Photovoltaic (PV) pumping offers the possibility of supplying water to remote and desert regions for their daily needs. The sizing of the PV pumping systems is a very significant step in order to optimize the power peak of the PV array and to ensure the best choice of the motor, the pump and the inverter. Two mathematical models were proposed in this article to contribute in the studies of PV pumping sizing. These models link directly the operating electrical power to the water flow rate of the pump versus total head. These models are based essentially on the experimentation of pumps on CDER PV pumping test facility. Two pumping systems are tested: the first uses a centrifugal pump and the second uses a positive displacement pump. The results obtained by the models are very satisfactory. Also, the models enabled us to simulate the electrical and hydraulic performances of two tested pumps. The performances are calculated using the measured meteorological data of different sites located in Sahara and coastline regions of Algeria.