Photovoltaic (PV) technology is considered one of the most effective and promising renewable sources of energy. The PV system’s efficiency strongly depends on its operating temperature, which acts as a defect to the electrical efficiency by increasing over 25 °C. In this work, a comparison was performed between three traditional polycrystalline solar panels simultaneously at the same time and under the same weather conditions. The electrical and thermal performances of the photovoltaic thermal (PVT) system integrated with a serpentine coil configured sheet with a plate thermal absorber setup are evaluated using water and aluminum oxide nanofluid. For higher mass flow rates and nanoparticle concentrations, an improvement in the PV modules short-circuit current (Isc) and open-circuit voltage (Voc) yield and electrical conversion efficiency is achieved. The enhancement in the PVT electrical conversion efficiency is 15.5%. For 0.05% volume concentration of Al2O3 and flow rate of 0.07 kg/s, an enhancement of 22.83% of the temperature of PVT panels’ surface over the reference panel has been obtained. An uncooled PVT system reached a maximum panel temperature of 75.5 °C at noontime and obtained an average electrical efficiency of 12.156%. Water and nanofluid cooling reduce the panel temperature by 10.0 °C and 20.0 °C at noontime, respectively.