(Home Energy Rating System) is an energy score calculated by a software program for a new or existing home by comparing it to an imaginary new home built to current energy code of the same size and shape as the home being rated.
The HERS Rating was established in 2006 by the Residential Energy Services Network (RESNET). To calculate a home’s HERS Rating, a rater uses an approved computer program. To calculate a home’s HERS Rating, a rater uses an approved computer program. After the rater has entered the building data about the home into the program, the software compares the home being rated to a “reference home.” This reference home is estimated to just meet the 2006 International Energy Conservation Code. The lower a home’s HERS Rating or score, the more energy efficient the home is considered to be.
For example, if the new home or existing home has better energy efficiency qualities than the referenced home then the energy score will be less than the referenced home. A HERS Score of 85 would be 15% more efficient than the referenced home.
The process for a new home and existing home are similar in some ways but different in one big way. With a home to be constructed and only existing on paper, the HERS Rating can be calculated and various scenarios changed in the design stage. This allows the owner to make decisions about orientation, insulation options, mechanical systems choices, etc. and effect the HERS Rating before it is constructed.
With existing homes, decisions have already been made that are harder to change. Either way, the HERS Rating provides good information to the owner about what energy decisions make the most sense for their home.
The HERS Index accounts for on-site energy production, if any, and energy used for lighting and appliances. The reference home is assigned a budget for lighting and appliances; if the home being rated includes energy-efficient appliances or lighting fixtures, these items can help lower (improve) the home’s HERS Index.