- The typical water heater is usually a cylindrical tank with a heat source that heats water from the incoming water supply and also maintains and stores the heated water until it is used.
- Most water heaters have a 40 to 50 gallon glass-lined steel tank, but there are 30 gallon tanks for smaller water requirements, and 65, 75 & 80 gallon tanks for larger water requirements available as well.
- The fuel types used to power the heat source can be either gas (natural or propane), oil or electricity.
- The life expectancy of the average water heater is 10 to 15 years, and in some cases even longer, depending on the amount of use (cycles) and the water quality.
Other types of hot water systems used in the United States are:
- Tank-less (coil) systems that uses a boiler to heat the water on demand.
- instant hot water heaters that are small (2 gallon), located near the tap design that provides hot water for only one tap and usually found in the kitchen.
- High efficiency gas systems.
- Combination systems that are tied into a geothermal, gas warm air furnace or boiler to take advantage of the additional heat source.