Abstract A detailed mathematical models is developed for a fully wetted absorber photovoltaic thermal (PVT) collector with and without phase change material (PCM) under its absorber channel. Thermal and electrical investigations were carried out using PCM OM37 for typical winter and summer days in Lyon, France. The system is analyzed under energy and exergy performances. PCM incorporation in a water PVT absorber improves the performance of system in terms of electrical and thermal parameters. Enhanced electrical and thermal energy is attributed to dissipation of excess heat of PV module by latent heat absorption mechanism that reduces the PV module temperature and release heat at the night as well, provides better electrical and thermal stabilities to the system. Overall thermal energy and overall exergy of PVT system for a winter day as well as for a typical summer day, are found to be strongly in favor of adding PCM. The effects of mass of PCM on module temperature, outlet water temperature, and PV module electrical efficiency, have also been investigated. During sunshine hours, increment in the PCM mass up to its optimal value decreases temperature resulting in higher electrical efficiency and also allows providing higher water temperature at the nighttime.