Cleaning, adding or replacing ducts: which has rules
Under the California Mechanical Code, CSLB's letter to C-20 contractors says adding ducting requires a building permit. San Diego's bulletin goes further and requires a HERS evaluation when more than 40 feet of new ductwork is installed. Neither list names cleaning.
SMUD's heating and cooling rebate adds a condition of its own: any new ductwork must be insulated to R-8 or better.
What duct cleaning costs in California
For this job in California, our estimate is $420 to $870 per job. That's a model, not a quote, built from national published cost ranges and adjusted by California's wage ratio to the US (1.16).
Duct cleaning is estimated at $420 to $870 per job, from 2 national published ranges adjusted by California's technician wage ratio of 1.16, so read it as an estimate, not a quote. It doesn't cover adding or replacing ductwork.
| Item | Figure | What it is |
|---|---|---|
| Estimated range, not a quote | $420 to $870 per job | Built from 2 national published ranges, adjusted by the California HVAC technician wage ratio (1.16). California company prices are shown separately. Basis: no state company sample (no counted California company price for this job), national estimate only. |
| Technician wage, California mean | $36.24 an hour | A wage (BLS, May 2025), not a price. |
How we estimate costs: the Estimated range row is a model, not a quote. We have no counted California company price for this job, so the range is our national estimate alone. Our national estimate takes two published national ranges for this job (cost guides from third-party sites that we have not verified and do not cite) and multiplies them by California's HVAC technician wage ratio to the US (1.16, BLS OEWS May 2025, heating, air conditioning and refrigeration mechanics and installers). The wage and permit rows below are what HVAC technicians are paid and what a city charges, and neither is a price. We have not collected quotes. Full method. Prices as of Oct 23, 2026.
Who may do duct work
CSLB's C-20 text covers the ducts, registers and air filters that go with a heating or air-conditioning system, so ask a cleaning-only company whether it holds that class. B&P 7048's exemption reaches casual, minor work under $1,000 that needs no building permit. It's lost once the person advertises as a contractor or hires someone to help. Check any number you're given on CSLB's lookup.
Claims to ask a company to support
No California agency page we cite rates duct cleaning or its health claims, so if a company says cleaning will cut allergies or save energy, ask it for the source. Ask which problem it saw, such as visible mold or heavy debris, and ask for photos of the inside of your ducts before and after.
When duct work shouldn't wait
- A gas smell near the furnace or the ducts: leave and call 911, then your utility.
- A carbon monoxide detector sounds near the furnace: go outside, then call 911.
- The ducts are dusty, with no smell and no visible mold.
- A register rattles.
What to check first
- Shine a flashlight into a few registers and look for mold or heavy debris.
- Change the filter before paying for anything else.
- Ask each company for the license number and a written scope.
Permits and HERS testing for ducts
Adding ducting needs a permit, and in San Diego more than 40 feet of new ductwork also brings a HERS evaluation. Since January 1, 2026, the CEC says, HERS field verification and diagnostic testing rules sit in the Energy Code itself. You're entitled to hire your own HERS rater, and you can ask the rater or the installer for the completed forms.
Before any work starts, get the license number and check it with your state's licensing board; our state pages link the lookup.
Questions people ask
How much should duct cleaning cost in California?
Our estimate for cleaning is $420 to $870 per job, not a quote. It's built from two national ranges and California's wage ratio, with no counted California company price behind it.
Does duct cleaning need a permit?
The sources we cite don't list cleaning as permit work; adding ducting does need one. CSLB's letter names adding ducting as permit work under the California Mechanical Code.
What is a HERS test?
Field verification and diagnostic testing by a HERS rater; San Diego requires a HERS evaluation for more than 40 feet of new ductwork. Since January 1, 2026 the CEC has put those testing rules in the Energy Code (Title 24, Part 6). The CEC says hiring the rater is the homeowner's right.
Does a duct cleaner need a contractor license?
Duct work falls under C-20, and B&P 7048 exempts some small jobs. The exemption covers casual work under $1,000 that needs no permit, and it ends if the person advertises as a contractor or hires help. Ask for the license number.
Does new ductwork have to be insulated?
For SMUD's rebate it does, to R-8 or better. It's a condition of SMUD's rebate, so ask the installer what insulation the quote specifies.
- U.S. Bureau of Labor Statistics, OEWS May 2025: Heating, Air Conditioning, and Refrigeration Mechanics and Installers (SOC 49-9021), California, mean hourly wage Read Oct 23, 2026.
- CSLB: C-20 Permit Enforcement Letter (PDF, 2010) Read Oct 20, 2026.
- City of San Diego DSD: What Permits Do I Need? Read Oct 20, 2026.
- CEC: Home Energy Rating System (HERS) Program Read Oct 20, 2026.
- SMUD: Home Performance Program (Improve Home Efficiency) Read Oct 20, 2026.
- CSLB: Licensing Classifications Detail, C-20 Read Oct 20, 2026.
- California Legislative Information: BPC 7048 Read Oct 20, 2026.
- CSLB: Check a License Read Oct 20, 2026.
- Gas Safety | PG&E Read Oct 20, 2026.
- Emergency Information | SoCalGas Read Oct 20, 2026.
- Gas safety | San Diego Gas & Electric Read Oct 20, 2026.
- HVACMatch: how we estimate costs, California (editorial policy) Read Oct 23, 2026.