About 90 percent of the energy used to wash clothes goes into heating the water. Using less water in the process saves energy dollars as well as the wet stuff, which makes it one very important element in efficient washing machine design. A conventional top-load washer uses a huge amount of water -- around 40 to 45 gallons for every load. Water slapping the agitator pummels the clothes clean using a process that hasn't changed much in decades. High-efficiency top-loaders use half the water of conventional top-load machines -- and still manage to get clothes as clean or cleaner.