China and India are heavily dependent on high-carbon fossil fuels. This article elaborates the implications of low-carbon energy transitions in the two countries, which can mitigate their serious contribution to climate change while allowing economic growth. Three modelling case studies are presented: for the Chinese power sector, the economy of Beijing and rural Indian households without access to electricity. They demonstrate a significant reduction in greenhouse gas emissions and energy use, while costs are likely to increase. Financial assistance and technology transfer will be needed to support their efforts towards a climate-friendly low-carbon economy.