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 we conduct our operations, the costs of those 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 the potential to 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:

With the closure of the wet pond system in 2023, 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 Supplemental Effluent Limitations Guidelines and Standards for the Steam Electric Power Generating Point Source Category (2024 ELG Rule) that further regulates the wastewater discharges associated with coal-fired power plants. The rule impacts Columbia and the Elm Road Units. The 2024 ELG Rule focuses on wastewater discharges from flue gas desulfurization, combustion residual leachate, and bottom ash transport water. The 2024 ELG Rule includes reduced 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. Although the 2024 ELG Rule is currently being challenged in federal court, the litigation is on hold while the EPA undertakes a reconsideration process. The 2024 ELG Rule builds upon the 2020 ELG Rule, which also remains under legal challenge and is similarly on hold pending the outcome of the EPA's review. In December 2025, the EPA published a rule (2025 Rule) that extended several rule deadlines. This rule is also under legal challenge. The operator of the Elm Road Units is in compliance with the 2024 ELG Rule. The operator of Columbia has indicated they are in compliance with the 2024 ELG Rule. MGE will continue to monitor the outcomes of the rule challenges and work with our co-owners on their compliance plans.

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 optimization study to demonstrate compliance with impingement BTA standards in the latest permit which needs to be completed by January 2028. 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. In March 2026, Columbia received an updated WPDES permit from the WDNR. The WPDES permit has indicated that Columbia's existing intake structure meets BTA standards. MGE does not, based on current information, anticipate any further requirements at Columbia and thus does not expect this rule to have a material effect on Columbia.

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 granted 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 established a process where states must submit plans to the EPA for establishing standards. States had two years from the publication date of these rules to submit plans to the EPA for review and approval. Preliminary evaluation of the final ruling showed that MGE met the requirements for the gas-fired boilers at Blount. Evaluations done by the owners of Columbia and the Elm Road Units in 2024 indicated that they have a plan for complying with the May 2024 rule. In June 2025, the EPA published a proposed rule with two potential options: (1) repeal the performance standards and emission guidelines under Section 111 of the Clean Air Act associated with GHG emissions from fossil fuel-fired power plants, or (2) retain only the efficiency-based requirements for new natural gas-fired power plants and repeal all other aspects of the rule. In July 2025, the EPA released a new proposed rule titled "Reconsideration of 2009 Endangerment Finding and Greenhouse Gas Vehicle Standards." In February 2026, the EPA finalized the repeal, which will effectively undo the basis for federal regulation of GHG under the Clean Air Act. Several states and stakeholders have initiated legal challenges to the repeal. The scope and timing of any impacts on federal GHG regulation remain uncertain pending litigation and potential further agency action. MGE will continue to monitor developments.

The Elm Road Units are located in Milwaukee County, Wisconsin, a nonattainment area for the 2015 Ozone NAAQS. The area was redesignated to serious nonattainment by the EPA in December 2024, effective January 2025, but is currently categorized as moderate nonattainment following a stay granted by the U.S. Court of Appeals for the Seventh Circuit in September 2025. 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 direct material effect on the Elm Road Units.

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 the 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. In February 2025, Wisconsin's Governor Evers submitted a state-wide attainment recommendation to the EPA. The 2024 rule is on hold pending the EPA's reconsideration of this rule.

Multiple states and industry groups challenged the March 2024 PM2.5 NAAQS rule in the United States Court of Appeals for the District of Columbia Circuit. In March 2025, the EPA announced reconsideration of the rule and the litigation was put on hold pending completion of that process. In November 2025, the EPA filed a motion with the D.C. Circuit requesting to vacate the 2024 rule entirely due to error in the rulemaking process. The EPA has indicated that they intend to formally propose a revised rule in 2026.

The final impact of this rule will not be known until 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.

The EPA's Good Neighbor Plan 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 NOx and SO2 from qualifying fossil fuel-fired power plants and industrial boilers in upwind "contributing" states. NOx and SO2 contribute to fine particulate pollution, and NOx 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 (Good Neighbor Plan). The Good Neighbor Plan impacts 23 states, including Wisconsin. For Wisconsin, the Good Neighbor Plan 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. Initial obligations under the Federal Implementation Plan were scheduled to begin during the 2023 ozone season. 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 Good Neighbor Plan.

Multiple legal challenges to the Good Neighbor Plan and related state implementation plan disapprovals are pending, including 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 Good Neighbor Plan and block its enforcement 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. The EPA has temporarily halted the enforcement of the Good Neighbor Plan's requirements for all pollution sources in states affected by the plan, including Wisconsin. While the EPA addresses these concerns, interim rules have been implemented in Wisconsin to address interstate pollution. Based on MGE's current evaluation, if the Good Neighbor Plan goes into effect as-is, the 2026 additional emission reductions may impact the Elm Road Units. However, final impact of the rules will not be known until judicial reviews are completed and/or the EPA takes further action regarding the 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.

Review of the Elm Road Units has indicated that the costs to comply with the CCR Rule are not expected to be significant.

In May 2024, the EPA published its final CCR Legacy Rule. The CCR Legacy Rule applies to previously closed disposal sites. In 2024, MGE recorded an 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 at Columbia. 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.

In February 2026, the EPA finalized the CCR Management Unit Deadline Extension Rule, which provides a one-year extension for the submission of Facility Evaluation Reports and extends the deadline for the implementation of groundwater monitoring systems at legacy CCR management units to February 2031. Columbia continues to evaluate the impact of this extension on its compliance timeline. This update is not expected to materially affect anticipated compliance costs. In April 2026, the EPA published a proposed rule that would amend the CCR regulations by eliminating certain closure requirements that previously applied to legacy surface impoundments and CCR management units. MGE will continue to monitor legal developments and any future updates to this rule.

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.

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 minimum commitments related to purchase contracts as of March 31, 2026: