What an audit is
A home energy audit, sometimes called an energy assessment, is a structured review of how a house uses energy and where it could use less. The result is typically a report listing findings and suggested improvements, often with rough cost and savings estimates. Audits range from a free or low-cost walkthrough to a detailed assessment with diagnostic testing. Terms, standards and programs differ by country and region, so what you receive depends on where you live and who does it.
This is general information, not an endorsement of any provider or program.
Types of audit
- Self-assessment or online tool. You answer questions about the home and its equipment, and software produces general suggestions. This is cheap and quick but relies on your inputs.
- Walkthrough audit. An assessor visually inspects the building, equipment and bills, then lists likely improvements.
- Comprehensive audit. In addition to the walkthrough, an assessor uses testing equipment and may build a computer model of the house to compare scenarios.
Some utilities and public programs offer discounted or free assessments, and some tie incentives to completing one. Check local availability.
What an auditor looks at
An assessor generally reviews:
- Your energy bills, usually a year of them, to see seasonal patterns and total use. Knowing how to read an energy bill helps you prepare.
- The building shell. The type and level of insulation in the attic, walls and floors, and the condition of windows and doors.
- Air leakage. Gaps around windows, doors, plumbing penetrations, recessed lights and attic hatches.
- Heating and cooling equipment. Type, age, condition, size, ducts and controls.
- Water heating. The heater type, tank insulation and pipe layout.
- Lighting and appliances. What is installed and how much it is used.
- Ventilation and safety. Whether combustion appliances vent properly and whether the house has adequate ventilation. Safety checks, such as for carbon monoxide risks, are important parts of a good assessment in many programs.
Common diagnostic tests
Blower door test. A calibrated fan is fitted into an exterior door frame to depressurize the house, which makes air leaks easier to detect and allows the leakage to be measured. Results are often expressed as air changes per hour or a flow rate at a set pressure. This gives a number for how leaky the building is and helps decide whether air sealing should come before other work.
Infrared (thermal) imaging. A camera shows surface temperature differences, which can reveal missing or uneven insulation, thermal bridges and some leaks. It works best when there is a large temperature difference between inside and outside, and the images need interpretation by a trained person, since a cold patch is not always a defect.
Duct leakage testing. Pressure tests measure how much air escapes from ducts, which is often significant in ducts running through unconditioned spaces.
Combustion safety checks. Testing furnaces, boilers or water heaters for proper venting and carbon monoxide.
Reading the report
Reports vary, but most include a list of measures, each with estimated cost, estimated annual savings and sometimes a simple payback time. Some points for reading them sensibly:
- Savings are estimates. They rely on models and assumptions about weather, occupant behavior and energy prices, all of which change. Treat them as a ranking tool more than a promise.
- Check the energy prices used. If the report assumed prices very different from yours, adjust your expectations. Energy prices change, so older reports may be out of date.
- Interactions matter. Savings from different measures do not simply add up. After insulating and sealing, a heating system needs to supply less heat, so the benefit of upgrading controls or equipment shrinks.
- Look at the order. Many auditors suggest building-shell measures such as air sealing and home insulation before new equipment, so the equipment can be sized for the improved house. Others prioritize cheap, quick fixes first.
- Separate energy from other benefits. Comfort, moisture control, safety and noise can matter as much as bills. A measure with a long payback might still be worthwhile for these reasons.
- Check for conflicts of interest. If the auditor also sells the work, the recommendations might lean toward products they offer. That does not make them wrong, but getting a second opinion on large items is reasonable.
Questions to ask before you book
- What does the audit include, and what testing is performed?
- What qualifications or certifications does the assessor hold under local programs?
- Will I receive a written report, and what does it contain?
- Is there a cost, and is any of it credited toward later work?
- Does the audit identify safety issues such as venting and combustion concerns?
- Can the assessor explain recommendations in order of priority?
Qualification schemes differ by place, so ask what recognised certification schemes apply locally and verify any claims with the issuing body.
After the audit
A report is only useful if acted on, but acting on every item is not necessary. A reasonable approach is to start with low-cost items, get several quotes for larger ones, and check available incentives before committing, since some require pre-approval. Use contractors who hold the required licenses, especially for electrical, gas or combustion work. Safety-critical changes should be performed by authorized people following local codes.
If you do make improvements, comparing bills before and after, adjusted for weather, gives a rough check of the outcome. Some programs offer a follow-up test, such as repeating the blower door test, to confirm that air sealing worked.
Limits to remember
An audit is a snapshot. It cannot predict future energy prices or how occupants will behave, and different auditors may reach different conclusions about the same house. Still, for a household that wants to move beyond guesses, it is one of the more reliable ways to find out where this particular house loses energy.