The HERS Index is the specific numeric scale used within the Home Energy Rating System, with a reference home built to a specific baseline standard scoring 100, and lower scores indicating better energy performance than that reference point, while higher scores indicate worse performance.
This scale allows for meaningful comparison, since a home scoring 70 on the HERS Index is understood to use approximately thirty percent less energy than the reference home baseline, providing an intuitive way to communicate relative efficiency improvement.
Some very high-performance homes, including certain net-zero energy designs, can achieve HERS Index scores of zero or even negative numbers, reflecting homes that produce as much or more energy than they consume through renewable energy generation combined with exceptional efficiency.
What Does the HERS Index Measure?
- Energy performance relative to a standardized reference home
- A baseline score of 100 for the reference standard
- Lower scores indicating better relative performance
- Potential for zero or negative scores in net-zero homes
Why Is the HERS Index Important?
This standardized numeric scale gives homeowners, builders, and real estate professionals a consistent, easily communicated metric for comparing energy performance across different homes, making it genuinely useful for marketing high-performance new construction or evaluating a potential home purchase’s relative efficiency. This clarity has driven the HERS Index’s growing prominence in new home sales and energy efficiency program requirements.
Many energy efficiency programs and green building certifications specifically reference HERS Index scores as qualification criteria, making this metric relevant not just for general comparison but for actual program eligibility and certification requirements in many jurisdictions.
HERS Index vs. HERS Rating
The HERS Index is the specific numeric scale itself, with 100 as the baseline reference point. HERS rating is the broader term for the overall assessment process and resulting score, encompassing the index as the specific metric that process produces.