If your utility bills keep climbing and your home feels drafty in winter and stuffy in summer, there's a good chance your house is wasting energy — and your money. The average American household spends over $2,000 per year on energy bills, and according to the Department of Energy, 25–30% of that is wasted due to inefficiency. That's $500–$600 a year going out the window. Literally, in many cases.
A home energy audit is the first step to fixing that. It's a comprehensive assessment of how your home uses (and loses) energy, with specific recommendations for improvements that can cut your bills by 5–30% or more. In this guide, we'll cover what an energy audit involves, whether to DIY or go pro, what it costs, and how to prioritize the recommendations you get.
What Is a Home Energy Audit?
A home energy audit (sometimes called an energy assessment) is a systematic evaluation of your home's energy performance. The auditor looks at your entire home as an interconnected system — the building envelope (walls, roof, windows, doors), insulation, HVAC equipment, air leakage, lighting, appliances, and more — to identify where energy is being wasted and recommend the most cost-effective improvements.
Think of it like a doctor's checkup, but for your house. The auditor diagnoses the problems, and then you decide which treatments to pursue based on cost, impact, and your budget.
Quick stat: Homes that implement energy audit recommendations typically see a 5–30% reduction in energy bills. For a household spending $2,400/year on energy, that's savings of $120–$720 annually — often paying for the audit itself within the first year.
What an Energy Auditor Checks
Blower Door Test
This is the signature test of a professional energy audit. A powerful fan is mounted in an exterior doorframe and depressurizes the house. This causes outside air to flow in through all the cracks and leaks in the building envelope, making them easy to detect.
The auditor then uses the blower door results (measured in CFM50 — cubic feet per minute at 50 pascals of pressure) to calculate your home's air change rate. A typical older home might have 10–15 air changes per hour, while a well-sealed home targets 3–5. The difference in energy waste is enormous.
Thermal Imaging (Infrared Camera)
With the blower door running, the auditor uses an infrared camera to scan your walls, ceilings, and other surfaces. The camera reveals temperature differences that indicate:
- Missing or inadequate insulation (shows as cold spots in winter)
- Air leaks around windows, doors, electrical outlets, and penetrations
- Moisture problems hidden behind walls
- Thermal bridging through studs and framing
This technology can literally see through your walls (thermally speaking) and pinpoint exactly where your home is losing energy.
Insulation Assessment
The auditor checks insulation levels throughout your home:
- Attic: Type, depth, and condition. Many homes have insufficient attic insulation — the recommended level for most US climate zones is R-38 to R-60 (roughly 10–16 inches of fiberglass or cellulose).
- Walls: Determined through thermal imaging and sometimes outlet-box checks. Older homes often have zero wall insulation.
- Basement/crawlspace: Rim joist insulation, floor insulation, and vapor barriers
- Ductwork: Insulation on ducts running through unconditioned spaces (attic, crawlspace)
Interested in the specifics? Our insulation cost guide breaks down prices for every type and location.
HVAC System Evaluation
The auditor evaluates your heating and cooling equipment:
- System age, type, and efficiency rating (SEER for AC, AFUE for furnace)
- Proper sizing (oversized or undersized systems waste energy)
- Duct leakage testing — in many homes, 20–30% of heated/cooled air escapes through leaky ducts before reaching living spaces
- Filter condition and maintenance history
- Thermostat type and programming
If your HVAC system is aging, check our HVAC replacement cost guide for current pricing on high-efficiency systems.
Window and Door Assessment
- Type (single-pane, double-pane, low-E)
- Condition of seals and weatherstripping
- Air leakage around frames
- Solar heat gain and orientation
Lighting and Appliance Review
- Percentage of LED vs. incandescent/CFL lighting
- Age and efficiency of major appliances (refrigerator, washer, dryer, dishwasher)
- Phantom loads (electronics drawing power while "off")
- Water heater type, age, and efficiency
Utility Bill Analysis
A good auditor will review at least 12 months of utility bills to understand your energy usage patterns, identify seasonal spikes, and benchmark your home against similar properties.
DIY Energy Audit vs. Professional Audit
| Feature | DIY Audit | Professional Audit |
|---|---|---|
| Cost | Free – $50 | $200–$600 |
| Blower door test | No | Yes |
| Thermal imaging | Limited (phone camera) | Professional IR camera |
| Duct leakage test | No | Yes |
| Detailed report | Self-notes | Professional report with prioritized recommendations |
| Rebate qualification | Usually no | Often required for rebates |
| Time | 1–2 hours | 2–4 hours |
| Best for | Quick assessment, tight budget | Comprehensive analysis, planning major improvements |
How to Do a Basic DIY Energy Audit
You won't get the precision of a professional audit, but you can identify many common issues yourself:
- Check for air leaks: On a windy day, hold a lit incense stick near windows, doors, outlets, pipe penetrations, and attic hatches. If the smoke wavers, you've found a leak. Also check where different building materials meet (brick to siding, chimney to wall).
- Inspect insulation: Look in your attic — can you see the ceiling joists? If so, you need more insulation. Measure the depth and compare to recommended levels for your climate zone.
- Check your windows: Can you feel drafts? Do you see condensation between panes (seal failure)? Are they single-pane?
- Evaluate your HVAC: Check the age of your furnace and AC (nameplate on the unit). Systems over 15 years old are significantly less efficient than modern equipment.
- Review your utility bills: Look for seasonal patterns and compare year-over-year. A steady increase might indicate declining equipment efficiency or worsening insulation.
- Check ductwork: Look for visible gaps, disconnections, or poorly sealed joints in accessible ductwork. Feel for air leaking at connections while the system is running.
How Much Does a Professional Energy Audit Cost?
| Audit Type | Cost | What's Included |
|---|---|---|
| Basic walk-through | $100–$200 | Visual inspection, basic recommendations |
| Standard audit (blower door + thermal imaging) | $200–$400 | Blower door test, IR camera, insulation check, detailed report |
| Comprehensive audit | $400–$600 | Everything above plus duct testing, combustion safety, detailed cost-benefit analysis |
| Utility-subsidized audit | $0–$100 | Many utilities offer free or discounted audits to customers |
Money-saving tip: Before paying for an audit, check with your utility company. Many electric and gas utilities offer free or heavily subsidized energy audits as part of their efficiency programs. Some states also offer free audits through their energy office.