New minimum energy-efficiency standards go into effect for nearly all residential gas and electric water heaters on April 16, 2015. The set of rigorous rules are the third generation of standards the U.S. Department of Energy (DOE) has issued for the equipment under the National Appliance Energy Conservation Act of 1987 (NAECA).
While the new efficiency standards do not require manufacturers to use any specific technologies to achieve the new EF (energy factor) ratings, they’ve already necessitated a significant redesign effort from manufacturers. Additionally, the increasing unit sizes pose transportation and installation challenges that have yet to be fully understood.