A conceptual design tool was built to explore power requirements of a hybrid-power system for Micro Air Vehicles (MAVs) comparable in size to the Cooper's Hawk. An inviscid aerodynamic code, Athena Vortex Lattice (AVL), and a motor-propeller analysis code, QPROP, provide overall lift, drag, and thrust data for power-required calculation as functions of many variables to include mass, platform geometry, altitude, velocity, and mission duration. Phoenix Technologies' Model Center was used to integrate multi-disciplinary components that employ specific power and specific energy of two power sources to determine power system mass required for a designated mission. The tool simulated a mission for the fixed wing Generic Micro Aerial Vehicle (GenMAV), and relative sizing between a high specific power source and a high specific energy source was investigated. Current small fuel cell technology provides inadequate specific power. It was found that a MAV-sized fuel cell-battery hybrid-power system would not perform better than a pure battery or battery-battery power system. A feasible fuel cell capability requirement of at least 325 W/kg matched with at least 921 W-hr/kg was identified as a fuel cell - Li-Po solution for a defined 30 min mission resulting in reduced power system mass compared to using only Li-Po batteries.