Abstarct: The photovoltaic water pumping system (PVWPS) is emerging as one of the best options for pumping water due to simple installation, maintenance, and long life-time operation. However, these systems suffer from some major disadvantages such as high capital cost as well as low reliability under variable weather conditions during the irrigation process. Therefore, the effective design and optimal sizing of components are essential for a sustainable and proper operation which significantly result in the reduction of costs. Hence, in this study, the required pumping power was determined with the aim of supplying the required water in a rice paddy with an area of one hectare located in northern Iran according to the required crop flow rate. Then with determining the optimum slope for the installation of PV array, the optimal number of PV modules required to supply the power of the motor-pump was determined using the NSGA-II optimization algorithm. Also, a battery bank was utilized as a backup system to increase system reliability and sustainability in cloudy or rainy days. For protecting the batteries from over-charge and over-discharge, charge controllers were employed. Suggesting Power Purchase Agreement (PPA) to compensate for the high cost of PVWPS compared to conventional pumping systems in non-irrigation months of the year is probably the most important part of this research along with the economical comparison of PVWPS and conventional pumping systems. The results indicate that the capital and installation costs of the off-grid and grid connected PVWPS in this study were ۲.۱۴۱ and ۲.۴۱ times as the capital and installation costs of the conventional pumping system. However, for the project life-time of ۲۵ years, the total life-cycle costs of the conventional pumping system were ۱.۲۶۸ and ۲.۴۴ times as those of the mentioned systems, respectively. The results of PVWPS environmental impact assessment showed that the system was able to reduce CO۲ emissions to the atmosphere by about ۸.۷۲۸ tons, equivalent to approximately ۱۶ mature trees (or ۳۰ young trees) during the irrigation period. Also, the conventional pumping system produces an average noise level of ۸۶ dB, which is not a healthy level of noise. It indicates the tangible superiority of PVWPS over its competitor in noise level context.