Most owner-builders meet their HERS rater at final inspection — when it’s too late to change anything. The score decides your utility bills for the next 30 years, and in many jurisdictions your certificate of occupancy too. Here’s how to use it as a design tool instead of a paperwork surprise.
How the HERS Score Actually Works
The reference point is simple: a home built to 2006 IECC standards scores exactly 100, and every point below that means 1% more efficient. A standard current-code build lands between 50 and 70. Energy Star requires 57 or lower. Net zero scores 0.
What moves your score, in rough order of impact:
| Factor | What the Rater Measures |
|---|---|
| Air sealing | Blower door test — ACH50 |
| Insulation | Installed R-value and coverage without voids |
| Windows | U-factor and SHGC |
| HVAC | SEER rating and duct leakage |
| Water heater | Heat pump units move the needle most |
| Lights & appliances | Smaller, but counted |
The rater visits twice: a rough-in inspection (insulation, before drywall) and a final (blower door, duct test, equipment verification). Skip the rough-in visit and the rater assumes worst-case insulation values — which tanks your score.
What HERS Scores Mean in Real Dollars
Here’s where the score stops being abstract. According to RESNET (Residential Energy Services Network), which administers the HERS program, every one-point improvement in HERS score reduces energy costs by roughly 1% compared to the reference home.
To put that in concrete terms for a 2,000 sq ft home with average US energy costs in 2026:
| HERS Score | Estimated Annual Energy Cost | Savings vs Score 100 |
|---|---|---|
| 100 (reference) | ~$2,400/year | — |
| 70 (current code) | ~$1,680/year | ~$720/year |
| 57 (Energy Star) | ~$1,370/year | ~$1,030/year |
| 40 (high performance) | ~$960/year | ~$1,440/year |
| 0 (net zero) | ~$0–$200/year | ~$2,200/year |
These are rough estimates — actual costs depend heavily on your climate zone, utility rates, and how your household uses energy. Climate zones 6, 7, and 8 (northern states, upper Midwest, mountain states) see the biggest dollar impact from a lower HERS score because heating loads are so much higher.
The HERS score is also increasingly used by mortgage lenders. Energy Efficient Mortgages (EEMs) and certain Fannie Mae and Freddie Mac programs allow buyers to qualify for larger loan amounts on homes with strong HERS scores, on the logic that lower utility bills offset the higher payment. If you’re planning to sell the home within 10 years, a low HERS score is a documented, quantifiable selling point — not just a feel-good number.
How HERS Connects to IECC Compliance and Energy Star Certification
Most states have adopted some version of the International Energy Conservation Code (IECC), which sets minimum efficiency requirements for new construction. The current edition in most jurisdictions is IECC 2021, though some states are still on 2018 or 2015. Your local building department will tell you which edition applies.
Here’s the important thing: passing IECC doesn’t guarantee a good HERS score, and a good HERS score doesn’t automatically satisfy IECC compliance. They’re related but not identical. IECC compliance is a pass/fail code check. HERS is a performance score on a continuous scale.
Energy Star certification for new homes (Version 3.2 as of 2026) requires a HERS score of 57 or lower, plus additional requirements around HVAC sizing, ventilation, and water management that go beyond the score itself. If Energy Star is a goal — whether for personal satisfaction, resale value, or mortgage financing purposes — plan for it from the beginning. Retrofitting a home to hit Energy Star after framing is expensive and often impossible without tearing into finished assemblies.
One practical note on IECC climate zones: the required R-values, window performance specs, and air sealing targets in the IECC all vary by climate zone. A home in climate zone 2 (Florida, South Texas, Hawaii) has very different code requirements than a home in climate zone 6 (Minnesota, Montana, upstate New York). Your HERS rater will run calculations using your specific climate zone — make sure they have the correct zone before the rough-in inspection.
What Owner-Builders Get Wrong About HERS Ratings
The single most common mistake is treating the HERS rating as a paperwork exercise rather than a design tool. Owner-builders who engage their HERS rater early — during design, before permits are pulled — can model different insulation packages, window specs, and HVAC options and see exactly how each choice affects the final score and projected energy cost. That’s an enormously valuable conversation to have when a change costs nothing.
By contrast, owner-builders who call the rater at rough-in stage are locked into whatever choices were already made. If the blower door test reveals an ACH50 of 5.0 when your jurisdiction requires 3.0 or lower (common under IECC 2021), you’re tearing into finished or semi-finished assemblies to find and seal the leaks. That’s a costly, frustrating problem that’s almost entirely preventable.
Other common HERS-related mistakes:
- Installing insulation correctly on the specification but incorrectly in the field — thermal bridging at rim joists, top plates, and framing members is where most air sealing failures occur
- Specifying a high-efficiency HVAC system but failing duct leakage testing because the ductwork was poorly sealed — duct leakage can add 10–15 points to a HERS score
- Forgetting that recessed lighting penetrations in insulated ceilings are major air leakage points unless you use airtight IC-rated fixtures
- Skipping mechanical ventilation because "the house will breathe" — under IECC 2021, whole-house mechanical ventilation is required in very tight homes (below 3 ACH50), and the HERS rater will flag its absence
A HERS score between 50 and 60 is achievable in most climate zones without exotic or expensive materials — it’s primarily a matter of attention to detail in air sealing, insulation installation, and mechanical system selection. The rater isn’t your enemy. Bring them in early and use their modeling capability as a design tool.
Frequently Asked Questions
What is a good HERS rating for a new home?
A HERS score below 70 means your home outperforms the 2006 code reference standard by 30% or more — that’s a reasonable baseline for new construction. Energy Star certification requires 57 or lower. High-performance and passive house builds often land in the 30–45 range. In cold climate zones (6–8), targeting a score below 55 is worth the additional investment because heating costs are high enough to make efficiency measures pay back quickly.
Is a HERS rating required for new construction?
It depends on your jurisdiction. Many states and counties require a HERS rating as part of demonstrating IECC compliance — especially those on IECC 2018 or 2021, which include performance path compliance options. Some jurisdictions allow a prescriptive compliance path instead, which doesn’t require a HERS score but is often more restrictive. Check with your local building department early. Even if it’s not required, having one done is worth the $300–$600 cost for the energy modeling alone.
What does the blower door test measure and what does failing mean?
The blower door test measures how airtight your home’s envelope is. A large fan is mounted in an exterior door, the house is depressurized to 50 pascals, and a meter reads how much air is flowing through the fan to maintain that pressure — expressed as ACH50 (air changes per hour). IECC 2021 requires 3.0 ACH50 or lower in most climate zones. Failing means your air sealing has gaps significant enough to require remediation before the certificate of occupancy is issued.
How much does a HERS rating cost?
Expect to pay $300–$600 for a full HERS rating including the rough-in inspection and final blower door and duct leakage tests. Costs vary by region and by how far the rater has to travel. Some energy raters bundle the HERS rating with energy modeling during design for an additional fee — typically $200–$400 more — which is worth it for owner-builders making their own design decisions. The HERS rating fee is a very small line item relative to the savings it can generate over the life of the home.
What is the difference between HERS rating and Energy Star certification?
A HERS rating is a score on a continuous scale (lower = more efficient). Energy Star certification for new homes is a program with specific threshold requirements — currently a HERS score of 57 or lower, plus additional requirements for HVAC sizing, indoor air quality, and building envelope performance. Achieving a HERS score of 57 doesn’t automatically earn Energy Star certification; you also need to meet the other program requirements and have an Energy Star verifier (who may or may not be the same person as your HERS rater) complete the certification process.
Does a lower HERS score increase home resale value?
Yes, increasingly so. Studies from the Lawrence Berkeley National Laboratory and RESNET have consistently shown that homes with documented energy efficiency certifications sell for 3–9% more than comparable uncertified homes, with stronger premiums in markets with high utility costs. A HERS certificate is a concrete, third-party-verified document that you can include in a listing — it translates directly into projected annual savings that a buyer can calculate. In competitive markets, it’s a genuine differentiator.