Progress Report - Program Basics
Program Basics
Program History
EPA's Power Plant Programs
The 1990 Clean Air Act Amendments launched a new era in environmental protection. New provisions created the innovative Acid Rain Program (ARP) to curtail acid-rain-causing emissions from the electric power sector through an emissions trading program.1 The success of the ARP in achieving significant emission reductions in a cost-effective manner led to use of this market-based approach to reduce power plant emissions in one state that travels long distances to impact air quality in a downwind state, also known as cross-state air pollution. As the power sector adapts to rapid and significant changes, allowance trading programs have evolved to address changing industry and environmental challenges. More recent emissions trading programs have ushered in several new enhancements to the cross-state air pollution programs.2
The suite of Cross-State Air Pollution Rules (CSAPR, CSAPR Update, Revised CSAPR Update, and Good Neighbor Plan (GNP)) are designed to address cross-state air pollution, which affects downwind states’ ability to attain and maintain air quality standards. In 2023, the “Good Neighbor” Plan was finalized to secure significant reductions in ozone-forming emissions of nitrogen oxides (NOX) from power plants and industrial facilities. On June 27, 2024, the Supreme Court of the United States granted emergency applications seeking a stay of the Good Neighbor Plan pending judicial review. Since this occurred after the 2023 ozone season and compliance determination, 2023 information is included in this year’s report, and subsequent changes will be noted in future reports.
The ARP and the suite of CSAPR programs apply to large electricity generating units – boilers, turbines, and combined cycle units – that burn fossil fuel, serve generators with nameplate capacity greater than 25 megawatts, and produce electricity for sale.
In 2011, EPA issued the Mercury and Air Toxics Standards (MATS), establishing national emission standards for mercury and other hazardous air pollutants (HAPs) for new and existing coal- and oil-fired power plants. The power plants affected by these programs include a range of unit types, including units that operate year-round to provide baseload power to the electric grid, as well as units that provide power only on peak demand days. On April 25, 2024, the EPA announced requirements to strengthen and update MATS for power plants, based on an evaluation of the residual risk and technology review (RTR).
The ARP, the CSAPR programs, and MATS have together delivered substantial reductions in power sector emissions of SO2, NOX, and hazardous air pollutants, along with significant improvements in air quality and the environment. In addition to the requirements of the power sector emission control programs described in this report, a variety of power industry trends have contributed to further declines of SO2, NOX, and hazardous air pollutant emissions.
Learn more about EPA's Power Sector Programs.
Figure 1: Program History Timeline
Acid Rain Program (ARP)
- In 2023, the ARP SO2 requirements applied to 3,236 fossil fuel-fired units at 1,135 power plants across the country; the ARP NOX program requirements applied to 429 units at 199 power plants.
Cross-State Air Pollution Rule (CSAPR), CSAPR Update, Revised CSAPR Update, and GNP
- In 2023, there were 2,041 regulated emissions sources at 641 power plants in the CSAPR SO2 programs. Of those, 1,640 (80 percent) were also covered by the ARP.
- In 2023, there were 2,041 regulated emissions sources at 641 power plants in the CSAPR NOX annual program and 2,433 regulated emissions sources at 783 power plants in the CSAPR NOX ozone season programs. Of those, 1,640 (80 percent) and 2,027 (83 percent), respectively, were also covered by the ARP.
Mercury and Air Toxics (MATS)
- In 2023, 352 units at 161 power plants were covered by the MATS program.
Find the latest emissions and controls data on Latest Emission Comparisons & Pollution Controls.
Figures
Figure 2: Map of Program Implementation
Figure 3: Electricity Generation from Affected Power Plants
Figure 4: Regulated Emissions Sources
1 Such trading programs are also known as “emissions trading programs,” “allowance trading programs” or “cap-and-trade” programs.
2 For example, the Revised CSAPR Update introduced budget adjustments to reflect retirements. The Good Neighbor Plan tightened budgets and introduced backstop daily emissions rates, allowance bank recalibration, and dynamic budgeting to promote additional controls and consistent operation of existing controls for a new ozone standard.