Regulated Emissions Sources
Regulated Emissions Sources Figures
Source: EPA, 2022
Last updated: 07/2022
Acid Rain Program (ARP)
- In 2021, the ARP SO₂ requirements applied to 3,243 fossil fuel-fired units at 1,150 power plants across the country; 493 units at 227 power plants were subject to the ARP NOₓ program.
Cross-State Air Pollution Rule (CSAPR)
- In 2021, there were 2,125 regulated emissions sources at 665 power plants in the CSAPR SO₂ programs. Of those, 1,713 (81 percent) were also covered by the ARP.
- In 2021, there were 2,125 regulated emissions sources units at 665 power plants in the CSAPR NOₓ annual program and 2,499 regulated emissions sources at 799 power plants in the CSAPR NOₓ ozone season program. Of those, 1,713 (81 percent) and 2,079 (83 percent), respectively, were also covered by the ARP.
Mercury and Air Toxics (MATS)
- The Mercury and Air Toxics Standards (MATS) set limits on the emissions of hazardous air pollutants from coal- and oil-fired electric utility steam generating units in all 50 states and U.S. territories. MATS was issued under section 112 of the Clean Air Act. EPA is including a summary of the mercury data submitted by regulated emissions sources in this report.
- In 2021, 406 units at 186 power plants reported hourly mercury emissions to EPA under MATS.
In general, the ARP and CSAPR programs (CSAPR, CSAPR Update, and the Revised CSAPR Update) 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. MATS applies only to coal- and oil-fired steam generating units (i.e., utility boilers). MATS does not apply to combustion turbines, combined cycle units, or to natural gas-fired utility boilers. 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. The ARP NOₓ program applies to a subset of these units that are older and historically coal-fired.