The costs for solar photovoltaics, wind, and battery storage have dropped markedly since 2010, bringing new prospects for the widespread penetration of renewables and extensive power-sector decarbonization. This study shows that if cost trends for renewables continue, 62% of China's electricity could come from non-fossil sources by 2030 at a cost 11% lower than a business-as-usual approach. China's power sector could cut half its 2015 carbon emissions at a cost about 6% lower than business-as-usual conditions.