Recent updates to HERS Software

Per ENERGY STAR, recent updates to HERS Software, for compliance with ANSI/RESNET Standard 301, will have little to no impact on ENERGY STAR Certification of homes.

Many ENERGY STAR partners are likely already aware that HERS software programs have been updated to align with ANSI/RESNET Standard 301. The use of these programs is required for homes permitted on or after January 1, 2017. As partners have familiarized themselves with the updated software, they have asked whether these updates will impact ENERGY STAR certification.

From the analysis described below, along with spot-checking of several house plans provided by partners, EPA believes that the recent software changes will have little to no impact on ENERGY STAR certification of homes.

To assess this, EPA generated the HERS index and the ENERGY STAR HERS Index Target for each of the home configurations used in the ENERGY STAR Certified Homes, Version 3, Cost & Savings Estimates analysis. This comprised 13 homes, including one gas heated home in Climate Zone 1 through 7 and one electric heated home in Climate Zone 1 through 61. Each home configuration was modeled using the current version of REM/RateTM, v15.3, and the last version that was available prior to the Standard 301 update, v14.6.1. The results are below.

Change in HERS Index Values from REM v14.6.1 to v15.3
(+ Indicates a Higher/Worse Score; - Indicates a Lower/Better Score)
Change In HERS Index

As can be seen, individual values changed by a magnitude of 1 to 5. However, the same change often occurred for both the HERS index of the Rated home and for its associated ENERGY STAR HERS Index Target. Because both of these scores moved in tandem, the overall impact was minimal.

We thank you for your continued support of the ENERGY STAR Certified Homes Program, and wish you continued success with ENERGY STAR in 2017. Please feel free to contact us with questions at

1For more details about the home configurations and methodology used in the Cost & Savings analysis, please see: