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HERS Energy Rating & HERS Index

To "rate" a home’s energy usage requires a comprehensive home energy audit of an existing home, plus a HERS Duct Test (if ductwork is outside the thermal envelope), and energy efficiency software capable of performing an energy analysis of a home including its construction characteristics. This analysis yields a HERS Index, or rating, comparing the home to other homes of comparable size in a similar weather climate.

A HERS Energy Rating is a recognized tool in the mortgage industry because of its level of detail and ability to provide a Home Energy Rating to compare against other homes of comparable size.  A Home Energy Rating is sometimes used by lending organizations for homeowners to qualify for various types of energy efficiency or energy improvement mortgages. And since the HERS Index makes it easier to understand a home’s performance it can also be useful to new home buyers to compare the energy efficiency of homes being considered.

The HERS Index

The HERS Index is a scoring system established by RESNET (Residential Energy Services Network) based on comparing homes built to the specifications of the HERS Reference Home.  The HERS Reference Home is considered a new home built today that meets the minimum standards of the 2004 International Energy Conservation Code.

The HERS Index baseline is 100, the rating for the HERS Reference Home. Conversely, a net zero energy home has a HERS Index score 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.