Unlocking the energy decarbonization potentials of rooftop photovoltaic-thermal collectors: A case study of Tarragona province's residential communities

The residential sector is a major contributor to global energy demand and carbon emissions, underscoring the need for scalable decarbonization strategies. This study assesses the technical, economic, and environmental potential of deploying simplified rooftop hybrid photovoltaic-thermal (PV-T) collectors across residential communities in Tarragona Province, Spain. Using high-resolution hourly simulation and an energy community framework, the analysis covered 184 municipalities with annual solar irradiation ranging from 1599.4 to 1804. 1 kWh/m 2 /yr . Flat-box, water-based PV-T collectors connected directly to municipal water supplies were modeled without auxiliary storage or pumping systems. Results show that with just 3.85% rooftop surface occupancy ( 0.125 m 2 /capita ), the proposed configuration can meet 11.8% of the domestic hot water (DHW) energy and 1.8% of the electricity demand collectively in the province, delivering 808.4 - 896.9 kWh th /m 2 and 233.0 - 259.6 kWh e /m 2 annually across the municipalities. The proposed integration of PV-T collectors economically attractive, achieving a payback of 5 - 6 years, net present values (NPV) of €1485.82 - €1755.86/m 2 , and a levelized cost of exergy (LCOEx) between 8.43 - 9.95 c€/kWh across the municipalities. Environmentally, the installations could mitigate approximately 29.3 ktCO 2 -eq annually, at a specific avoidance cost of €13.80/tCO 2 -eq . These findings demonstrate that simplified integration of rooftop PV-T collectors offer a cost-effective and replicable pathway for decarbonizing energy use in the residential sector.