Traditional Water Heaters

• Instant water heaters are just what they sound like: water heaters that instantly create hot water on demand. Traditional hot water heaters use large storage tanks to provide hot water. The storage tank is usually heated by a natural gas burner, and it's kept at a constant temperature by a thermostat that turns the burner on and off. When someone in the house needs water, hot water flows out of the tank and new water flows in, to be heated again. Instant heaters dispense with this system in favor of something simpler and more efficient.

Instant Water Heaters

• In a gas-powered instant heater, water flows in a pipe over a burner, heating the water as it goes. The exhaust gas is then vented, as in a traditional heater. In an electric instant water heater, an electric element provides the heat instead of a gas burner.

  Instant water heaters are not on all the time. Instead, they turn on only when a flow meter detects that the hot water valve has been turned on and water is flowing through the heater. The flow meter sends a signal that turns on and ignites the gas in a gas heater or turns on the current to the electric element in an electric one. This results in a short delay between the time the water is turned on and the time it is heated and a little bit of water is wasted, but usually not very much.

Advantages of Instant Water Heaters

• Instant heaters are generally much more efficient than regular heaters because they heat the water only when it is being used. In a hot water tank, heat constantly dissipates. Even when the water is not being used, the burner often has to turn on just to keep the water from cooling off. Since instant water heaters don't have to keep the water at a certain temperature, they use energy only when they are on.

  In addition, instant water heaters are more convenient because they provide an unlimited supply of water. A hot water heater will eventually use up its tank, but an instant heater keeps heating the water for as long as it remains on.