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DOE's new "Uniform Energy Factor" for water heaters

Water heaters that have been introduced to the market after July 13, 2015 are required to use DOE's new test procedures in order to provide a "UEF" (Uniform Energy Factor). AHRI is currently keeping units with UEF ratings in a separate list only available via pdf, here. Starting in June, all of these newer water heaters will be searchable in the regular AHRI database.

Interestingly, the product I was searching the database for, Rheem's new heat pump water heaters, jump from a 3.50 EF in the old test regime to 3.60 for 50-gallon and 3.80 for 65 + 80-gallon models under the new test protocols....not sure if the new test better represents reality for heat pump water heaters...


  • David ButlerDavid Butler Posts: 3,889
    Thanks for posting this, John. I was wondering why the regular AHRI certification directory didn't reflect the ratings. I see they added a note on the water heater search page, with link to the new rating PDF you posted.

    I think any test procedure you might come up with for HPWH's would be problematic as a predictor. As with heat pump space heating systems, supplemental heat and ambient conditions have a big impact on overall efficiency depending on site-specific usage pattern, The UEF provides a reasonable comparison among HPWH model, but it's much less useful as a basis for comparing HPHW's with other types of water heaters.

    Here's a slide show from Navigant that summarizes the new test procedure. And here's a lively discussion on this topic in advance of the new rule.

    BTW, there was 6-month transition period where the new UEF test procedure was voluntary. Manufacturers could apply a conversion factor to the old EF in lieu of using the new procedure.
  • Hi David,
    I just got my first question about this from one of the Raters from Energy Raters of Massachusetts. He was asking,for the sake of HERS Ratings, whether we should convert the new UEF to the old EF and how. I haven't heard anything about this from RESNET or the HERS software providers. Has anyone else?
    And thanks for helping us all with this forum. I just signed up when I found it by searching on "Uniform Energy Factor" and RESNET.