About
ASAP

Residential Water Heaters

Last Updated: June 2010
See the federal standards main page to view current status

THE PRODUCT: Residential water heaters are used primarily to provide hot water to residences for consumer use, appliances, and other functions. Water can be heated by electricity, gas, or oil. There are two main types of water heaters: typical heater/storage units and instantaneous water heaters.

POTENTIAL STANDARD: DOE released the final rule for updated standards for residential water heaters on April 16, 2010, which will become effective April 16, 2015. The required energy factor (EF) varies depending on the fuel source and the rated storage volume. For more information on the efficiency calculations, click here for the final rule.

KEY FACTS: Water heating represents 20% percent of total annual household energy consumption in the U.S. About 53% of U.S. households use natural gas water heaters, while 38% use electric and less than 4% use oil (EIA 2008a). A baseline .90 EF electric water heater consumes around 2,700 kWh annually (DOE 2009b). Though electric water heaters are rated with higher energy factors than gas or oil, these ratings do not account for the fact that about 3 Btus of fuel need to be burned to generate 1 Btu of electricity. All water heaters generally waste a portion of fuel they use to keep storage water heated: for example, in a conventional gas water heater, only 43% of the fuel energy actually reaches the point of use. The remaining 57% dissipates through standby losses, distribution losses, or combustion losses (Thorne Amman, Wilson and Ackerly 2007). Thicker tank insulation can increase the efficiency of all types of water heaters, but this has decreasing gains at higher efficiency levels, which already have relatively thick insulation. The current rulemaking will essentially exhaust the efficiency potential of conventional tank gas and electric water heaters. Bringing electricity to the gas tank water heater allows multiple improvements, particularly the use of a vent damper (which dramatically reduces standby losses) or a condensing operation (where latent heat is captured by condensing the water vapor that is a byproduct of combustion vapor). For electricity, the only central technology option is the heat pump water heater, with an energy factor greater than 1 and possibly greater than 2.5 in the long run.

• Federal Documentation (DOE Web site)

Filing
Comments on the Framework Document for the water heater, pool heater and direct heating equipment rulemaking.
February 12, 2007

News Update
Water Heater Efficiency Standard Update: VP Gore Announces Proposal to Improve Water Heater Efficiency