Tankless Hot Water Heaters: Get into Hot Water

A tankless water heater supplies on-demand hot water to your bath or laundry room—saving money AND energy.


| September/October 2006



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Tired of high home energy bills? Water heater on the fritz? Building a new home and hoping to put a lid on fuel bills? Consider installing a tankless water heater; they’re fuel efficient and can provide years of trouble-free service.

To understand how tankless water heaters operate—and why they’re more efficient than standard water heaters—let’s look first at storage water heaters, common in most American homes. A storage water heater consists of a 40- to 80-gallon glass tank wrapped in insulation and encased in steel. Cold water enters the tank and is heated by a gas burner or electric heating elements that start every time the water temperature inside the tank drops below a predetermined setting, ideally around 120°F.

Storage water heaters work well, although they may not provide enough hot water when demand is high. They also lose a lot of energy maintaining a constant temperature between active periods—what’s referred to as “standby” losses, which typically account for about 20 percent of the energy they consume.

Hot water when you want it

One key advantage of a tankless model over a storage water heater is that by using a device known as a heat exchanger, it heats on demand rather than maintaining a 24-hour-per-day hot-water reservoir. In natural-gas or propane tankless water heaters, the heat exchanger consists of a combustion chamber surrounded by pipes through which water circulates. In electric models, high temperatures are created by an electric heating element. When a hot-water faucet is turned on, cold water flows through pipes in the wall of the heat chamber. The burner or electric heating element turns on, and the flowing water raises from 50°F to 120°F in the blink of an eye.

In gas or propane-powered models, a flue pipe exhausts unburned gases and pollutants, such as carbon monoxide, out of the house. No venting is required for electric models. When the hot-water faucet is turned off, the flow through the water heater ceases and the flame goes out (or the electric heating element shuts off).





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