HERS Rating: What It Means and How the Rating Works
Two homes can look nearly identical during a showing and perform very differently after move-in. One may hold an even temperature with modest heating and cooling costs. The other may have leaky ducts, thin attic insulation, or an HVAC system that runs far longer than expected.
A HERS rating puts a number on that hidden performance. It lets buyers, owners, and builders compare a house with a standardized reference version of the same building. This guide explains what the score means, how it is calculated, and which improvements can lower it.
What Is a HERS Rating?
A HERS rating is an energy assessment completed under standards maintained by the Residential Energy Services Network, or RESNET. It combines building information, diagnostic testing, and energy modeling. The lower the resulting HERS Index score, the more efficient the home is relative to its reference home.
It is not a general home inspection and does not replace an evaluation of the roof, foundation, plumbing, electrical system, or other property conditions. A home energy audit can serve a broader diagnostic purpose when the goal is to identify energy waste and prioritize improvements.
What Does HERS Stand For?
HERS stands for the Home Energy Rating System. It is often compared with a miles-per-gallon label for a house because it reduces many building and equipment details to one recognizable score.
Like an MPG figure, however, it comes from standardized assumptions and cannot predict exactly how an individual household will use energy.
Terminology differs in California, where the state HERS program includes field verification for certain code and HVAC measures. That does not automatically mean a home received a RESNET HERS Index score, so ask which rating or certificate is being discussed.
What Is the HERS Index and Who Developed It?
RESNET established the HERS Index as a national framework for comparing residential energy performance. A HERS Index rating is widely used in new construction, efficiency programs, and selected code-compliance pathways.
The rater compares the house with a modeled reference home of the same general size, shape, and type. The result reflects how the actual envelope and mechanical systems perform relative to that matching design.
A score of 100 represents the RESNET Reference Home, which is based on the 2006 International Energy Conservation Code. A score of 70 indicates approximately 30% less modeled energy use than that reference. A score of 130 indicates about 30% more.
Why Does a HERS Rating Matter for Homeowners and Homebuyers?
Fresh finishes do not reveal how much air leaks through the ceiling or whether ducts lose conditioned air in the attic. A verified rating can help with several decisions:
Comparing homes: Buyers can consider modeled energy performance alongside price, taxes, insurance, and maintenance.
Planning improvements: Rating information can identify envelope or equipment features that increase estimated energy use.
Documenting performance: Builders may need a rating for certification, rebates, or code compliance. Certain mortgage programs may also use an energy assessment, subject to lender rules.
Supporting resale: A strong score gives sellers a documented efficiency feature, although it does not guarantee a higher appraisal or sale price.
Understanding comfort: Air sealing, insulation, sound ducts, and efficient equipment often produce steadier temperatures. A tight home also needs planned ventilation.
How Does the HERS Rating Scale Work?
The scale runs in the opposite direction from a school grade. A lower score is better. A HERS 0 home produces enough renewable energy over the modeled year to offset its modeled annual use, while scores above 100 indicate greater consumption than the reference.
HERS Score Meanings and Typical Home Types
The categories below are for orientation; they are not code approvals by themselves.
HERS Score | Modeled Energy Use Relative to the Reference Home | General Interpretation | Example of What the Score May Represent |
0 | Net annual modeled energy use of zero | Net-zero energy performance after qualifying on-site generation is counted | Very efficient home with enough renewable generation to offset modeled annual use |
40–49 | About 51%–60% less | High-performance construction, often with advanced envelope and mechanical systems | Efficient new home that may also include solar PV |
50–59 | About 41%–50% less | Strong modern performance | Near the recent average for homes receiving HERS ratings nationwide |
60–69 | About 31%–40% less | More efficient than the 2006 reference | Efficient new construction, depending on design, climate, and program requirements |
70–99 | About 1%–30% less | More efficient than the reference home | A home with some energy-efficient features but room for further improvements |
100 | Reference level | Matches the modeled RESNET Reference Home | Home built to the reference specifications based on the 2006 IECC |
Above 100 | Greater than the reference home | Higher modeled energy use than the reference | An older or less efficient home with higher heating, cooling, or air leakage losses |
RESNET reported that homes rated during 2025 averaged a HERS Index of 53. That figure describes homes that actually received ratings, most of which were connected with new construction or efficiency programs. It should not be treated as the average score of the entire U.S. housing stock.
Lower Scores and Better Performance
There is no single “good” score for every property. A HERS 70 existing home may represent a major improvement, while a new high-performance home may be expected to score considerably lower.
Compare similar homes in the same climate and ask whether solar panels are included. A score without PV, when available, provides a clearer view of the envelope and mechanical systems.
Good HERS Ratings for Different Homes
Older existing homes have historically been represented by a HERS Index of around 130, according to RESNET’s published reference materials. Newly rated homes generally achieve lower scores, although results vary by climate zone, construction standards, and whether solar generation is included. A score below 50 generally indicates strong energy performance relative to the reference home, while a score of 0 reflects net-zero modeled annual energy use.
HERS Reference Home Comparison
The reference is not a generic house. It is a modeled counterpart with dimensions and basic characteristics corresponding to the rated home. This allows the Index to compare different designs, but it does not make the score a measure of total consumption. A large efficient house may still use more energy than a much smaller one with a higher score.
A score of 100 is not a current nationwide passing grade. It is the reference point based on 2006 efficiency specifications. Modern code requirements vary by state, municipality, adopted code year, climate zone, and compliance path. Some jurisdictions use an Energy Rating Index pathway with maximum scores, but those limits should be checked locally rather than inferred from a national chart.
How Is a HERS Rating Calculated?
The rating combines plans or building records with field observations and diagnostic tests. A new-construction rater may visit several times so insulation and air sealing can be checked before the walls close. Existing-home ratings rely on accessible conditions, records, testing, and approved assumptions.
HERS Home Energy Assessment Process
The rater records the home’s geometry, orientation, assemblies, windows, HVAC equipment, water heater, ductwork, and ventilation. A blower door measures whole-building leakage, while duct testing measures leakage from the distribution system when applicable.
Infrared imaging may help reveal missing insulation, but it is not included automatically. Ask whether thermography, combustion-safety testing, or an improvement report is part of the service.
The model uses standardized occupancy and operating schedules. That permits comparison, but it also means modeled use may differ from bills for a household with unusual thermostat settings, hot-water demand, or plug loads.
Insulation, Air Sealing, and Window Performance
The rater documents insulation levels and installation quality throughout the thermal boundary. Voids, compression, and misplaced material may reduce performance even when the nominal R-value looks adequate. Blower door results show total leakage under standardized pressure. Windows are modeled using U-factor, solar heat gain coefficient, area, and orientation. The appropriate glazing depends on climate and exposure; a west-facing window in Arizona presents a different load from one in Minnesota.
HVAC, Water Heating, and Ventilation Efficiency
Heating, cooling, and water heating make up a large share of modeled use. The calculation considers efficiency, fuel, distribution losses, controls, and relevant installation details. A high-efficiency heat pump may help, but leaky ducts or poor airflow can reduce the benefit. A tight enclosure also needs appropriate mechanical ventilation.
An ENERGY STAR-certified heat pump water heater can use about 70% less energy than a standard electric resistance model under standardized comparisons. Actual savings depend on hot-water use, operating mode, installation temperature, and local electricity prices.
Solar Panels and On-Site Energy Features
Qualifying solar generation can lower the final Index by offsetting modeled annual electricity use. Because that score does not show how the building performs without the panels, buyers should also request the Index without PV when available.
A home battery serves a different purpose: saving solar for later, shifting grid purchases, or supporting loads during an outage. Moving electricity from one hour to another does not automatically reduce annual modeled use or the HERS score. Ask the rater how the current standard treats the proposed system.
Final HERS Score Verification
HERS rating certification depends on verified characteristics and test results entered into accredited software. The file passes through an accredited Rating Provider responsible for quality assurance and may then be recorded in the RESNET Registry.
Before relying on a listing, request the documentation and confirm the address, date, and whether solar is included. RESNET also offers a public search for rated homes.
How Can You Improve Your Home's HERS Rating?
The most effective sequence usually starts by reducing waste. Air sealing and insulation lower the load before new equipment is selected, and solar can later offset a smaller demand.
Improve Insulation and Seal Air Leaks
Common leakage points include attic penetrations, top plates, plumbing chases, rim joists, and gaps around ducts or utility lines. Insulation should follow a continuous air boundary without voids or compression. Correct moisture problems first. Energy-efficient home upgrades are most effective when they address measured leakage and insulation gaps before larger equipment is replaced.
Blower door testing can establish a baseline and verify major work. Homes with fuel-burning appliances need appropriate combustion-safety review, while very tight homes may need planned ventilation.
Upgrade to Energy-Efficient Heating and Cooling Systems
Replacing old equipment can lower modeled use, but sizing and installation matter as much as the label. Ask for an ACCA Manual J load calculation. Oversized equipment may cycle poorly, while restrictive or leaking ducts waste part of the improvement.
Current air conditioners and heat pumps use SEER2 and, for heat pumps, HSPF2 ratings. Compare complete matched systems. In cold regions, also review low-temperature capacity and COP.
Install Energy-Efficient Windows and Water Heaters
Windows are expensive to replace, so air sealing, attic insulation, and duct repair may offer a better return when existing units remain serviceable. When replacement is necessary, choose U-factor and solar-gain values suited to the climate.
A heat pump water heater can substantially improve on electric resistance equipment. Confirm room volume, condensate drainage, electrical requirements, noise, recovery rate, and tank size before installation.
Add Solar Panels and Consider Home Battery Storage
Once the building load has been reduced, rooftop solar may bring the final score closer to zero. Size it around roof area, shade, electricity use, interconnection rules, and local compensation.
Under time-of-use rates or net billing such as California’s Solar Billing Plan, often called NEM 3.0, a battery may increase the share of solar used in the home. With approved integration equipment, it can also support selected circuits during an outage.
For homeowners who already have rooftop solar or plan to add it, the EcoFlow TITAN 5000 Plus can store compatible solar generation for use after sunset or during an outage. It supports up to 8kW of compatible solar input and can also work with an existing compatible third-party rooftop solar system through an AC-coupled configuration, so the original solar equipment may not need to be completely replaced. This can help increase the share of solar energy used in the home, although battery storage does not automatically reduce annual modeled energy use or lower the HERS score.
Storage changes when electricity is available; insulation and air sealing change how much the building needs.
How Much Does a HERS Rating Cost, and Is It Worth It?
Cost depends on whether the project is an existing home or new build, along with property size, complexity, location, and program requirements.
HERS Rating Cost in the U.S.
A stand-alone existing-home rating often falls around $350 to $800, although complicated properties may exceed $1,000. New-construction fees may run about $800 to $1,500 or more because plan review and several inspections can be involved.
These are planning ranges, not national fee schedules. Ask for an itemized quote showing visits, tests, registry fees, and optional reports. Some utilities or programs subsidize part of the cost.
HERS Assessment Timeline
For an existing home, the on-site work commonly takes about 2 to 4 hours. Modeling, quality review, and documentation may require several more business days.
A new-home rating follows construction. The rater may review plans, inspect insulation before drywall, and return for final blower door, duct, and equipment verification. A missed inspection can be difficult to recreate after the work is concealed.
HERS Ratings for Buying or Building a Home
Most existing-home sales do not require a HERS rating. Buyers should coordinate access and testing with the seller. The rating may reveal efficiency opportunities, but it should accompany—not replace—a conventional inspection.
For new construction, a rating may support certification, rebates, a builder commitment, or a local code pathway. Identify the governing program and required documentation before construction begins.
Energy Bill Savings and Home Value
fuel, household size, plug loads, electric vehicles, and thermostat habits. Buyers should pair the score with recent utility history. For sellers, it supplies credible documentation, although resale value remains a local question.
Battery storage should be evaluated separately from the HERS score. When paired with compatible home-integration equipment, a system such as the EcoFlow TITAN 5000 can store compatible solar generation or lower-cost off-peak electricity for later household use. This may help reduce grid purchases during higher-priced periods, although actual savings depend on the utility rate, household usage, system losses, and installed configuration. Battery storage does not by itself guarantee a lower HERS score or a higher home value.
Conclusion
A HERS rating turns insulation levels, leakage tests, equipment ratings, and building details into one comparable score. It can help buyers look beyond finishes, give builders a measurable target, and show owners where improvements may matter most.
The number still needs context. Check its date, confirm whether solar is included, and remember that standardized modeling cannot predict every utility bill. Reduce the building load first through air sealing, insulation, ductwork, and properly selected equipment. Solar and storage can then support the larger energy plan.
Is a HERS Rating Required for All New Homes?
No, a HERS rating is not universally mandated at the federal level, though many local jurisdictions adopt energy codes (such as IECC performance pathways) that require a certified HERS rating to receive a certificate of occupancy.
Is a HERS Rating the Same as an Energy Star Certification?
No. A HERS Index is a numerical measure of a home’s modeled energy performance, while ENERGY STAR certification requires meeting the applicable EPA program requirements and third-party verification. A HERS rating may be used in the certification process, but it does not automatically qualify a home for ENERGY STAR certification.
Can an Existing Home Get a HERS Rating?
Yes, existing homes can receive a HERS rating at any time through an on-site energy assessment, which provides homeowners with an exact baseline score alongside tailored improvement recommendations.
Does a HERS Rating Affect Home Insurance or Mortgage Eligibility?
Indirectly, yes. While standard home insurance premiums rarely hinge on the score, a verified rating can qualify buyers for energy-efficient mortgages (EEMs), larger financing thresholds, and specialized green lending rates.
How Often Should a Home's HERS Rating Be Updated?
A HERS rating documents a home’s energy performance at the time of assessment. If major changes are made to insulation, HVAC equipment, windows, or solar systems, a new rating may be useful to reflect the updated performance. Some programs may have their own documentation or timing requirements.
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