This morning, the Environmental Protection Agency (EPA) released its proposed replacement for the Clean Power Plan (CPP) titled the “Affordable Clean Energy Rule,” which would regulate greenhouse gas emissions at existing coal-fired power plants. The proposed rule gives discretion to states for determining the greenhouse gas performance standards achievable for existing coal-fired power plants within their state. Specifically, the proposed rule would require states to evaluate a menu of heat rate improvement options and, taking into account the unit’s remaining useful life and other factors, determine the lb/MWh CO2 emission rate achievable at each affected unit. While the rule proposes to allow for emissions averaging among affected units at an individual source, it does not provide for broader averaging or emissions trading. To facilitate the heat rate improvement projects, EPA also has proposed an option for states to adopt a new emissions test under the New Source Review program for EGUs that is based on both hourly and annual emissions.