Water entering a home through a system of pipes is usually cold. A water heater provides the hot water which makes it possible to take a hot shower or use a dishwasher or washing machine. Traditional water heaters look like big metal cylinders and are generally installed in a basement or laundry room. Approximately 20% of the average United States household annual energy cost comes from hot water heating. Water heaters can be fueled by gas, electric, liquid propane, oil, or even solar energy. The water heaters located here are for residential applications.