Hybrid power system sizing involves determination of local load and energy resources’ conditions as well as availability of generating system components. Each component of the system is preliminarily sized individually using prevailing load, resource and conversion system’s conditions. The Net Present Cost (NPC), Cost of Energy (COE) may be included in determining the configuration of the most optimal system that can meet all the desired power system’s goals. In order to refine the sizing and design process, a simulation software is used to select and size system components that can serve the load effectively. In this study, a Solar PV, Wind and Grid hybrid power system was systematically sized to meet the demand of a commercial consumer, East African School of Aviation (EASA). HOMER software was used to simulate the operation of the proposed HPS. The most suitable HPS was found to consist of Wind generation of an installed capacity of 200 kW, solar PV of 120 kW and the Grid. This system had an NPC of KSh 77,684,050 and a COE of KSh 8.34/kWh.