This regulation establishes new standards and guidelines under Section 111 of the Clean Air Act to limit greenhouse gas (GHG) emissions from fossil fuel-fired electric generating units (EGUs). Key provisions include:
- New Source Performance Standards (NSPS): Sets emission limits for new, modified, and reconstructed fossil fuel-fired EGUs.
- Emission Guidelines: Provides guidelines for existing fossil fuel-fired EGUs to reduce GHG emissions.
- Repeal of the Affordable Clean Energy (ACE) Rule: Revokes the previous ACE rule, which had set less stringent standards.
The EPA determined that the best system of emission reduction (BSER) for new coal-fired units is the most efficient demonstrated steam cycle combined with best operating practices, rather than carbon capture and storage, due to cost and feasibility considerations. The BSER is determined based on (i) technological feasibility, (ii) cost-effectiveness, (iii) environmental impact and (iv) energy requirements.The EPA has categorised new and reconstructed combustion turbines into three subcategories based on their operational load (low, intermediate and base) and also set compliance timeline.

