EPA MATS NESHAP Repeal 2026: What Really Changes for Coal and Oil-Fired Power Plants

The MATS Repeal Is Not a Facility Exemption—What April 27 Really Means

If you own a coal or oil-fired electric utility generating unit (EGU), April 27, 2026 is a significant date. That’s when the EPA’s Mercury and Air Toxics Standards (MATS) repeal takes effect.

But here’s what many facility managers get wrong: this is not a wholesale exemption. The EPA is not eliminating mercury and air toxics requirements. It’s rolling back only the 2024 tightening, returning coal and oil-fired utilities to the stricter 2012 baseline. If you’ve been operating under MATS for the past decade, you’re not suddenly free from compliance—you’re free from the most recent increase in stringency.

The distinction matters for your budget, your monitoring plan, and your quarterly reporting timeline.

This post walks you through exactly what changes, what stays the same, and what you must do before April 27 to ensure you’re compliant under the reinstatement.

The Regulatory Context: What the Repeal Actually Covers

The Federal Register finalized the MATS repeal on February 24, 2026, with an effective date of April 27, 2026. The EPA is repealing three specific components of the May 7, 2024 amendments to 40 CFR Part 63 Subpart UUUUU:

The tightened filterable particulate matter (fPM) standard. The 2024 amendment lowered the fPM limit for existing coal-fired EGUs from 0.030 lb/MMBtu to 0.010 lb/MMBtu. The repeal reverts this back to 0.030 lb/MMBtu—the original 2012 limit.
The mandatory PM CEMS requirement. The 2024 amendment made continuous emissions monitoring systems (CEMS) the only acceptable method to demonstrate fPM compliance. As of April 27, facilities can revert to alternative methods: quarterly performance testing (stack testing), parametric monitoring systems (CPMS), or other EPA-approved techniques.
The stricter mercury standard for lignite-fired EGUs. This narrow requirement is also repealed, though the core mercury limits for all coal types remain in full effect.

What’s crucial to understand: The original 2012 MATS rule is not being eliminated—it’s being fully reinstated. Coal and oil-fired utilities with capacity exceeding 25 megawatts must continue meeting:

Mercury emission limits of 1.2 lb/TBtu for standard coal and 4.0 lb/TBtu for low-rank coal (until July 6, 2027)
Hydrogen chloride (HCl) and non-mercury HAP metals standards
Quarterly performance testing or continuous emissions monitoring
Quarterly MATS compliance reporting to EPA’s ECMPS system

This is not relief from environmental regulation—it’s a partial reversal of a recent tightening.

Who Is Actually Affected—And Who Isn’t

The scope of the MATS repeal is narrow: only electric utility generating units (EGUs) over 25 megawatts firing coal or oil. This is a critical distinction because many facility operators misidentify their regulatory obligations.

You ARE affected if:

Your facility generates electricity for sale to the electrical grid
Your primary fuel is coal or oil
Your electric generating capacity exceeds 25 MW
You are classified as a utility, independent power producer (IPP), or merchant generator

There are approximately 219 coal-fired EGUs across the United States that fit this profile, with an estimated 12 in Kansas based on prior EPA filings.

You are NOT affected if:

Your facility operates an industrial, commercial, or institutional boiler under 40 CFR 63 Subpart DDDDD (Boiler MACT)
You operate a co-generation facility that does not export electricity to the grid as a primary business
Your facility is natural gas-only or biomass-only
You operate a non-utility combined heat and power (CHP) system
Your facility is a manufacturing facility boiler or process heater, regardless of size or fuel type

The self-qualification test: If your facility’s primary purpose is to generate electricity for external sale and you fire coal or oil, MATS applies. If your facility burns fuel primarily for on-site steam or heat, or if your electric capacity is under 25 MW, MATS does not apply—even if you’re a large industrial facility.

This is where many manufacturers and industrial operators get confused. The repeal won’t affect your facility unless you’re a utility.

Your Monitoring Options Just Got More Flexible

One of the most practical consequences of the April 27 repeal is the return of monitoring flexibility. The 2024 amendment mandated particulate matter CEMS as the only compliance demonstration method. On April 27, this mandate disappears.

As of the repeal date, your facility can choose from multiple compliance pathways:

Quarterly performance testing (stack testing). Third-party certified testing at fixed intervals. This is proven, lower-cost for facilities already using it, and acceptable to EPA.
PM Continuous Parametric Monitoring Systems (CPMS). Parameter-based monitoring (inlet/outlet temperature differentials, pressure drop, etc.) that correlates to emission rates without direct measurement.
Mercury Continuous Emissions Monitoring Systems (CEMS). Real-time direct measurement. Required only if you choose this method.
Sorbent trap mercury monitoring. Under specific conditions, for facilities with compatible burners.
Fuel analysis for mercury. Pre-combustion analysis paired with fuel flow data, where applicable.

The significance: Facilities that installed PM CEMS purely to comply with the 2024 amendment can now request permit modifications to revert to cheaper, less operationally complex methods—typically quarterly stack testing.

If your facility spent capital on CEMS installation in 2024 or 2025, you have grounds to revisit that investment. You may be able to achieve compliance at lower operational cost using the method you used before 2024.

The Compliance Action Items: What You Must Do by April 27

The repeal does not trigger an emergency filing requirement, but it does require you to act before April 27 to ensure uninterrupted compliance:

1. Confirm Your Applicability Status

If you haven’t explicitly confirmed whether your facility is subject to MATS, do this first. Your facility is presumed subject to MATS if it’s a coal or oil-fired EGU with capacity over 25 MW. The burden is on you to prove exemption if you claim one.

If you’re unsure, consult EPA’s MATS fact sheets or work with an environmental consultant.

2. Choose Your Monitoring Method for Post-April 27

Review your current monitoring plan. If you installed or expanded PM CEMS in 2024-2025 to comply with the stricter fPM standard, you’re now eligible to request modification back to a less burdensome method.

If you were already using quarterly stack testing before the 2024 amendment, you can continue. If you switched to CEMS, evaluate whether reverting to stack testing makes financial sense for your operation.

3. Update Your Air Permit or Monitoring Plan (If Needed)

If you’re requesting a modification to your monitoring method, work with your state environmental agency or local permitting authority to request the change under 40 CFR 63 permit modification procedures. This does not require EPA approval, but it does require state/local documentation.

Plan to complete this by Q4 2026 to align with your first quarterly compliance report under the revised method.

4. Prepare for the First Quarterly Report (Due ~May 1, 2026)

Your facility must submit a MATS Compliance Report to EPA’s ECMPS Reporting Tool within 30 days of the end of each quarter. The first report under the reinstated 2012 standards will cover Q2 2026 and is due around May 1, 2026.

This report must include:

Facility and unit identification
Fuel type and heat input data
Mercury, HCl, and fPM emission rates or testing results
Monitoring system downtime and any exceedances
Boiler tune-up documentation (work practice standard)

Your compliance staff should confirm that your reporting systems are aligned with the 2012 limits—not the 2024 limits—before the first report is due.

5. Document Your Compliance Baseline

Establish clear documentation of which standard you’re operating under (2012 MATS limits) and which monitoring method you’re using as of April 27. This creates a defensible record if EPA questions your compliance approach later.

The Regional Compliance Picture: State Adoption Matters

A question many multi-site operators ask: Does the federal repeal mean state-level relief too?

The short answer is no—not in iSi’s primary service region. The federal Clean Air Act does not preempt or eliminate state emission standards. State environmental agencies are free to maintain their own standards independent of federal requirements.

In iSi’s region, the adoption pattern is uniform:

Kansas adopts the EPA MATS standard by reference under K.A.R. 28-19 (revised February 8, 2024). The Kansas Bureau of Air enforces the 2012 MATS rule with no additional state-specific mercury standards. The April 27 repeal applies immediately in Kansas.

Texas implements EPA MATS but maintains independent air toxics monitoring through TCEQ. Texas has the authority to develop more stringent standards, but currently aligns with federal MATS. The repeal applies in Texas as well.

Oklahoma, Missouri, Nebraska, and Colorado adopt EPA MATS by reference via state implementation plans (SIPs). None of these states maintain mercury standards exceeding federal MATS. The April 27 repeal takes effect statewide.

The regional takeaway: If your facility operates in Kansas, Texas, Oklahoma, Missouri, Nebraska, or Colorado, the April 27 repeal has immediate and uniform effect across all locations. You don’t face different compliance baselines in different states—you face the 2012 MATS baseline everywhere in iSi’s core region.

This is a significant advantage for multi-site operators who don’t have to manage layered state-specific standards.

The Enforcement Window: What Happens After April 27

Facility owners often ask: If the standard is less stringent, does EPA enforcement become less likely?

The answer is nuanced. EPA retains full enforcement authority under the 2012 MATS rule. Facilities operating below the 2012 limits remain in violation and are subject to penalties.

The historical enforcement pattern shows this is serious. In August 2024, EPA settled an enforcement action against Applied Energy Systems (AES) in Puerto Rico for MATS violations, including mercury monitoring failures and improper particulate monitoring. The civil penalty: $3.1 million. This was for monitoring violations, not even emissions exceedances.

What the April 27 repeal does accomplish is reduce the likelihood of exceedance penalties for facilities currently operating above 2012 limits but below 2024 limits. If your facility was struggling to meet the 2024 standard, the reversion to 2012 limits may bring you back into compliance.

However, EPA’s enforcement posture on MATS remains active. The EPA Enforcement Response Policy for MATS is explicit about penalty escalation for repeated violations, reporting failures, and monitoring system circumvention.

The bottom line: The repeal reduces stringency, not enforcement attention. Ensure your compliance program continues to operate at the level of rigor you’ve maintained under MATS since 2012.

The Judicial Review Timeline: A Floating Deadline

Here’s a detail that matters for long-term planning: Petitions for judicial review of the MATS repeal must be filed by April 27, 2026 in the U.S. Court of Appeals for the District of Columbia Circuit.

If environmental groups, states, or other stakeholders challenge the repeal in court and succeed, the 2024 standards could be reinstated. This is not a near-certainty—the EPA’s legal arguments for repealing the amendment are substantial—but it is a nonzero risk.

What this means for your facility:

Don’t make irreversible decisions about PM CEMS equipment or monitoring infrastructure. If you’ve installed CEMS in the last two years, keep the hardware operational and documented. A successful legal challenge could reinstate the mandatory CEMS requirement, and you’d want infrastructure already in place rather than facing emergency retrofit.

For most facilities, this suggests a pragmatic approach: Revert to less burdensome monitoring methods (stack testing) where it makes operational sense, but don’t decommission equipment entirely. The long-term legal risk is low, but it’s not zero.

What This Means for Your Compliance Program

The April 27 MATS repeal is a specific, technical change affecting a narrow class of facilities—utility-scale coal and oil-fired power plants. It is not a repeal of environmental responsibility or an elimination of mercury and air toxics oversight.

For facilities within scope, the repeal offers immediate advantages: lower stringency, monitoring flexibility, and reduced operational burden. The path forward is clear: confirm applicability, choose your monitoring method, update your permits, and align your quarterly reporting with the 2012 baseline.

For industrial facilities outside the utility classification, the repeal does not apply—even if you operate large boilers firing coal or oil. Your compliance obligations remain under the Boiler MACT standard (40 CFR 63 Subpart DDDDD), which is not affected.

If you’re uncertain whether MATS applies to your facility, or if you need to update your monitoring plan or air permit before April 27, iSi can help you navigate the compliance pathway and confirm your obligations under the reinstated 2012 standards. We work with facilities across the EGU and industrial sectors to keep compliance programs aligned with the current regulatory baseline.