The military used less energy in fiscal year 2013 than in any year since at least 1975, according to the U.S. Energy Information Administration.
The Department of Defense used 0.75 quadrillion British thermal units worth of energy in fiscal year 2013, compared with almost twice that much, 1.36 quadrillion Btu, in 1975.
Although the military was out of the energy-intensive Vietnam War by 1975, the cost of petroleum had remained low until the early 1970s, providing little motivation to use less energy.
The EIA also reported that the DOD’s share of energy use by the federal government fell from 87 percent in 1975 to 78 percent in federal year 2013.
DOD energy use is divided into installation and operational uses, the latter of which accounts for the 70 percent of energy used for transporting and sustaining military operations. The Air Force used just more than half of operational energy in fiscal year 2013, mainly for jet fuel.
Meanwhile, the Army used the biggest share of installation energy, consuming about a third of the total.
While the wind down of combat operations in Afghanistan helped to lower energy use, several other initiatives also contributed, the EIA said.
The 2007 Energy Independence and Security Act included a goal to reduce energy use in federal buildings and a mandate to cut petroleum use in noncombat vehicles.
The DOD has also been developing ways of generating energy at the points of operations rather than relying completely on costly transportation of fuels.