Small-sized hybrid wind-hydro-solar power generation systems may be designed to solve the power supply problem in some rural areas. Optimal design models are developed to design the hybrid generation systems including battery banks and to provide the optimum system configuration. It is ensured that the annualized cost of the systems is minimized while satisfying the required loss of power supply probability. A genetic algorithm is used to find the optimum configuration. Moreover, four membership grades of the systems, such as the reliability, the economical efficiency, the complement and the environmental benefit, are created by a linearly-weighted fuzzy algorithm to search the configuration. The optimal algorithms are applied to a practical project. The optimal design of the project is gotten and analyzed, which shows that the complement and the environmental benefit are taken full advantage of, and the corresponding system cost is minimized with enough power supply reliability.