Quick answer
An HVAC energy audit, usually called a home energy audit or assessment, is an inspection and set of measured tests, such as a blower door test and duct leakage test, that shows where a building loses energy through its envelope, ducts and heating and cooling equipment, and ranks the fixes worth making.
It looks at the house and the HVAC system together, because a leaky house or leaky ducts can waste as much as an old furnace.
Quick facts
The key facts about HVAC Energy Audit, with sources:
- Also called
- Home energy assessment, whole-house audit
- Key tests
- Blower door (house airtightness), duct leakage, combustion safety, infrared scan
- DOE Home Energy Score
- 1–10 scale; 10 is most efficient; by DOE-trained assessors 2
- HERS Index
- RESNET’s industry rating of home energy efficiency 1
- Federal 25C audit credit
- Expired: covered property placed in service before 31 Dec 2025 4
Key takeaways
- An energy audit measures the house and its HVAC, then ranks fixes by value.
- The core tests are a blower door test and a duct leakage test, covered by ANSI/RESNET/ICC 380 1.
- Two scores you may see: RESNET’s HERS Index and DOE’s 1–10 Home Energy Score 1 2.
- Do the audit before replacing HVAC. Fixing leaks first can shrink the system you need.
- The federal 25C credit, which included up to $150 for an audit, expired for 2026; it covered items placed in service before 31 December 2025 4.
What an energy audit covers
Your heating and cooling system works against the house. Air leaks, thin insulation, sunny windows and leaky ducts all add load. An audit measures that load and shows which parts cost the most.
A professional audit combines an inspection with tests. The blower door test depressurizes the house to measure how leaky it is. A duct leakage test measures how much air escapes ducts.
RESNET’s testing standard, ANSI/RESNET/ICC 380, covers envelope airtightness, duct airtightness and ventilation airflow 1. The auditor also checks insulation, windows, the HVAC equipment, water heating and combustion safety.
Auditors may hold a RESNET Home Energy Rater credential or a BPI Building Analyst credential, offered as Technician (BA-T) and Professional (BA-P) 1 3. Some also produce a DOE Home Energy Score 2.
How a professional audit runs
- Interview and bill review → where comfort and costs are worst
- Walk-through: attic, crawl space, ducts, equipment, windows
- Blower door test → house air leakage, leak hunting with smoke or infrared
- Duct leakage test → air lost from ducts
- Combustion safety checks on gas appliances
- Report → ranked fixes, sometimes a HERS rating or Home Energy Score
Types of energy audit and score
| Type | What it is | Who does it |
|---|---|---|
| DIY walk-through | Owner checklist for obvious problems | Homeowner |
| Professional home energy audit | Inspection plus measured tests | BPI- or RESNET-credentialed auditor 3 1 |
| HERS rating | RESNET index of home energy efficiency, verified by inspection and testing | Certified RESNET Home Energy Rater 1 |
| DOE Home Energy Score | 1–10 score of a home’s energy assets, with a report of improvements | DOE-trained assessor 2 |
| Utility audit | Program-run assessment, sometimes free or reduced price | Utility contractor |
| Weatherization assessment | Audit for income-eligible homes | DOE Weatherization Assistance Program providers 5 |
Energy audit vs HVAC service visits
| Visit | Looks at | Answers |
|---|---|---|
| Energy audit | Whole house plus HVAC and ducts | Where is energy wasted, and what to fix first? |
| Tune-up | HVAC equipment | Is the system clean and adjusted? |
| Commissioning | New HVAC system | Does it run as designed? |
| HVAC inspection | Equipment condition | What shape is it in? |
| Manual J | Heating and cooling load | What size system does the house need? |
Homeowner checklist: a DIY pre-audit walk-through
- Pull 12 months of utility bills. Note the highest months and compare with weather.
- Look at the HVAC filter; note size and how dirty it gets in a month.
- In the attic (only if safe to enter), look for gaps in insulation, crushed or disconnected ducts, and open chases around pipes and flues.
- Feel for drafts at outlets on outside walls, around windows, doors and attic hatches on a windy day.
- Look at ducts in the basement, crawl space or garage for open joints and missing insulation.
- Note rooms that are always too hot or cold, and when.
- Check the age and nameplate of the furnace, AC or heat pump; the system age lookup decodes serial numbers.
- Write down any condensation, musty smells or ice on refrigerant lines.
- Do not open gas appliances, electrical panels or refrigerant lines. Leave combustion checks to the pro.
Example: how an audit changes an HVAC plan
A 1980s house with high bills and a hot upstairs. The homeowner plans a bigger AC. An audit finds these issues (example findings).
| Finding | Test or check | Fix | Effect on HVAC |
|---|---|---|---|
| House is very leaky | Blower door 1 | Air seal attic and rim joist | Lower heating and cooling load |
| Attic ducts leak and are poorly insulated | Duct leakage test 1 | Seal and insulate ducts | More delivered air upstairs |
| Thin attic insulation | Visual inspection | Add insulation | Lower summer gain |
| Furnace drafting weakly | Combustion safety test | Licensed repair | Safety fixed first |
After these fixes, a new Manual J may call for the same or a smaller system, not a bigger one. That is the main reason to audit before replacing HVAC. NIST also lists duct leakage among the faults that most raise heat pump energy use 6.
Where audits come up
What an audit is worth
Benefits
- Ranks fixes by impact, so money goes to the biggest losses first.
- Finds safety problems such as poor combustion drafting.
- Can shrink the HVAC system you need.
- Gives a score buyers and programs recognize.
Limits
- Only as good as the auditor; credentials help.
- Savings estimates are models, not guarantees.
- Does not fix anything by itself.
- Some reports upsell products; ask for a ranked list with reasons.
What an audit cannot tell you
Audit software estimates savings from typical weather and use. Your results depend on habits, thermostat settings and future prices. Treat the numbers as a guide to order, not a promise.
A standard audit also checks the HVAC system only lightly. For refrigerant charge, airflow and static pressure, you need an HVAC technician’s measurements as well.
Cost drivers and incentives
Price depends on house size, the tests included, whether a HERS rating or Home Energy Score is produced, and whether a utility program subsidizes it.
The federal 25C credit allowed up to $150 for a home energy audit within its annual limits, but it expired: it covered property placed in service before 31 December 2025, and it is not available for 2026 4. Check utility and state programs instead; see utility rebates and the rebate finder.
Sources: [4]
How to get a useful audit
- Ask your utility whether it offers or subsidizes audits.
- Hire an auditor with a RESNET or BPI credential 1 3.
- Confirm the audit includes a blower door test and, if you have ducts outside the living space, a duct leakage test.
- Have bills and your checklist notes ready.
- Ask for a ranked list of fixes with expected effect and safety items first.
- Do envelope and duct fixes, then size any new HVAC with a Manual J.
After the audit
- Keep the report with your HVAC records.
- Re-test after major air sealing to confirm the result.
- Keep up seasonal HVAC checks 7.
- Re-check ventilation after air sealing; a tighter house may need mechanical ventilation.
Sources: [7]
Warning signs an audit is overdue
- Bills rising with no change in use or rates.
- Rooms that never get comfortable.
- Ice dams, condensation or mold.
- Drafts and dust around outlets and baseboards.
- Any carbon monoxide alarm: leave and call 911 or the gas utility before anything else.
Standards, scores and programs
ANSI/RESNET/ICC 380 sets procedures for measuring envelope and duct airtightness and ventilation airflow 1. RESNET Home Energy Raters produce HERS ratings 1. BPI sets home performance standards and credentials, including Building Analyst 3. DOE’s Home Energy Score, developed with its national labs, rates homes 1 to 10 2.
DOE’s Weatherization Assistance Program funds audits and upgrades for income-eligible homes 5. The IRS lists the home energy audit credit under 25C, which expired for property placed in service after 2025 4.
Misconceptions
- Myth A new HVAC system fixes high bills.
- Reality Often the house and ducts are the bigger loss.
- Myth Audits are just sales visits.
- Reality A credentialed audit with measured tests is independent of any product.
- Myth There is still a federal tax credit for audits.
- Reality The 25C credit expired for 2026 4.
- Myth Tighter houses are unhealthy.
- Reality Tight houses need planned ventilation, which the audit should address.
Programs and climate vary by state
Audit programs, prices and rebates vary by state and utility. Climate decides what matters most: attic heat and duct leaks in Arizona and Texas, air leakage and insulation in Ohio and Washington. Check your state guide and degree days.
When to get an audit
Get one before replacing HVAC, before a heat pump conversion, when bills climb or comfort is poor, or before buying a home. A useful rule: fix the house and ducts first, then size the equipment.
Next step: estimate savings with the energy savings calculator, then get HVAC options sized to the audited house.
Questions about HVAC Energy Audit
What is a home energy audit?
A home energy audit is an inspection with measured tests that shows where a house loses energy and what to fix first. It usually includes a blower door test for air leakage, a duct leakage test, insulation and window checks, an HVAC look and combustion safety tests on gas appliances.
What happens during a blower door test?
A powerful fan is fitted in an exterior door and pulls air out of the house to lower its pressure. Instruments measure how much air leaks in through gaps. The auditor then hunts for leaks with smoke or an infrared camera. ANSI/RESNET/ICC 380 sets the testing procedure.
What is the difference between a HERS rating and a Home Energy Score?
A HERS rating is RESNET’s industry index of home energy efficiency, produced by a certified Home Energy Rater with inspection and testing. The DOE Home Energy Score rates a home’s energy assets from 1 to 10, with 10 the most efficient, and comes with suggested improvements.
Is there a tax credit for a home energy audit in 2026?
No. The federal 25C credit allowed up to $150 for a home energy audit, but it expired; it covered property placed in service before 31 December 2025. Some utilities and states offer free or reduced-price audits, so check local programs.
Should I get an energy audit before replacing my HVAC?
Yes, when you can. Sealing air leaks, fixing ducts and adding insulation can lower your heating and cooling load. A new Manual J after those fixes may call for a smaller system, which can cost less and run better.
Who performs home energy audits?
Look for an auditor with a RESNET Home Energy Rater credential or a BPI Building Analyst credential. DOE-trained assessors provide Home Energy Scores. Many utilities keep lists of approved auditors for their programs.
How long does a home energy audit take?
A professional audit with a blower door test often takes a few hours for a typical home, longer for large or complex houses. A DIY walk-through can take an hour or two. Ask the auditor what tests are included and how long the report takes.
Can I do my own energy audit?
You can do a useful walk-through: review bills, check filters, look for drafts, gaps in attic insulation and leaky ducts, and note uncomfortable rooms. Measured tests and combustion safety checks need a trained auditor with the right equipment.
Sources
- RESNET, HERS Index (and ANSI/RESNET/ICC 380 testing standard), retrieved .
- U.S. DOE, Home Energy Score, retrieved .
- Building Performance Institute (BPI), retrieved .
- IRS, Energy Efficient Home Improvement Credit (25C), retrieved .
- U.S. DOE, Weatherization Assistance Program, retrieved .
- NIST Technical Note 1848, Sensitivity Analysis of Installation Faults on Heat Pump Performance (2014), retrieved .
- ENERGY STAR, Maintenance Checklist for heating and cooling, retrieved .
Expert review
Written by the HyreHVAC Research team. Not yet reviewed by an outside expert. We say so rather than imply a review that has not happened; see our editorial policy.
How the numbers were checked: Tests and credentials from RESNET and BPI pages; score scale from DOE’s Home Energy Score page; 25C audit amount and end date from the IRS page; program facts from DOE WAP. The audit example uses illustrative findings.
Suggest a correction. We fix errors and say what changed.