A hybrid wind/photovoltaic/fuel cell generation system is designed to supply power demand. The aim of this design is minimization of annualized cost of the hybrid system over its 20 years of operation. Optimization problem is subject to reliable supply of the demand. Three major components of the system, i.e. wind turbine generators, photovoltaic arrays, and DC/AC converter, may be subject to failure. Also, solar radiation, wind speed, and load data are assumed entirely deterministic. System costs involve investments, replacement, and operation and maintenance as well as loss of load costs. Prices are all empirical and components are commercially available. An advanced variation of Particle Swarm Optimization algorithm is used to solve the optimization problem. Results reveal the impact of component outages on the reliability and cost of the system, so they are directly dependent on components' reliabilities, i.e. outages result in need for a larger generating system for supplying the load with the acceptable reliability. Additionally, it is observed that the inverter's reliability is an upper limit for the system's reliability. Moreover, an approximate method for reliability evaluation of the hybrid system is proposed which considerably reduces the time and computations. (C) 2009 Elsevier Ltd. All rights reserved.