Alternative-energy-vehicles deployment delivers climate, air quality, and health co-benefits when coupled with decarbonizing power generation in China

China is the world's largest carbon emitter and suffers from severe air pollution, which results in approximately one million premature deaths/year. Alternative energy vehicles (AEVs) (electric, hydrogen fuel cell, and natural gas vehicles) can reduce carbon emissions and improve air quality. However, climate, air quality, and health benefits of AEVs powered with deeply decarbonized power generation are poorly quantified. Here, we quantitatively estimate the air quality, health, carbon emission, and economic benefits of replacing internal combustion engine vehicles with various AEVs. We find co-benefits increase dramatically as the electricity grid decarbonizes and hydrogen is produced from non-fossil fuels. Relative to 2015, a conversion to AEVs using largely non-fossil power can reduce air pollution and associated premature mortalities and years of life lost by similar to 329,000 persons/year and similar to 1,611,000 life years/year. Thus, maximizing climate, air quality, and health benefits of AEV deployment in China requires rapid decarbonization of the power system.