Almost 90% of the energy used to wash clothes is spent on heating the water, according to the U.S. Department of Energy. Save money and energy. Wash your clothes in warm or cold water instead of hot, using a detergent formulated for cold-water use. Turning the dial from hot to warm will cut your energy use by 50% per load, and save you up to $63 a year, according to the Alliance to Save Energy.