In this paper, the study was conducted on the subject of the hybrid electric vehicles used by the military, and analyzed the energy sources for fuel economy considering energy supply to the mission equipments. For the analysis of the vehicles, a method based on the geometry and some assumptions was applied with basic vehicle dynamics. The sources of energy supply in the military hybrid electric vehicles are Engine, Battery and Ultra-capacitor. The optimal operation point between Engine, Battery and Ultra-capacitor can be found by minimizing energy consumption of driving powertrain and mission equipments. Using fuel efficiency of the vehicle during the driving cycle, it was possible to analyze the character of energy sources.