The U.S. Department of Defense defines installation energy security as the ability to assure access to reliable sources of energy and deliver that power to meet operational needs on its bases in the United States and abroad. The U.S. military needs safe, secure, reliable, and affordable energy to operate facilities on an uninterrupted basis. To meet essential power requirements, defense leaders have initiated far-reaching steps to harness advanced technologies capable of conserving energy, enabling on-site production from renewable sources, and saving taxpayers millions of dollars. That effort began in earnest in 2008, when the department convened a prestigious task force, formed by the Defense Science Board, to explore the key energy challenges facing the military in the 21st century. The panel's report, "More Fight -- Less Fuel," called on the U.S. military to address two major challenges: the significant and growing demand for fuel in combat operations, and the vulnerability associated with almost complete reliance by military installations on the nation's aging and vulnerable commercial power grid. "More Fight -- Less Fuel" prompted immediate responses by the U.S. armed forces. Across the Department of Defense, or DOD, a wide range of initiatives has been launched to address operational and installation energy challenges. The Pew Charitable Trusts tracks these energy initiatives. This latest report examines how the military is leveraging private-sector expertise and resources at home to deploy clean and efficient energy in service of economic, environmental, and national security interests. The report's research is derived from publicly available information, close collaboration with DOD officials and experts, site visits to installations across the United States, and a partnership with Navigant Research, a leading market research firm that analyzes global clean energy technology markets. The Department of Defense has one of the world's largest inventories of real estate, with 550,000 buildings and structures encompassing an estimated 2.3 billion square feet. These facilities require energy to run the lights; power communications, computers, and other advanced electronics; and provide heating and cooling. To support and advance its missions, the military has prioritized energy security at all installations. The research in this report details how defense leaders have initiated wide-ranging steps to harness advanced technologies to conserve energy, enable on-site production from renewable sources, and save taxpayers millions of dollars at these DOD facilities in the United States.