Rooftop photovoltaic (PV) systems reduce reliance on fossil fuels but may unintentionally exacerbate urban heat. This study investigates the competing thermal effects of rooftop PV –microclimate warming versus panel shading through environmental monitoring and building energy simulations during July 2024 heatwaves in a humid subtropical climate. Field measurements showed that PV installations elevated ambient temperatures by over 5 °C compared to conventional bare roof, creating localized “PV heat islands”. Energy simulations of top-floor spaces revealed that PV-induced warming fully offset shading benefits, resulting in a net 1.5 % increase in cooling energy demand. While generating 71 % of monthly electricity demand at 50 % coverage, PV-induced warming significantly increased occupants ‘Extreme Danger’ heat exposure by 29.8 % during power outages. This highlights a critical resilience paradox: while rooftop PV systems enhance energy sustainability, they may compromise thermal safety during extreme heat. These findings highlight the need for climate-adaptive PV designs that balance energy generation with urban heat mitigation, particularly in heat-vulnerable urban areas.