But this was his first foray into making power. Cows walk as many as eight hours a day while grazing, and one day Taylor realized that he could turn that free motion into electricity. On his Livestock Power Mill, a cow stands on a nonpowered inclined belt that the animal will slowly slide down unless it walks forward, turning the belt, which spins a gearbox to drive a generator. A feed box entices the cow to keep trekking. The one-cow prototype generates up to two kilowatts, enough to power four milking machines. A small farm could earn back a 50-cow system's estimated $100,000 price in three years.