Transportation is undergoing rapid electrification, with electric buses at the forefront of public transport, especially in China. This transition, however, could strain electricity grids. Using a large-scale dataset with over 200 million global positioning system records from 20,992 buses in Beijing, we explore the technical, economic and environmental implications of transforming public transport depots into renewable energy hubs. Here we show that solar photovoltaic reduces the grid’s net charging load by 23% during electricity generation periods and lowers the net charging peak load by 8.6%. Integrating energy storage amplifies these reductions to 28% and 37.4%, respectively. Whereas unsubsidized solar photovoltaic yields profit 64% above costs, adding battery storage cuts profits to 31% despite offering grid benefits. Negative marginal abatement gains for CO₂ emissions underscore the economic sustainability. Our findings provide a model for cities worldwide to accelerate their commitments towards sustainable transport and energy systems.