Rooftop photovoltaics and energy equity: quantifying socio-energy trade-offs in urban energy transitions

Rooftop photovoltaic systems, while central to urban decarbonization, can unintentionally exacerbate social inequalities through uneven thermal and economic outcomes. This study demonstrates that rooftop PV deployment generates inequitable socio-energy trade-offs within cities, where disadvantaged communities bear higher societal costs for the same clean-energy gains. To quantify these disparities, we developed a Socio-Energy Trade-off Index (SETI) that links PV-induced warming, heat-related health risks, and economic benefits within an integrated WRF-forced Canopy Model – Building Energy Model framework applied to six global cities. Results reveal that PV-induced warming is both widespread and unequal, with midday temperature increases from 0.27 °C in Cairo to 0.58 °C in Guangzhou and a Gini index up to 0.322. Less developed communities consistently record higher SETI values due to compact urban form and limited financing access. Furthermore, technological improvements—such as enhanced panel efficiency and emissivity—reduce total trade-offs but disproportionately benefit formal, self-financed neighborhoods, widening relative inequity. These findings reframe the Photovoltaic Heat Island (PVHI) effect as an energy-system externality, emphasizing that equitable solar deployment requires integrating efficiency and justice in urban energy transitions.