Modeling and optimization of a hybrid power system comprising several different power sources provides a tool to size the individual power system components and to optimize the power system control variables. The hybrid power system is required to meet the demanding requirements of long duration mission of unmanned surface vehicles (USVs). These demands for power may be met by a combination of renewable energy resources, conventional fossil-fueled energy sources and energy storage options. The hybrid power system being considered here comprises a solar array, an ocean wave energy converter, a fuel cell system, a diesel generator and a lithium ion battery pack. The approach gives high priority to natural energy sources, i.e. solar and wave energy converter within the discrete time domain followed by minimization of a cost/energy ratio associated with the storage based energy elements, i.e., battery pack, fuel cell system (H(2) storage) and diesel generator (fuel storage). The results show that optimization has been achieved with 19.6% contribution by solar power during daylight hours and 5.53% contribution of the wave energy harvester to meet the load demands. The battery bank contributes 39.7% which is 4.4% above the fuel cell contribution. The diesel generator does not contribute during the stealth mode of operation of the USV mission. The average percentage energy contribution from each source confirmed the priorities based on minimization of cost/energy ratio of hybrid power elements. However, in the first case study the optimized result shows a constraint violation when fuel cell performs slightly higher than the battery. Later, in the second case study, it is corrected by increasing the size of the battery bank. (C) 2011 Elsevier B.V. All rights reserved.