The study aims to investigate the overall impact of rooftop photovoltaic (PV) systems on the energy performance of residential buildings in hot-humid climates. The study area spans over 100 km(2) encompassing 33,000 residential units in the city of Al-Khobar in Saudi Arabia. It examines the restrictions towards the utilizability of building rooftops for PV application. The total building rooftop area and its corresponding PV output at the urban scale level has been estimated with the help of geographic information systems and PV simulation tools. The secondary contribution by PV in terms of heat gain reduction has also been investigated through EnergyPlus simulation engine. It is found that villas and apartment buildings respectively offer 21% and 28% of their rooftops for PV application. Results suggest that solar PV can offset 19% of the electricity demand when 25% of the building roof is utilized, in addition to a cooling load reduction of 2% due to the shading effect of panels. For the total study area, the annual electricity generation potential for tilted and flat application of PV with the existing roofs conditions turns out to be 797 GWh and 757 GWh respectively. (C) 2018 Published by Elsevier Ltd.