The Defense and Interior departments joined together to pursue renewable-energy resources, with the intent of reducing the $4 billion spent on installations’ utility costs annually. In making the Aug. 6 announcement, Defense Secretary Leon E. Panetta and Interior Secretary Ken Salazar outlined a goal to increase the use of geothermal, solar, wind, and biomass energy sources to provide one gigawatt of energy at or near each installation by 2025. The Defense Department and the Bureau of Land Management intend to develop pilot solar-energy projects at the Barry M. Goldwater Range and Yuma Proving Ground, Ariz., and Fort Irwin, Calif.