In engineering, simulation is an effective and economical, commonly used to make preliminary or comparative studies, both during development (design) and normal operation of systems. Currently, several simulation tools, using HOMER, are used in academia. Thus, in this work, we present the principle of feasibility study and optimization of a stand alone hybrid system (wind-photovoltaic-diesel). Furthermore, we determined the price per kWh of electricity supplied by the stand alone hybrid system, which amounts to $ 1417 / kWh. The site considered in this study represents the Adrar site located in the south west Algeria. Thus, we have inferred from this work as part of a configuration of the stand alone hybrid system obviously depends on available energy resources and constraints. On the other hand we have highlighted the role of the renewable energy uses in reducing emissions of greenhouse gas (CO2 rate = 16086 kg / year for a system using only the generator diesel and is 599 kg / year for the stand alone hybrid system studied).