HERS Ratings Explained: What They Mean for Home Appraisals
If you have bought, sold, or appraised a home with energy efficiency features in the last few years, you may have encountered a HERS rating. It shows up in listing descriptions, builder marketing materials, and increasingly in appraisal workfiles. But what a HERS rating actually measures, and what it means for an appraisal, is often misunderstood.
This guide explains what the HERS index is, how it is calculated, where to find one, and how appraisers are expected to use it in an assignment.
What is a HERS rating
HERS stands for Home Energy Rating System. It is a standardized scoring system developed by RESNET, the Residential Energy Services Network, to measure the energy efficiency of a home. The score is calculated by a certified HERS rater who conducts an on-site inspection and energy analysis of the home.
The HERS index works on a scale where a lower score means a more efficient home. A score of 100 represents the energy use of a standard reference home built to 2006 energy code. A score of 0 represents a net-zero energy home. A typical new home built today scores around 55 to 65.
How a HERS rating is calculated
A certified HERS rater conducts an inspection that typically includes a blower door test to measure air leakage, a duct blaster test to measure duct leakage, and a review of the home's mechanical systems and building envelope. The data is entered into specialized energy modeling software that calculates the HERS score.
The process is third-party verified, which is what gives the HERS rating its credibility as a standardized measure. A homeowner's claim that a home is energy efficient is not the same as a verified HERS rating from a certified rater.
Where to find a HERS rating
HERS ratings are registered with RESNET and can be accessed through the RESNET registry. The certificate issued at the time of rating includes the score, the rater's name and certification number, and the date of the rating.
For new construction, builders who pursue Energy Star certification typically have HERS ratings as part of that process. For existing homes, a rating may or may not exist depending on whether the previous owner pursued one.
How appraisers use HERS ratings
A HERS rating tells appraisers that a home has been measured for energy efficiency by a certified third party. It is a data point, not a value conclusion. What the appraiser does with that data point depends on what the market shows.
Verification
The first step is verifying the rating. A HERS certificate with the rater's name, certification number, and registration information is the appropriate documentation. A listing that mentions a HERS score without documentation cannot be treated as a verified feature.
Market analysis
Once the rating is verified, the question is what buyers in that market have demonstrated they are willing to pay for homes with lower HERS scores compared to similar homes with higher scores. The HERS score itself does not determine the adjustment. The market evidence does.
UAD 3.6 and HERS
UAD 3.6, which takes effect in November 2026, includes a dedicated energy section that addresses how appraisers report energy features including HERS ratings. Appraisers should prepare accordingly before the implementation date.
What agents and homeowners need to know
Having the documentation ready
If a home has a HERS rating, having the certificate available before the appraisal is ordered helps the process move smoothly. The appraiser needs to see the documentation to include the rating in the analysis.
Understanding the limits
A low HERS score is evidence of energy efficiency. Homeowners and agents who have invested in energy improvements should have realistic expectations about how those improvements are reflected in an appraisal. The market has the final say.
Getting a rating for an existing home
Homeowners who want a HERS rating for an existing home can hire a certified HERS rater directly. RESNET maintains a directory of certified raters by location.
Key things to understand about HERS ratings and appraisals
- A HERS score is a standardized, third-party verified measure of energy efficiency
- Lower scores indicate more efficient homes, with zero representing net-zero energy
- Appraisers need the actual HERS certificate to include the rating as a verified feature
- The score is a data point that informs the analysis, not a value conclusion
- Market evidence determines whether a HERS rating supports an adjustment
- UAD 3.6 introduces new reporting requirements for energy features including HERS ratings
Frequently asked questions
What does a HERS score of 50 mean?
A HERS score of 50 means the home uses approximately 50 percent of the energy that a standard reference home built to 2006 code would use. The lower the score, the more efficient the home.
Does a HERS rating expire?
HERS ratings do not have a formal expiration date, but they reflect the condition of the home at the time of the rating. If significant changes have been made since the rating was conducted, it may no longer accurately reflect current performance.
Can a HERS rating be used in place of comparable sales data?
No. A HERS rating is evidence of energy performance, not market evidence. Comparable sales analysis is still required. The HERS rating can inform how energy features are identified and described, but it does not replace the market data needed to support an adjustment.
What is the difference between a HERS rating and an Energy Star certification?
Energy Star certification for homes uses the HERS index as one of its verification tools, but they are not the same thing. Energy Star certification requires meeting a specific HERS score threshold as well as other requirements. A home can have a HERS rating without being Energy Star certified.
How do appraisers handle a property where a HERS rating is claimed but not documented?
If a HERS rating is mentioned in the listing or by the seller but no certificate is available, the appraiser cannot include the rating as a verified feature. It cannot be given weight in the analysis without documentation.
Are HERS ratings common on older homes?
HERS ratings are more common on new construction. For existing homes, ratings are less common but are available for any home where the owner chooses to commission one.
The role of energy data in modern appraisal practice
Energy features are becoming a more significant part of residential appraisal as homes become more efficient and as buyers increasingly factor energy costs into their decisions. The HERS rating is one of the more reliable data points available for measuring and communicating energy performance.
Insight Solar supports appraisers in analyzing energy features and building defensible workfiles for these assignments. Learn more at Banks Technologies