A Home Energy Rating or HERS involves an analysis of a home's construction criteria. Based on the home's building criteria, the Home Energy Rater uses an energy efficiency software package to perform an energy analysis of the home's design. This analysis yields a current home condition HERS Index (pre-HERS). To determine the building criteria, a Home Performance Audit and onsite inspection are performed prior to the HERS modeling.
Upon completion of the pre-HERS, the rater will work with the homeowner to identify the energy efficiency improvements needed to reduce the HERS Index or to ensure the house will meet certain program guidelines such as ENERGY STAR which are separate from the HERS rating.
Following the completion of the recommended improvements, the RESNET rater re-tests the home and re-enters the new building criteria into the energy efficiency software. A post-HERS score and report are generated. The difference between the pre-HERS and the post-HERS represents the energy savings estimate associated with the energy efficiency improvements.
Since a rating quantifies the energy performance of a home, the HERS Index provides an easily understandable means to compare the relative energy efficiency of different homes. Many of REEIS’s investor and real estate clients utilize the HERS score to market their properties as energy efficient. With the availability of the pre and post HERS scores, a benchmark savings can be used to compare the energy consumption of the energy efficient home in comparison to similar homes in the neighborhood.
Unlike a Home Performance Audit, a home energy rating is a recognized tool in the mortgage industry. Home energy ratings can be used in a variety of ways to quantify energy savings or used for underwriting a loan and marketing homes.
The 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 2004 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 score, 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.
Many older homes will score as high as 250 on the HERS analysis. This indicates that the home consumes 150% more than a home built to the 2004 building code.