The photovoltaic cells will exhibit long-term degradation if the temperature exceeds a certain limit. Photovoltaic cells are the heart of photovoltaic water pumping systems. In order to utilize PV power and increase photovoltaic water pumping system efficiency, it is necessary to keep PV cell temperature and cell reflection as low as possible. The purpose of this study is to investigate the possibility of improving the performance of a photovoltaic water pumping system. This is performed by spraying water over the photovoltaic cells. The results are compared with traditional systems. Experimental results show that the cells power is increased due to spraying water over the photovoltaic cells. This can significantly increase the system and subsystem efficiency and the pump flow rate when operating under different heads. Measurements of the short circuit current of the module, which is nearly temperature-independent, indicated that the water spray improved the system optical performance. (c) 2008 Elsevier Ltd. All rights reserved.