argest energy consumer Energy usage of the United States military United States Department of Defense Source 4.6 billion US gallons of fuel making some attempts one of the biggest energy consumers in the world U.S. Department of Defense (DoD) http://en.wikipedia.org/wiki/Energy_usa ... s_military United States Department of Defense 4.6 billion US gallons of fuel 4.6 billion US gallons of fuel thanks wiki United States Department of Defense