Under CAA section 111(b), EPA sets New Source Performance Standards (NSPS) for GHG emissions from new, modified, and reconstructed fossil fuel-fired power plants. In 2015, EPA finalized regulations to limit GHG emissions from new fossil-fuel fired utility boilers and from natural gas-fired stationary combustion turbines. That rulemaking determined that the best system of emission reduction (BSER) for greenhouse gases (GHGs) for newly constructed coal-fired steam generating units (i.e., EGUs) is efficient generation in combination with partial carbon capture and storage, the BSER for natural gas-fired base load combustion turbine EGUs is efficient generation (i.e., the use of combined cycle technology), and the BSER for non-base load and multi-fuel-fired combustion turbine EGUs is the use of clean fuels. In 2018, EPA proposed to revise the BSER for coal fired EGUs to be efficient generation. To date, that proposed action has not been finalized. The purpose of this action is to conduct a comprehensive review of the NSPS and, if appropriate, amend the emission standards for new fossil fuel fired EGUs. EPA anticipates issuing a proposed rule in spring 2023, and promulgating a final rule by Summer 2024.