Existing Power Plants
EPA is regulating greenhouse gas emissions from power plants under Section 111 of the Clean Air Act which allows EPA and the states greater flexibility in crafting and implementing a standard. Emissions from new and modified power plants have been finalized under Section 111(b) as described below. Emissions for existing power plants are still being developed under Section 111(d).
In August 2018, EPA proposed GHG emission guidelines for existing fossil fuel-fired power plants and accompanying revisions to how GHG guidelines are implemented in the Affordable Clean Energy (ACE) Rule. If finalized, the rule would direct states to require coal-fired power plants to use prescribed technologies to improve their heat rate, a measure of efficiency.
The ACE Rule is expected to reduce power sector emissions by about 1 percent from a business-as-usual scenario. It would replace the Clean Power Plan, finalized in August 2015, that had set state-specific emission rates and provided various market-based flexible compliance provisions.
The Clean Power Plan has never been implemented because of a U.S. Supreme Court stay issued in February 2016. The formal repeal of the rule is being implemented by EPA at the same time that the ACE Rule, which would replace the Clean Power Plan, is being developed.