An energy audit is the single best first step for almost any California homeowner trying to reduce energy use. Before spending $10,000 on a heat pump or $30,000 on solar, a $0–$600 audit tells you exactly what’s wrong with your specific home — and in what order to fix it. Most CA utilities offer them free.
The problem isn’t that audits are hard to find. It’s that nobody in the industry has a financial incentive to lead with them. HVAC contractors want to sell you equipment. Solar installers want to sell you panels. An auditor hands you a prioritized list and then mostly leaves. That’s exactly why you should call one first.
What a professional energy audit actually includes
A real audit is not a sales call. It’s a structured diagnostic of your home’s energy performance. Here’s what a full Level 2 audit covers:
Walk-through inspection. The auditor examines insulation levels in the attic and crawlspace, window condition and frame age, HVAC equipment age and condition, water heater type, and major appliances. This gives them a baseline before any testing begins.
Blower door test. A large calibrated fan mounts in your front door and depressurizes the house to a standard 50 Pascals of pressure. The test measures how much air flows in to maintain that pressure. The result — ACH50, or air changes per hour at 50 pascals — tells you exactly how leaky your home is and whether air sealing should be the first thing you do. It can also be combined with smoke sticks or a fog machine to visually locate specific leaks while the house is pressurized.
Thermal infrared imaging. The auditor photographs your walls, ceilings, and floors with an infrared camera. The camera sees temperature differences, revealing hidden insulation gaps and air infiltration pathways that would take hours to find by physical inspection alone. On a cool morning or warm afternoon, the results can be striking.
Duct leakage test. HVAC ducts in most older homes leak conditioned air into unconditioned spaces — attics, crawlspaces, wall cavities — before it ever reaches the rooms it’s supposed to heat or cool. A duct blaster test quantifies exactly how much you’re losing, and where.
Written report. After the testing, you get a prioritized list of recommended improvements with estimated costs and projected energy savings for each. This is the deliverable. It tells you which fixes have the best payback for your specific home, in your specific climate zone, with your specific usage patterns.
Levels of audits
Not all audits are the same. There are effectively three tiers:
Level 1 — Walk-through only ($100–$250). An auditor visually inspects the home and gives you general recommendations. Useful for a quick orientation, but it misses everything the diagnostic equipment reveals. You won’t know your ACH50 or where your ducts are leaking.
Level 2 — Full diagnostic ($250–$650). Includes the blower door test, infrared camera, and duct leakage test. This is what you actually want. The difference in cost is small relative to the value of the information. If you’re going to spend $10,000+ on improvements, the Level 2 audit is not a significant line item.
Free utility audit. PG&E, SCE, SDG&E, LADWP, and SMUD all offer free or subsidized home energy audits. Quality varies by program and contractor — some programs include a full blower door test, others are more limited. Call your utility and ask specifically what’s included. Even a basic utility audit is a good starting point, and it costs you nothing.
The blower door test: what the numbers mean
ACH50 (air changes per hour at 50 pascals) is the standard measure of how leaky a home is. Here’s how to interpret your number:
| ACH50 | What it means | What to do |
|---|---|---|
| > 10 | Very leaky older home | Major air sealing opportunity — high ROI, do this first |
| 5 – 10 | Average older CA home | Significant improvements possible, cost-effective |
| 3 – 5 | Reasonably tight | Marginal opportunity, focus on other priorities |
| < 3 | Tight home | Now needs mechanical ventilation (ERV/HRV) or air quality suffers |
Most California homes built before 1990 come in between 5 and 12 ACH50. If yours is above 7, air sealing is almost certainly the highest-ROI improvement you can make — higher than insulation, higher than a new heat pump, often higher than solar. The auditor can quantify this for your specific situation.
What the infrared camera shows
Thermal imaging adds a layer that no walk-through can replicate. On a day with significant temperature difference between inside and outside, the IR camera reveals:
- Missing or inadequate insulation as cold patches in winter (or hot patches in summer) on ceilings and walls where insulation is absent or compressed
- Air infiltration paths as cold streaks moving down walls or across ceilings, tracing the actual flow of cold outside air entering the house
- Moisture intrusion which shows up as temperature anomalies that the auditor can distinguish from simple air leakage
- Bypasses and thermal bridges at framing members, top plates of interior walls, and anywhere building materials with different thermal conductivity meet
The camera can identify issues in 20 minutes that would take a week to find by physical inspection. It’s one of the most compelling reasons to insist on a Level 2 audit rather than settling for a walk-through.
How to find a good auditor in California
Start with your utility. PG&E, SCE, SDG&E, LADWP, and SMUD all offer free or subsidized audits. Call them before you do anything else. The program varies by utility and sometimes by geography, but you will very likely find a program available to you at no cost.
BPI-certified auditors. The Building Performance Institute (BPI) is the main professional certification body for residential energy auditors. A BPI-certified auditor has passed technical exams and demonstrated competency. Find one at bpi.org.
HERS raters via RESNET. The Home Energy Rating System (HERS) is the California standard rating for home energy performance. HERS raters are trained to perform full diagnostic audits and can produce an official HERS score. Find one at resnet.us.
CHEERS. California Home Energy Efficiency Rating System — a CA-specific auditor and contractor network tied to state programs. Useful for finding auditors who are connected to California rebate programs.
Red flag to watch for: Any auditor who leads with a product pitch before finishing the diagnostic portion is not doing an audit — they’re doing a sales call. A real audit takes 2–4 hours. The recommendations come from the test results, not from whatever the company happens to sell.
What to ask the auditor
- “What’s the single highest-ROI improvement for my specific home?”
- “What’s the payback period for each recommendation?”
- “Do you do air sealing work yourself, or can you refer someone who does?”
- “What is my current ACH50 reading?”
- “What would my HERS score be if I made the top three improvements?”
The first question is the most important. Every home is different. A 1960s ranch house in Sacramento has different priorities than a 1985 condo in San Diego. The audit is valuable precisely because it makes recommendations for your home — if the auditor can’t tell you what’s most important for your specific situation, the audit isn’t very good.
The 25C tax credit — what happened to it
There was a $150 federal tax credit for qualified home energy audits under Section 25C of the tax code, part of the Inflation Reduction Act. It covered audits performed by a certified auditor and helped offset the cost of a Level 2 diagnostic.
That credit expired December 31, 2025. As of 2026, there is no federal tax credit for home energy audits. If you’re reading this and planning to get an audit this year, don’t budget for that credit — it’s gone.
The good news is that utility-subsidized and free audits are still widely available, and that was always the better path for most CA homeowners anyway. Start with your utility program before considering a paid audit.
After the audit: what actually happens
You get a report with a prioritized list. For most California homes, air sealing and attic insulation are at the top. The report also gives you a baseline — your current ACH50, your duct leakage percentage, your estimated annual energy use — that you can measure against after improvements are made.
Some auditors offer post-work verification: they come back after you’ve completed the air sealing work and run the blower door again to confirm the improvement. This is worth paying for. It tells you whether the contractor actually did the work properly, and it gives you a measurable before/after number you can use to evaluate future investments.
The single biggest mistake homeowners make with energy audits is getting one and not acting on it. The report sits in a drawer. Six months pass. The window for the project season closes. Three years later, the house is still leaking at 9 ACH50.
Schedule the audit. Read the report. Pick the top recommendation and get it done within 60 days. The audit itself is just information — it’s only worth the decision it produces.
Call your utility this week and schedule a free energy audit. Even a basic walk-through will tell you more than any YouTube video about what your specific home needs. PG&E: 1-800-743-5000 — SCE: 1-800-655-4555 — SDG&E: 1-800-411-7343 — LADWP: 1-800-342-5397 — SMUD: 1-888-742-7683.
Some “auditors” are really sales reps for insulation companies or window manufacturers. A real audit takes 2–4 hours and includes a blower door test. A 45-minute walk-through that ends with a product pitch is not an audit.