Energy-efficient On-demand Water Heaters

Enlarge Image Image Gallery You could save up to $75 a year with an on-demand water heater! KEITH WARD

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Although some conventional water heaters are more energy-efficient, most older water heaters and many lower-priced models waste about 20 percent of the energy they consume. Much of the heat they produce escapes through the wall of the tank as the hot water sits unused for many hours at a time. This is known as standby loss.

Besides being inefficient, storage water heaters (conventional water heaters) don’t last long — only about 13 years. Homeowners can increase the life of their water heaters by lowering the temperature to a more reasonable setting, by periodically flushing sediment from the bottom of the tank, and by replacing the anode rod. Some of these measures also save energy.

If your water heater is more than 10 years old and has not been maintained, it may be approaching the end of its useful life. If it’s leaking or showing signs of rust, it definitely needs to be replaced. So consider your options before it goes kaput and you have to make a rushed decision to get hot water back. Now might be the time to install a tankless water heater.

How Do Tankless Water Heaters Work?

Also known as “instantaneous” or “tankless” water heaters, on-demand water heaters are surprisingly compact units. Some are designed to meet the needs of a laundry room or bathroom, but others provide hot water for an entire house.

Like conventional storage water heaters, tankless water heaters provide hot water 24 hours a day, 365 days a year. However, they meet this need without the standby losses of storage tank heaters.

Tankless water heaters don’t suffer from standby losses because they don’t store hot water — they generate it as it’s needed. When a hot-water faucet is turned on, cold water begins to flow into the water heater. A flow sensor inside the tankless water heater detects water flow and sends a signal to a tiny computer inside the unit. The computer sends a signal to the gas burner or electric heating element in the water heater, turning on the heat source. Water flowing through the heat exchanger in the tankless water heater heats up rapidly — increasing in temperature from about 50 degrees to 120 degrees in a matter of seconds.

Estimated Energy Savings

Because tankless water heaters eliminate standby losses, replacing an old, inefficient water heater with a compact tankless water heater will reduce your annual energy bills. The U.S. Department of Energy (DOE) projects savings up to 30 percent on the cost of heating water, compared to a storage water heater.

Actual savings depend on several factors, primarily the efficiency of the new water heater and the amount of hot water a family uses each day. Also, using electricity instead of natural gas is a much more costly way to heat water.

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