A case study is conducted to evaluate the photovoltaic (PV) performance in a horizontal and in an inclined PV solar thermal collector (PVT) for two different PVT geometries; the series flow and the parallel series flow. It is shown that the series flow gives a better photovoltaic performance at a horizontal PVT surface as compared to the parallel series flow. At mass flow rate of 0.03 kg/s and zero inclination angle (horizontal PVT surface), the PV efficiencies are 14.32 % and 14.25 % for series and parallel series flow, respectively. But for an inclined PVT surface, the parallel series performs better than that of the series flow. At mass flow rate of 0.03 kg/s and inclination angle of 45 °C, the PV efficiencies are 13.76 % and 13.87 % for series and parallel series flow, respectively. It can be concluded that the inclination angle is one of the essential parameters that can be used to evaluate any PVT design and make better comparison between different designs. It is also beneficial for researchers and PVT product designers to know the effectiveness of their collector designs for cooling the PV panel at the early product design stage and to base on the optimum inclination angle of the region.