Table of Contents

Filing Format4

Forward-Looking Statements4

Forward-Looking Statements

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Where to Find More Information4

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Definitions, Abbreviations, and Acronyms Used in the Text and Notes of this Report5

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PART I.7

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Item 1. Business.7

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Item 1A. Risk Factors.17

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Item 1B. Unresolved Staff Comments.27

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Item 2. Properties.28

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Item 3. Legal Proceedings.30

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Item 4. Mine Safety Disclosures.Disclosures30

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PART II.31

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Item 5. Market for Registrants' Common Equity, Related Stockholder Matters, and Issuer Purchases of Equity Securities.31

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Item 6. Selected Financial Data.33

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Item 7. Management's Discussion and Analysis of Financial Condition and Results of Operations.34

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Item 7A. Quantitative and Qualitative Disclosures About Market Risk.Risk55

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Item 8. Financial Statements and Supplementary Data.62

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Item 9. Changes in and Disagreements with Accountants on Accounting and Financial Disclosure.116

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Item 9A. Controls and Procedures.116

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Item 9B. Other Information.116

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PART III.117

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Item 10. Directors, Executive Officers, and Corporate Governance.117

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Item 11. Executive Compensation.117

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Item 12. Security Ownership of Certain Beneficial Owners and Management and Related Stockholder Matters.117

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Item 13. Certain Relationships and Related Transactions, and Director Independence.117

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Item 14. Principal Accounting Fees and Services.118

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PART IV.119

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Item 15. Exhibits and Financial Statement Schedules.119

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Item 16. Form 10-K Summary.122

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Signatures - MGE Energy, Inc.127

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Signatures - Madison Gas and Electric Company128

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Definitions, Abbreviations, and Acronyms Used in the Text and Notes of this Report

Abbreviations, acronyms, and definitions used in the text and notes of this report are defined below.

MGE Energy and Subsidiaries:

CWDCCentral Wisconsin Development Corporation

MAGAELMAGAEL, LLC

MGEMadison Gas and Electric Company

MGE EnergyMGE Energy, Inc.

MGE PowerMGE Power, LLC

MGE Power Elm RoadMGE Power Elm Road, LLC

MGE Power West CampusMGE Power West Campus, LLC

MGE ServicesMGE Services, LLC

MGE State Energy ServicesMGE State Energy Services, LLC

MGE TranscoMGE Transco Investment, LLC

MGEE TranscoMGEE Transco, LLC

North MendotaNorth Mendota Energy & Technology Park, LLC

Other Defined Terms:

2006 PlanMGE Energy's 2006 Performance Unit Plan

2013 PlanMGE Energy's 2013 Director Incentive Plan

2017 Tax ActTax Cuts and Jobs Act of 2017

2020 PlanMGE Energy's 2020 Performance Unit Plan

2021 Incentive PlanMGE Energy's 2021 Long-Term Incentive Plan

ACEAffordable Clean Energy

AFUDCAllowance for Funds Used During Construction

ANRANR Pipeline

AROAsset Retirement Obligation

ATCAmerican Transmission Company LLC

ATC HoldcoATC Holdco, LLC

Badger Hollow IBadger Hollow I Solar Farm

Badger Hollow IIBadger Hollow II Solar Farm

BARTBest Available Retrofit Technology

BlountBlount Station

BTABest Technology Available

CACertificate of Authority

CAAClean Air Act

CAVRClean Air Visibility Rule

CCRCoal Combustion Residual

CO₂Carbon Dioxide

codificationFinancial Accounting Standards Board Accounting Standards Codification

ColumbiaColumbia Energy Center

Cooling degree daysMeasure of the extent to which the average daily temperature is above 65 degrees Fahrenheit, which is considered an indicator of possible increased demand for energy to provide cooling

COVID-19Coronavirus Disease 2019

COSOCommittee of Sponsoring Organizations

CPPClean Power Plan

CSAPRCross-State Air Pollution Rule

CWAClean Water Act

D.C. CircuitUnited States Court of Appeals for the District of Columbia Circuit

DthDekatherms

EEIEdison Electric Institute

electric marginElectric revenues less fuel for electric generation and purchase power costs, a non-GAAP measure

ELGEffluent Limitations Guidelines

Elm Road UnitsElm Road Generating Station

EPAUnited States Environmental Protection Agency

FASBFinancial Accounting Standards Board

FERCFederal Energy Regulatory Commission

Forward WindForward Wind Energy Center

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FTRFinancial Transmission Rights

GAAPGenerally Accepted Accounting Principles

gas marginGas revenues less cost of gas sold, a non-GAAP measure

GHGGreenhouse Gas

heating degree days (HDD)Measure of the extent to which the average daily temperature is below 65 degrees Fahrenheit, which is considered an indicator of possible increased demand for energy to provide heating

ICFInsurance Continuance Fund

IPCCIntergovernmental Panel on Climate Change

IRSInternal Revenue Service

kVAKilovolt Ampere

KWKilowatt, a measure of electric energy generating capacity

kWhKilowatt-hour

MISOMidcontinent Independent System Operator, Inc. (a regional transmission organization)

MROMidwest Reliability Organization

MWMegawatt

MWhMegawatt-hour

NAAQSNational Ambient Air Quality Standards

NasdaqThe Nasdaq Stock Market

NERCNorth American Electric Reliability Corporation

NNGNorthern Natural Gas Company

NOVNotice of Violation

NO_xNitrogen Oxides

NYSENew York Stock Exchange

O'BrienO'Brien Solar Fields

OSCEState of Wisconsin's Office of Sustainability and Clean Energy

Paris AgreementParis Agreement under the United Nations Framework Convention on Climate Change

PCBsPolychlorinated Biphenyls

the PetitionPetition for Judicial Review of Agency Action

PGAPurchased Gas Adjustment clause

PHMDCPublic Health Madison & Dane County

PHMDC DirectivesPublic Health Madison & Dane County's Forward Dane Plan and related emergency orders

PJMPJM Interconnection, LLC (a regional transmission organization)

PMParticulate Matter

PPAPurchased power agreement

PSCWPublic Service Commission of Wisconsin

RECRenewable Energy Credit

RERRenewable Energy Rider

RiversideRiverside Energy Center in Beloit, Wisconsin

ROEReturn on Equity

RTORegional Transmission Organization

SaratogaSaratoga Wind Farm

SCRSelective Catalytic Reduction

SECSecurities and Exchange Commission

SIPState Implementation Plan

SO₂Sulfur Dioxide

the StateState of Wisconsin

Stock PlanDirect Stock Purchase and Dividend Reinvestment Plan of MGE Energy

Two CreeksTwo Creeks Solar Farm

UWUniversity of Wisconsin at Madison

VIEVariable Interest Entity

WCCFWest Campus Cogeneration Facility

WDNRWisconsin Department of Natural Resources

WEPCOWisconsin Electric Power Company

working capitalCurrent assets less current liabilities

WPDESWisconsin Pollutant Discharge Elimination System

WPLWisconsin Power and Light Company

WPSCWisconsin Public Service Corporation

WRERAWorker, Retiree and Employer Recovery Act of 2008

XBRLeXtensible Business Reporting Language

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number of customers, approximately 87% were residential and 13% were commercial or industrial.

Electric retail revenues for 2018, 2017,2020, 2019, and 20162018 were comprised of the following:

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operation of the transmission grid within its area of coverage, administers a competitive wholesale electricity market, and plans regional transmission expansion improvements to maintain grid reliability and relieve congestion.

Fuel supply and generation

MGE satisfies its customers' electric demand with internal generation and purchased power. MGE's current fuel mix for generation will fluctuatefluctuates from year-to-year due to fuel pricing in the market, generating unit availability, weather, and customer demand. MGE has a responsibility to its customers to dispatch the lowest cost generation available pursuant to regulatory requirements.

MGE's Energy 2030 framework details our plan for growth in generation for renewables. This growth will continue as legacy fossil fuel-fired generation assets are retired and replace with renewables, such as wind and solar assets. The transition or displacement of coal-fired resources is ongoing and active. Currently two utility-scale solar projects are awaiting regulatory approval, totaling approximately 100 MW of MGE's combined ownership share.

MGE's carbon intensity is expected to decrease as our use of coal decreases over time, due in part to our investments in cost-effective, efficient renewables like the Saratoga Wind farm, which is expected to come online inDuring 2020, 2019, and the purchase of the Forward Wind farm in 2018.

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Generation sources

MGE receives electric generation supply from coal-fired, gas-fired, and renewable energy sources. These sources include owned facilities as well as facilities leased from affiliates and accounted for under our nonregulated energy operations. See Item 2. Properties for more information regarding these generation sources, including location, capacity, ownership or lease arrangement, and fuel source. See "Nonregulated"Nonregulated Energy Operations"Operations" below for more information regarding generating capacity leased to MGE by nonregulated subsidiaries.

Purchased power

MGE enters into shortshort- and long-term purchase power commitments with third parties to meet a portion of its anticipated electric energy supply needs. The following table identifies purchase power commitments as of December 31, 2018,2020, with unaffiliated parties for the next five years.

Gas Utility Operations

MGE transports and distributes natural gas in a service area covering 1,684 square miles in seven south-central Wisconsin counties. The service area includes the city of Madison, Wisconsin and surrounding areas.

As of December 31, 2018,2020, MGE supplied natural gas service to approximately 161,000166,000 customers in the cities of Elroy, Fitchburg, Lodi, Madison, Middleton, Monona, Prairie du Chien, Verona, and Viroqua; 25 villages; and all or parts of 4948 townships. Of the total number of customers, approximately 90% were residential and 10% were commercial or industrial. Gas revenues for 2018, 2017,2020, 2019, and 20162018 were comprised of the following:

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Gas operations accounted for approximately 28.2%26.8%, 26.4%28.1%, and 24.8%28.2% of MGE's total 2018, 2017,2020, 2019, and 20162018 regulated revenues, respectively.

MGE can curtail gas deliveries to its interruptible customers. These are customers who agree to reduce their load in the case of an emergency interruption. Approximately 3% of retail gas deliveries in 20182020, 2019 and 2016 and approximately 4% in 20172018 were to interruptible customers.

Gas supply

MGE has physical interconnections with ANR Pipeline Company (ANR) and Northern Natural Gas Company (NNG). MGE's primary service territory, which includes Madison and the surrounding area, receives deliveries at one NNG and four ANR gate stations. MGE's outlying territory receives deliveries at NNG gate stations located in Elroy, Prairie du Chien, Viroqua, and Crawford County. Interconnections with two major pipelines provide competition in interstate

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wholly-owned subsidiary. As of December 31, 2018,2020, MGEE Transco held a 4.4% ownership interest in ATC Holdco. In the near term, it is expected that ATC Holdco will be pursuing transmission development opportunities that typically have long development and investment lead times before becoming operational.

Environmental

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 theywe conduct theirour operations, the costs of those operations, as well as capital and operating expenditures. Regulatory initiatives, proposed rules, and court challenges to adopted rules, have the potential to have a material effect on our capital expenditures and operating costs. In addition to the regulations discussed below, MGE continues to track state and federal initiatives such as potential state and federal regulations governing surface water and/or groundwater containing per- and polyfluoroalkyl substances, potential changes to regulations governing polychlorinated biphenyl (PCB), potential changes to air and water standards, and potential climate change legislation.

In February 2021, MGE and the other co-owners of Columbia announced plans to retire that facility. The co-owners intend to retire Unit 1 by the end of 2023 and Unit 2 by the end of 2024. Final timing and retirement dates for Units 1 and 2 are subject to PSCW and regional regulatory reviews, including identification and approval of energy and capacity resources to replace Columbia. Effects of environmental compliance discussed below will depend upon the final approved retirement dates and compliance requirement dates.

Federal and State Environmental Compliance During the Current Pandemic

MGE was identified as an essential business under the State of Wisconsin's Safer at Home directive. It has been operating with full staff and has continued to prioritize its compliance with all applicable environmental regulations. MGE continues to follow local orders, as well as state Department of Health and Center for Disease Control guidance to operate in a manner to address potential spread of COVID-19 in order for the essential utility services to operate without interruptions. Due to the essential nature of the work that many MGE employees perform, MGE requested and received approval for certain critical employees to be included in Phase 1B of Wisconsin's Vaccination Distribution Plan as part of the "Non-EMS First Responder" group. Vaccinations for this group are forthcoming; a tentative date is set for March 1, 2021. The EPA and the WDNR have both provided guidance for regulated entities if compliance with regulations becomes unfeasible due to the current severity of COVID-19. In late June 2020, the EPA announced that COVID-19 guidance would sunset on August 31, 2020. MGE has developed contingencies for remaining in compliance during the pandemic and does not expect to rely on state or federal noncompliance relief. However, management cannot predict with certainty whether COVID-19 will disrupt these compliance activities. MGE expects to continue to build contingencies into compliance operations and communicate with regulators as needed during this unprecedented time.

Water Quality

EPA's Effluent Limitations Guidelines and Standards for Steam Electric Power Generating Point Source Category

In November 2015,August 2020, the EPA published its finalfinalized rule settingmodifications to the Effluent Limitations Guidelines (ELG) for the steam electric power generating industry. The ELG rule establishes federal limits on the amount of metals and other pollutants that can be discharged in wastewater from new and existing steam electric generation plants. The rule will be applied to Wisconsin-based power plants as they renew their WPDES permits, but no later than December 31, 2023. The operators of the Columbia and Elm Road Units have indicated that equipment upgrades may be necessaryare subject to comply withthis rule. See Footnote 16.a. of the new discharge standards.Notes to the Consolidated Financial Statements in this Report for further discussion of compliance plans for Columbia and the Elm Road Units. Management believes that any compliance costs will be recovered in future rates based on previous treatment of environmental compliance projects.

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Section 316(b) rule. The Blount plant'sBlount's WPDES permit assumes that Blountthe plant meets best technology available (BTA) for the duration of the permit, which expires in 2023. However, MGE needs tomust perform an entrainment study by the end of 2021 to determine future BTA, which will be included with the next permit renewal. Section 316(b) applies to river intakes at the Columbia plant. TheColumbia's operator received a permit in 2019 requiring studies of intake structures to help determine BTA. BTA improvements may not be required given that Columbia could be fully retired before the issuance of the Columbia plantnext permit, which is in the process of a WPDES permit renewal. The draft permit directs the Columbia operatorexpected to conduct similar studies on their intake structures. The study requirements will not be known until the permit is final. Future BTA requirements at Blount and Columbia will be based on the results of these required intake studies and will be specified in the next permits issued in 2023 or later. MGE expectswill continue to work with Columbia's operator to evaluate all regulatory requirements applicable to the planned retirements. Management believes that the Section 316(b) rule will not have a material effect on its existing plants.

Energy Efficiencyplants and Renewables

The Wisconsin Energy Efficiency and Renewables Act requires that 10% of the state's electricityany compliance costs will be generated from renewable sources. MGE is in compliance with the requirement. The costs to comply with the Act and its accompanying regulations are being recovered in rates.future rates based on previous treatment of environmental compliance projects.

Air Quality

Air quality regulations promulgated by the EPA and Wisconsin Department of Natural Resources (WDNR) in accordance with the Federal Clean Air Act and the Clean Air Act Amendments of 1990 impose restrictions on emission of particulates, sulfur dioxide (SO₂), nitrogen oxides (NO_x), hazardous air pollutants and other pollutants, and require permits for operation of emission sources. These permits must be renewed periodically. Various newly enacted and/or proposed federal and state initiatives may result in additional operating and capital expenditure costs for fossil-fueled electric generating units.

Ozone NAAQS

In May 2018, the EPA issued a final rule which designateddesignating the northeast portion of Milwaukee County as being in nonattainment with Ozone National Ambient Air Quality Standards (NAAQS). The Elm Road Units are located in Milwaukee County, outside the designated nonattainment area. In August 2018, several environmental groups, the City of Chicago, and the State of Illinois filed federal lawsuits challenging several of the EPA's attainment designation decisions, including the EPA's partial Milwaukee County designation as being too narrow and not sufficiently protective. In July 2020, the U.S. District Court of the District of Columbia remanded the partial Milwaukee County attainment designation back to the EPA for further explanation. If the entire county were to be considered in nonattainment, the State of Wisconsin would need to develop an implementation plan that addressed emissions that contribute to ozone (NO_x and volatile organic compound emissions) for the county, which could affect operations and emissions control obligations of the Elm Road units. MGE is monitoring the outcome of this lawsuitthe EPA’s remand analysis and how it may affect theour Elm Road Units in Milwaukee County. See Footnote 1716.a. of the Notes to Consolidated Financial Statements in this Report for additional information.

EPA's Cross-State Air Pollution Rule:Rule (CSAPR): Proposed Ozone Season Update based on 2008 Ozone NAAQS

The EPA's CSAPR is anand its progeny are a suite of interstate air pollution transport rulerules designed to reduce ozone and fine particulate (PM2.5) air levels in areas that the EPA has determined areas being significantly impacted by pollution from neighboring and upwind states. This is accomplished in the CSAPR through a reduction in SO₂ and NO_x from qualifying fossil-fuel fired power plants in upwind or "contributing" states. NO_x and SO₂ contribute to fine particulate pollution and NO_x contributes to ozone formation in downwind areas. Reductions are achieved through a cap and trade system. Individual plants can meet their caps through modifications and/or buying allowances on the market. CSAPR has been subject to ongoing legal challenges.

In October 2016, the EPA finalized rulemakinga CSAPR Update Rule to address pollution transport related to an updated ozone NAAQS. In September 2019, the U.S. Court of Appeals for an update to CSAPR that incorporated 2008 Ozone NAAQS standards intothe District of Columbia Circuit (D.C. Circuit) remanded the rule (the original CSAPR is based on 1997 Ozone NAAQS standards) and began further reducing summertime ozone season NO_x allowances in 2017. The update affects 22 states, including Wisconsin, by further limiting statewide NO_x allowances in each of those states. The rule also includes revisions to CSAPR that are designed to address issues remaining from the D.C. Circuit remand of CSAPR, including Wisconsin's inclusion in the NO_x ozone season portion of the rule. The State of Wisconsin filed a legal challenge to the CSAPR update rule asserting, among other things,EPA holding that the rule over-controls NO_ximproperly provided only a partial remedy for addressing interstate transport of pollutants from upwind to downwind states. In October 2020, the EPA published a proposed CSAPR Update Rule to address the remand that explicitly excludes Wisconsin. The EPA is under court order to finalize this update by March 2021. If the proposed rule is finalized as written, Wisconsin will not be subject to the emissions reductions included in Wisconsin.the CSAPR Update Rule but will remain subject to the reductions required by the original CSAPR.

MGE has met our CSAPRits current obligations in 2017 and 2018 through a combination of reduced emissions through pollution control (e.g. SCR installation at Columbia), as well as owned, received, and purchased allowances. ThereWhile uncertainty remains uncertainty around CSAPR due to legal challenges, however, MGE expects that we willto meet ongoing CSAPR obligations for the foreseeable future. MGE will continue to monitor developments and litigations to this rule.

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which may require pollution control retrofits. Columbia's existing pollution control upgrades, and the EPA's stance that compliance with the CSAPR equals compliance with BART, should mean that Columbia will not need to do additional work to meet BART requirements. At this time, however, the BART regulatory obligations, compliance strategies, and costs remain uncertain in Wisconsin due to the continued legal challenges surrounding CSAPR and CAVR. MGE will continue to monitor developments to this rule.

Columbia Clean Air Act Litigation

Columbia is a coal-fired generating station operated by WPL and in which WPL, WPSC, and MGE have ownership interests. In December 2009, the EPA sent a Notice of Violation (NOV) to the co-owners, including MGE. The NOV alleged that WPL and the Columbia co-owners failed to comply with appropriate pre-construction review and permitting requirements and, as a result, violated the Prevention of Significant Deterioration program requirements, Title V Operating Permit requirements of the CAA, and the Wisconsin SIP. In June 2013, the court approved and entered a consent decree entered by the EPA, Sierra Club, and the co-owners of Columbia. One of the requirements of the consent decree required installation of an SCR system at Columbia Unit 2 by December 31, 2018. Installation of the SCR was approved by the PSCW and the SCR was placed in service in 2018. The consent decree remains open for compliance monitoring, but significant additional operating and capital expenditures are not expected.

Global Climate Change

MGE is a producer of greenhouse gas (GHG) emissions, primarily from the fossil fuel generating facilities it uses to meet customers' energy needs, as well as from its natural gas pipeline system and fleet vehicles. Climate change and the regulatory response to it could significantly affect our operations in a number of ways, including increased operating costs and capital expenditures, restrictions on energy supply options, operational limits on our fossil fuel fired plants, permitting difficulties, and emission limits. MGE management would expect to seek and receive rate recovery of such compliance costs, if and when required. MGE continues to monitor proposed climate change legislation and regulation.

MGE has taken steps to address GHG emissions through voluntary actions. In 2005, MGE implemented its Energy 2015 Plan, which committed to ensuring a balanced, economic energy supply with reduced environmental emissions. The Plan emphasized increased renewable energy, energy efficiency, and new cleaner generation – three strategies that reduced GHG emissions. Under the Plan and other actions, our CO₂ emissions declined from 2005 to 2015 by approximately 20% even though total system delivered energy increased. In 2015, MGE announced its Energy 2030 framework that continues steps to reduce CO₂ emissions. Subject to regulatory approvals and other conditions, MGE aims to increase renewable energy to 25% of retail electric sales by 2025 and to 30% by 2030. Under our Energy 2030 framework we will also workprior to the announcement of the Columbia retirement, our plan was to reduce CO₂ emissions by 40% from 2005 levels by 2030. With the retirement of Columbia, we currently expect to achieve a reduction of 65% by 2030. Beyond 2030, we are targeting net-zero carbon electricity by 2050.

Federal Action on Climate Change

Executive Actions:

President Biden's actions on climate change, including multiple executive orders and the recommitment of the U.S. to the Paris Agreement under the United Nations Framework Convention on Climate Change (the Paris Agreement), indicate that he intends to make climate considerations a broad focus of his administration.

Executive Order on Tackling the Climate Crisis at Home and Abroad

This executive order establishes climate change as an essential element of domestic and international governmental policy. The order indicates that the U.S. will develop its emissions reduction targets under the Paris Agreement, instructs executive staff and federal departments and agencies to take actions to combat climate change using a government-wide approach, and creates several interagency working groups tasked with providing recommendations to meet the order's goals. MGE is following the development of recommendations and plans developed by agencies as a result of this order, as well as other executive actions taken by the new administration, to determine their applicability to MGE's decarbonization plans and to evaluate any potential impact to our operations.

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Executive Order on Protecting Public Health and the Environment and Restoring Science to Tackle the Climate Crisis

In January 2021, President Biden signed an executive order that establishes a list of national objectives for federal action (including regulations) taken under his administration. The order includes initiatives for protecting the environment, addressing climate change, and addressing public health. Executive departments and agencies are directed to immediately review all federal actions taken under the previous presidential administration to determine whether or not they meet the objectives set out in the order. Departments and agencies are further committedinstructed to reducing carbon emissionstake applicable action, including suspending, revising or rescinding rules to correct any federal action under the previous administration that does not meet the national objectives set forth in this order. MGE will monitor and evaluate any potential regulation, guidance, and/or other federal directives that are developed as a result of this order and other executive actions taken by 80% from 2005 levelsthe new administration.

Legislative Actions:

MGE is monitoring current legislative actions on climate change to determine their level of significance to MGE's decarbonization plans.

State and Regional Action on Climate Change

Executive Actions

Executive Order Relating to Clean Energy Wisconsin

In August 2019, Wisconsin Governor Tony Evers signed an executive order to establish the Office of Sustainability and Clean Energy (OSCE). The order tasks the OSCE with, among other things, ensuring that the actions of the State of Wisconsin are aligned with the goals and recommendations of the Paris Agreement, verifying that electricity consumed by 2050.the State of Wisconsin is 100% carbon-free by 2050, and developing a comprehensive multi-sector clean energy plan for the state. The OSCE has put forth preliminary recommendations and is in the process of creating the statewide plan. MGE is engaged in this process and is participating on a Stakeholder Advisory Team in a voluntary capacity. MGE will be evaluating this plan for its applicability to MGE's decarbonization plans and to evaluate potential impact to our operations.

Legislative Actions

MGE continues to monitor current legislative actions on climate change. There are no legislative actions to report at this time.

EPA's Greenhouse Gas Reduction Guidelines under the Clean Air Act 111d111(d) Rule

The EPA's Clean Power Plan (CPP) rule became effective in December 2015, setting guidelines for states to use in developing plans to control GHG emissions from existing fossil fuel-fired EGUsIn January 2021, the D.C. Circuit vacated and systems. When fully implemented in 2030, the CPP was projectedremanded to reduce GHG emissions from this sector by 32% below 2005 levels. States were given up to three years to submit a plan or be subject to a federal plan to meet the reduction goals, and states were expected to meet interim goals starting in 2022 and the final goals in 2030. Implementation of the rule was expected to have a direct impact on coal and natural gas fired generating units, including possible changes in dispatch and additional operating costs.In February 2016, the U.S. Supreme Court stayed implementation of the CPP which remains in effect. In October 2017, the EPA proposed to rescind the CPP.

In August 2018, the EPA proposed the Affordable Clean Energy (ACE) rule which would replace the CPP, if successfully implemented. The ACE proposal directs states to submit plans to the EPA for approval that implement standards of performance (called Best System of Emissions Reductions, or BSER) for individual EGUs over 25 MW. ACE defines BSER as on-site, heat-rate efficiency improvements, whereas theCPP defines BSERs using carbon

dioxide emission performance rates. Simple cycle units such as the smaller combustion units, and combined cycle units such as the WCCF are exempt from the proposed rule. Under the ACE proposal, if a state fails to prepare a plan, or its plan is not approved by the EPA, a federal implementation plan will be issued for that state. The proposed ACE as it is currently written has the potential to impact Blount, Columbia,Rule (ACE Rule) and the Elm Road Units.

Givenrepeal of the pending CPP legal proceedings, andpredecessor Clean Power Plan Rule (CPP Rule), both of which regulated greenhouse gas emissions from existing electric generation units pursuant to Section 111(d) of the proposed ACE rule, the nature and timing of any final requirements is subject to uncertainty.Clean Air Act. MGE is unable to determine with any certainty the impact of the CPP and proposed ACE ruleevaluating this D.C. Circuit decision for what impacts it may have on ourMGE's operations. If an ACE rule is implemented substantially in the form of the CPP rule, it is expected to have a material impact on MGE. MGE will continue to evaluate the rule development and monitor developments with the proposed ACE rule, the CPP rule,ongoing and related litigation.potential legal proceedings.

Solid Waste

EPA's Coal Combustion Residuals Rule

The EPA's 2015 Coal Combustion Residuals Rule (CCR), which regulates coal ash from burning coal for the purpose of generating electricity as a solid waste 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 to managefor coal combustion residuals by regulating their design, location, monitoring, and operation.

In July 2018, the EPA published a final rule that included amendments to the CCR. The amendments include the allowance of alternative performance standards for landfills and surface impoundments, revised risk-based groundwater protection standards, and an extension of the deadline by which certain facilities must cease the placement of waste in CCR units. In August 2018, the D.C. Circuit vacated parts of the 2015 CCR for not being sufficiently protective of the environment. In August 2020, the EPA revised the CCR rule is implementedto require owners or operators of coal-fired power plants to stop transporting CCR and non-CCR wastewater (a process known as "sluicing") to unlined surface impoundments. In addition, regulated entities must initiate impoundment closure as

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soon as feasible and in phasesno event later than April 2021, unless the EPA grants an extension. Columbia requested an extension to allow for sites with onsite storage and/or disposal to evaluate their compliance withcomply by October 2022. The EPA will address the rule's design criteria. Landfills, impoundments and ash storage systems, such as ash ponds, that cannot meet design criteria will need to close formally within defined timeframes.remaining issues on remand in a subsequent action.

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activity can lead to lower consumption of electricity and gas that may not be offset by residential consumption.

Delay in, and possible loss of, payments for utility service

During the first several months of the pandemic, the PSCW ordered Wisconsin utilities not to charge for late payments and not to disconnect customers for non-payment, which, in combination with the economic hardship caused by quarantine or stay-at-home orders, could result in losses as those payments are received late or not at all. Further, significant delays in those payments could affect our liquidity. Although the PSCW order was lifted in July 2020, we have undertaken to continue to waive late fees until April 1, 2021.

Regulatory delays

We operate in a regulated environment. Delays in regulatory proceedings or the issuance of required permits or variances, due to limited operations, hours or ability to convene necessary meetings, could delay required approvals or permits and affect the timing of activities. The failure to get timely variances could expose us to fines and penalties.

Regulatory recovery of deferred costs

Certain incurred costs are being deferred as regulatory assets for future recovery and not being recognized in the statements of income, reflecting a March 24, 2020, PSCW Order. These costs can affect our cash, but are not presently recoverable in rates. If recovery of those regulatory assets in customer rates is not approved or is no longer deemed probable, these deferred costs would be recognized as a current period expense, which could be material in the period in which such recognition is required.

Employee and supplier disruptions

Employee absences and supply interruptions could affect our ability to operate and maintain our system.

Volatility in the capital markets

Concerns about COVID-19 and its effects have caused, and may continue to cause, significant volatility in the capital markets. Market volatility as a result of COVID-19 may have a material adverse impact on the value of our employee benefits trusts investments, which could impact our costs for those benefits. The price of our common stock has been volatile. The COVID-19 pandemic and the significant uncertainties it has caused for the global economy, business activity, and business confidence have had, and are likely to continue to have, a significant effect on the market price of securities generally, including our securities.

The situation around COVID-19 remains fluid and the potential for a material impact on the results of operations, financial condition, and liquidity increases the longer the virus disrupts the local economy. Although we expect sales for future periods in 2021 to be negatively impacted by the COVID-19 pandemic, we cannot reasonably estimate with any degree of certainty the actual impact COVID-19 may have on our results of operations, financial position, and liquidity. The extent to which the COVID-19 pandemic may impact our business, operating results, financial condition, or liquidity will depend on future developments, including the duration of the outbreak, business and workforce disruptions, and the effectiveness of actions taken to contain and treat the disease.

Moreover, the effects of the COVID-19 pandemic may heighten many of the other risks described in this section including, but not limited to, interest rate changes, rating agency actions, governmental actions and market volatility.

Regulatory Risk

We are subject to extensive government regulation in our business, which affects our costs and responsiveness to changing events and circumstances.

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Our business is subject to regulation at the State and Federal levels. We are subject to regulation as a holding company by the PSCW. The PSCW regulates the following aspects of MGE's business: rates, terms and conditions of service; various business practices and transactions; financing; and transactions between it and its affiliates, including MGE Energy. MGE is also subject to regulation by the FERC, which regulates certain aspects of its business. ATC, in which we have an investment, is subject to regulation by FERC as to, among other things, rates. The regulations adopted by the State and Federal agencies affect how we do business, our ability to undertake specified actions since pre-approval or authorization may be required for projects, the costs of operations, and the rates charged to recover suchthose costs. Our ability to attract capital also depends, in part, upon our ability to obtain a fair return from the PSCW.

Our utility revenues are subject to regulatory proceedings, which can affect our ability to recover, and the timing of recovery of, costs that we incur in our operations.

Our utility customer rates have a material impact on our financial condition, results of operations, and liquidity. Our ability to obtain adjustments to those rates depends upon timely regulatory action under applicable statues and

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Mandating increasing purchases of renewable energy, which affects the use of existing generation, and energy efficiency initiatives, which affect revenues.revenues.

We may be subject to future laws, regulations, or actions associated with public concern with fossil-fuel generation, greenhouse gases, and the effects of global climate change.

Our subsidiaries operate or co-own electric power plants that burn fossil fuels, deliver natural gas, and deliver electricity to customers. These business activities are subject to evolving public concern regarding greenhouse gases (GHG), and legislative and regulatory action, and possible litigation in response to that public concern. The primary greenhouse gas associated with our subsidiaries' combustion of fossil fuels, and the largest emission in our system overall, is carbon dioxide (CO₂).

Our subsidiaries couldhave incurred and are expected to continue to incur costs from themore stringent regulation of GHG from power plants, natural gas delivery, greenhouse gases used in power distribution, and efficiencies lost during power distribution. While it is difficult to know the current Stateextent of possible legislation or regulatory activity, the federal government is likely to consider and Federal governments are unlikely to pass comprehensivesome form of greenhouse gas legislation or regulations in the immediate future, future legislation is likely.regulations. In addition, litigation by environmental nongovernment organizations (NGOs) targeting GHG emissions from the electric power industry is also likely if the federal government fails to act on greenhouse gas initiatives.

Climate change could affect us in several other ways:

Changes in weather patterns, including swings in intensity, could affect use of electricity and gas by our customers, affecting revenues; and could affect the condition of our facilities, affecting our costs.

We may also incur costs associated with actions taken due to investor interest in reducing our subsidiaries' reliance on fossil fuel generation, and coal in particular. Investors may also move away from investing in fossil fuel generated electricity for reputational or perceived risk-related reasons. reasons, which could raise our costs of attracting capital.

If we are not seen as being proactive in addressing concerns, we may experience reputational issues among our customers and the communities that we serve. Those issues could affect customers' energy choices, including efforts at self-supply, and could affect the handling and treatment of our rate requests and cost recovery.

These matters represent uncertainties in the operation and management of our business.

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earn depends on multiple factors, including facility generation, the cost of qualifying property, and the applicable tax credit rate. The disallowance of these tax credits in whole or in part as a result of changes in tax law or regulation could adversely impact our earnings and cash flows.

If corporate tax rates or policies are changed with future federal or state legislation, we may be required to take material charges against earnings. The 2017 Tax Act is still being interpreted and implemented by the IRS as well as state income tax authorities, and the 2017 Tax Act could continue to be subject to potential amendments and technical corrections, any of which could lessen or increase certain adverse impacts of the 2017 Tax Act.

There is still uncertainty as to when or how credit rating agencies, capital markets, the FERC, or state public utility commissions will treat any additional impacts of the 2017 Tax Act. These impacts could subject us or any of our subsidiaries to further credit rating downgrades. It is unclear whether additional opportunities may evolve for us to manage the adverse impacts of the 2017 Tax Act. In addition, certain financial metrics used by credit rating agencies, such as our funds from operations-to-debt percentage, could be negatively impacted by future rulings related to the 2017 Tax Act.

We may not be able to use all tax credits for which we are eligible.

We have historically reduced our consolidated federal and state income tax liability with the use of various tax credits under the applicable tax codes. We may not be able to fully use tax credits if our future federal and state taxable income and related income tax liability is insufficient to permit their use. In addition, any future disallowance of some or all of those tax credits as a result of legislation or an adverse determination by one of the applicable taxing jurisdictions could materially affect our tax obligations and financial results.

Operating Risk

We are affected by weather, which affects customer demand and can affect the operation of our facilities.

The demand for electricity and gas is affected by weather. Very warm and very cold temperatures, especially for prolonged periods, can dramatically increase the demand for electricity and gas for cooling and heating, respectively, as opposed to the softening effect of more moderate temperatures. Our electric revenues are sensitive to the summer cooling season and, to a lesser extent, the winter heating season. Similarly, very cold temperatures can dramatically increase the demand for gas for heating. A significant portion of our gas system demand is driven by heating. Extreme summer conditions or storms may stress electric systems, resulting in increased maintenance costs and limiting the ability to meet peak customer demand.

We could be adversely affected by changes in the development, and utilization by our customers, of power generation, storage, and use technologies.

Our revenues and the timing of the recovery of our costs could be adversely affected by improvements in power generation, storage, and use technology.

Advancements in power generation technology, including commercial and residential solar generation installations and commercial micro turbine installations, are improving the cost-effectiveness of customer self-supply of electricity. Improvements in energy storage technology, including batteries and fuel cells, could also better position customers to meet their around-the-clock electricity requirements. Improvements in the energy efficiency of lighting, appliances, and equipment will also affect energy consumption by customers. Such developments could reduce customer purchases of electricity but may not necessarily reduce our investment and operating requirements due to our obligation to serve customers, including those self-supply customers whose equipment has failed for any reason to provide the power they need whether due to inadequate on-site resources, restricted operating hours, or equipment failure. In addition, since a portion of our costs are recovered through charges based upon the volume of power delivered, a reduction in electricity deliveries will affect the timing of our recovery of those costs and may require changes to our rate structures.

Changes in power generation, storage, and use technologies could have significant effects on customer behaviors and their energy consumption. Customers could engage in individual conservation efforts by voluntarily reducing their consumption of electricity through changes in energy use and through the use of more energy efficient

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lighting, appliances, and equipment. They could also change their consumption of electricity from us through the installation of alternative energy sources, such as rooftop solar panels and micro turbines for self-supply. Customer energy conservation could adversely affect our results of operations by reducing our revenues without necessarily changing our operating costs due to our obligation to serve.

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to repair or replace equipment and facilities may take place over prolonged periods or may be unsuccessful. We may also be unable to make the necessary improvements to our operational system, causing service interruptions. Furthermore, our facilities are interconnected with third-party transmission providers. Damage to or failures of these providers' equipment or facilities is out of MGE'sour control but could lead to service interruptions. The resulting interruption of services would result in lost revenues and additional costs. We are also exposed to the risk of accidents or other incidents that could result in damage to or destruction of our facilities or damage to persons or property. Such issues could adversely affect revenues or increase costs to repair and maintain our systems.

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supplier operations; requiring substantial expenditures and adversely impact our operationsexpenses to repair, replace and financial condition.

restore normal business operations; and reducing investor confidence. Facilities for electric generation, transmission, and gas and electric distribution are potential targets of terrorist threats and activities. A terrorist act or catastrophic event at our facilities or the facilities of other companies to which we are interconnected could result in a disruption of our ability to generate, transmit, transport, purchase, or distribute electricity or natural gas. A possible attackSuch an event would have additional adverse effects, including environmental ramifications, increased security and insurance costs, as well as general economic volatility or uncertainty within our service territories. The inability to maintain operational continuity and any additional costs incurred for repairing our facilities or making alternative arrangements could materially and adversely affect our financial condition and results of operations.

Failure to attract and retain an appropriately qualified workforce could affect our operations.

An aging workforce and the retirement of key employees without appropriate replacements may lead to operating challenges and increased costs. Some of the challenges include lack of resources, loss of knowledge, and time required for replacement employees to develop necessary skills. Failure to identify qualified replacement employees could result in decreased productivity and increased safety costs. If we are unable to attract and retain an appropriately qualified workforce, our operations could be negatively affected.

We face construction risk in connection with the completion of the Saratoga Wind Farm project.significant capital projects.

The 66-megawatt (MW) wind farm project isOur capital projects, such as our renewable generation projects, are subject to various risks that could cause costs to increase or delays in completion. These risks include shortages of, the inability to obtain, the cost of, and the consistency of, labor, materials and equipment; the inability of the contractors to perform under their contracts; the inability to agree to terms of contracts or disputes in contract terms; work stoppages; adverse weather conditions; the inability to obtain necessary permits in a timely manner; changes in applicable laws or regulations; adverse interpretation or enforcement of permit conditions; governmental actions; legal action; and unforeseen engineering or technology issues. In the case of our renewable generation projects, we may face delays in the completion of the necessary transmission system connection or upgrades to accommodate the project.

If a capital project exceeds the approved project is over budget,costs approved by the PSCW, we may not be able to recover those excess costs. costs through regulated customer rates. If that happens, we may have to finance overruns through cash from operations, which may delay other projects, or by securing additional financing. Any or all of these methods may not be available when or in the amounts needed or may adversely affect our financial condition, results of operations and cash flows.

Inability to recover excess costs, or inability to complete the project in a timely manner, could adversely impact our financial condition and results of operations. Further, our revenues and cash flows may not increase immediately following our expenditure of funds on a particular project, which could affect our liquidity and financial position.

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and operating costs, or inability to implement the project successfully and in a timely manner, could adversely impact our financial condition and results of operations.

We do not own all of the land on which our facilities are located, and we access certain facilities through rights-of-way which could disrupt our operations.

We do not own all of the land on which certain of our facilities are located, and we are, therefore, subject to the risk of increased costs to maintain necessary land use. We obtain the rights to construct and operate certain of our related facilities on land owned by third parties for a specific period of time. Our loss of these rights, through our inability to renew right-of-way contracts on acceptable terms or increased costs to renew such rights, could have a material adverse effect on our financial condition, results of operations and cash flows.

Failure to attract and retain an appropriately qualified workforce could affect our operations.

An aging workforce and the retirement of key employees without appropriate replacements may lead to operating challenges and increased costs. Some of the challenges include lack of resources, loss of knowledge, and time required for replacement employees to develop necessary skills. Failure to identify qualified replacement employees could result in decreased productivity and increased safety costs. If we are unable to attract and retain an appropriately qualified workforce, our operations could be negatively affected.

Financial Risk

We are exposed to commodity price risk relating to our purchases of natural gas, electricity, coal, oil, and environmental allowances.

We face commodity price risk exposure with respect to the purchase of natural gas, electricity, coal, oil, and environmental allowances. We also face risk through our use of derivatives such as futures, forwards, and swaps, to manage our commodity price risk. We could experience increased costs as a result of volatility in the market values of those commodities. We could also experience losses on our derivative contracts as a result of that market value volatility or if a counterparty fails to perform under a contract. In the absence of actively quoted market prices and pricing information from external sources, the valuation of these derivative contracts involves our exercise of judgment and use of estimates. As a result, changes in the underlying assumptions or use of alternative valuation methods could affect the reported fair value of these contracts.

Our business is concentrated in Wisconsin.

Our business activities, including those of our subsidiaries, are concentrated in Wisconsin. Changes in the economies of Wisconsin and surrounding regions could negatively impact the growth opportunities available to us and our subsidiaries, and the financial condition of our customers and prospects.

Interest rate movements and market performance affects our employee benefit plan costs.

Prevailing interest rates affect our assessment and determination of discount rates and are a key assumption in the determination of the costs and funding of our defined benefit pension plans. Changes in rates may impact the amount of expense and timing of contributions to those plans. The performance of the capital markets affects the values of the assets that are held in trust to satisfy the future obligations under our pension and postretirement benefit plans. We have significant obligations in these areas and hold significant assets in these trusts. A decline in the market value of those assets may increase our current and longer-term funding requirements for these obligations. Changes in the value of trust fund assets may affect the level of required contributions to these trusts to meet benefit obligations. Reduced benefit plan assets could result in increased benefit costs in future years and may increase the amount and accelerate the timing of required future funding contributions.

We are exposed to interest rate risk.

We are exposed to interest rate risk on our variable rate financing. Borrowing levels under commercial paper arrangements vary from period to period depending upon capital investments and other factors. Such interest rate risk means that we are exposed to increased financing costs and associated cash payments as a result of changes in

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the short-term interest rates.

We are exposed to counterparty credit risk primarily through our regulated energy business.

Credit risk is the loss and additional expense that may result from counterparty nonperformance. We face credit risk primarily through MGE's regulated energy business. Failure of contractual counterparties to perform their obligations under purchase power agreements, commodity supply arrangements, or other agreements may result in increased expenses for MGE as a result of being forced to cover the shortfall in the spot or short-term market, where prices may be more volatile. That risk may be increased during periods of weak or stressed economic conditions.

As a holding company, we are dependent on upstream cash flows from our subsidiaries for the payment of dividends on our common stock.

As a holding company, we have no operations of our own, and our ability to pay dividends on our common stock is dependent on the earnings and cash flows of our operating subsidiaries and their ability to pay upstream dividends or to repay funds to us. Our subsidiaries have financial obligations that must be satisfied before funding us. These obligations include debt service and obligations to trade creditors, among others. Our subsidiaries are also subject to contractual and regulatory restrictions on the payment of dividends.

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The stock market has experienced, and may continue to experience, fluctuations that significantly impact the market prices of securities issued by many companies. Many factors affect the volatility and price of our common stock in addition to our operating results and prospects, including economicchanges in conditions changes locally and in the broader economy. These conditions include technological change, the level of interest rates and yields on other investments, and the effects of the other risk factors discussed in this report. Our stock price could fluctuate significantly in response to our quarterly or annual results, as well as factors affecting the broader economy that are beyond our control.

Item 1B. Unresolved Staff Comments.

MGE Energy and MGE

None.

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Item 2. Properties.

Electric Generation

Net summer rated capacity in service as of December 31, 2018,2020, was as follows: