Supplying water in desert areas or isolated sites is the perfect job for along sun pumping systems. However, due to their relatively high cost, the sizing of these systems implies the use of an accurate tool. This paper presents a method that Could be used for the sizing of an along the sun pumping system based on energetic considerations, simple modeling and fitting methods. The model described allows to predict the flow rate hour per hour for a given daily solar irradiance profile. It uses a three-phase induction machine, a voltage inverter and a centrifugal pump. Some experimental results are also confronted with the calculated ones in order to show the accuracy of the model. The accuracy of the model is shown to be good and essentially depends on the precision used to model each element in the overall system. (C) 2008 Elsevier Ltd. All rights reserved.