A mathematical model for a photovoltaic (PV) solar-powered water pumping system has been developed. It takes into account the effect of solar intensity and temperature on the power generated by the PV array, the torque-speed characteristics of the dc motor, the head-discharge characteristics of the pump, and the hydraulic losses in the pipeline. A computer program simulates the performance of the system under a specified solar condition by computing a series of quasi-steady states, each lasting for a short interval. By determining the operating point of the pump, the amount of water pumped during the simulation period is calculated. The computed results are compared with those obtained from actual tests on a 2-HP water pumping unit supplied from 4-kW PV array.