The United States EPA is proposing new source performance standards for emissions of carbon dioxide (CO2) for new affected fossil fuel-fired electric utility generating units (EGUs). The EPA is proposing these requirements because CO2 is a greenhouse gas (GHG) and fossil fuel-fired power plants are the country’s largest stationary source emitters of GHGs. The proposed requirements, which are strictly limited to new sources, would require new fossil fuel-fired EGUs greater than 25 megawatt electric (MWe) to meet an output-based standard of 1,000 pounds of CO2 per megawatt-hour (lb CO2/MWh), based on the performance of widely used natural gas combined cycle (NGCC) technology. In its base case analysis, the EPA does not project any new coal-fired EGUs without CCS to be built in the absence of this proposal through 2030. New coal-fired or pet coke-fired units could meet the standard either by employing carbon capture and storage (CCS) of approximately 50% of the CO2 in the exhaust gas at startup, or through later application of more effective CCS to meet the standard on average over a 30-year period. The 30-year averaging option could also provide flexibility for owners and operators of coal or pet coke units implementing CCS at the outset of the unit’s operation that were designed and operated to emit at less than 1,000 lb CO2/MWh to address startup concerns or short term interruptions in their ability to sequester captured carbon dioxide.