Renewable energy is gaining currency around the globe, but China and the United States are central to its development. They are the world's top-two countries in terms of energy consumption, net oil imports, and carbon emissions, as well as gross domestic product (GDP) and manufacturing. Their large territories harbor some of the best sites to generate renewable energy. If the United States and China cooperate-and compete-effectively, renewable energy can contribute to economic growth, energy security, and climate change mitigation. The past two years saw important developments, including a bilateral agreement to phase down hydrofluorocarbon emissions (June 2013) and a joint announcement to reduce greenhouse gas emissions (November 2014). China is often touted for its rapid adoption of renewable energy technologies. Long-term industry plans and new legislation suggest Beijing will maintain this policy direction, in line with its overall expansion of energy production capacity. In the United States, by contrast, renewable energy is a divisive issue. There are disagreements about how, if at all, the government should support alternative energy sources when natural gas is abundant, emissions are declining, and energy demand is slowing.