II [Member] | Natural gas | MGE [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, plant capacity (in MW) | MW		25		25
Darien, Paris, and Koshkonong Units [Member]
Allowance for Funds Used During Construction
AFUDC		$ 1,900	$ 800	$ 4,700	$ 1,900
[1] Estimated costs are expected to exceed PSCW previously approved Certificate of Authority (CA) levels. Notifications are provided to the PSCW when costs increase above CA levels. MGE has and will continue to request recovery of the updates in its rate case proceedings. Excluding AFUDC. Paris Solar-Battery Park is located in the Town of Paris in Kenosha County, Wisconsin. Darien Solar Energy Center is located in Walworth and Rock Counties in southern Wisconsin. Koshkonong Solar Energy Center is located in the Towns of Christiana and Deerfield in Dane County, Wisconsin.

Revenue (Details-1)

Revenue (Details-1) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Total Operating Revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	$ 168,480	$ 160,528	$ 505,529	$ 525,779
Electric [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	147,790	138,891	384,298	377,627
Electric [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	52,834	50,008	134,296	131,552
Electric [Member] | Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	73,517	70,795	197,541	193,760
Electric [Member] | Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	3,459	3,715	10,314	10,578
Electric [Member] | Other-retail/municipal
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	11,346	10,991	31,439	30,853
Electric [Member] | Total Retail [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	141,156	135,509	373,590	366,743
Electric [Member] | Sales To The Market [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	5,799	3,305	8,394	9,617
Electric [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	835	77	2,314	1,267
Gas [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	20,476	21,424	120,761	147,677
Gas [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	13,069	13,719	72,057	86,131
Gas [Member] | Commercial/Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	5,892	6,016	43,292	55,726
Gas [Member] | Total Retail [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	18,961	19,735	115,349	141,857
Gas [Member] | Gas Transportation [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	1,417	1,587	5,003	5,354
Gas [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	98	102	409	466
Non Regulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	$ 214	$ 213	$ 470	$ 475

Segment Information (Details)

Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Segment Reporting Information [Line Items]
Operating revenues	$ 168,480	$ 160,528	$ 505,529	$ 525,779
Equity in earnings of investment			8,427	7,930
Net Income (Loss)	40,939	37,857	98,547	97,616
Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues	147,790	138,891	384,298	377,627
Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues	20,476	21,424	120,761	147,677
Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues	214	213	470	475
Transmission Investment [Member]
Segment Reporting Information [Line Items]
Operating revenues	0	0	0	0
All Others [Member]
Segment Reporting Information [Line Items]
Operating revenues	0	0	0	0
Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	168,480	160,528	505,529	525,779
Equity in earnings of investment	2,901	2,690	8,427	7,930
Net Income (Loss)	40,939	37,857	98,547	97,616
Operating Segments [Member] | Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues	147,746	139,403	384,144	378,280
Equity in earnings of investment	0	0	0	0
Net Income (Loss)	35,035	31,126	66,458	65,996
Operating Segments [Member] | Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues	24,683	24,971	132,352	160,655
Equity in earnings of investment	0	0	0	0
Net Income (Loss)	(2,026)	(801)	8,638	10,539
Operating Segments [Member] | Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues	11,266	10,611	33,295	31,618
Equity in earnings of investment	0	0	0	0
Net Income (Loss)	6,101	5,627	17,968	16,667
Operating Segments [Member] | Transmission Investment [Member]
Segment Reporting Information [Line Items]
Operating revenues	0	0	0	0
Equity in earnings of investment	2,901	2,690	8,427	7,930
Net Income (Loss)	2,112	1,957	6,130	5,770
Operating Segments [Member] | All Others [Member]
Segment Reporting Information [Line Items]
Operating revenues	0	0	0	0
Equity in earnings of investment	0	0	0	0
Net Income (Loss)	(283)	(52)	(647)	(1,356)
Consolidation Elimination Entries [Member]
Segment Reporting Information [Line Items]
Operating revenues	(15,215)	(14,457)	(44,262)	(44,774)
Equity in earnings of investment	0	0	0	0
Net Income (Loss)	0	0	0	0
Consolidation Elimination Entries [Member] | Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues	(44)	512	(154)	653
Consolidation Elimination Entries [Member] | Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues	4,207	3,547	11,591	12,978
Consolidation Elimination Entries [Member] | Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues	11,052	10,398	32,825	31,143
Consolidation Elimination Entries [Member] | Transmission Investment [Member]
Segment Reporting Information [Line Items]
Operating revenues	0	0	0	0
Consolidation Elimination Entries [Member] | All Others [Member]
Segment Reporting Information [Line Items]
Operating revenues	0	0	0	0
MGE [Member]
Segment Reporting Information [Line Items]
Operating revenues	168,480	160,528	505,529	525,779
Net Income (Loss)	33,333	30,465	75,924	76,820
MGE [Member] | Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues	147,790	138,891	384,298	377,627
MGE [Member] | Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues	20,476	21,424	120,761	147,677
MGE [Member] | Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues	214	213	470	475
MGE [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	168,480	160,528	505,529	525,779
Net Income (Loss)	33,333	30,465	75,924	76,820
MGE [Member] | Operating Segments [Member] | Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues	147,746	139,403	384,144	378,280
Net Income (Loss)	35,035	31,126	66,458	65,996
MGE [Member] | Operating Segments [Member] | Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues	24,683	24,971	132,352	160,655
Net Income (Loss)	(2,026)	(801)	8,638	10,539
MGE [Member] | Operating Segments [Member] | Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues	11,266	10,611	33,295	31,618
Net Income (Loss)	6,101	5,627	17,968	16,667
MGE [Member] | Consolidation Elimination Entries [Member]
Segment Reporting Information [Line Items]
Operating revenues	(15,215)	(14,457)	(44,262)	(44,774)
Net Income (Loss)	(5,777)	(5,487)	(17,140)	(16,382)
MGE [Member] | Consolidation Elimination Entries [Member] | Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues	(44)	512	(154)	653
MGE [Member] | Consolidation Elimination Entries [Member] | Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues	4,207	3,547	11,591	12,978
MGE [Member] | Consolidation Elimination Entries [Member] | Non Regulated Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues	$ 11,052	$ 10,398	$ 32,825	$ 31,143