The HERS Index is a scoring system in which a home built to the specifications of the HERS Reference Home (based on the 2009 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. A home with a HERS Index of 80 is 20% more energy efficient.
Much like checking the miles per gallon rating on a car before purchasing, smart homebuyers should examine the HERS Index score to determine a home’s energy efficiency before buying.