This book describes how to optimize and to obtain the best performances of photovoltaic water pumping systems (PVWPS) by using simulation based on experimental data. We have presented a mathematical motor-pump model for PV applications which allow us to contribute in the studies of PV pumping sizing. The modeled motor-pump characteristic is flow rate-power (Q, P). The nonlinear relation between flow rate and solar power has been obtained experimentally in a first step and then used for performance prediction. The model proposed enabled us to simulate the electric and hydraulic performances of helical pumps versus the total water heads for different PV array configurations. The goals of the experimental work done in desert environment for a deep well are: - Selection of optimal combined PVWPS configuration in term of cost and demand of the load. - Determination of the effect of pumping head on PVWPS using the optimum PV array configuration, adequate to supply a DC Helical pump with an optimum energy amount, under the outdoor of desert environment. The best system efficiency has been obtained for the head of 80 m. We recommend the use of SQF submersible pump for a deep head.