EPA Issues Final Rule Repealing Most 2024 Power Plant GHG Standards and a Proposal That Would Eliminate the Remaining Power Plant GHG Standards

On September 14, 2026, the U.S. Environmental Protection Agency (EPA) took two related actions to substantially change the federal framework for regulating greenhouse gas (GHG) emissions from fossil fuel-fired power plants under Clean Air Act Section 111.

First, the EPA finalized a rule repealing most of the 2024 Carbon Pollution Standards (CPS). The final rule removes the emission guidelines for existing coal, oil, and gas-fired steam generating units, as well as carbon capture and sequestration/storage (CCS)-based standards for certain modified coal-fired units and new baseload combustion turbines. The rule rests primarily on the EPA’s reassessment of the best system of emission reduction (BSER) determinations reflected in the 2024 rule, and removes those requirements as of the effective date of the newly finalized rule.

Second, the EPA issued a supplemental proposal that would repeal all remaining Section 111 GHG emission standards for fossil fuel-fired power plants. The EPA bases this supplemental proposal on its proposed conclusion that Congress did not authorize the EPA to regulate power-plant emissions under Section 111 for the purpose of addressing global climate change, teeing up that fundamental question regarding the EPA’s authority to regulate GHG emissions.

Reduced Compliance for Fossil Fuel-Fired Plants

In its June 2025 proposed rule, as we reported previously, the EPA offered two paths for reconsidering the 2024 CPS. The final rule adopts the narrower alternative approach – to repeal the GHG emission standards for most power plants because there is no method for controlling GHG emissions that meets the BSER. In doing so, the EPA declines to adopt the agency’s broader proposal to find that power-plant GHG emissions do not “contribute significantly” to dangerous air pollution.

The final rule makes several principal changes to the requirements, including:

• Existing fossil fuel-fired steam units. The EPA repeals the Section 111(d) emission guidelines for existing coal, oil, and gas-fired steam generating units.
  • For existing coal units expected to operate long term, the EPA rejects the 2024 rule’s 90% CCS-based BSER, concluding that 90% CCS is not adequately demonstrated, that its costs are unreasonable, and that the necessary capture, pipeline, and sequestration infrastructure is unlikely to be available by the January 2032 compliance date.
  • The EPA also rejects the 40% natural-gas co-firing BSER for medium-term coal units, reasoning that it would constitute impermissible generation shifting under West Virginia v. EPA, would be an inefficient use of natural gas, and would depend on pipeline infrastructure unlikely to be available by January 1, 2030.
  • The EPA further concludes that retaining state-plan obligations solely for the remaining natural-gas and oil-fired steam units would consume state resources while producing few or no emission reductions.
• Modified coal units and new baseload combustion turbines. The final rule also repeals CCS-based standards for coal-fired EGUs undertaking a large modification and for new baseload stationary combustion turbines.
• Some new-source requirements remain, for now. The final rule does not eliminate every federal powerplant GHG standard. The EPA identifies remaining partial CCS-based and efficiency standards for certain new, reconstructed, or modified steam generating units and integrated gasification combined-cycle facilities, as well as efficiency-based standards for new or reconstructed stationary combustion turbines. Those remaining standards are the subject of the supplemental proposal. The EPA’s accompanying fact sheet estimates that the two actions are expected to produce more than US$300 billion in cost savings.

The Supplemental Proposal’s Narrower View of Section 111

The supplemental proposal would repeal all remaining GHG standards for fossil fuel-fired power plants under Section 111 and rescind 2015 findings that support federal GHG regulation of fossil fuel-fired EGUs. The EPA advances several overlapping rationales and theories:

• The EPA proposes a narrower reading of Section 111(b)(1)(A). That provision requires the EPA to determine that a source category “causes, or contributes significantly to, air pollution which may reasonably be anticipated to endanger public health or welfare.” The EPA proposes that, in statutory and historical context, “air pollution” in Section 111 refers to pollution that threatens health or welfare through local or regional exposure, rather than GHG emissions whose asserted effects occur through changes in global atmospheric concentrations and the global climate.
• The EPA invokes limits on major agency action. The EPA relies on the major questions doctrine, including the Supreme Court’s decisions in West Virginia v. EPA and Utility Air Regulatory Group v. EPA, and also cites Loper Bright Enterprises v. Raimondo, which requires courts to exercise independent judgment on questions of statutory authority. The EPA proposes that regulating the power sector to address global climate change presents a question of sufficient economic and political significance to require clear congressional authorization, and that Section 111 contains no such authorization.
• The EPA points to the modeled effect of U.S. power-sector emissions. The EPA models the hypothetical elimination of all CO2 emissions from the U.S. power sector (an outcome beyond what the existing Section 111 rules would achieve) and concludes that even that scenario would have only de minimis modeled effects on global temperature and sea-level change.
• Finally, the EPA identifies additional concerns with the 2015 regulatory foundation. Among other things, the EPA proposes that the Agency effectively created a combined “fossil fuel-fired EGU” source category in 2015 without making a new Section 111(b)(1)(A) listing determination. The EPA also points to its February 2026 rescission of the 2009 GHG Endangerment Finding, on which the 2015 power-plant findings had relied in part.

Next Steps

Potential Impact on Pending Supreme Court Litigation. The final rule is expected to be challenged in court, although the positions taken by the EPA in the rule and the supplemental proposal could have more immediate implications. In Suncor Energy (U.S.A.) Inc. v. County Commissioners of Boulder County, set for argument on October 5, 2026, the Court will consider whether federal law precludes state-law claims seeking relief for injuries allegedly caused by the effects of interstate and international GHG emissions on the global climate. The United States is participating as amicus curiae in support of petitioners.

In its May 2026 amicus brief, the United States argued that the Clean Air Act preempts Boulder’s claims because the statute places the EPA and states in charge of emissions regulation. The brief contends Congress delegated to the EPA the decision “whether and how to regulate” carbon-dioxide emissions from power plants and describes Section 111 as making the EPA the primary regulator of domestic stationary sources. The brief distinguishes the EPA’s February 2026 conclusion that it lacked authority to regulate motor-vehicle GHG emissions on climate-change grounds, stating the conclusion did not apply to the EPA’s Section 111 authority over stationary sources. The EPA’s new supplemental proposal would now take the additional position that Section 111 likewise does not authorize the EPA to regulate power-plant GHG emissions for purposes of addressing global climate change.

While the federal government has also advanced arguments independent of its Clean Air Act preemption theory, the relationship between the EPA’s proposed limits on its own stationary-source authority and the federal government’s reliance on federal primacy over GHG regulation may receive attention as the Supreme Court considers the case.

Public comment. The supplemental proposal will be subject to public comment for 45 days after publication in the Federal Register.

This post is as of the posting date stated above. Sidley Austin LLP assumes no duty to update this post or post about any subsequent developments having a bearing on this post.