In this paper, a theoretical study of a hybrid photovoltaic cum thermal (PV/T) solar system is presented. The system investigated consists of a solar cell panel for electricity generation, and air/water is made to flow in a duct placed below the surface on which the solar cells are mounted to extract heat from the system, thereby cooling the cells and increasing their efficiency. The mathematical model developed for predicting the performance of the system is based on energy balance equations written for the various nodes of the system, and the coupled differential equations obtained are solved by using the forward step marching finite difference technique. The temperatures of the solar cells and of the outlet fluid as a function of time are predicted. The performance of the PV/T system is compared with that of a conventional photovoltaic panel.