In this paper a detailed sizing method of stand-alone Photovoltaic–Wind hybrid systems is proposed and evaluated by the design and the development of flexible software basing on techno-economic analysis and using Object-Oriented Programming. First, a short review of the different sizing programs is given after, a detailed sizing methodology for PV–Wind systems is presented; finally, new software for sizing such systems is conceived. This computer program is building around fundamentals photovoltaic and wind generators models, storage capacity model, Loss of Power Supply Probability (LPSP) algorithm and a proposed techno-economic algorithm to determine the system that would guarantee a reliable energy supply with a lowest investment.