Water heaters consume much of their energy just to keep a supply of hot water ready and waiting in the tank. The heat gradually leaks out of the tank until the heater turns on again to heat the water back up. To minimize this heat loss, ready-made kits for insulating water heaters and hot water pipes are available at hardware stores and building supply stores. Your utility company may also provide these at a discounted cost or offer a rebate on your purchase. Be careful not to cover the thermostat when insulating your water heater and always follow manufacturer's instructions.