Renewable energy has stronger relationship with human development than ever. According to extensive studies on existed stand alone wind and photovoltaic (PV) hybrid power system, a novel method of optimum sizing was presented to obtain proper combination of wind and solar generation and effectively analyzed economic performance. Annual total cost model was proposed and genetic algorithm (GA) was used to search global minimum solution. Compared with other system models, it simplified solving process, improved computational efficiency, and effectively avoided premature convergence. It is helpful to program the hybrid power system and popularize stand alone generating system for home usage in remote area.