The real penetration of renewable energy sources (RES) under varying weather conditions required an optimal sizing of hybrid renewable power generation systems. The present paper proposes a methodology based on iterative technique, to perform the optimal sizing of a stand-alone hybrid photovoltaic/wind/hydrogen system supplying a desalination unit which feeds the area's inhabitants with fresh water. The methodology aims at finding the optimal technical-economic configuration among a set of systems components. Taking into account the models of the main hybrid system components and the hourly meteorological data and load profile for any site located worldwide, the recommended algorithm gives all possible configurations that can completely cover the fresh water requirements of isolated consumers. Afterward, the optimal configuration is predicted on the basis of the minimum initial investment cost. A case study is conducted to analyze a hybrid project, which is designed to supply a seawater desalination unit installed on the Kerkennah islands located in the south of Tunisia. (C) 2015 Elsevier Ltd. All rights reserved.