Partial Repeal of the Carbon Pollution Standards for Fossil Fuel-Fired Electric Generating Units

A. Cost Savings II. General Information

A. Where To Get a Copy of This Document and Other Related Information

B. Action Applicability

C. Statutory Authority

1. Regulation of Emissions From New Sources

2. Regulation of Emissions From Existing Sources

3. Key Elements of Determining a Standard of Performance

D. Severability

E. Reliance Interests III. Background

A. EPA Regulation of GHG Emissions Under CAA Section 111

B. Carbon Pollution Standards

C. Changes in Trends in Fossil Fuel-Fired EGUs

D. June 2025 NPRM IV. Repeal of Sections of the Carbon Pollution Standards

A. Repeal of the Emission Guidelines for Existing Fossil Fuel- Fired Steam Generating Units

1. CCS-Based Requirements for Long-Term Existing Coal-Fired Steam Generating Units

2. Natural Gas Co-Firing-Based Requirements for Existing Medium- Term Coal-Fired Steam Generating Units

3. Requirements for Existing Natural Gas- and Oil-Fired Steam Generating Units

4. Conclusion

B. Repeal of the CCS-Based Requirements for Coal-Fired Steam Generating Units Undertaking a Large Modification

C. Partial Repeal of the 2024 Standards for New Combustion Turbine EGUs

1. Phase 2 CCS-Based Requirements for New Base Load Combustion Turbines

2. Summary of Substantial Comments on the 2024 Efficiency-Based Requirements for New Intermediate and Base Load Combustion Turbines

3. Conclusion

D. Consideration of Alternatives V. Statutory and E.O. Reviews

A. E.O. 12866: Regulatory Planning and Review and E.O. 13563: Improving Regulation and Regulatory Review

B. E.O. 14192: Unleashing Prosperity Through Deregulation

C. Paperwork Reduction Act (PRA)

1. 40 CFR Part 60, Subpart TTTT

2. 40 CFR Part 60, Subpart TTTTa

3. 40 CFR Part 60, Subpart UUUUb

D. Regulatory Flexibility Act (RFA)

E. Unfunded Mandates Reform Act (UMRA)

F. E.O. 13132: Federalism

G. E.O. 13175: Consultation and Coordination With Indian Tribal Governments

H. E.O. 13045: Protection of Children From Environmental Health Risks and Safety Risks

I. E.O. 13211: Actions Concerning Regulations That Significantly Affect Energy Supply, Distribution, or Use

J. National Technology Transfer and Advancement Act (NTTAA) and 1 CFR Part 51

K. Congressional Review Act (CRA)

In this final rule, the EPA is finalizing the repeal of most of the GHG standards promulgated in the 2024 Carbon Pollution Standards (“2024 CPS”) for fossil fuel-fired power plants.\1\ Specifically, the EPA is finalizing the repeal of the emission guidelines for existing fossil fuel-fired steam generating units, the CCS-based standards for coal-fired steam generating units undertaking a large modification, and the 2024 CCS-based standards for new base load stationary combustion turbines.

\1\ 89 FR 39798 (May 9, 2024).

With this final action, the EPA addresses much of the regulatory uncertainty brought by the Agency's novel attempts to regulate GHG emissions from fossil fuel-fired power plants under CAA section 111. The EPA attempted to restrict GHG emissions from power plants for the first time in 2015, when the Agency issued both new source performance standards (NSPS) for new power plants (“2015 NSPS”) \2\ and emission guidelines for existing power plants (the Clean Power Plan (“2015 CPP”)).\3\

\2\ 80 FR 64510 (October 23, 2015).

\3\ 80 FR 64662 (October 23, 2015).

In West Virginia v. EPA, the U.S. Supreme Court struck down \4\ these efforts in large part, ruling that CAA section 111 does not authorize the EPA to adopt a regulatory scheme that “cap[s] carbon dioxide emissions at a level that will force a nationwide transition away from the use of coal to generate electricity.” \5\ Rather than change course, however, the EPA in 2024 promulgated a new rule that embraced the goals of the 2015 NSPS and 2015 CPP by expanding restrictions on certain new sources and regulating existing sources in a similar manner.

\4\ The Supreme Court stayed the 2015 CPP after the U.S. Court of Appeals for the D.C. Circuit declined to do so prior to merits briefing. West Virginia v. EPA, 577 U.S. 1126 (2016).

\5\ 597 U.S. 697, 735 (2022).

The EPA's most recent effort to regulate GHG emissions from the power sector, the 2024 CPS, includes standards of performance for new and reconstructed fossil fuel-fired combustion turbines and for certain modified fossil fuel-fired steam generating power plants, as well as rules directing States to set standards of performance for existing fossil fuel-fired steam generating power plants. During the rulemaking and subsequent litigation over the 2024 CPS, numerous States, regulated entities, and other stakeholders warned that these requirements are based on technologies that have not been adequately demonstrated, are unachievable, threaten to impose massive costs on the power sector, and do not adequately ensure the national interest in affordable, reliable electricity.

On January 20, 2025, President Trump issued Executive Order (E.O.) 14154, “Unleashing American Energy,” which directs Federal agencies, including the EPA, to review existing regulations “to identify those agency actions that impose an undue burden on the identification, development, or use of domestic energy resources--with particular attention to oil, natural gas, coal, hydropower, biofuels, critical mineral, and nuclear energy resources.” \6\ The E.O. further affirms that it is “the policy of the United States to ensure that all regulatory requirements related to energy are grounded in clearly applicable law.” \7\ During the course of this review, the EPA has identified GHG emissions standards for power plants as one such action, including the 2024 CPS requirements that are the subject of this final rule.\8\

\6\ 90 FR 8353 (January 20, 2025).

\7\ Id.

\8\ References to “GHG standards” here and elsewhere include NSPS promulgated under CAA section 111(b) and emission guidelines for existing sources promulgated under CAA section 111(d). See 42 U.S.C. 7411(b), (d).

On February 19, 2025, President Trump issued E.O. 14219, “Ensuring Lawful Governance and Implementing the President's `Department of Government Efficiency' Deregulatory Initiative,” which directs Federal agencies, including the EPA, to identify and consider taking action to repeal “regulations that are based on anything other than the best reading of the underlying statutory authority or prohibition” and “regulations that implicate matters of social, political, or economic significance that are not authorized by clear statutory authority.” \9\ The EPA identified GHG emissions standards for power plants during the course of this review, including the 2024 CPS requirements that are the subject of this final rule.

\9\ 90 FR 10583 (February 25, 2025).

On April 8, 2025, President Trump issued E.O. 14261, “Reinvigorating America's Beautiful Clean Coal Industry and Amending Executive Order 14241,” which determined that “coal is essential to our national and economic security” and established “a national priority to support the domestic coal industry by removing Federal regulatory barriers that undermine coal production.” \10\ E.O. 14261 specifically found that “coal resources will be critical to meeting the rise in electricity demand due to the resurgence of domestic manufacturing and the construction of artificial intelligence data processing centers” and to increasing “energy supply,” lowering “electricity costs,” stabilizing the power grid, creating “high paying jobs,” supporting “burgeoning industries,” and assisting allies abroad.\11\ Accordingly, E.O. 14261 directed the EPA, among other Federal agencies, to “identify any guidance, regulations, programs, and policies within their respective executive department or agency that seek to transition the Nation away from coal production and electricity generation” and “consider revising or rescinding Federal actions identified in subsection (a) of this section consistent with applicable law.” \12\ The EPA identified GHG emissions standards for power plants during the course of this review as well, including the 2024 CPS requirements that are the subject of this final rule and are estimated to result in mass closures of coal-fired power plants.

\10\ 90 FR 15517 (April 14, 2025).

\11\ Id.

\12\ Id.

The EPA reviewed the GHG emissions standards for the power sector, as directed by E.O. 14154, E.O. 14219, and E.O. 14261, and has substantial concerns about the legal and technical underpinnings of the Agency's efforts to regulate GHG emissions from fossil fuel-fired power plants. Based on a reassessment of the legal and technical conclusions in the 2015 NSPS and 2024 CPS, the EPA issued a notice of proposed rulemaking in June 2025 (“June 2025 NPRM”) that included both a primary proposal and an alternative proposal. The primary proposal would have repealed all GHG emissions

standards for new and existing sources in the fossil fuel-fired EGU source category.\13\ Specifically, the EPA proposed to determine that CAA section 111 requires the Agency to make a finding that GHG emissions from fossil fuel-fired power plants “cause[ ], or contribute significantly” to “air pollution which may reasonably be anticipated to endanger public health or welfare” (which we shorthand as “dangerous air pollution”) as a predicate to regulating GHG emissions from those plants. The EPA further proposed to find that GHG emissions from fossil fuel-fired power plants do not contribute significantly to dangerous air pollution. The EPA is not acting on those proposed determinations at this time and is instead concurrently issuing a supplemental proposal soliciting additional public comment on the underlying question raised in the primary basis of the June 2025 NPRM: Whether the EPA lacks statutory authority to regulate GHG emissions from fossil fuel-fired power plants under CAA section 111. Whereas the primary proposal in the June 2025 NPRM sought public comment on whether fossil fuel-fired EGUs “contribute significantly” to air pollution, the supplemental notice seeks public comment on the distinct question whether global climate change concerns satisfy the threshold requirement in CAA section 111(b)(1)(A) that fossil fuel-fired power plant emissions contribute significantly to “air pollution which may reasonably be anticipated to endanger public health or welfare.”

\13\ 90 FR 25752 (June 17, 2025).

The EPA's alternative proposal was based on the Agency's reexamination of the best system of emission reduction (BSER) determinations and associated requirements for fossil fuel-fired power plants in the 2024 CPS, which it undertook to ensure that all regulatory requirements are grounded in applicable law. Under CAA section 111(a)(1), the EPA determines the BSER which, taking into account cost and any nonair quality and environmental impacts and energy requirements, has been adequately demonstrated. Based on the review of the BSER and associated requirement, the EPA proposed, in the alternative, to repeal parts of the 2024 CPS including the emission guidelines and other CCS-based requirements. As discussed below, the EPA is finalizing the alternative proposal repealing parts of the 2024 CPS and revising the associated BSER determinations as follows.

The EPA is finalizing the repeal of the emission guidelines for existing fossil fuel-fired steam generating units in their entirety. Specifically, the EPA is finalizing the determination that 90 percent CCS is not the BSER for existing long-term coal-fired steam generating units because 90 percent CCS has not been adequately demonstrated, the costs of 90 percent CCS are not reasonable, and the associated degree of emission limitation is not achievable. In a change from the 2024 CPS, the EPA concludes that previous projects that failed to achieve 90 percent CCS were not a sufficient basis to conclude the technology has been adequately demonstrated. Additionally, the carbon dioxide (CO2) capture, pipeline, and sequestration infrastructure necessary to implement 90 percent CCS for the fleet of existing coal- fired steam generating units does not currently exist and would need to be broadly deployed. Because it is significantly unlikely that the necessary infrastructure for CCS can be deployed by the January 1, 2032 compliance date, the EPA is finalizing the determination that the degree of emission limitation in the 2024 CPS for long-term coal-fired steam generating units is not achievable.

The EPA is finalizing the determination that 40 percent natural gas co-firing is not the BSER for existing medium-term coal-fired steam generating units because 40 percent natural gas co-firing constitutes impermissible generation shifting under West Virginia and because the Agency erred in the 2024 CPS by construing West Virginia too narrowly in this respect. Additionally, a thorough consideration of the “energy requirements” BSER factor in CAA section 111(a)(1) shows that natural gas co-firing in a steam generating unit is an inefficient use of natural gas. Moreover, because it is unlikely that the necessary pipeline infrastructure can be deployed by the January 1, 2030 compliance date, the EPA is finalizing the determination that the degree of emission limitation is not achievable. Based on these conclusions, the EPA is repealing the requirements in the emission guidelines related to existing long-term and medium-term coal-fired steam generating units.

The EPA is also repealing the requirements in the emission guidelines related to natural gas- and oil-fired steam generating units. The EPA believes that requiring States to develop, submit, and implement plans solely for natural gas- and oil-fired steam generating units would be an inefficient use of State resources, as these sources comprise a relatively small part of the source category and the requirements under the 2024 emission guidelines for these sources would result in few or no emission reductions.

Furthermore, because the EPA is finalizing that 90 percent CCS has not been adequately demonstrated, the costs are not reasonable, and the degree of emission limitation is not achievable, the EPA is finalizing the repeal of the CCS-based requirements for coal-fired steam generating units undertaking a large modification.

The EPA is also finalizing that 90 percent CCS has not been adequately demonstrated and that the costs are not reasonable for new base load stationary combustion turbines. Furthermore, because it is unlikely that the infrastructure necessary for CCS can be deployed by the January 1, 2032 compliance date, the EPA has determined that the phase 2 standards of performance in the 2024 CPS for new base load combustion turbines are not achievable. The contrary determinations in the 2024 CPS appear to be in error for many of the same reasons that apply to existing coal-fired steam generating units. Consequently, the EPA is finalizing repeal of the phase 2 CCS-based requirements for new base load stationary combustion turbines.

The EPA solicited comment in general on the other GHG requirements for fossil fuel-fired EGUs and received comments suggesting that the 2024 efficiency-based standards (i.e., the phase 1 standards) for new stationary combustion turbines are not achievable. However, the EPA is not revising or repealing those requirements in this final rule. The EPA acknowledges commenters' meritorious concerns regarding the 2024 efficiency-based standards for new stationary combustion turbines. While the EPA is not repealing or otherwise revising the 2024 efficiency-based standards in this final action, the Agency notes that it is concurrently issuing a supplemental proposal that, if finalized, would repeal all GHG standards for the fossil fuel-fired EGU source category under CAA section 111, including the 2024 efficiency-based standards in question. That action, if finalized as proposed, would resolve commenters' concerns.

CAA section 111(b)(1)(A) authorizes the Administrator to publish, and from time-to-time revise, a list of categories of stationary sources that the Administrator, “in his judgment,” finds “causes, or contributes significantly to, air pollution which may reasonably be anticipated to endanger public health or welfare.” Once the EPA lists a source category under CAA section 111(b)(1)(A), the EPA must, under CAA section 111(b)(1)(B), establish “standards of performance” for “new sources” in the source category. These standards are referred to as new source performance standards, or NSPS. The NSPS are national requirements that apply directly to new sources within the relevant source category.

CAA section 111(a)(2) defines a “new source” as “any stationary source, the construction or modification of which is commenced after the publication of regulations (or, if earlier, proposed regulations) prescribing a standard of performance under this section, which will be applicable to such source.” CAA section 111(a)(4) defines “modification” as “any physical change in, or change in the method of operation of, a stationary source which increases the amount of any air pollutant emitted by such source or which results in the emission of any air pollutant not previously emitted.” While this provision treats modified sources as new sources, the EPA's regulations also treat a source that undergoes “reconstruction,” by substantially replacing its components, as a new source.\18\

\18\ 40 CFR 60.15.

CAA section 111(a)(1) defines “standard of performance” as “a standard for emissions of air pollutants” that must be promulgated or revised in a specified manner. When the EPA establishes or revises a performance standard, CAA section 111(a)(1) provides that such a standard must “reflect[ ] the degree of emission limitation achievable through the application of the best system of emission reduction which (taking into account the cost of achieving such reduction and any nonair quality health and environmental impact and energy requirements) the Administrator determines has been adequately demonstrated.” Thus, the term “standard of performance,” as used in CAA section 111, makes clear that the EPA must determine both the “best system of emission reduction . . . adequately demonstrated” for emissions of the relevant air pollutants by regulated sources in the source category and the “degree of emission limitation achievable through the application of the [BSER].” \19\ As explained elsewhere in this preamble, to determine the BSER, the EPA first identifies the “system[s] of emission reduction” that are “adequately demonstrated” and then determines the “best” of those adequately demonstrated systems, “taking into account” factors including “cost,” “nonair quality health and environmental impact,” and “energy requirements.” The EPA has discretion in determining the BSER, and has historically followed a “technology-based approach” that focuses on “measures that improve the pollution performance of individual sources,” such as “add-on controls.” \20\ (If no system of emission reduction can be deemed adequately demonstrated in light of the EPA's consideration of these factors, then it may be the case that EPA cannot identify BSER).

\19\ West Virginia, 597 U.S. at 709.

\20\ See id. at 727 (quoting the 2015 CPP).

After determining the BSER, the EPA derives the “degree of emission limitation achievable” through “application” of the BSER. A standard of performance is “achievable” if a technology can reasonably be projected to be available to an individual source at the time it is constructed so as to allow it to meet the standard.\21\ The EPA must then, under CAA section

111(b)(1)(B), promulgate “standard[s] for emissions”--the NSPS--that reflect that level of stringency. The EPA may determine that different sets of sources have different characteristics relevant for determining the BSER for emissions of the relevant air pollutants and may subcategorize sources accordingly pursuant to CAA section 111(b)(2).\22\

\21\ Portland Cement Ass'n v. Ruckelshaus, 486 F.2d 375, 391 (D.C. Cir. 1973).

\22\ 42 U.S.C. 7411(b)(2).

The EPA has generally used CAA section 111 to establish standards for emissions of air pollutants from new sources within a category. In the rare instances where new stationary source standards concern air pollutant emissions that are not regulated under the National Ambient Air Quality Standards (NAAQS) program pursuant to CAA sections 108-110 or under the National Emission Standards for Hazardous Air Pollutants (NESHAP) program pursuant to CAA section 112, the statute provides a separate authority for addressing emissions of such air pollutants from existing sources in the source category.\23\ In these limited circumstances, the promulgation of standards for new stationary sources triggers the EPA's authority to promulgate regulations for emissions of that pollutant from existing sources within the same category under CAA section 111(d).\24\

\23\ 42 U.S.C. 7411(d)(1)(A)(i)-(ii).

\24\ See West Virginia, 597 U.S. at 710 (“Section 111(d) thus `operates as a gap-filler,' empowering EPA to regulate harmful emissions not already controlled under the Agency's other authorities. . . . Reflecting the ancillary nature of Section 111(d), EPA has used it only a handful of times since the enactment of the statute in 1970.”).

In contrast to the national regime for new sources under CAA section 111(b), CAA section 111(d) establishes a framework of “cooperative federalism for the regulation of existing sources.” \25\ CAA section 111(a)(6) defines an “existing source” as “any stationary source other than a new source.” CAA section 111(d)(1) provides that when air pollutants covered by an NSPS for a source category are not already encompassed within the NAAQS program or NESHAP program, the EPA “shall prescribe regulations which shall establish a procedure similar to that provided by” CAA section 110 “under which each State shall submit to the Administrator” a plan for addressing emissions of such air pollutants by existing sources within such source category.\26\ Reference to CAA section 110 incorporates the statute's provision for State submission and EPA review of state implementation plans (SIPs) that provide for the implementation, maintenance, and enforcement of the NAAQS for the areas within such State.\27\ In a comparable manner, State plans required by the regulations authorized in CAA section 111(d) must “establis[h] standards of performance for any existing stationary source” for the air pollutant at issue and “provid[e] for the implementation and enforcement of such standards of performance.”

\25\ Am. Lung Ass'n v. EPA, 985 F.3d 914, 931 (D.C. Cir. 2021), rev'd in part sub nom. West Virginia, 597 U.S. 697.

\26\ 42 U.S.C. 7411(d)(1). CAA section 111(a)(6) defines an “existing source” as “any stationary source other than a new source.” 42 U.S.C. 7411(a)(6).

\27\ 42 U.S.C. 7410.

In the relatively few instances in which the EPA applies CAA section 111(d), the Agency generally promulgates regulations, termed “emission guidelines,” that identify the BSER and the degree of emission limitation achievable through the application of the BSER. These regulations then require States to establish standards of performance for emissions of the air pollutant at issue by covered sources that reflect that level of stringency.\28\ States need not compel regulated sources to adopt the particular components of the BSER itself. Rather, States have discretion in designing the policies and rules their sources will use to achieve the degree of emission limitation required by the emission guidelines. The statute also requires the EPA's regulations to permit a State “in applying a standard of performance to any particular source” to “take into consideration, among other factors, the remaining useful life of the existing source to which such standard applies.” \29\ Once the EPA approves a State's plan, its provisions become federally enforceable against the source in the same manner as the provisions of an approved SIP under the CAA.\30\ If a State elects not to submit a plan or submits a plan that the EPA does not find “satisfactory,” the CAA authorizes the Agency to promulgate a plan that establishes Federal standards of performance for the State's existing sources.\31\

\28\ As discussed below, CAA section 111(d)(1)(B) provides that, in certain circumstances, States may apply standards of performance that are less stringent than the degree of emission limitation that the EPA determines in the emission guidelines. See 42 U.S.C. 7411(d)(1)(B).

\29\ 42 U.S.C. 7411(d)(1).

\30\ 42 U.S.C. 7411(d)(2)(B).

\31\ 42 U.S.C. 7411(d)(2)(A).

Congress first defined the term “standard of performance” when enacting CAA section 111 in the 1970 CAA, amended the definition in the 1977 CAA Amendments, and amended the definition again in the 1990 CAA Amendments to largely restore the definition as in the 1970 CAA. The D.C. Circuit has reviewed CAA section 111 rulemakings on numerous occasions since the early 1970s and developed a body of case law that interprets the term.\32\

\32\ Am. Lung Ass'n, 985 F.3d at 914; Delaware v. EPA, No. 13- 1093 (D.C. Cir. May 1, 2015); Portland Cement Ass'n v. EPA, 665 F.3d 177 (D.C. Cir. 2011); Lignite Energy Council v. EPA, 198 F.3d 930 (D.C. Cir. 1999); Sierra Club v. Costle, 657 F.2d 298 (D.C. Cir. 1981); Essex Chem. Corp. v. Ruckelshaus, 486 F.2d 427 (D.C. Cir. 1973); Portland Cement Ass'n, 486 F.2d at 375.

Whether promulgated by the EPA under CAA section 111(b) or established by the States under CAA section 111(d) in response to emission guidelines promulgated by the Agency, the basis for standards of performance is the “degree of emission limitation” that is “achievable” by sources in the source category by application of the “best system of emission reduction” that the EPA determines is “adequately demonstrated.” As explained in this section, systems are not “adequately demonstrated” if they are “purely theoretical or experimental.” \33\ The D.C. Circuit has stated that in determining the “best” adequately demonstrated system for the pollutants at issue, the EPA must also take into account “the amount of air pollution” reduced.\34\ The D.C. Circuit has also stated that the EPA may weigh the various factors identified in the statute and case law to determine the “best” system and has emphasized that the EPA has significant discretion in weighing the factors.\35\

\33\ Essex Chem. Corp., 486 F.2d at 433-34.

\34\ Sierra Club, 657 F.2d at 326; see id. at 347 (stating that the EPA must take “technological innovation” into account).

\35\ Lignite Energy Council, 198 F.3d at 933 (“Because section 111 does not set forth the weight that should be assigned to each of these factors, we have granted the agency a great degree of discretion in balancing them.”).

After determining the BSER, the EPA sets an achievable emission limit based on application of the BSER.\36\ For a CAA section 111(b) rule, the EPA determines the standard of performance that reflects that achievable emission limit. For a CAA section 111(d) rule, the States establish the standards of performance that reflect the degree of emission limitation that the EPA has included in

an emission guideline. In applying these standards to existing sources, States are permitted to consider a source's remaining useful life and other factors.\37\

\36\ See, e.g., 77 FR 49490, 49494 (August 16, 2012) (describing the three-step analysis in setting a standard of performance).

\37\ 42 U.S.C. 7411(d)(1).

In identifying “system[s] of emission reduction,” the EPA historically has followed a “technology-based approach” that focuses on “measures that improve the pollution performance of individual sources,” such as “add-on controls.” \38\ In the 2015 CPP, the EPA significantly departed from its historical approach to standard setting under CAA section 111(b) by setting a BSER in which the “system” of emission reduction involved shifting electricity generation from one type of fuel to another. In West Virginia, the U.S. Supreme Court applied the major questions doctrine to hold that neither the term “system” nor any other provision of the CAA provided the requisite clear authorization to support the 2015 CPP's BSER, which the Court described as “carbon emissions caps based on a generation shifting approach” \39\ that capped GHG “emissions at a level that will force a nationwide transition away from the use of coal to generate electricity[.]” \40\ The Court explained that the EPA's BSER “forc[es] a shift throughout the power grid from one type of energy source to another,” which constituted “unprecedented power over American industry” and was different in kind from the type of “system” of emission reduction envisioned by CAA section 111(d).\41\

\38\ See West Virginia, 597 U.S. at 727 (quoting 80 FR 64662, 64784 (October 23, 2015)).

\39\ Id. at 732.

\40\ Id. at 734.

\41\ Id. at 728 (citation omitted).

To qualify as the BSER, the system of emission reduction must be “adequately demonstrated” as “the Administrator determines.” \42\ The plain text of CAA section 111(a)(1), and in particular the terms “adequately” and “the Administrator determines,” confers upon the EPA the discretion to identify the appropriate system, including making scientific and technological determinations and considering a broad range of policy considerations.\43\ However, the terms “adequately” and “demonstrated,” as well as applicable case law, make clear that the EPA may not determine that a “purely theoretical or experimental” system is “adequately demonstrated.” \44\ Moreover, applicable case law and the text and structure of CAA section 111, including the requirement that the resulting emission limitation be “achievable” and the eight-year review requirement in CAA section 111(b)(1)(B), place an outer bound on the EPA's discretion to project technological development into the future.

\42\ 42 U.S.C. 7411(a)(1).

\43\ Nat'l Asphalt Pavement Ass'n v. Train, 539 F.2d 775, 786 (D.C. Cir. 1976); Essex Chem. Corp., 486 F.2d at 434.

\44\ Essex Chem. Corp., 486 F.2d at 433-34; see Portland Cement Ass'n, 486 F.2d at 391-92 (the EPA may not base an “adequately demonstrated” determination on a “ `crystal ball' inquiry”) (citation omitted).

In addition, CAA section 111(a)(1) requires the EPA to account for “the cost of achieving [the emission] reduction” in determining the adequately demonstrated BSER. Although the CAA does not describe how the EPA should account for costs to affected sources, the D.C. Circuit has formulated the cost standard in various ways, including by stating on the upper bound that the EPA may not adopt a standard the cost of which would be “excessive” or “unreasonable.” \45\ The EPA has discretion in considering cost under CAA section 111(a), both in determining the appropriate level of costs and in balancing costs with other BSER factors.\46\ The D.C. Circuit has repeatedly upheld the EPA's consideration of cost in reviewing standards of performance.\47\

\45\ Sierra Club, 657 F.2d at 343; see 79 FR 1430, 1464 (January 8, 2014); Lignite Energy Council, 198 F.3d at 933 (costs may not be “exorbitant”); Portland Cement Ass'n v. Train, 513 F.2d 506, 508 (D.C. Cir. 1975) (costs may not be “greater than the industry could bear and survive”).

\46\ Sierra Club, 657 F.2d at 343.

\47\ See Essex Chem. Corp., 486 F.2d at 440; Portland Cement Ass'n, 486 F.2d at 387-88; Sierra Club, 657 F.2d at 313.

Under CAA section 111(a)(1), the EPA must take into account “any nonair quality health and environmental impact and energy requirements” in determining the BSER. Nonair quality health and environmental impacts may include the impacts of the disposal of byproducts of the air pollution controls or requirements of the air pollution control equipment for water.\48\ Energy requirements may include the impact, if any, of the air pollution controls on the source's own energy needs.\49\ In addition, based on the D.C. Circuit's interpretations of CAA section 111, energy requirements may also include the impact, if any, of the air pollution controls on the energy supply for a particular area or nationwide.\50\ Furthermore, the EPA has considered under this statutory factor whether possible controls would create risks to the reliability of the national electricity system.\51\

\48\ Portland Cement Ass'n, 486 F.2d at 387-88.

\49\ For details on the modeled energy requirements associated with CCS, please see section 6.4 of the RIA for this final rule.

\50\ See Sierra Club, 657 F.2d at 327-28 (quoting 44 FR 33580, 33583-84 (June 11, 1979)); 79 FR 1430, 1465 (January 8, 2014) (citing Sierra Club, 657 F.2d at 351).

\51\ See, e.g., 89 FR 39886 (May 9, 2024).

The D.C. Circuit has also held that the term “best” authorizes the EPA to consider factors that further the purpose of the statute in addition to the ones enumerated in CAA section 111(a)(1). In particular, consistent with the plain language and the purpose of CAA section 111(a)(1), which requires the EPA to determine the “best system of emission reduction” (emphasis added), the D.C. Circuit has previously held that the Agency must consider the quantity of emissions at issue.\52\ The EPA has broad discretion in determining which adequately demonstrated system of emission reduction is the “best.” In Sierra Club, the D.C. Circuit explained that “section 111(a) explicitly instructs the EPA to balance multiple concerns when promulgating a NSPS” and emphasized that “[t]he text gives the EPA broad discretion to weigh different factors in setting the standard,” including the amount of emission reductions, the cost of the controls, and the nonair quality environmental impacts and energy requirements.\53\

\52\ Sierra Club, 657 F.2d at 326. The D.C. Circuit has also held that Congress intended for CAA section 111 to create incentives for new technology, and therefore that the EPA is to consider technological innovation as one of the factors in determining the “best system of emission reduction.” See id. at 346-47.

\53\ Sierra Club, 657 F.2d at 319, 321; see also New York v. Reilly, 969 F.2d 1147, 1150 (D.C. Cir. 1992).

A standard of performance is “achievable” if a technology can reasonably be projected to be available to an individual source at the time it is constructed so as to allow the source to meet the standard.\54\ The courts have established this approach for achievability in cases concerning CAA section 111(b) NSPS. A generally comparable approach applies to CAA section 111(d), although the BSER may differ in some cases between new and existing sources due to, for example, higher costs and feasibility of retrofit.\55\ For existing sources, CAA section 111(d)(1) requires the EPA to establish regulations for State plans that, in turn, must include “standards of performance.” As the Supreme Court has recognized, the EPA generally carries out this provision by promulgating emission guidelines that determine the BSER for a source category and then identify the degree of

emission limitation achievable by application of the BSER.\56\

\54\ See Portland Cement Ass'n, 486 F.2d at 391.

\55\ See, e.g., 40 FR 53340 (November 17, 1975).

\56\ See West Virginia, 597 U.S. at 710; 40 CFR 60.21(e), 60.21a(e) (definition of “emission guideline” includes provision of the degree of emission limitation achievable through the application of the BSER as determined by the Administrator).

In this final rule, the EPA is repealing (1) the emission guidelines for existing fossil fuel-fired steam generating EGUs in 40 CFR part 60, subpart UUUUb; (2) the 90 percent CCS-based standards of performance for coal-fired steam generating units undertaking a large modification in 40 CFR part 60, subpart TTTT; and (3) the 90 percent CCS-based standards of performance for new base load stationary combustion turbines in 40 CFR part 60, subpart TTTTa. Although the record evidence supporting each of these separate actions may overlap, particularly pertaining to 90 percent CCS, the repeal of each is supported by its own, standalone rationale and is severable from the others. That is, the repeal of the emission guidelines for existing sources in subpart UUUUb does not impact the 90 percent CCS-based standards of performance for coal-fired steam generating units undertaking a large modification and new base load stationary combustion turbines, as these rules apply to different sets of sources. Similarly, the repeal of the 90 percent CCS-based standards of performance either for modified sources or for new sources does not impact either of the two other rules. Again, while the records supporting each of these separate actions may overlap, application of the record evidence to each of the separate sets of regulated sources may yield different outcomes. If a court were to invalidate one or more of those actions, the EPA would still be able to implement the repeal of the remaining action or actions.

Additionally, within the group of existing fossil fuel-fired steam generating units (the sources regulated by 40 CFR subpart 60 subpart UUUUb), each of the following actions is severable: repeal of the BSER determination and associated requirements for the subcategory of long- term coal-fired steam generating EGUs, repeal of the BSER determination and associated requirements for the subcategory of medium-term coal- fired steam generating EGUs, and repeal of the requirements for the subcategory of oil- and natural gas-fired steam generating EGUs. That is, the repeal of the requirements for each separate subcategory of existing fossil fuel-fired steam generating units is based on an independent rationale and is severable from the repeal of the requirements for each other subcategory of existing units. If a court were to invalidate the EPA's action with regard to one or more subcategories of existing units, the Agency would still be able to implement the repeal of the requirements for the remaining subcategories or subcategory. This is because the requirements for each subcategory are self-contained in the regulations and, due to the design of the emission guidelines in subpart UUUUb, it would have been relatively difficult for sources to shift between subcategories. Thus, the repeal of the requirements for each subcategory of existing fossil fuel-fired steam generating units is severable.

The EPA requested comment on reliance interests on the 2015 NSPS and the 2024 CPS in the June 2025 NPRM that commenters believed the Agency should consider in formulating a final action.\57\ Potentially significant and legitimate reliance interests may arise, for example, when regulated parties or other stakeholders expend resources to comply with existing standards, including by pricing compliance into costs for consumers. Significant and legitimate reliance interests may also arise when stakeholders reasonably factored the existence of standards into concrete plans that cannot be readily modified. Under relevant case law, these and other reliance interests may be a relevant consideration to weigh against competing rationales when deciding whether to change the Agency's position.\58\ However, the EPA notes that general interests in retaining the at-issue 2024 CPS requirements for the sake of regulating GHG emissions from fossil fuel-fired power plants do not justify such retention in the absence of statutory authority and a reasoned basis for particular control requirements. To the extent the EPA is repealing aspects of the 2024 CPS based on applicable statutory requirements, the unlawful nature of those aspects necessitates repeal; the change-in-position doctrine does not expand an agency's statutory authority for the purpose of addressing reliance interests. Where possible and appropriate, the Agency considered whether any asserted reliance interests are significant and legitimate and, if so, whether different or additional regulatory actions could address such concerns, consistent with the requirements of the statute.\59\

\57\ 90 FR 25752, 25777 (June 17, 2025).

\58\ See, e.g., DHS v. Regents of Univ. of Cal., 591 U.S. 1, 30 (2020).

\59\ The Agency also notes that because this final rule addresses certain requirements of the 2024 CPS only, we are not addressing any potential reliance interests on the 2015 NSPS at this time.

The EPA carefully reviewed public comments to assess whether any aspects of this final action should be adjusted to account for reliance interests. The Agency received no comments on reliance interests arising from the 2024 CPS from regulated entities. To our knowledge, no expenditures on projects involving fossil fuel-fired power plants have been made exclusively in response to the 2024 CPS requirements that the EPA is repealing. The EPA notes that under the compliance dates and assumed project schedules for the two control strategies that served as the basis for requirements in the 2024 CPS concerning coal-fired power plants--90 percent CCS and 40 percent natural gas co-firing--affected sources would not yet have incurred significant expenditures. The compliance dates for these requirements, as well as the alternative compliance option of ceasing operations, were not scheduled to begin until 2032. Although, as discussed elsewhere in this preamble, the requirements involved a long implementation timeline and many fossil fuel-fired EGUs are subject to long planning horizons, much of the required buildout was anticipated to be on the part of third parties (pipeline infrastructure and injection wells, for example), and this rulemaking occurred far enough in advance to forestall the vast majority of sunk costs that would otherwise have been incurred. Based on information available to the Agency, such costs would have begun to accrue in earnest around the time of this final rule, making the action both timely and supporting reliance on the cost- and achievability- based rationales discussed herein.

Similarly, the EPA did not receive any comments from States on any resource expenditures they may have made to develop State plans in response to the emission guidelines for existing sources under 40 CFR part 60, subpart UUUUb. The EPA has not received any State plan submissions to date, and such plans were subject to extension opportunities and review that may have involved different timelines and further efforts in any event. Nor has the EPA promulgated a Federal plan in the absence of approved State plans, meaning air agencies have not expended resources participating in such a rulemaking or assisting regulated sources with compliance.

The EPA received one comment asserting State-related reliance interests, summarized below. However, upon careful examination, the EPA determined that this comment asserted general interests that are not properly understood as significant and serious reliance on the 2024 CPS that would warrant a different or additional regulatory outcome as to the 2024 CPS requirements at issue in this rulemaking. Therefore, the Agency is not aware of any substantial reliance interests that would have informed its decision making for purposes of this final action.

Comment: One commenter asserted that State and local air agencies are relying on potential non-GHG emission reduction co-benefits from the 2024 CPS to reach NAAQS attainment for criteria pollutants. The commenter asserted that State and local agencies have invested significant staff hours and funds in planning, outreach, modeling, and rule development to implement SIPs for NAAQS attainment. The commenter stated that the proposed repeal potentially required States to develop planning scenarios with and without the 2024 CPS. The commenter stated that State and local agencies must develop new attainment strategies and incur additional expenditures.

EPA Response: The EPA disagrees that State and local air agencies have reasonably relied on the at-issue 2024 CPS requirements to the extent that the impact of repeal on planning activities would amount to serious and irreversible harms. While the EPA acknowledges there may be overlaps between NAAQS attainment planning and the GHG control strategies that States would have had to develop under the 2024 CPS, these programs are governed by separate statutory provisions and address different pollutants on different timelines and under different regulatory paradigms. That is, while GHG control strategies States may have been developing pursuant to the 2024 CPS may have had co-benefits in terms of reductions of criteria air pollutants, we disagree that such co-benefits engender serious reliance interests relevant to this rulemaking because they do not justify retaining a GHG regulatory program that is not consistent with the relevant statutory requirements. This final action does not impact any of the EPA's criteria pollutant standards of performance for power plants regulated under and listed in various pre-2015 source categories pursuant to CAA section 111, which are more directly relevant to NAAQS attainment.

Moreover, the absence of comments raising resource expenditures related to State and local air agency implementation of the 2024 CPS emission guidelines suggests that air agencies have not, in fact, expended significant resources developing GHG control strategies because of the 2024 CPS. NAAQS attainment efforts are ongoing, and the projected criteria emission co-benefits in the 2024 CPS for the at- issue requirements are small in absolute terms. That is not surprising given the relatively long time horizon involved in developing such submissions and the short period of time that elapsed between finalization of the 2024 CPS and the announcement of reconsideration. To the extent the commenter asserts that State and local air agencies worked to develop options with and without the 2024 CPS, the Agency notes that such considerations are expected when analyzing the many options available to States in exercising their considerable discretion in developing strategies to attain and maintain the NAAQS and that requirements, particularly at the proposal stage, are necessarily subject to change.

While it is reasonable for States to consider the different control strategies they will be applying to their sources in a coordinated manner, the 2024 CPS requirements at issue could not have engendered serious reliance interests under the circumstances sufficient to warrant different or additional regulatory actions in this rulemaking. The Agency finalized the CPS in May 2024 and announced its intention to reconsider the rule in March 2025.\60\ At the same time, NAAQS attainment planning has been ongoing, in many cases, for decades. It is therefore not likely that States could have relied on the existence of and obligations under the 2024 CPS for NAAQS attainment planning purposes. And, in all likelihood, State and local air agencies would necessarily have to take into consideration other developments in the electric power sector due to changes in, e.g., electricity demand, such that they would be considering the adequacy of their NAAQS attainment planning even absent the repeal of the 2024 CPS requirements being finalized in this action. Moreover, it is a normal course of action for State and local air agencies to re-evaluate their planning in response to changes in Federal air regulations.

\60\ “Trump EPA Announces Reconsideration of Biden-Harris Rule, `Clean Power Plan 2.0,' ” That Prioritized Shutting Down Power Plants While Raising Costs on American Families” (March 12, 2025). Available at: https://www.epa.gov/newsreleases/trump-epa-announces-reconsideration-biden-harris-rule-clean-power-plan-20-prioritized.

Considering these factors, the EPA believes that the commenter's concerns do not constitute a serious reliance interest warranting a different outcome. Such co-benefit considerations would not be an adequate basis to retain the at-issue 2024 CPS requirements, which must be justified under and consistent with statutory requirements with respect to the subject of the regulations (i.e., GHG emissions). The 2024 CPS regulates GHG emissions in the form of CO2 for the fossil fuel-fired EGU source category and the Agency did not, in the 2024 CPS, analyze or promulgate the at-issue requirements as multi- pollutant standards.

This section discusses the EPA's efforts to regulate GHG emissions under CAA section 111 since 2015, including the regulation of fossil fuel-fired EGUs, associated case law that is relevant to this action, and the EPA's asserted legal basis for regulating GHG emissions under CAA section 111.

The EPA has regulated air pollutants from power plants under CAA section 111 since 1971, when the Agency listed “fossil fuel-fired steam generators of more than 250 million British thermal units per hour (MMBtu/h) heat input” as a source category under CAA section 111(b)(1)(A) \61\ and subsequently promulgated NSPS for certain air pollutants.\62\ In 1977, the EPA listed fossil fuel-fired “stationary gas turbines” in a category under CAA section 111(b)(1)(A) \63\ and subsequently promulgated NSPS for certain air pollutants.\64\ However, the EPA did not invoke CAA section 111 to regulate GHG emissions from power plants until 2015, when the Agency promulgated the 2015 NSPS, which addressed GHG emissions as measured by the equivalent of CO2 emissions, from new fossil fuel-fired EGUs under CAA section 111(b); \65\ and the 2015 CPP, which set emission guidelines directing States to regulate GHG emissions as measured by the equivalent of CO2 emissions from existing EGUs under CAA section 111(d).\66\

\61\ 36 FR 5931 (March 31, 1971).

\62\ See, e.g., 36 FR 24876 (December 23, 1971); 40 CFR 60, subpart Da.

\63\ See 42 FR 53657 (October 3, 1977).

\64\ See, e.g., 44 FR 62792 (September 10, 1979); 40 CFR 60, subpart KKKK.

\65\ 80 FR 64510 (October 23, 2015).

\66\ 80 FR 64662 (October 23, 2015).

In the 2015 NSPS, the EPA laid out a novel legal basis for regulating GHG emissions based on global climate change concerns under CAA section 111. Additionally, in that rule, the EPA asserted that the Agency was not required to make a finding of significant contribution under CAA section 111 before regulating GHG emissions. The EPA explained that CAA section 111(b)(1)(A) requires the Administrator to list any source category that “causes, or contributes significantly to, air pollution which may reasonably be anticipated to endanger public health or welfare.” The EPA posited that, unlike other CAA provisions, CAA section 111(b)(1)(A) does not require the EPA to make endangerment and significant contribution findings for individual pollutants. Rather, the EPA asserted that once such findings are made for any pollutant emitted by a source category, the Agency has discretion to regulate all pollutants emitted by the source category subject only to rational basis constraints.\67\

\67\ 80 FR 64510, 64529-30 (October 23, 2015).

Using this framework, the EPA created a new source category (i.e., all fossil fuel-fired EGUs) consisting of the type of power plants previously listed in the 1970s under separate source categories. Specifically, the EPA took the step of “combining the steam generator and combustion turbine categories into a single category of fossil fuel-fired electricity generating units for purposes of promulgating standards of performance for GHG emissions.” \68\ The EPA explained that “[c]ombining the two categories is reasonable because they both provide the same product: Electricity services,” and that combining the source categories in the 2015 NSPS was consistent with the Agency's decision to combine the categories “in the CAA section 111(d) rule for existing sources that accompanies [the 2015 NSPS],” i.e., in the 2015 CPP.\69\ The Agency maintained, however, that it was not listing a new source category and therefore was not required to make any endangerment or significant contribution finding for the fossil fuel-fired EGU source category to promulgate NSPS.

\68\ See id. at 64531.

\69\ Id.

The EPA determined that it had a rational basis for concluding that emissions of CO2 from fossil fuel-fired power plants merit regulation under CAA section 111. In reaching that conclusion, the Agency stated that it had determined in the 2009 Endangerment Finding that GHG emissions may reasonably be anticipated to endanger public health or welfare and that more recent information confirmed this determination. The EPA explained that the approach it was taking with regard to endangerment and GHG emissions from the fossil fuel-fired EGU source category was “substantially similar to that reflected in the 2009 Endangerment Finding and the 2010 denial of petitions to reconsider.” \70\ The EPA added that “the high level of GHG emissions from fossil fuel-fired EGUs makes clear that it is rational for the EPA to regulate GHG emissions from this sector.” \71\

\70\ Id. at 64531; see 75 FR 49556 (August 13, 2010) (denying petitions for reconsideration of the 2009 Endangerment Finding).

\71\ 80 FR 64510, 64530 (October 23, 2015).

The EPA explained the legal basis for its interpretation of CAA section 111(b)(1)(A) as follows: The Agency noted that the EPA had listed fossil fuel-fired steam generators as a source category in 1971 and combustion turbines as a source category in 1979, in each case on the basis of the sources' emissions of non-GHG air pollutants, and the EPA acknowledged that the Agency had not considered GHG emissions at the time of those listings. Even so, in the 2015 NSPS, the EPA stated that the Agency interpreted CAA section 111 to provide that after the EPA listed a source category once, the CAA authorized the Agency to promulgate NSPS for any air pollutant from a source listed in that source category, so long as the EPA had a rational basis for doing so.\72\

\72\ Id. at 64529-31.

The EPA received comments on the 2015 NSPS stating that CAA section 111 did not authorize regulation of GHGs from fossil fuel-fired EGUs until the Agency first makes a finding that emission of GHGs from these power plants contributes significantly to air pollution which may reasonably be anticipated to endanger public health or welfare. The EPA disagreed with those comments. The EPA took the position that CAA section 111(b)(1)(A), 111(b)(1)(B), and 111(a)(1), read together, authorize the Agency to regulate an air pollutant from a listed source category, subject to the standards of rationality under CAA section 307(d)(9)(A), and do not require the EPA to make an additional determination, as a predicate for regulation, that the air pollutant contributes significantly to dangerous air pollution.\73\

\73\ Promulgation of NSPS under CAA section 111(b)(1)(B) is subject to the requirements of CAA section 307(d), under CAA section 307(d)(1)(C). See 42 U.S.C. 7607(d)(1)(C).

Notwithstanding the EPA's position in the 2015 NSPS that CAA section 111 does not require a pollutant-specific significant contribution finding for GHG emissions, the Agency purported to make, in the alternative, separate endangerment and significant contribution findings pursuant to CAA section 111(b)(1)(A) for GHG emissions from fossil fuel-fired EGUs. In doing so, the EPA asserted that the information and conclusions in the preamble to the 2015 NSPS provided a sufficient basis for such findings.\74\ That is, the EPA took the position that regardless whether the Agency needed only a rational basis to regulate CO2 emissions from fossil fuel-fired EGUs or was instead required to make new endangerment and significant contribution findings, we had made the requisite determinations based on the 2009 Endangerment Finding and the additional information presented in the preamble to the 2015 NSPS.

\74\ 80 FR 64510, 64530-31 (October 23, 2015).

The 2015 NSPS promulgated standards of performance to limit emissions of GHGs, manifested as CO2, from newly constructed, modified, and reconstructed fossil fuel-fired electric utility steam generating units (i.e., utility boilers and integrated gasification combined cycle (IGCC) combustion turbines) and newly constructed and reconstructed stationary combustion turbines. These final standards are codified in 40 CFR part 60, subpart TTTT. In promulgating the 2015 NSPS for newly constructed fossil fuel-fired steam generating units, the EPA determined the BSER to be a new, highly efficient, supercritical pulverized coal (SCPC) EGU that implements post-combustion partial CCS technology.

The 2015 NSPS also included standards of performance for steam generating units that undergo a “reconstruction” as well as units that implement “large modifications” (i.e., modifications resulting in an increase in hourly CO2 emissions of more than 10 percent). The 2015 NSPS did not establish standards of performance for steam generating units that undertake “small modifications” (i.e., modifications resulting in an increase in hourly CO2 emissions of less than or equal to 10 percent), due to the limited information available to inform the analysis of a BSER and corresponding standard of performance.

The 2015 NSPS also finalized standards of performance for newly constructed and reconstructed natural gas-fired stationary combustion turbines that operate at base load and non-base load, based on efficient natural gas

combined cycle (NGCC) technology or the use of lower-emitting fuels (referred to as clean fuels in the 2015 NSPS) as the BSER. The EPA did not promulgate final standards of performance for modified stationary combustion turbines under CAA section 111(d) due to lack of information.

Petitioners challenged the 2015 NSPS in the D.C. Circuit, and the case has been held in abeyance over the years since in light of the EPA's subsequent rulemakings.

In the 2015 CPP--promulgated at the same time as the 2015 NSPS--the EPA interpreted CAA section 111(d) to require the Agency to regulate GHG emissions from existing sources in the newly combined source category because we had promulgated the 2015 NSPS for GHG emissions from new sources in that source category under CAA section 111(b).\75\ The Agency noted that GHGs, and CO2 in particular, are not separately regulated under the NAAQS program under CAA sections 107-110 or the NESHAP program under CAA section 112. The EPA determined that the BSER for existing fossil fuel-fired EGUs consisted primarily of generation shifting measures, as described in section II.C of this preamble.\76\ The Supreme Court stayed the 2015 CPP pending review in February 2016,\77\ and the D.C. Circuit held the litigation in abeyance and ultimately dismissed the challenges to the 2015 CPP in light of subsequent developments.\78\

\75\ 80 FR 64662, 64702 (October 23, 2015).

\76\ Id. at 64728-29.

\77\ West Virginia v. EPA, 577 U.S. 1126 (2016).

\78\ Am. Lung Ass'n, 985 F.3d at 937.

In 2018, following a change in administration, the EPA proposed to revise the NSPS for new, modified, and reconstructed fossil fuel-fired steam generating units and IGCC units (2018 NSPS Proposal).\79\ The EPA proposed to revise the NSPS for newly constructed units based on a revised BSER of a highly efficient EGU without partial CCS. The EPA also proposed to revise the NSPS for modified and reconstructed units. The EPA never finalized the 2018 NSPS Proposal, and the Agency rescinded the proposal as part of the 2024 CPS.

\79\ 83 FR 65424 (December 20, 2018).

In 2019, the EPA repealed the 2015 CPP and replaced that rulemaking with the Affordable Clean Energy (ACE) Rule.\80\ In the ACE Rule, the Agency determined that the statutory “text and reasonable inferences from it” indicate that the best “system” of emission reduction as defined in CAA section 111(a)(1) “is limited to measures that can be applied to and at the level of the individual source,” meaning the BSER must be control measures for reducing emissions at individual sources.\81\ The Agency concluded that generation shifting is not such a control measure.\82\ In addition, the EPA further concluded that the 2015 CPP was a “major rule” subject to the major questions doctrine and therefore must be supported by “a clear statement from Congress.” Because the statutory phrase “best system of emission reduction” does not clearly speak to generation shifting, the Agency reasoned that CAA section 111 should not be read to encompass generation-shifting measures.\83\ To replace the 2015 CPP, the EPA promulgated as part of the ACE Rule a new set of emission guidelines for existing coal-fired steam-generating EGUs.\84\ In these new emission guidelines, the EPA determined the BSER for existing coal-fired EGUs to be heat rate improvements alone. Specifically, the EPA listed various technologies that could improve heat rate and identified the “degree of emission limitation achievable” by providing ranges of expected emission reductions associated with each of the technologies.\85\ The EPA also explained that we were not determining CCS as the BSER in part because of unreasonable expense and was not determining natural gas co-firing as the BSER because co-firing was an inefficient use of natural gas.\86\

\80\ 84 FR 32520 (July 8, 2019).

\81\ See id. at 32523-24.

\82\ See id. at 32546.

\83\ See id. at 32529.

\84\ See id. at 32532.

\85\ Id. at 32535-38.

\86\ Id. at 32545.

In 2021, a divided panel of the D.C. Circuit vacated the ACE Rule, including the repeal of the 2015 CPP.\87\ The panel majority held, among other things, that CAA section 111 did not limit the EPA, in determining the BSER, to measures applied at and to an individual source and that CAA section 111 authorized the Agency to determine generation shifting is the BSER. The panel majority also rejected in the argument that generation-shifting implicated “the so-called `major questions' doctrine” based on its interpretation of the Supreme Court's decisions in Massachusetts and AEP.\88\ As a result, the D.C. Circuit vacated both the repeal of the 2015 CPP and the ACE Rule.\89\ The court did not address most other challenges to the ACE Rule, including the arguments concerning the heat rate improvement BSER.

\87\ Am. Lung Ass'n, 985 F.3d at 914.

\88\ Id. at 959.

\89\ Id. at 995. In a partial dissent, Judge Walker argued that the 2015 CPP (and aspects retained in the 2019 ACE Rule) violated the major questions doctrine because CAA section 111 does not include a clear statement of authority to regulate GHG emissions from power plants. Id. at 995-1003.

Several petitioners argued that the ACE Rule was invalid on the grounds that the EPA had predicated regulation of GHG emissions from existing EGUs on the new source GHG emissions standards in the 2015 NSPS. In addition, petitioners argued that those standards were flawed because CAA section 111 required them to be predicated on a pollutant- specific significant contribution finding with identified standards or criteria for determining significance. The D.C. Circuit held that it did not need to decide whether CAA section 111 requires a pollutant- specific significant contribution finding for GHG emissions from EGUs as a predicate for CAA section 111 regulation because the EPA had made such a finding in the alternative. The court rejected the petitioners' argument that the significant contribution finding was flawed due to lack of identified criteria for significance and explained that the magnitude of GHG emissions from EGUs supported the significance finding without identified criteria for significance.\90\

\90\ Id. at 974-77.

In 2022, the U.S. Supreme Court in West Virginia reversed the D.C. Circuit's decision to vacate the ACE Rule's embedded repeal of the 2015 CPP.\91\ As noted in section II.C of this preamble, the Supreme Court concluded that the 2015 CPP's BSER of “generation shifting” implicated the major questions doctrine and exceeded the EPA's statutory authority because CAA section 111 does not clearly authorize the Agency to regulate GHG emissions in a manner that forces a nationwide transition away from using coal to generate electricity.\92\

\91\ West Virginia, 597 U.S. 697.

\92\ Id. at 734-35.

Following the U.S. Supreme Court's decision in West Virginia, the EPA informed the D.C. Circuit that the Agency intended to replace the ACE Rule.\93\ On October 27, 2022, the D.C. Circuit took the necessary steps to, among other things, respond to the Supreme Court's decision by ensuring that the 2015 CPP remained repealed and stay further proceedings with respect to the challenges to the ACE Rule given the EPA's plans to replace that rule.\94\

\93\ Am. Lung Ass'n v. EPA, D.C. Cir. No. 19-1140, Motion to Govern, Doc. #196782 (October 3, 2022).

\94\ Am. Lung Ass'n v. EPA, D.C. Cir. No. 19-1140, Order, Doc. #1970895 (October 27, 2022).

On May 9, 2024, the EPA promulgated the CPS, which consisted of several separate actions.\95\ The first action was the repeal of the ACE Rule. The EPA explained, among other things, that the suite of heat rate improvements that was identified in the ACE Rule as the BSER is not an appropriate BSER for existing coal-fired EGUs.\96\

\95\ 89 FR 39798 (May 9, 2024).

\96\ In the CPS, the EPA also withdrew the separate proposed revisions to the New Source Review (NSR) regulations that were included the ACE Rule proposal. See 83 FR 44746, 44773-83 (August 31, 2018).

In addition, the 2024 CPS included emission guidelines for GHG emissions from existing fossil fuel-fired steam generating units, which include the separate subcategories of coal-fired units, oil-fired units, and gas-fired units.\97\ For long-term coal-fired units, the EPA finalized 90 percent CCS as the BSER, with a presumptive standard of an 88.4 percent reduction in annual emission rate and a compliance deadline of January 1, 2032. The EPA asserted that 90 percent CCS is an adequately demonstrated technology that achieves significant emissions reduction and that costs are reasonable, considering the supposedly declining costs of the technology and the Internal Revenue Code (IRC) section 45Q tax credit available for a certain number of years to generating sources that use CCS technology. In recognition of the significant capital expenditures involved in deploying CCS and previously announced retirement dates for several coal-fired steam generating units, the EPA finalized a separate subcategory for existing coal-fired units that demonstrate that they plan to permanently cease operation before January 1, 2039. For this subcategory, the BSER is co- firing with natural gas at a level of 40 percent of the unit's annual heat input, the presumptive standard is a 16 percent reduction in annual emission rate, and the compliance deadline is January 1, 2030. In addition, the EPA exempted existing coal-fired units that demonstrate that they plan to permanently cease operation prior to January 1, 2032. The EPA determined that these controls were cost- effective primarily by reference to two metrics used in prior rulemakings. The first metric determines the annualized cost in dollars for each ton, or other quantity, of the regulated air pollutant removed through the system of emission reduction. The second metric, which the EPA particularly relied on in rules for the electric power sector, determines the annualized cost of controls relative to the electricity generated by the EGU in dollars per megawatt-hour ($/MWh) of generation.\98\

\97\ Although the EPA also proposed emission guidelines for GHG emissions from existing fossil fuel-fired combustion turbines in the proposed CPS, the Agency did not finalize those emission guidelines.

\98\ 89 FR 39798, 39882 (May 9, 2024).

For existing natural gas- and oil-fired steam generating units, the EPA further subcategorized them into base load (units with annual capacity factors greater than or equal to 45 percent), intermediate load (units with annual capacity factors greater than or equal to eight percent and less than 45 percent), and low load (units with annual capacity factors less than eight percent) subcategories. The EPA finalized routine methods of operation and maintenance as the BSER for base load and intermediate load units, with presumptive standards for base load units of 1,400 pounds (lb) CO2/MWh-gross, and for intermediate load units of 1,600 lb CO2/MWh-gross.\99\ For low load units, the EPA finalized a uniform fuels BSER and a presumptive input-based standard of 170 lb CO2/MMBtu for oil-fired sources and a presumptive standard of 130 lb CO2/ MMBtu for natural gas-fired sources.

\99\ “Gross” refers to the electricity generated by the EGU, as opposed to “net,” which is equivalent to the electricity delivered to the grid and accounts for the loss due to the electricity used by auxiliary equipment at the facility.

The 2024 CPS also included standards of performance for new and reconstructed combustion turbines organized into three subcategories: base load, intermediate load, and low load. For base load turbines, the standard consisted of two components in two phases. The first component is based on a BSER of highly efficient generation (which was determined based on the emission rates achieved by the best performing units), and the EPA required compliance with this first component upon the effective date of the 2024 CPS. The second component is based on a BSER of 90 percent CCS, and the EPA required compliance with this second component on January 1, 2032. For intermediate load turbines, the EPA determined that highly efficient simple-cycle generation is the BSER. For low load combustion turbines, the EPA determined that the use of lower-emitting fuels is the BSER.

In addition, the EPA revised the standards of performance for coal- fired steam generating units that undertake a large modification (i.e., a modification that increases the hourly emission rate of the source by more than 10 percent) to be based on the BSER of 90 percent CCS. Finally, the EPA withdrew the 2018 NSPS Proposal for GHG emissions from coal-fired EGUs.\100\

\100\ 83 FR 65424 (December 20, 2018).

Following promulgation of the 2024 CPS, many States and industry groups filed petitions for review in the D.C. Circuit, and many subsequently filed motions to stay the rule. The D.C. Circuit denied the stay motions on July 19, 2024,\101\ and the Supreme Court denied these motions on October 16, 2024.\102\ Justice Thomas would have granted a stay, and Justice Kavanaugh, joined by Justice Gorsuch, wrote that “the applicants have shown a strong likelihood of success on the merits as to at least some of their challenges to the [EPA's] rule.” \103\ The parties briefed the merits, and the D.C. Circuit held oral argument on December 6, 2024. Following a change in administration, the D.C. Circuit agreed to hold the case in abeyance pending further actions by the Agency.

\101\ West Virginia v. EPA, D.C. Cir. No. 24-1120, Order, Doc. #2065493 (July 19, 2024).

\102\ West Virginia v. EPA, 145 S. Ct. 2 (2024).

\103\ Id.

In the 2024 CPS, the historical data that supported the analysis that the EPA conducted and relied on to assess the rule's projected impacts showed only incremental increases in electricity demand: a 13 percent increase between 2000 and 2022, with demand remaining relatively flat from 2007 to 2022. At the same time, the share of coal- fired electricity decreased in both relative and absolute terms, declining 58 percent and going from delivering 52 percent of total net generation in 2000 to 19 percent in 2022. Natural gas-fired net generation increased by 181 percent over this period, delivering 39 percent of net generation in 2022. The combination of wind and solar net generation grew 172 percent over this period, delivering 15 percent of total net generation in 2022. Natural gas surpassed the total net generation from coal on an absolute basis in 2016, and renewables surpassed the total net generation from coal on an absolute basis in 2022.\104\ The information that the EPA analyzed for purposes of the 2024 CPS indicated that the sector trend of moving away from coal-fired generation was likely to continue, the

share of electricity generation from natural gas-fired sources would likely decline, and the share of generation from non-emitting technologies would likely continue to increase. In the 2024 CPS, the EPA anticipated that the recent trend of retirements of coal-fired capacity (at an average annual rate of 10 gigawatt (GW) from 2015 to 2023) would continue due to the economics of coal-fired generation. At the time of the 2024 CPS final rule, more than half of the coal-fired steam generating units in operation had announced that they would retire or convert to natural gas by 2039.\105\

\104\ Power Sector Trends Technical Support Document for the New Source Performance Standards for Greenhouse Gas Emissions from New, Modified, and Reconstructed Fossil Fuel-Fired Electric Generating Units; Emission Guidelines for Greenhouse Gas Emissions from Existing Fossil Fuel-Fired Electric Generating Units; and Repeal of the Affordable Clean Energy Rule at 5-6, Document ID No. EPA-HQ-OAR- 2023-0072-8920.

\105\ 89 FR 39798, 39816-18 (May 9, 2024).

In contrast, updated information and analysis of power sector trends indicates a significantly different landscape moving forward. As noted in the June 2025 NPRM, the EPA believes that coal-fired steam generating unit capacity and generation will continue to comprise a substantial portion of the nation's electricity supply due to increasing electricity demand.\106\ Several key factors play major roles in reshaping projections of electricity markets over the coming decades. Demand growth across the U.S. is significantly higher than prior estimates. According to the 2024 North American Electric Reliability Corporation (NERC) Long Term Reliability Assessment, peak demand remained static nationwide over the ten-year period from 2013 through 2022.\107\ In 2022, NERC projected a 0.65 percent compound annual growth rate for summer peak demand based on the ten-year period of 2022 through 2031.\108\ In contrast, in late 2024, NERC projected a 1.67 percent compound annual growth rate for summer peak demand based on the ten-year period of 2025 through 2034.\109\ Increasing amounts of large commercial and industrial loads, particularly those related to data center demand for artificial intelligence (AI) applications, are primarily driving this nearly 2.6-fold increase in projected growth rates. Sub-nationally, these impacts are even more striking. The Electric Reliability Council of Texas' (ERCOT) 2025 long-term load forecast projects summer peak demand rising at an 8.9 percent annual growth rate based on the six-year period of 2025 to 2031.\110\ The 2025 long-term load forecast for PJM, a regional transmission organization serving large parts of the eastern US, projects a 3.1 percent annual growth rate in summer peak demand based on the ten-year period of 2025 to 2035.\111\ NERC concludes that critical reliability challenges face the sector when considering the need to meet this higher level of demand, manage ongoing thermal retirements, and develop additional transmission and support resources.\112\ A recent Department of Energy (DOE) report, which examines reliability implications of ongoing thermal retirements in the face of projected increases in electricity demand, echoes these findings and further states that the risk of power outages may increase by a hundred fold in some instances if firm resources continue to retire in the face of projected load growth.\113\

\106\ See 90 FR 25752, 25772, 25774 (June 17, 2025).

\107\ NERC 2023 Long-Term Reliability Assessment (December 2024). Available at: https://www.nerc.com/pa/RAPA/ra/Reliability%20Assessments%20DL/NERC_Long%20Term%20Reliability%20Assessment_2024.pdf.

\108\ NERC 2021 Long-Term Reliability Assessment (December 2022). Available at: https://www.nerc.com/our-work/assessments/past-reliability-assessments.

\109\ NERC 2023 Long-Term Reliability Assessment (December 2024). Available at: https://www.nerc.com/our-work/assessments/past-reliability-assessments.

\110\ ERCOT. 2025 System Planning Long-term Hourly Peak Demand and Energy Forecast. Available at: https://www.ercot.com/files/docs/2025/04/08/2025_LTLF_Report.docx.

\111\ PJM. 2025 Long-Term Load Forecast Report. Available at: https://www.pjm.com/-/media/DotCom/library/reports-notices/load-forecast/2025-load-report.pdf.

\112\ NERC 2023 Long-Term Reliability Assessment (December 2024). Available at: https://www.nerc.com/our-work/assessments/past-reliability-assessments.

\113\ U.S. Department of Energy, Resource Adequacy Report Evaluating the Reliability and Security of the United States Electric Grid (2025). Available at: https://www.energy.gov/sites/default/files/2025-07/DOE%20Final%20EO%20Report%20%28FINAL%20JULY%207%29.pdf.

The passage of the One Big Beautiful Bill Act of 2025 (OBBBA) will also have important impacts on the power sector. The phaseout of tax subsidies to wind and solar resources will likely reduce incremental builds of these technologies, particularly after 2028. This, in turn, will further increase the need for retaining existing thermal resources (including coal-fired steam generating units) and building new thermal (including new combustion turbines) resources to help meet increasing electricity demand. Considering these changes, the EPA expects the OBBBA to produce a net effect of reducing factors that boosted the economic competitiveness of wind and solar resources and improving the economic competitiveness of thermal generation (including coal and natural gas-fired generation).

Moreover, higher levels of electricity demand result in greater demand for around-the-clock power, which results in a higher utilization of coal- and gas-fired resources in the EPA's current analysis than in the EPA's 2024 analysis underpinning the 2024 CPS.\114\ The trends the EPA has incorporated into the updated analysis result in projections that show total electricity generation will increase by approximately 15 percent by 2030 and 25 percent by 2035,\115\ significantly higher than projections in the 2024 analysis for the 2024 CPS.\116\

\114\ See memorandum entitled Trends Relating to Fossil Fuel- fired Electric Generating Units in the docket for this rulemaking (Docket ID No. EPA-HQ-OAR-2025-0124).

\115\ Id.

\116\ U.S. EPA. Regulatory Impact Analysis for the New Source Performance Standards for Greenhouse Gas Emissions from New, Modified, and Reconstructed Fossil Fuel-Fired Electric Generating Units; Emission Guidelines for Greenhouse Gas Emissions from Existing Fossil Fuel-Fired Electric Generating Units; and Repeal of the Affordable Clean Energy Rule (May 2024). Document ID No. EPA-HQ- OAR-2023-0072-8913.

This recent change in demand for around-the-clock power already is effecting changes in the current market, as shown by a number of coal- fired steam generating units that are delaying or canceling their scheduled retirements due to increased electricity demand.\117\ Using the latest available data from the Energy Information Administration (EIA), in 2024, the U.S. power sector had approximately 174 GW of coal- fired EGUs that collectively consumed approximately 7.0 quadrillion British thermal units (Btus) of energy. According to data reported by the owners and operators of coal-fired capacity, the EIA expects 146 GW of this capacity to remain in service through 2032. In addition, the EIA now expects 24.5 GW of combined cycle additions and 11.5 GW of combustion turbine additions over the next five years,\118\ demonstrating a sharp increase from the August 2023 EIA data underlying the analysis of the 2024 CPS, which cited roughly 9.6 GW of combined cycle and 1.9 GW of combustion turbine additions planned for construction between 2025 and 2030.\119\

\117\ Power. U.S. Coal Plants Get Reprieve as Market and Policies Change. Available at: https://www.powermag.com/u-s-coal-plants-get-reprieve-as-market-and-policies-change.

\118\ U.S. Energy Information Administration. EIA Power Monthly (October 2025). Available at: https://www.eia.gov/electricity/data/eia860m/xls/october_generator2025.xlsx.

\119\ U.S. Energy Information Administration. EIA Power Monthly (August 2023). Available at: https://www.eia.gov/electricity/data/eia860m/xls/august_generator2023.xlsx.

The EPA's updated projections reflect these changes.\120\ As a specific example, at the end of 2024, 174 GW of coal-fired EGUs were active in the power sector

nationwide.\121\ In the 2024 CPS, the EPA projected that, in the baseline absent requirements, approximately 40 GW of existing coal capacity would still be active by 2040.\122\ However, the EPA has revisited the 2024 baseline in light of the information above. The EPA now projects that, absent the requirements of the 2024 CPS, approximately 100 GW of coal capacity would be active in 2040,\123\ more than twice the capacity EPA previously projected. Similarly, in the 2024 CPS, the EPA projected approximately 26 GW of incremental NGCC capacity additions by 2035.\124\ The EPA now projects, absent the requirements of the 2024 CPS, approximately 155 GW of new NGCC capacity by 2035. Based on the EPA's updated projections, informed by the recent and consequential changes in the electricity market, a much larger number of EGUs would be subject to the requirements of the 2024 CPS than previously estimated for the purposes of that rulemaking.

\120\ See memorandum entitled Trends Relating to Fossil Fuel- fired Electric Generating Units in the docket for this rulemaking (Docket ID No. EPA-HQ-OAR-2025-0124).

\121\ U.S. Energy Information Administration. EIA Power Monthly (December 2024). Available at: https://www.eia.gov/electricity/monthly/archive/december2024.pdf.

\122\ U.S. EPA. RIA for 2024 CPS. Document ID No. EPA-HQ-OAR- 2023-0072-8913. Table 3-14.

\123\ See memorandum entitled Trends Relating to Fossil Fuel- fired Electric Generating Units in the docket for this rulemaking (Docket ID No. EPA-HQ-OAR-2025-0124).

\124\ U.S. EPA. RIA for 2024 CPS. Document ID No. EPA-HQ-OAR- 2023-0072-8913. Table 3-14.

In June 2025, the EPA issued a NPRM that included two proposals: a primary proposal and an alternative proposal. The primary proposal would have repealed all GHG regulations for fossil fuel-fired EGUs under CAA section 111 on the basis that the source category does not significantly contribute to dangerous GHG air pollution. Specifically, the EPA proposed to conclude that CAA section 111 is best read to require, or at least authorize the EPA to require, the Administrator's determination that an air pollutant emitted by a source category causes, or contributes significantly to, air pollution which may reasonably be anticipated to endanger public health or welfare as a predicate to establishing emission standards for that pollutant. The EPA further proposed to determine, in a change from the 2015 NSPS and the 2024 CPS, that GHG emissions from fossil fuel-fired power plants do not contribute significantly to dangerous air pollution as required for the promulgation of new and existing source standards. The EPA proposed to find that the contribution of this source category is not significant because GHG emissions from those sources are a small and decreasing part of global emissions, cost-effective control measures are not reasonably available, and this Administration's priority is to protect the environment, public health, and welfare through energy dominance and independence secured through the use of fossil fuels to generate power. On the basis of the proposed finding that GHG emissions from fossil fuel-fired power plants do not contribute significantly to dangerous air pollution, the EPA proposed to repeal all GHG emissions standards for the power sector under CAA section 111, specifically the 2015 NSPS (codified in 40 CFR part 60, subpart TTTT) and the 2024 CPS (codified in 40 CFR part 60, subparts TTTTa and UUUUb).

In the alternative, based largely on a review of the BSER determinations in the 2024 CPS, the EPA proposed to repeal the emission guidelines for existing steam generating units in 40 CFR part 60, subpart UUUUb, the CCS-based requirements for coal-fired steam generating units undergoing a large modification in 40 CFR part 60, subpart TTTTa, and the CCS-based phase 2 requirements for new base load combustion turbines in 40 CFR part 60, subpart TTTTa. The EPA also solicited comment, in general, on the other standards (e.g., phase 1 standards for new combustion turbines).

The EPA is finalizing the repeal of the emission guidelines in the 2024 CPS for existing fossil fuel-fired steam generating units in 40 CFR part 60, subpart UUUUb. The EPA also is finalizing the repeal of the requirements for coal-fired steam generating units undertaking a large modification in 40 CFR part 60, subpart TTTTa and the phase 2 CCS-based requirements for new base load combustion turbine EGUs in 40 CFR part 60, subpart TTTTa. As discussed in more detail in this section of the preamble, the EPA is finalizing those repeals on the bases that (1) 90 percent CCS is not the BSER for existing long-term coal-fired steam generating units and the degree of emission limitation in the 2024 CPS is not achievable, (2) 40 percent natural gas co-firing is not the BSER for medium-term coal-fired steam generating units and the degree of emission limitation is not achievable, (3) it would be imprudent to require States to submit plans for oil- and natural gas- fired steam generating units, and (4) 90 percent CCS is not the BSER for new base load combustion turbines and the associated standards of performance are not achievable.

The EPA acknowledges the uncertainty created by the 2024 CPS, particularly given the consequential changes to projected trends in electricity demand and generation.\125\ To provide near-term relief to affected sources from the regulatory burdens of the 2024 CPS that are the cause of this uncertainty, the EPA is finalizing, based largely on the unreasonableness of the BSER determinations in the 2024 CPS, the repeal of the emission guidelines for existing steam generating units, the CCS-based requirements for coal-fired steam generating units undergoing a large modification, and the CCS-based phase 2 requirements for new base load combustion turbines.

\125\ See, e.g., Comments of the Power Generators Air Coalition on EPA's Proposed Repeal of Greenhouse Gas Emissions Standards for Fossil-Fuel Fired Electric Generating Units at 6, Document ID No. EPA-HQ-OAR-2025-0125-0610; Comments from the Edison Electric Institutes on the Proposed Rule Repeal of Greenhouse Gas Emissions Standards for Fossil Fuel-Fired Electric Generating Units at 6-12, Document ID No. EPA-HQ-OAR-2025-0125-0897.

Specifically, the EPA is finalizing the determination that 90 percent CCS is not the BSER for existing long-term coal-fired steam generating units because it has not been adequately demonstrated and because the costs are not reasonable. Furthermore, because it is unlikely the infrastructure for CCS can be deployed by the January 1, 2032 compliance date, the EPA is finalizing the determination that the degree of emission limitation in the 2024 CPS for long-term coal-fired steam generating units is not achievable. The EPA is also finalizing the determination that 40 percent natural gas co-firing is not the BSER for existing medium-term coal-fired steam generating units for several reasons. First, 40 percent natural gas co-firing cannot be BSER because 40 percent natural gas co-firing is a type of generation-shifting and is precluded by the Supreme Court's decision in West Virginia. Additionally, 40 percent natural gas co-firing cannot be BSER because consideration of the energy requirements shows that 40 percent natural gas co-firing has adverse consequences for the energy system. Moreover, because it is unlikely the infrastructure for 40 percent co-firing can practicably be deployed by the January 1, 2030 compliance date, the EPA is finalizing the determination that the degree of emission limitation in the 2024 CPS for medium-term coal-fired steam generating units is not achievable. Therefore, the EPA is repealing the BSER determinations, presumptive standards of performance, and all

related requirements in the emission guidelines for existing long-term and medium-term coal-fired steam generating units.

Additionally, the EPA is repealing the requirements for existing natural gas- and oil-fired steam generating units because it would be an inefficient use of State resources to develop, submit, and implement state plans solely for natural gas- and oil-fired steam generating units, which comprise a relatively small part of the source category and would contribute few or no emission reductions under the existing emission guidelines. That is, it would not be reasonable for the EPA to require States to prepare plans for existing natural gas- and oil-fired steam generating units given that the Agency is repealing the requirements for existing coal-fired steam generating units.

The EPA is thus repealing the substantive requirements and, on that basis, is repealing 40 CFR part 60, subpart UUUUb--the emission guidelines for existing fossil fuel-fired steam generating units--in its entirety.

Because the EPA is determining that 90 percent CCS is not the BSER for existing long-term coal-fired steam generating units, the EPA is also repealing the CCS-based requirements for coal-fired steam generating units undertaking a large modification. The EPA is also determining that 90 percent CCS is not the BSER for new base load combustion turbine EGUs because it has not been adequately demonstrated and the costs are not reasonable. Furthermore, because it is unlikely that the infrastructure necessary for CCS can be deployed by the January 1, 2032 compliance date, the EPA is determining that the phase 2 standards of performance in the 2024 CPS for new base load combustion turbines are not achievable. Consequently, the EPA is repealing the phase 2 CCS-based requirements for new base load combustion turbine EGUs.

Although the EPA discusses each relevant repeal and the associated bases below, several observations about the 2024 CPS reinforce the fundamental issues with that prior action--and the 2015 CPP that preceded it--and support the Agency's decision to proceed with these repeals, including the repeal of standards predicated on 90 percent CCS.

First, the 2024 CPS reflected an overly restrained reading of the Supreme Court's assessment of the 2015 CPP in West Virginia. The EPA initially viewed that decision as barring only standards that expressly require generation shifting.\126\ Upon further consideration, the EPA now accepts that decision as holding that the Agency may not impose standards with the objective or result of generation shifting at the scale the Court found to raise a major question reserved for Congress. Information reviewed since promulgation of the 2024 CPS demonstrates that standards predicated on achieving 90 percent CCS cross that threshold. Regulated sources in the relevant subcategories (i.e., coal plants) were given the choice between complying with the standards by 2032 or ceasing operations by 2032. Because, for the reasons discussed throughout this preamble, emission limitation requirements based on 90 percent CCS are not achievable, the 2024 CPS effectively requires coal plants to shut down by 2032--a form of generation shifting. Under these circumstances, retaining these aspects of the 2024 CPS would be improper.

\126\ See, e.g., US working on power plant standards for energy transition: US EPA head, July 29, 2023, available at https://www.world-energy.org/article/34841.html (“We are working on a proposed power plant standard in the United States that helps us to transition from heavily fossil fuel resources to clean resources. . . .”).

Second, the 2024 CPS reflected an overbroad reading of CAA section 111 that did not recognize or account for limits on the EPA's ability to identify a BSER requiring the deployment of new infrastructure over a long time horizon. In promulgating the 2024 CPS, the EPA projected-- based on, as discussed below, optimistic assumptions--that complex carbon capture, transmission, and injection infrastructure that did not yet exist could be deployed nationwide within seven years, and did not view the inherent uncertainties and long time horizon as a barrier to adopting, or reason not to adopt, 90 percent CCS as the BSER. Upon further consideration, the Agency concludes that the inherent difficulties in accurately projecting such large-scale deployments counsel against selecting BSERs predicated on large-scale national infrastructure buildouts years into the future, particularly given the statute's eight-year cycle for reviewing the effectiveness of promulgated standards.

Third, and relatedly, the 2024 CPS reflected an overbroad reading of CAA section 111 that did not recognize or account for the scale of the infrastructure required for compliance, including the difference between systems that sources can apply to meet the standards that apply to them and systems that require significant investment and performance by third parties. Owners and operators of power plants subject to 90 percent CCS-based requirements are dependent on third parties to develop and operate virtually all the components of CCS. Transport and storage, in particular, differ from the types of equipment the Agency has historically selected as BSER. All relevant third parties would need to timely complete their components of the infrastructure across large geographic areas for the owners and operators to be able to implement the CCS requirements by the compliance date, and thereafter, owners and operators must rely on the continued cooperation and operation of these third parties. Upon further consideration, the EPA concludes that the scale of the necessary infrastructure, including the necessary involvement of third parties nationwide, is different in kind from control measures historically considered under CAA section 111 and counsels against selecting 90 percent CCS as BSER.

The remainder of this section details the rationale for the repeal of the emission guidelines for existing fossil fuel-fired steam generating units, the CCS-based requirements for coal-fired steam generating units undertaking a large modification, and the 2024 CCS- based requirements for new combustion turbine EGUs. The EPA carefully considered the comments received on the June 2025 NPRM in the development of this final rulemaking and the supporting rationale. The EPA discusses some of the overarching comments received on the June 2025 NPRM and provides responses in this section of the preamble.\127\

\127\ Responses to substantial comments on specific issues are addressed in the relevant sections of this preamble. Responses to additional comments are in the RTC, available in the docket for this rulemaking (Docket ID No. EPA-HQ-OAR-2025-0124).

Comments: The EPA received extensive comments on both the primary and alternative proposals of the June 2025 NPRM. Among the group of commenters generally in favor of the proposals, some supported finalizing the primary proposal, some supported finalizing the alternative proposal, and others supported finalizing both proposals. Among the commenters in favor of finalizing both proposals, some recommended finalizing the alternative proposal first, followed by the primary proposal, while others urged the EPA to finalize both proposals simultaneously. Other commenters opposed both proposals.

EPA Response: Based on consideration of those comments and other factors, in this final rule, the EPA is finalizing only the alternative proposal in the June 2025 NPRM--that is, the proposal to repeal the emission guidelines for existing steam generating

units and the CCS-based requirements for new base load combustion turbine EGUs and coal-fired steam generating units undertaking a large modification. This final action is based on a record-focused reevaluation of the BSER determinations for the relevant subcategories. As previously explained, the EPA is taking this final action to provide near-term relief from regulatory requirements it now finds are unlawful or otherwise unreasonable. The EPA is not, in this rulemaking, finalizing the primary proposal in the June 2025 NPRM to repeal all GHG regulations for fossil fuel-fired EGUs under CAA section 111 on the basis that the source category does not significantly contribute to qualifying air pollution. The EPA is instead issuing a supplemental proposal soliciting additional public comment on the underlying question raised in the primary basis of the June 2025 NPRM: Whether the EPA lacks statutory authority to regulate GHG emissions from fossil fuel-fired power plants under CAA section 111 under the applicable statutory standard for such regulation. The primary proposal in the June 2025 NPRM sought public comment on whether fossil fuel-fired EGUs “contribute significantly” to air pollution, and the supplemental notice seeks public comment on the distinct question whether global climate change concerns satisfy the threshold requirement in CAA section 111(b)(1)(A) that the source category emissions contribute significantly to “air pollution which may reasonably be anticipated to endanger public health or welfare.” We will evaluate both proposed approaches and rationales in taking final action, as both issues-- contribution and endangerment--were the subject of significant interpretive and policy changes in the 2009 Endangerment Finding and the 2015 NSPS (as retained by the 2024 CPS) that extended the Agency's novel approach to power plant stationary sources. The EPA therefore is responding in this final rule only to comments on the alternative proposal that the Agency is finalizing--the proposal to repeal 40 CFR part 60, subpart UUUUb and certain components of 40 CFR part 60, subpart TTTTa. The EPA is not responding at this time to comments that relate solely to the June 2025 primary proposal.

Comments: Some commenters opposed to the proposal to repeal the emission guidelines and other CCS-related requirements asserted that such repeal would be unlawful because the EPA must consider alternatives to the BSER determinations and requirements at issue and/ or immediately promulgate different requirements based on alternative BSERs. Commenters asserted that the CAA requires the EPA to set standards of performance under CAA section 111(b) for GHG emissions from fossil fuel-fired power plants because they are listed as a source category under CAA section 111 and that the Agency has previously determined that such emissions contribute significantly to GHG air pollution that endangers public health and welfare. Additionally, these commenters asserted that CAA section 111(d) requires the EPA to promulgate emission guidelines for existing sources that would be subject to the standards under CAA section 111(b) if the sources were new sources. Commenters asserted that the repeal of the 2024 CPS's emission guidelines and standards of performance at issue in this rulemaking would leave these legal mandates unfilled and that repealing these requirements without considering and/or promulgating alternative requirements based on alternative BSERs would be arbitrary and capricious.

EPA Response: The EPA disagrees with these comments. The EPA carefully considered alternatives to repeal of the emission guidelines and standards of performance (e.g., whether to revise the BSER determinations or compliance schedules for the affected sources and whether to promulgate different standards immediately) and is determining that it is not necessary to do so at this time. The EPA remains concerned that it lacks the requisite statutory authority to regulate GHG emissions from power plants in the first instance under the applicable statutory standard for regulation. Indeed, other commenters urged that the EPA must resolve this predicate question before promulgating additional or different standards. Accordingly, the EPA is exercising its discretion to proceed through multiple steps that will address the totality of the problem before it in an orderly fashion.

In a concurrently issued supplemental proposal, the EPA is proposing to find that the Agency lacks the requisite legal basis to regulate GHG emissions from fossil fuel-fired power plants under CAA section 111. These proposed bases are in addition to those presented in the primary proposal in the June 2025 NPRM and will be considered together with the bases previously presented in taking final action. If finalized as proposed, this subsequent action would abrogate any legal requirement and authority to replace the BSER determinations and associated requirements that the EPA is repealing in this final rule. Such action would render it inappropriate and unnecessary to promulgate any alternative BSER determinations, standards of performance, or compliance schedules. Conversely, if the EPA determines that it has the requisite statutory authority, the Agency would conduct additional analyses and propose any necessary and appropriate additional requirements for the fossil fuel-fired EGU source category at that time, having confirmed its statutory basis for doing so.

As a general matter, “[n]othing prohibits federal agencies from moving in an incremental manner.” \128\ The EPA notes that CAA section 111 contemplates that the Agency need not immediately promulgate standards upon listing a source category and that review of regulations for a previously listed source category occurs on an eight-year cycle. Moreover, CAA section 111(b)(1)(B) does not require the Agency to regulate all types of emissions simultaneously, and CAA section 111(d) does not provide a deadline for promulgating emission guidelines. Even with respect to source categories for which no regulations exist, Congress previously provided a prioritization scheme in CAA section 111(f) under which the EPA was required to promulgate such regulations over the course of a six-year period. The EPA has consistently taken the position that it need not, in any particular CAA section 111 rulemaking, address all potential issues relevant to the at-issue source category. This final action does not repeal all requirements applicable to the fossil-fuel fired EGU source category, and as noted elsewhere in this preamble, nothing in this final action disturbs criteria pollutant emission standards applicable to power plants regulated under pre-2015 listings.

\128\ Fox Television Stations, 556 U.S. at 522; see, e.g., Pub. Safety Spectrum All. v. FCC, No. 24-1363, slip op. 20 (D.C. Cir. July 21, 2026) (it was reasonable for the FCC to defer making relevant decisions to a subsequent action).

Thus, the EPA need not analyze and promulgate alternative BSERs and associated requirements to address serious issues identified with certain existing standards. In this context, this final rule simply represents a permissible first step in a multi-step process.\129\ As noted above, the EPA is

taking this first step to provide near-term relief from 2024 CPS requirements that it is now determining to be unlawful or otherwise unreasonable and which, absent further action, would imminently begin forcing the expenditure of significant resources. Promulgation of alternative BSERs or compliance schedules at this time would require completing multiple additional steps, including resolving questions regarding the Agency's statutory authority and analyzing competing alternative BSERs and requirements, all of which would delay resolution of the distinct issues addressed in this rulemaking and defeat the purpose of resolving these distinct issues before regulated sources are put to the choice between expending significant resources to comply, or planning to close, before the current 2032 compliance deadline (or other upcoming compliance deadlines, as applicable).

\129\ See Grand Canyon Air Tour Coal. v. FAA, 154 F.3d 455, 471 (D.C. Cir. 1998) (“ordinarily, agencies have wide latitude to attack a regulatory problem in phases and . . . a phased attack often has substantial benefits”); Las Vegas v. Lujan, 891 F.2d 927, 935 (D.C. Cir. 1989) (upholding agency action that was a first step toward a “complete solution,” stating that “agencies have great discretion to treat a problem partially”); Nat'l Ass'n of Broadcasters v. FCC, 740 F.2d 1190, 1210 (D.C. Cir. 1984) (it is reasonable for an agency to “defer resolution of issues raised in a rulemaking even when those issues are `related' to the main ones being considered”; the inquiry into when agencies may defer resolution of issues raised in a rulemaking to a subsequent action is “a pragmatic one”).

The EPA does not believe its repeal of certain 2024 CPS standards and requirements runs afoul of case law such as Regents of the University of California and State Farm. These cases stand for the proposition that when an agency “rescinds a prior policy its reasoned analysis must consider the `alternative[s]' that are `within the ambit of the existing [policy].” \130\ In concluding that the CAA and general principles of administrative law do not require the EPA to analyze and promulgate alternative, replacement BSER determinations or requirements immediately and as part of this discrete repeal, the Agency again emphasizes that this action is the first step in what is intended to be a multi-step rulemaking process. If the second step of this process is finalized as proposed, the “existing policy” will be mooted based on the lack of legal basis for that policy in the first instance. The EPA is thus not promulgating new standards for existing coal-fired steam generating units or for new base load combustion turbines in this final rule, and, accordingly, need not develop alternative BSER determinations to support such new and additional standards.

\130\ Regents, 591 U.S. at 30 (quoting State Farm, 463 U.S. at 51).

In analyzing this aspect of the problem, the EPA reviewed the alternatives it considered prior to selecting the BSER and standards finalized in the 2024 CPS to examine the scope and nature of possible regulatory alternatives. The Agency believes that its prior consideration and rejection of other potential BSERs in the 2024 CPS rulemaking demonstrates that further analyzing additional alternative BSERs and requirements would be unnecessary under the circumstances here. In the 2024 CPS, the EPA considered and rejected a range of potential alternatives to the BSERs ultimately selected. For long-term coal-fired steam generating units now subject to standards based on 90 percent CCS, the EPA considered partial CCS at lower capture rates, natural gas co-firing, and heat rate improvements.\131\ The EPA rejected partial CCS “because it achieves substantially fewer unit- level reductions at greater cost, and because CCS at 90 percent is achievable.” \132\ The Agency also noted that “the IRC section 45Q tax credit may not be available to defray the costs of partial CCS and the emission reductions would be limited.” \133\ As explained in section IV.A.1 of this preamble, the EPA now rejects the conclusion that 90 percent CCS is adequately demonstrated and achievable and further finds that the IRC section 45Q tax credit should not be accounted for when evaluating the reasonableness of the costs of the BSER. The EPA therefore believes the costs of partial CCS would be significantly higher than anticipated in the 2024 CPS and therefore remains an inappropriate alternative. With regard to natural gas co- firing as an alternative to 90 percent CCS, as discussed in section IV.A.2 of this preamble, the EPA is determining in this final rule that this control strategy amounts to impermissible generation shifting, thereby disqualifying it from being the BSER. And the EPA explained in the 2024 CPS that it was not finalizing heat rate improvements as the BSER “because of the limited reductions and potential rebound effect.” \134\ Similarly, for medium-term coal-fired EGUs, the 2024 CPS considered CCS and heat rate improvements as potential BSERs and rejected each.\135\ Thus, based on the EPA's earlier assessments and the further analysis conducted for purposes of this final rule, potential alternatives to 90 percent CCS for long-term coal-fired units and 40 percent natural gas co-firing for medium-term coal-fired units are not obvious and suffer from their own shortcomings. As noted above, fully analyzing and working through these issues is a distinct task that warrants a distinct process that would be most appropriate to undertake after, and pending the results of, the Agency's consideration of the scope of its statutory authority.

\131\ 89 FR 39798, 39846 (May 9, 2024).

\132\ Id.

\133\ Id.

\134\ Id.

\135\ Id. at 39895-96.

For new base load combustion turbines, the 2024 CPS included consideration of potential alternative BSERs including lower-emitting fuels, high efficiency generation, and hydrogen co-firing.\136\ In the 2024 CPS, the EPA explained that lower-emitting fuels are not the BSER for new base load combustion turbines because they would achieve few emission reductions.\137\ And the EPA further explained that, “[i]n light of public comments and additional analysis, uncertainties regarding projected costs prevent the EPA from determining that low-GHG hydrogen is a component of the BSER at this time.” \138\ This previous evaluation of potential alternative BSERs in the 2024 CPS corroborates the EPA's conclusion in this rulemaking that it is not necessary for the Agency to consider alternatives to repeal of the 90 percent CCS, phase 2 BSER for new base load combustion turbines.

\136\ Id. at 39924.

\137\ Id.

\138\ Id. at 39939.

Comments: Some commenters asserted that the EPA's proposed repeal of the 2024 CPS failed to consider the disbenefits of that proposal, namely, forgone emissions reductions. One commenter noted that the standards the Agency was proposing to repeal would reduce CO2 emissions by 1.38 billion metric tons over roughly two decades. The commenter further stated that the standards the EPA was proposing to repeal would also secure reductions of tens of thousands of tons of particulate matter, sulfur dioxide, and nitrogen oxide emissions. Commenters argued that the Agency had failed to consider the public health benefits of the 2024 CPS and the corresponding disbenefits of repealing certain requirements of that rule, and that this purported oversight rendered the proposed repeal inconsistent with the Administrative Procedure Act and the CAA.

EPA Response: The EPA disagrees with these comments. The Agency acknowledges that CO2 emission reductions are a relevant consideration in making BSER determinations under a regulatory framework that addresses GHG emissions from the affected sources. The EPA also recognizes that this action to repeal requirements of the 2024 CPS forgoes the CO2 emission reductions that were projected to be

achieved under the 2024 CPS. However, the EPA emphasizes that the repeal of the 2024 CPS requirements is based on the Agency's technical determinations that 90 percent CCS and 40 percent natural gas co-firing do not satisfy certain threshold legal criteria to be eligible to be the BSER. For 90 percent natural gas co-firing, the EPA is determining, among other things, that CO2 capture at this rate is not adequately demonstrated; the Agency is also determining that 40 percent natural gas co-firing is impermissible generation shifting. Because each of these determinations disqualifies the emissions control strategy from further consideration, the amount of CO2 emission reductions available through implementation of these strategies cannot compel a different outcome. Further, as discussed in the relevant subsections of this preamble, many of the selected control strategies underlying the at-issue 2024 CPS requirements are infeasible, and the EPA has significantly revised its projections and analysis in the 2024 CPS with respect to the timeline for implementation. These issues mean that the emissions reductions projected in the 2024 CPS were not likely to come to fruition in any event absent outcomes inconsistent with the CAA (i.e., forced plant closures because compliance by the applicable deadline is not possible).

Separately, the EPA is also determining that the cost of 90 percent CCS is unreasonable and that the energy impacts associated with 40 percent co-firing are unreasonable. The amount of CO2 emission reductions is relevant to the balancing of the BSER factors, which also include cost and nonair quality health and environmental impacts and energy requirements. As explained in this section of the preamble, the EPA has considered the available emission reductions associated with 90 percent CCS and 40 percent natural gas co-firing and is finding that, on balance, these emission control strategies are unreasonable. Furthermore, as explained in section IV.3 of this preamble, the EPA is repealing the requirements for oil and natural gas-fired steam generating units in part because the BSERs for these units in the 2024 CPS would not have achieved appreciable CO2 emission reductions. The EPA has thus considered the foregone CO2 emission reductions and determined that its action is reasonable notwithstanding.

While the EPA acknowledges that the 2024 CPS would have also resulted in reductions of co-pollutants including particulate matter, sulfur dioxide, and nitrogen oxides, reductions of these pollutants in the 2024 CPS, or foregone emission reductions of these pollutants in this action, did not factor into the Agency's BSER determinations for the regulated pollutant--CO2--emitted from the regulated sources. And even if the EPA were to consider these incidental reductions of co-pollutants, the Agency would determine that the costs and energy impacts of the controls should be weighted more heavily than those forgone reductions.

The EPA's consideration of foregone emission reductions together with costs in relation to projections in the 2024 CPS is consistent with the Supreme Court's statement in Michigan v. EPA, 576 U.S. 743 (2015), that “reasonable regulation ordinarily requires paying attention to the advantages and the disadvantages of agency decisions.” \139\ That is, the EPA has considered the reductions that the 2024 CPS would have achieved in CO2 emissions, as well as the reductions in the other pollutants emitted by power plants, including particulate matter, sulfur dioxide, and nitrogen oxides. The EPA has also considered the health impacts of reducing emissions of these pollutants. Those emissions reductions and health impacts are noted in section V.A of this preamble. However, the EPA believes that any benefits from them are outweighed by the costs of the 2024 CPS, including the costs to the industry (and, in many instances, to the ratepayers who will absorb those costs through higher electricity bills) of complying with the requirements, as also noted in section V.A of this preamble, as well as the adverse energy impacts of using natural gas for co-firing, as noted in section IV.A.2.a of this preamble. In the EPA's view, this relative weighting is confirmed by the uncertainty of actually achieving the benefits attributed to the 2024 CPS, in light of the record and legal deficiencies in the 2024 CPS's determination of CCS and co-firing as BSER, as noted in sections IV.A.1 and IV.A.2 of this preamble. Accordingly, the EPA believes that today's action to repeal the 2024 CPS is reasonable and consistent with the Michigan statement cited above concerning reasonable regulation.

\139\ Michigan, 576 U.S. at 753 (emphasis in original).

This section details the rationale for the repeal of the emission guidelines for existing fossil fuel-fired steam generating units. 1. CCS-Based Requirements for Long-Term Existing Coal-Fired Steam Generating Units

In the 2024 CPS, the EPA determined the BSER for long-term coal- fired steam generating units to be 90 percent CCS. The EPA premised that BSER specifically on 90 percent CO2 capture using an amine solvent-based system, CO2 transport through a pipeline, and geologic sequestration of the CO2 in a saline reservoir. In the 2024 CPS, the EPA argued that 90 percent CCS, including the 90 percent CO2 capture component, was adequately demonstrated. The EPA further argued that 90 percent CCS satisfied the other criteria for BSER, including that costs were reasonable based on counting the IRC section 45Q as a reduction in the cost to the affected source of 90 percent CCS. Based on application of the 90 percent CCS BSER to the affected sources, the EPA established a degree of emission limitation and argued this was achievable by the compliance date of January 1, 2032, considering the time necessary to deploy capture equipment, transport, and sequestration.

The EPA proposed to repeal the requirements for long-term coal- fired steam generating units based largely on a reassessment of the record for the 2024 CPS. Specifically, the EPA proposed that 90 percent CO2 capture, and therefore 90 percent CCS as a whole, have not been adequately demonstrated. The EPA further proposed that the average unit-level costs of 90 percent CCS were unreasonable. In the June 2025 NPRM, the EPA evaluated the average unit level costs assuming a lower capacity factor of the host EGU and operation beyond the 12- year period of availability of the IRC section 45Q tax credit. The reduced amount of CO2 that would be captured and eligible for the IRC section 45Q tax credit resulted in higher costs than in the 2024 CPS. The EPA further proposed that the IRC section 45Q should not be counted as a reduction in the costs of 90 percent CCS. Finally, the EPA proposed that the degree of emission limitation in the 2024 CPS is not achievable because it is unlikely that the infrastructure (including the capture system, pipelines, and sequestration) for CCS can be deployed by the January 1, 2032 compliance date.

The EPA has reassessed the record underlying the 2024 CPS. The EPA is finalizing the determination that CCS with 90 percent capture is not the BSER for long-term existing coal-fired steam generating units because 90 percent CO2 capture and, therefore, 90 percent CCS have not been adequately demonstrated

and the costs are unreasonable. Additionally, the capture, pipeline, and sequestration infrastructure necessary for 90 percent CCS for the fleet of existing coal-fired steam generating units does not currently exist and would need to be broadly deployed. It is unlikely the infrastructure necessary for CCS can be deployed by the January 1, 2032 compliance date, and the EPA is therefore finalizing the determination that the degree of emission limitation in the 2024 CPS for long-term coal-fired steam generating units is not achievable. Consequently, for the reasons explained in the June 2025 NPRM \140\ and discussed below, the EPA is finalizing the repeal of the requirements in the emission guidelines pertaining to long-term existing coal-fired steam generating units.

\140\ 90 FR 25752, 25769-73 (June 17, 2025).