A two-tiered approach to environmental regulation in the United States has long allowed existing coal-fired power plants to emit air pollutants at far higher rates than new facilities. The potential for reducing the emissions of existing coal-fired facilities is quantified via two hypothetical scenarios: the installation of available retrofit control technologies, or the imposition of New Source Performance Standards (NSPS). Available control technologies could have reduced year 2005 emissions by 56% for NOx and 72% for SO2 for a cost of $11.3 billion/year (2004$), likely yielding far larger benefits to human health. Slightly more emission reductions would be achieved by upgrading or replacing existing facilities to achieve the NSPS emissions limits required of all new facilities. Potential CO2 reductions are more speculative due to the emerging nature of carbon capture and efficiency retrofit technologies. Recent policies such as the Cross-State Air Pollution Rule would likely achieve most of the NOx and SO2 reduction potential identified by the scenario analyses for grandfathered facilities. However, escalating obstacles to new generation capacity may perpetuate the reliance on an aging fleet of power plants, resulting in higher rates of coal consumption and CO2 emissions than could be achieved by new or retrofit units. (C) 2011 Elsevier Ltd. All rights reserved.