The U.S. Department of Energy regulates minimum energy efficiency requirements for water heaters. The first set of regulations – known as the National Appliance Energy Conservation Act (NAECA) – were created in 1990 and later updated in 2004 to the current standards. A new update to the rules for increasing minimum energy efficiency standards was enacted in 2010 and goes into effect on April 16, 2015.
These design changes will require that most residential water heaters under 55 gallons of capacity produced after April 16, 2015, to be larger in size. Therefore, they will require more installation space in both single-family and multi-family housing. Most water heaters under 55 gallons will grow by approximately 2″ in height and diameter. Units over 55 gallons will require even more drastic changes.