Home Energy Rating System (HERS)

HERS rating index showing the rating scale from energy efficient to inefficient

A Home Energy Rating (HERS) is an analysis of a home’s energy efficiency. The HERS index is a scoring system established by the Residential Energy Services Network (RESNET). The HERS score can be described as a sort of miles per gallon (MPG) score for houses.

HERS ratings are used for energy code compliance, establishing eligibility for energy efficiency rebates, qualifying for energy efficient mortgages, and earning Energy Star designations. Upon completion, houses receiving a HERS rating have a sticker with the score and efficiency information permanently attached to the electrical panel.

What is a HERS rating?

A HERS rating is an overall efficiency rating of your home similar to an MPG rating that we see on cars. A HERS rating incorporates the insulation levels of the building shell, the windows, all mechanical systems, appliances, lighting, orientation and renewables. HERS ratings are administered by the Residential Energy Network (RESNET). Visit www.hersindex.com to learn more about HERS ratings.

RESNET HERS Raters are trained and certified to inspect and evaluate a home’s energy features, prepare a home energy rating and make recommendations for improvements that will save the homeowner energy and money. HERS Raters undergo rigorous training, testing, assessment, professional development, and adhere to quality assurance standards.

RESNET HERS Rater Candidates are required to attend a Rater Training Course which includes using a RESNET accredited HERS Rating Software Program, pass RESNET core competency tests, and accurately complete probationary ratings overseen by a RESNET Candidate Field Assessor through a RESNET Accredited Rating Provider. The RESNET HERS Rater candidate then can be certified by a RESNET Accredited Rating Provider and issued a unique Rating Identification Number (RTIN). Every three years a RESNET HERS Rater must be recertified by the Rating Provider. At a minimum, the rater must complete 18 hours of RESNET approved professional development training.

Azimuth Home Energy Solutions energy audits are performed by an experienced, RESNET Certified HERS rater who's credentials include extensive experience in the building industry.

Marc Simon's HERS Rater Certificate

What is a good HERS score?

A HERS score compares new and existing homes to a reference home score of 100, which represents a home built to the 2006 International Energy Conservation Code standards. Each 1% reduction in energy use relative to this standard results in a 1 point reduction in the HERS score. A home that is 10% more efficient than a house built to the 2006 code level would have a HERS score of 90, and a house that was 40% more efficient would have a HERS score of 60. The less energy a house uses the lower the HERS score.

How is a HERS score calculated?

HERS ratings consider the house as a complete system. A HERS score is an analysis of data about the building shell, testing results, mechanical systems efficiency, appliance efficiency, and lighting. Software certified by the Residential Energy Network (RESNET) is used to generate an overall efficiency rating and predict operating costs. Massachusetts communities which have adopted the Stretch Energy Code now require a HERS score of 55 or lower in order to be certified for occupancy.

Visit these pages for more information on energy audits for new homes, existing homes, and commercial buildings, and the HERS Rating/Energy Audit Process.

What are some factors leading to good HERS scores?

Some things which lead to good HERS scores include:

  • High levels of insulation
  • High efficiency heating, cooling, and hot water systems
  • High efficiency appliances
  • High efficiency window glass
  • 90-100% LED lighting
  • Low leakage in blower door testing
  • Low leakage in duct leakage testing
  • Renewables – PV systems or geothermal

Are HERS ratings required in all Massachusetts communities?

As of 7/18/19 there were 272 communities in Massachusetts that had adopted the Stretch Energy Code that requires all new homes to get HERS rated as part of the code requirements. In Stretch Code communities new homes must achieve a HERS rating of 55 or lower to meet code. Click here to see the list of towns that have adopted the Stretch Energy Code that requires HERS ratings.

What are some of the benefits of houses/condos built to the Stretch Code standards?

Houses and condominiums built to the Stretch Code standards have a positive cash payback for the increased costs of higher efficiency. For an analysis of payback benefits visit mass.gov Stretch Code “Residential Cash Flow Analysis”.

What is required in the communities that have not adopted the Stretch Energy Code?

Communities that have not adopted the Stretch Energy Code are under the requirements of the 2015 International Energy Conservation Code (IECC). In these communities the code requires blower door testing and certification, duct testing and certification, and ventilation testing and certification. These tests are usually administered by a certified HERS rater as well.

What information is on a HERS rating certificate?

As you can see in the sample HERS rating certificate below, a HERS rating certificate includes general information, features of the mechanical systems, building shell, light and appliance, estimated energy costs and statistics.

HERS energy rating certificate that is given to the homeowner or builder after the inspection

Click the Home Energy Rating Certificate above to enlarge.



2015 International Energy Concervation Code (IECC) certificate that is given to the homeowner or builder after the inspection

Click the 2015 IECC certificate to enlarge.