If you're looking for ways to cut down your energy use, consider switching from a storage water heater to a tankless unit. According to the Department of Energy, a tankless water heater can be 24% to 34% more energy-efficient than a storage water heater.
Tankless, or demand, water heaters have been common in Europe and Japan for years, but are just catching on in the U.S. They work by directly heating water on demand. When a household member turns on the hot water tap, cold water flows into the tankless water heater, and is heated by a gas burner or an electric element, then travels on to the faucet where it is needed.
A storage water heater, by contrast, heats all of the water in its 20- to 80-gallon tank at any given time, whether there is a call for the hot water or not, which results in a significant standby heat loss.
"There are clear advantages to tankless water heaters," says Paul Marquis, education coordinator for the Sustainable Performance Institute () in Boston. "They save energy, they last longer than conventional tanks (20 years for tankless versus 12 years for storage) and they can be serviced, unlike storage water heaters, which just give out at a certain point."
To figure out if switching to a tankless water heater makes sense for your house, consider:
*Capacity: Tankless water heaters provide hot water at a rate of two to five gallons per minute. Calculate your typical needs by adding up the hot water demand at any one time. For example, if you want to run a kitchen faucet with a flow rate of .75 gallons a shower with a flow rate of 2.5 gallons per minute, you would need a tankless water heater with a flow rate of at least 3.25 gallons per minute. (Determine flow rates in your home by putting a jug of a known volume under each faucet, and running the water for exactly one minute.)
*Placement: "You want to avoid long piping runs," says Marquis. Because the water is being heated on demand, the closer the water heater is to where the water is needed, the better. Some homeowners are installing more than one tankless unit: as long you have electricity for the electric units, and a gas line for the gas units (which can be vented directly through an exterior wall), you can place a tankless unit in a closet, an attic, or laundry room—close to where the hot water is needed.
*Cost and Installation: The initial cost of a tankless unit can be 50% more than a storage heater when you consider the tankless unit itself the labor involved in installation. Typically an electrician and/or a plumbing contractor will need to make adjustments to your electrical and gas lines and ductwork. But a tankless unit lasts longer, and saves energy.
For more information, check the Department of Energy website:
Tankless water heater manufacturers include: