Regulatory processes, decisions, and mechanisms deeply affect power sector investment, operations, and emissions in complex and sometimes subtle ways. This paper describes developments and trends in power sector regulation and their impact on power sector emissions in the United States, European Union, and Brazil. The authors highlight major developments, debates, and examples of best practices in regulation that are important to emissions reduction, including use of energy efficiency as a power system resource, managing and integrating variable renewable resources, generator dispatch, and integrating carbon pricing with other emission-reduction policies. Drawing on the experiences in the U.S., EU, and Brazil, the authors also make recommendations for adapting these policies given China’s particular conditions and regulatory challenges.