In April 2010, the U.S. Department of Energy issued new efficiency standards for residential storage water heaters — gas-fired, oil-fired and electric — and gas-fired tankless water heaters. These efficiency standards become effective in April 2015.
The current efficiency standards for gas-fired storage units require an Energy Factor of 0.59. The new standards will require gas-fired water heaters less than 55 gal. to have an EF of 0.62 and gas-fired units more than 55 gal. to have an EF of 0.76. For electric storage, standards will increase from the current 0.90 EF to 0.95 for units less than 55 gal. and 2.00 for units more than 55 gal.