In recent years, hundreds of large power plants have retired across the United States, with hundreds more nearing the end of their useful lives. At the same time, large-scale growth in natural gas, wind, and solar power is changing the nation’s electricity mix. Although much research has been carried out on the decommissioning of nuclear power plants, far less work has examined what happens to plant sites when generating units that burn coal, oil, or natural gas are retired or when wind or solar facilities reach the end of their lives. This report describes the options faced by plant owners after a plant has been retired. It examines the costs associated with decommissioning different plant types and highlights key issues that present opportunities and challenges for generating companies, regulators, local governments, and communities. Key issues include the large costs of environmental remediation and monitoring for coal-fired power plants and their combustion residuals, whether companies in deregulated markets are adequately saving for decommissioning, state and local policies for wind and solar decommissioning, and the economic and fiscal impacts of decommissioning power plants in rural areas.