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The HERS Index & ENERGY STAR: Understanding the Differences

The rating standards used to determine home energy efficiency are often confused. This article sheds some light on the differences between the HERS Index and ENERGY STAR.

What Is the HERS Index?

The Home Energy Rating System (HERS) Index is the industry standard by which a home’s energy efficiency is measured. It’s also the nationally recognized system for inspecting and calculating a home’s energy performance.


The Residential Energy Services Network (RESNET) developed the HERS Index, simplifying how we determine home energy efficiency while enabling us to compare home energy performance nationwide.

What is The Residential Energy Services Network (RESNET)?

The Residential Energy Services Network or RESNET is a not-for-profit, membership corporation that is governed by a board of directors (who are elected by membership).

In April 1995, the National Association of State Energy Officials and Energy Rated Homes of America founded the Residential Energy Services Network (RESNET) to develop a national market for home energy rating systems and energy efficient mortgages.

RESNET is a recognized national standards-making body for building energy efficiency rating and certification systems in the United States involving:

  • A consensus based standard development and amendment process
  • Transparent review and adoption process
  • Formal public review and comment process


Resnet HERS Index

Additionally, RESNET developed the HERS H20 rating system, analyzing the differences between outdoor and indoor residential water usage.

As a RESNET-certified Home Energy Rater, Radiant helps homeowners throughout Long Island optimize their energy efficiency, saving them money while fostering a more sustainable environment. We have thousands of hours of field experience, going above and beyond to ensure client satisfaction.


ENERGY STAR is administered by the U.S. Environmental Protection Agency. Thousands of organizations—including nearly 40% of the Fortune 500®—partner with ENERGY STAR. Together with EPA, they deliver cost-saving energy efficiency solutions that protect the climate, improve air quality, and protect public health.


ENERGY STAR developed the Energy Rating Index (ERI), a non-proprietary program that measures home energy efficiency.

The Home Energy Rating System (HERS) Index and the Energy Rating Index (ERI)

The ENERGY STAR “ERI” target used to be referred to as the ENERGY STAR “HERS” target. “HERS” is a proprietary term specific to one of our recognized HCO’s that reflects a particular version of ANSI/RESNET/ICC 301. In current program documents, ENERGY STAR instead uses the non-proprietary term “ERI”, but references essentially the same version of ANSI/RESNET/ICC 301 that is used to calculate the HERS index.


Basically, the ERI and HERS Index implement similar practices to determine your home’s energy efficiency. The lower your home’s ERI and/or HERS score, the more energy-efficient your home is.

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