The Department of Defense is the largest single consumer of energy in the United States. In 2006, it spent $13.6 billion to buy 110 million barrels of petroleum fuel (about 300,000 barrels of oil each day), and 3.8 billion kWh of electricity. In pursuit of Energy Security the US Department of Defense is assembling a diversified energy portfolio tailored to the assets and needs of individual facilities necessary for national defense. Without specifying it as such, DoD is taking a holistic approach to their transformation.