Winter climate–energy trade-offs of rooftop photovoltaics under green, cool, and super cool roofs in cities

Urban rooftop photovoltaic systems are increasingly integrated with green, cool and super cool roofs to simultaneously support renewable energy generation, building energy efficiency and climate adaptation. However, whether these objectives remain aligned during winter is poorly understood. Here we show that winter atmospheric stability largely confines rooftop thermal effects to the near-roof environment, resulting in only modest reductions in ambient temperature (−0.2 to −1.0 °C). In contrast, substantial cooling occurs at roof and photovoltaic panel surfaces, with panel temperatures decreasing by up to 14.7 °C. These cooler operating conditions increase photovoltaic electricity generation by 2.1–6.1%. However, the same cooling processes enhance nocturnal heat loss through building envelopes, increasing winter heating load by 1.1–3.48%. These findings reveal a previously overlooked winter climate–energy trade-off, emphasizing the need to balance photovoltaic efficiency with building thermal performance in urban energy transitions.