HERS Index

The HERS Index is a scoring system established by the Residential Energy Services Network (RESNET) in which a home built to the specifications of the HERS Reference Home (based on the 2006 International Energy Conservation Code) scores a HERS Index of 100, while a net zero energy home scores a HERS Index of 0. The lower a home's HERS Index, the more energy efficient it is in comparison to the HERS Reference Home.

Each 1-point decrease in the HERS Index corresponds to a 1% reduction in energy consumption compared to the HERS Reference Home. Thus a home with a HERS Index of 85 is 15% more energy efficient than the HERS Reference Home and a home with a HERS Index of 80 is 20% more energy efficient.

The HERS Index for a home is very similar to the EPA's estimated MPG for an automobile. It provides a score so the customer is aware of the efficiency of the product before they make a purchase.

ESG Energy's HERS Raters can measure your home using the HERS Index and make recommendations about how to improve your score. Your HERS Rater will review the construction plans and complete at least one on-site inspection of the home to conduct blower door and duct blast tests to test the leakiness of the house and the ductwork. Results of these tests are entered into software along with data derived from the construction plans and a HERS score with estimated annual energy costs generated by the software.

What are some common HERS scores? A new home built to ENERGY STAR guidelines generally has a HERS of 85 or lower and energy costs are estimated to be at least 15% less than a code-built home. A 20-year-old home will usually score 120 - 150 on the HERS index, while a 70-year-old home may have a score of 250 or higher. A score of 200 means that annual energy costs will be 100% higher than for a home built to the building code of 2011. This is why it is so important to consider the price tag but also the monthly energy costs when buying a home.

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