Uniform Energy Factor for Residential & Commercial Water Heaters

The Uniform Energy Factor

The Uniform Energy Factor for residential and certain commercial water heaters refers to its efficiency when run under standardized conditions for a 24-hour period. Expressed as a decimal, the Uniform Energy Factor is determined by running a Department of Energy specified simulated use test (SUT). Depending on a product’s First Hour Rating (FHR), the SUT is run using one of four different draw patterns. When compared to standard products of the same fuel type, a water heater with a higher Uniform Energy Factor rating uses less energy, resulting in both energy and monetary savings. Though, products must be compared to other products in the same draw bin.
Uniform Energy Factor (UEF) Bulletin

First Hour Rating

The First Hour Rating (FHR) in gallons, is determined by running a Department of Energy specified test with the outlet temperature of 125°F (+/- 5°F). A draw of three gallons per minute starts and then discontinues once the hot water outlet temperature drops 15°F. The water heater is then allowed to recover and the process continues repeatedly until one hour elapses. The sum of the amount of hot water drawn during the test is the First Hour Rating.

National Average Energy Costs
  • $0.1200 Cost per kWh. (Electric)
  • $1.0900 Cost Per Therm. (Nat. Gas)
  • $2.4100 Cost Per Gal. (Propane Gas)
  • Information Supplied by the Air-Conditioning, Heating, and Refrigeration Institute and Bradford White.
  • The Uniform Energy Factor Chart is subject to change without notice in accordance with our policy of continuous improvement.
  • The ratings documented on this chart are also listed at www.ahrinet.org and www.energystar.gov.
  • For FTC guide information, please visit www.ahrinet.org
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