At an isolated forward operating base (FOB) in Afghanistan, helicopters would fly in once a week to deliver 800 gallons of fuel.Of that, 600 gallons were to keep the generators running. It was an enormously expensive way to deliver fuel, Maj. Gen. Michael Tucker said.One week, along with supplies, the helicopters also delivered an "operational energy adviser" who had been specially trained in energy efficiency.Through "a few quick fixes," such as pairing the right size generators with the equipment they were operating, turning some equipment off at certain times and preaching energy conservation to the 220 soldiers at the FOB, the energy adviser cut fuel consumption by 280 gallons, Tucker told an audience at an Institute of Land Warfare Contemporary Military Forum."We saw savings overnight," Tucker, the Army’s assistant deputy chief of staff for operations, plans and training, said.Energy, no longer abundant and cheap, is a growing concern for the Army.Speaking Oct. 23 at the Association of the United States Army’s Annual Meeting and Exposition, Katherine Hammack said, "For the Army, energy is a big business" costing $5 billion a year for battlefield operations and to run bases.Hammack, the panel moderator, is the Army’s assistant secretary for installations, energy and environment.It has also become a risky business. In Afghanistan, 70 percent of the cargo aboard supply convoys is fuel or water, and there is a casualty in one of every 46 convoys, according to Army statistics.The danger of driving convoys through hostile territory is obvious, but there is danger, too, in depending on increasingly unreliable domestic energy grids, Hammack said.In recent years, the number of power outages at Army bases has increased fourfold as U.S. generating capacity is taxed by increasing power consumption and inadequate investment.The Army’s answer is to become more energy self-reliant.In April, the Army committed to building a gigawatt’s (1,000 megawatts) worth of power production capacity for itself on its installations, Hammack said.That’s enough power to supply 250,000 homes.By 2025, the Army hopes to generate 2.5 million megawatts – 25 percent of the Army’s annual power consumption, she said.Electricity will come from solar, geothermal, wind, biomass and other sources, she added.At the same time, the Army is determined to conserve. It is pushing bases to become "net zero" consumers of power – that is, they are to use no more electricity than they produce.To cut energy consumption, bases are "right sizing" non-tactical fleets by replacing gasoline-powered cars and trucks with electric-powered vehicles. They’re installing microgrids to manage power delivery and installing solar panels to generate power locally.For helicopters, the Army is developing turbine engines designed to use 25 percent less energy, but produce more power.As important as saving energy, the Army is working to create a culture of energy awareness so that soldiers use energy wisely, Lt. Gen. Michael Ferriter, assistant chief of staff for installation management and commanding general of the Army Installation Management Command, said.The Army has cut energy consumption by 13 percent since 2003 despite increasing the force by 20 percent, he said.For soldiers in combat, energy consumption has skyrocketed.During World War II, the Army consumed about two gallons of fuel per soldier per day. Today fuel consumption is about 22 gallons per soldier per day, Lt. Gen. Raymond Mason, deputy chief of staff for logistics, said.And, in addition to fuel, soldiers require batteries to power a multitude of electronic devices.For example, soldiers have six different battery-powered sensors for detecting improvised explosive devices – and each has a different type of battery, Command Sgt. Maj. John Troxel, command sergeant major of I Corps, said.Then there are radios, global positioning devices, small computers and other battery-powered devices. For a 72-hour patrol, a typical soldier needs 70 batteries – about 16 pounds worth, Troxel said.To reduce the load, the Army is also switching to rechargeable batteries.