In the photovoltaic water pumping (PVP) systems without batteries as energy storage, the role of dc / dc converter determines the performance and efficiency of the system. the dc/dc converter functions to adjust the output voltage in accordance with the voltage input of the load which is a dc motor. Because the load is a dc motor, the output converter voltage setting is not constant or varies according to the intensity of solar radiation. As a result, when the intensity of solar radiation is high, the voltage output converter is high so that the motor-rotation becomes faster. and the water volume be produced also becomes more. On the contrary, when the intensity of solar radiation is low, the voltage output converter goes down that the motor rotation is slowly and the water volume is pumped is also low. With the dc converter, voltage output can be adjusted to the intensity of solar radiation. These effects that the PVP system has the high efficiency and good performance.