Hybrid energy systems can be efficient alternatives for supplying potable water to and satisfying the electrical loads of remote areas. The objective of this article is to optimize the size of a reverse osmosis desalination-based diesel and photovoltaic power plant for increasing fresh water availability and meeting the electrical load demand of a stand-alone region in Iran. The size of the battery bank, the area of the photovoltaic system, and the fuel consumption of the diesel generator within the proposed hybrid system are optimized so as to minimize the life cycle cost of the system. For this aim, a power management strategy is designed, and an efficient metaheuristic technique based on tabu search is used. The results are compared with those obtained by harmony search and simulated annealing algorithms. Furthermore, the effects of varying fuel cost, interest rate, photovoltaic initial cost, and battery initial cost on the economic parameters of the hybrid system are also discussed. From the results it is seen that the photovoltaic/diesel/battery/reverse osmosis desalination system is economically and environmentally advantageous to a single diesel system or a single photovoltaic system for the investigated region. Moreover, tabu search provides more promising results than the other investigated algorithms.