(Originally published in the March 2015 Housing Journal)

Energy Department Mandates More Energy-Efficient Water Heaters

Effective April 16, 2015, new guidelines from the U.S. Department of Energy (DOE) take effect, mandating higher Energy Factor (EF) ratings on virtually all residential (and some light duty commercial) gas, electric, oil and tankless water heaters. The DOE is authorized under the National Appliance Energy Conservation Act (NAECA) to establish minimum efficiency standards for residential and some light duty commercial water heaters.

In advance of the April 16 deadline, some water heater manufacturers may have already changed their production lines over to manufacture only the new EF water heaters. Supply houses may already be limited to the stock-on-hand for the older, standard water heaters.

This chart shows you the new EF requirements effective 4/16/2015.

Product Classes Affected by Change

Rated Storage Volumes/Inputs Affected by Change
> 20 gal and < 55 gal, < 75,000 BTU/Hr.
> 55 gal and < 100 gal, < 75,000 BTU/Hr.

NAECA Updated Energy Factor Requirements
0.675 – (0.0015 x V)
0.8012 – (0.00078 x  V)


< 50 gal, < 105,000 BTU/Hr.

0.68 – (0.0019 x V)


> 20 gal and < 55 gal, < 12 KW inpu
> 55 gal and < 120 gal, < 12 KW input

0.960 – (0.0003 x V)
2.057 – (0.00113 x V)

Instantaneous Gas-fired
Instantaneous Electric

< 2 gal, < 200,000 BTU/Hr.
< 2 gal, < 12 KW input

0.82 – (0.0019 x V)
0.93 – (0.00132 x V)

How will these changes affect home builders?

Residential and multi-family home builders will be impacted by the 2015 NAECA standards in several ways.

First, mechanical rooms may need to be enlarged, as new NAECA-compliant water heaters (gas, electric and oil models) with capacities under 55 gallons will likely be larger, both in height by 1-2 inches and in diameter by 2 inches. As a result, home builders will need to accommodate for this increased product size, including applicable required service clearances (required service clearances vary by model and can be found in the product’s installation manual), and allow for additional overall space at the installation site.

Next, home builders installing larger capacity residential water heaters higher than 55 gallons will need to make several adjustments:

  • For gas-fired products over 55 gallons (≤ 75,000 BTU/Hr.), fully condensing combustion technology will likely be required, based on currently available technologies that are capable of meeting the new requirements. As a result, home builders will need to include one or two extra electrical outlets as well as a means for condensate disposal at the installation site, possibly by installation of a waste pump.
  • Electric water heaters over 55 gallons (≤ 12 kW input) will likely utilize integrated heat pumps to meet the new EF requirements, based on currently available technology. Heat pump water heaters are generally taller than standard electric water heaters and require a 10 ft. x 10 ft. room or a duct to an adjoining room to operate properly. Home builders must also be aware of the impact of noise, as heat pump models will operate at a higher noise level.

Finally, the home builder will need to make the decision on whether to design in two mechanical closets, so large homes can have two separate locations for smaller water heaters instead of one large one. The smaller water heaters are not expected to require heat pumps, which generate more noise, but two smaller units will mean twice the maintenance, and possibly two pumps to remove the condensate waste.

This change has been in the works for several years, as the first step occurred over five years ago when the DOE asked appliance manufacturers if they could produce water heaters that were more energy efficient. Once the answer came back from the manufacturers that it was possible, that industry worked with the DOE to develop the guidelines that take effect on April 16.