A hybrid wind/solar powered reverse osmosis desalination system has been modeled and simulated. The results of the simulation have been used to optimize the system for the minimum cost per cubic meter of the desalinated water. The performance of the hybrid wind/solar powered RO system has been analyzed under Dhahran, Saudi Arabia, weather data for a typical year. The performance has been evaluated under a constant RO load of 1 kW for 12 h/day and 24 h/day. The simulation results revealed that the optimum system that powers a I-kW RO system for 12 h/day that yields a minimum levelized cost of energy comprises 2 wind turbines, 40 PVs modules and 6 batteries and the levelized cost of energy of such system is found to be 0.624 $/kW h. On the other hand, for a load of 1-kW for 24 h/day, the optimum system consists of 6 wind turbines, 66 PVs modules and 16 batteries with a minimum levelized cost of energy 0.672 $/kW h. Depending on the salinity of the raw water, the energy consumption for desalination ranges between 8 and 20 kW h/m(3). This means that the cost of using the proposed optimum hybrid wind/solar system for water desalination will range between $3.693/m(3) and $3. 812/m(3) which is less than the range reported in the literature. (C) 2013 Elsevier Ltd. All rights reserved.