This paper deals with the optimal design of a stand-alone hybrid photovoltaic and fuel cell power system without battery storage to supply the electric load demand of the city of Brest, Western Brittany in France. The proposed optimal design study is focused on economical performance and is mainly based on the loss of the power supply probability concept. The hybrid power system optimal design is based a simulation model developed using HOMER. In this context, a practical load demand profile of Brest city is used with real weather data.