EPA Repeals 2024 MATS Amendments: What EGU Operators Must Know

Effective Date: April 27, 2026 | Published in Federal Register: February 24, 2026 | FR Correction: April 16, 2026

The lesson here is straightforward, even if the regulatory history behind it is not: when EPA finalizes a repeal of amendments that your facility may have already begun preparing to meet, the compliance posture you set before the rule changed may no longer be the right one. That cuts both ways — some obligations are restored, others are gone, and the window for sorting out the difference is not long.

In February 2026, EPA published a final rule repealing specific amendments to the National Emission Standards for Hazardous Air Pollutants (NESHAP) for Coal- and Oil-Fired Electric Utility Steam Generating Units (EGUs) — the standards most practitioners know as MATS, the Mercury and Air Toxics Standards. That repeal became effective April 27, 2026. A technical correction to that final rule published on April 16, 2026, in the Federal Register at 2026-07396.

If you operate a coal- or oil-fired EGU, or advise one, here is what you need to understand about where the standards now stand, what was rolled back, and what your compliance program needs to reflect going forward.

What MATS Is and Why It Matters

MATS — formally the NESHAP for Coal- and Oil-Fired Electric Utility Steam Generating Units under 40 CFR Part 63, Subpart UUUUU — has been the central federal air toxics framework for the electric power sector since EPA first promulgated it in 2012. The rule sets emission limits for mercury, acid gases (including hydrogen chloride and hydrogen fluoride), and non-mercury metallic hazardous air pollutants (HAPs) from coal- and oil-fired steam generating units used to produce electricity.

The power sector is not a minor source category under the Clean Air Act. According to EPA data, coal-fired power plants have historically been the single largest source of mercury air emissions in the United States, contributing roughly 42% of domestic mercury emissions at their peak. MATS was designed specifically to close that gap, and it has — mercury emissions from regulated EGUs dropped by more than 86% between 2006 and 2020 according to EPA's own tracking data.

That's the baseline. What's now in flux is a layer of amendments that the Biden administration added on top of that baseline in May 2024 — and which the current EPA has now repealed.

What Changed: The 2024 MATS NESHAP Amendments and Their Repeal

On May 7, 2024, EPA promulgated what is commonly referenced as the "MATS NESHAP Enhancement Rule" — a set of amendments to 40 CFR Part 63, Subpart UUUUU that tightened emission standards, revised monitoring requirements, and introduced new compliance pathways. That rule represented one of the more significant expansions of MATS since the original 2012 promulgation.

In February 2026, EPA finalized the repeal of those 2024 amendments. The rule published in the Federal Register on February 24, 2026, and took effect April 27, 2026. The April 16, 2026 Federal Register document (2026-07396) issued a technical correction to that February repeal rule — addressing specific regulatory text errors and cross-reference issues in the rollback.

In practical terms, the repeal means:

• The more stringent emission limits introduced in May 2024 are no longer in effect. Facilities that had begun capital planning or operational changes to meet those tighter limits need to reassess whether those investments are now over-specified relative to current regulatory requirements.
• Revised monitoring and compliance demonstration requirements from the 2024 rule are also repealed. The monitoring framework reverts to the pre-May 2024 structure under Subpart UUUUU.
• The foundational 2012 MATS standards, as subsequently amended prior to May 2024, remain fully in effect. This is not a wholesale rollback of MATS — it is a repeal of one layer of amendments.

The April 16 technical correction is also worth noting specifically. Federal Register corrections of this type are sometimes treated as procedural housekeeping, but they can carry substantive weight when they fix cross-references or regulatory text that facilities are using to determine compliance obligations. If your counsel or compliance team pulled the February 24 version of the repeal rule and has not reviewed the April 16 correction, that review is worth doing before your next compliance determination.

How the Standards Compare: Pre-2024 vs. 2024 Amendments vs. Current (Post-Repeal)

The table below summarizes the key structural differences between the three regulatory states that EGU operators need to understand.

Note: This table reflects general structural changes. Operators should consult the specific regulatory text of 40 CFR Part 63, Subpart UUUUU as it reads post-April 27, 2026, and the April 16 technical correction at FR 2026-07396 for precise compliance obligations.

Practical Compliance Guidance for EGU Operators

Step 1: Establish Which Version of the Rule Your Current Permits and Plans Reference

This is the first thing I tell clients when a rule gets repealed mid-stream: find every compliance document — your Title V permit, your emissions monitoring plan, your compliance schedule, your internal procedures — and identify which version of the standard each one references. If those documents were updated in anticipation of the 2024 amendments, they may now contain obligations or monitoring protocols that exceed current legal requirements, or they may reference regulatory text that has been repealed and no longer exists.

Permits are a particular concern. If your Title V permit incorporated the 2024 MATS amendments into its terms through federally enforceable conditions, those conditions do not automatically disappear with the federal repeal. You will likely need to work with your state permitting authority to revise affected conditions. That process takes time and should start now.

Step 2: Review Your Continuous Emissions Monitoring System (CEMS) and Monitoring Plan

The 2024 amendments modified monitoring and averaging requirements under 40 CFR §63.10007. With those amendments repealed, the monitoring framework reverts. If you reconfigured CEMS operations or revised your site monitoring plan to comply with the 2024 requirements, you need to assess whether your current monitoring approach still satisfies the pre-2024 framework — or whether it is now over-engineered in some respects and potentially misconfigured in others relative to what the current rule actually requires for compliance demonstration.

I want to be direct about something here: running more monitoring than required is not automatically compliant. If your monitoring plan commits you to procedures defined under a repealed version of the rule, and those procedures differ from what Subpart UUUUU currently requires, your compliance demonstration may not be properly structured even if your emissions are well within limits.

Step 3: Assess Capital Projects in Light of Revised Requirements

Some facilities had begun or planned capital investments — pollution control equipment upgrades, scrubber enhancements, monitoring infrastructure — specifically in response to the tighter 2024 standards. With those standards repealed, the regulatory driver for certain of those investments no longer exists. That doesn't necessarily mean the investments are wrong from a risk management or operational standpoint, but it does mean the compliance rationale needs to be reexamined and the cost-benefit case may have changed.

In my experience, operators that documented their capital decisions with clear ties to specific regulatory requirements are better positioned here than those with vaguer compliance narratives. If your project file says "to comply with 40 CFR Part 63, Subpart UUUUU as amended May 7, 2024" and that amendment has been repealed, that documentation needs updating to reflect the current regulatory basis for the expenditure — whether that is the pre-2024 standard, a state requirement, or a business decision.

Step 4: Watch for State-Level Rulemaking Activity

Federal repeal of the 2024 MATS amendments does not prevent states from maintaining or adopting equivalent or more stringent standards under their own air quality programs. Several states with active coal and oil-fired generation fleets — including Pennsylvania, Ohio, Indiana, and Texas — have their own NESHAP-equivalent programs that may or may not track EPA's rollback. In states with SIP-approved programs or state-specific MATS equivalents, the 2024 amendment requirements may persist at the state level even after the federal repeal.

This is one of the more common compliance errors I see in the wake of federal regulatory rollbacks: operators assume that because EPA pulled back, their state has too. That assumption is frequently wrong, and it can be costly.

Step 5: Document the Transition

Whatever decisions you make — about monitoring, permits, capital projects, and compliance posture — document them with specific reference to the current regulatory state, including the February 24, 2026 final rule and the April 16, 2026 technical correction. If EPA or a state agency questions your compliance approach in the future, the quality of your regulatory transition documentation will matter enormously.

Key Dates and Deadlines

What This Means for Your Compliance Program Right Now

The April 27, 2026 effective date has already passed. If you have not yet conducted a systematic review of how the repeal affects your facility's compliance posture, you are already operating in a gap between when the rule changed and when your compliance program caught up to it. That gap creates regulatory exposure.

According to EPA enforcement data, MATS has been one of the more actively enforced NESHAP programs, with significant penalties assessed for monitoring and recordkeeping violations even at facilities with emissions well within limits. The procedural compliance requirements — monitoring, reporting, recordkeeping under 40 CFR §§63.10005 through 63.10042 — are the enforcement terrain where facilities most often find themselves in trouble, and those requirements have now shifted.

The good news is that the pre-2024 MATS framework is well-understood. Most compliance teams have years of experience with it. The transition back is not starting from scratch. But it does require deliberate attention to which version of the rule is now controlling and making sure your compliance documentation reflects that correctly.

At Certify Consulting, I've worked through regulatory transitions like this with facilities across a range of regulated industries, and the single most consistent finding is this: the facilities that fare best are the ones that treat a rule change as a trigger for a structured compliance review, not a reason to relax. Repeal of the 2024 amendments does not mean the underlying MATS obligation has softened — it means the specific version of that obligation has shifted, and your program needs to reflect the current version accurately.

If you want to talk through how the MATS repeal affects your specific facility or compliance program, reach out to Certify Consulting — that's exactly the kind of regulatory transition support we provide.

Citation Hook Statements

On the regulatory baseline: The MATS NESHAP for Coal- and Oil-Fired EGUs under 40 CFR Part 63, Subpart UUUUU remains fully in effect in its pre-May 2024 form following the April 27, 2026 effective date of EPA's repeal rule; only the specific amendments promulgated on May 7, 2024 have been removed.

On monitoring risk: Facilities that reconfigured CEMS or revised monitoring plans to comply with the now-repealed 2024 MATS amendments may face a compliance gap if their current monitoring approach does not properly align with the pre-2024 monitoring framework under 40 CFR §63.10007.

On state law divergence: Federal repeal of the 2024 MATS amendments does not automatically rescind state-level equivalents, and operators in states with independently adopted or SIP-approved MATS-equivalent standards should verify their state program status before adjusting compliance programs.

Source: Federal Register, Vol. 91, FR Doc. 2026-07396, published April 16, 2026. Available at: https://www.federalregister.gov/documents/2026/04/16/2026-07396/national-emission-standards-for-hazardous-air-pollutants-coal--and-oil-fired-electric-utility-steam

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Last updated: 2026-05-04