Future rooftop photovoltaics will weaken carbon mitigation but offer promising water and land benefits

Rooftop photovoltaics are widely recognized for the carbon mitigation benefits, yet uncertainties persist regarding their future dynamics and broader impacts on water and land. Here we develop a city-level integrated framework to quantify rooftop photovoltaics potential across 349 Chinese cities, and evaluate evolving carbon-water-land tradeoffs under shared socioeconomic and representative concentration pathways. By 2050, projections across 15 combined scenarios indicate China's rooftop photovoltaic areas will increase by 9.2 to 34.8 percent relative to 2020 levels. Installed capacity ranges from 7.19 to 9.05 terawatts in 2050, expanding rapidly in eastern coastal cities. Under a moderate socioeconomic and climate scenario, the national carbon mitigation benefits peak during 2035 to 2040, accumulating 2.04 to 2.18 gigatons of carbon dioxide equivalent by 2050. In contrast, the water and land saving benefits continue to rise, reaching 16.5 to 17.4 cubic kilometers and 281 to 297 thousand square kilometers by 2050. These findings underscore the critical need for multidimensional planning to optimize future sustainable photovoltaics deployment.