In summary, a very simple but accurate procedure to model the photovoltaic water pumping system has been presented. The procedure is applied to the Solar Star 1000 pumping system to arrive at a model that predicts the volume flow rate, given the head and the irradiance. The model predicts the flow rate to within 8% of the measured values. The deviation, though small, is attributed to fluctuations in the solar irradiance and unsteady module temperatures during the measurements.