Solar-powered public transit: evaluating photovoltage deployment strategies for battery electric bus networks

As global cities transition toward low-carbon mobility, integrating photovoltaic (PV) technologies into battery electric bus systems has emerged as a promising solution to reduce grid dependency, operational costs, and greenhouse gas emissions. This study holistically evaluates three PV deployment strategies, namely onboard PV panels (solar-powered buses), station-based PV infrastructure, and a hybrid configuration, through a comparative analysis across multiple scenarios using an optimization-based framework. Using real-world data on charging patterns and irradiance conditions, we quantitatively investigate how each strategy affects grid load, return on investment (ROI), payback period, and discounted life-cycle economic performance. The results show that all PV-based strategies reduce electricity expenditure relative to the grid-only benchmark, while exhibiting different trade-offs in short-term cost-effectiveness, long-term economic value, and grid interaction. Under first-pass economic indicators, depot-based PV systems offer the shortest payback period and the highest ROI, whereas hybrid systems provide the most substantial grid peak shaving and the largest absolute annual savings. To further strengthen the economic comparison, we conduct a net present value analysis under different discount rates. The results show that although station-based PV remains more attractive from a short-term recovery perspective, the hybrid configuration delivers larger discounted lifetime net benefits, and its additional investment remains economically justifiable over the project life. A spatial analysis further categorizes global regions based on PV suitability, showing that tropical and subtropical cities are the most promising for large-scale implementation. Future projections incorporating PV and energy storage system (ESS) cost trends suggest that declining technology costs will substantially enhance investment performance, making PV deployment increasingly feasible by 2030–2035. Overall, the results provide actionable insights for transit agencies and policymakers seeking resilient, grid-friendly, and cost-effective energy strategies for public transportation electrification.