Egypt is now facing the problem of invasion of the desert and the scarcity of water for agriculture and lack of energy in remote locations. This research has been concentrated on determination of critical irradiance and overall efficiency of PV panel and centrifugal pump system was used to lift water from wells. Therefore, the experimenters were carried out in summer and winter 2014/2015 at Faculty of Agriculture, Kaferelsheikh University, Egypt. The experimental studies were confined to determine: the effect of daytime, solar radiation intensity and 2, 3 and 4m water heads. The results indicated that, the critical irradiance at heads of 2m, 3m and 4m were 257.14, 328.57 and 628.57W/m2, respectively in summer. It was 242.86, 285.71 and 571.43W/m2 at water heads of 2, 3 and 4m, respectivelyin winter. The maximum values of pump discharge were 48.82, 47.92, 44.91ℓ/min at heads of 2, 3, 4m, respectively in daytime of 1PM and summer. The maximum values of pump discharge were 48.83, 47.54, 44.49ℓ/min at 2, 3, 4m, respectively in daytime of 12PM and winter. The maximum time intervals were about of 10, 9.5 and 9h in summer and 8.0, 7.5 and 7.0h in winter at 2, 3 and 4m water head, respectively. When solar radiation increased by 42.86% and the output electric power by 36.67%, the pump discharge and hydraulic power increased by 27.39 and 34.22% in summer 34.47 and 13.33%, winter, respectively at head of 4m. Winter in comparison to summer, the overall efficiency of system increased by 35.02, 37.78 and 40.57% at water heads of 2, 3 and 4m, respectively.