To power an air conditioner at a remote outpost in land-locked Afghanistan, a gallon of fuel has to be shipped into Karachi, Pakistan, then driven 800 miles over 18 days to Afghanistan on roads that are sometimes little more than “improved goat trails,” Anderson says. “And you’ve got risks that are associated with moving the fuel almost every mile of the way.”

Anderson calculates more than 1,000 troops have died in fuel convoys, which remain prime targets for attack. Free-standing tents equipped with air conditioners in 125 degree heat require a lot of fuel. Anderson says by making those structures more efficient, the military could save lives and dollars.

Still, his $20.2 billion figure raises stark questions about the ongoing war in Afghanistan. In the wake of President Obama’s announcement this week that about 30,000 American troops will soon return home, how much money does the U.S. stand to save?