RESNET issues Formal Standard Interpretation on Water Heater UEF

November 30th, 2017 - Posted by under RESNET News

The RESNET Standard Development Committee 300 is developing a method for use of the new federal Universal Energy Factor (UEF) in Standard ANSI/RESNET/ICC 301-2014 Energy Ratings. However, the new rating takes effect June 2017 so an interpretation is needed to advise how the UEF is to be used in ratings until such time that the amendment of Standard 301 is final and adopted.

The RESNET Standard Development Committee 300 has adopted the following standard interpretation No. 301-2014-12 “Water Heater UEF”:

Where RESNET Accredited Rating Software requires Energy Factor (EF) as input for water heater efficiency, the EF may be calculated from the Uniform Energy Factor (UEF).

You can access the interpretation here:

Interpretation 301-2014-012 Water Heater UEF

Access the spreadsheet calculator here:

RESNET EF Calculator 2017

The RESNET EF Calculator 2017_10_30.xlsx and interpretation are also posted on the RESNET website (

The effective date of this interpretation is December 9, 2017

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