Enabling maximum decarbonization from districts in Kyoto through rooftop PVs by integrating with EVs as battery

• Rooftop PV only system is suited to decarbonize the central part of the city. • PV systems integrated with EVs are highly effective in residential districts. • PV + EV has nearly double cost savings than PV only system in residences in 2030. Urban decarbonization is critical to addressing climate change, especially in densely populated areas facing spatial constraints for renewable energy deployment. This study evaluates the “SolarEV City Concept,” integrating rooftop photovoltaic (PV) systems with electric vehicles (EVs) as energy storage at a district scale in Kyoto, Japan. Using 1 × 1 km mesh analysis, we examine optimal rooftop PV capacity, energy demand, and the techno-economic feasibility of “PV only” and “PV + EV” systems under future cost and policy scenarios. Results show significant district-level variation: central urban areas achieve high PV self-consumption but low self-sufficiency due to limited rooftop space, while suburban districts achieve up to 90 % CO₂ emission reductions, high self-sufficiency, and substantial cost savings through PV-EV integration. These findings encourage prioritizing “PV + EV” systems in suburban areas, expanding EV adoption, and enhancing grid flexibility for inter-district energy sharing. This study highlights the transformative potential of coupling decentralized energy generation with mobile storage to enhance urban energy resilience, reduce fossil fuel dependence, and advance equitable energy transitions globally.