Highlights •The coupled heat transfer process of rooftop photovoltaic shading units and indoor heat gain are analyzed.•The energy-saving potential of photovoltaic rooftops compared to traditional rooftops is revealed.•The energy-saving performance of photovoltaic and traditional rooftops under different roof reflectivity are summarized.•The impact of the optimal tilt angle on the power generation of the photovoltaic rooftop are discussed.•An energy-saving scheme for applying rooftop photovoltaic systems in hot summer areas is proposed.