This study evaluated the electrical performance of a photovoltaic-thermal (PVT) system using water as a cooling fluid (PVT/w), with adaptation, in a photovoltaic module of a device for heating water without direct contact with the cell and with air as the secondary working fluid. The PVT/w system with forced and natural circulation was compared in a regime of thermal accumulation of hot water and supply by a boiler reservoir relative to the same PV panel with the original factory characteristics. The average system temperature, open circuit voltage, current and voltage with load, and generated electric power were analyzed during seven non-consecutive days, with ten repetitions every thirty minutes between 9:30 am and 2:00 pm in the city of Dourados-MS, Brazil, between June and July 2021. The PVT system with forced circulation (PVT/w_CB) presented the best electrical performance compared to the PVT system with natural circulation (PVT/w_SB), in the order of 3.7%.