How to get a C-20 Warm-Air Heating, Ventilating and Air-Conditioning license in California
Who qualifies, what CSLB asks for, the two exams you sit, what it all costs and how many people pass the C-20 exam, in the order it happens.
What a C-20 license covers
A warm-air heating, ventilating and air-conditioning contractor fabricates, installs, maintains, services and repairs warm-air heating systems and water heating heat pumps, complete with warm-air appliances; ventilating systems complete with blowers and plenum chambers; air-conditioning systems complete with air-conditioning unit; and the ducts, registers, flues, humidity and thermostatic controls and air filters in connection with any of these systems. This classification shall include warm-air heating, ventilating and air-conditioning systems which utilize solar energy.
Source: 16 CCR §832.20.
You apply for the classification your experience is in, and the C-20 exam is the trade exam for that classification. Already licensed in another classification? Adding C-20 takes only the C-20 exam, not Law and Business again.
Who qualifies
Every license has a qualifier: the person who directly supervises and controls the construction work done under it. That can be you, or someone else who meets the bar on your behalf. For C-20, the qualifier must:
- be at least 18 years old;
- have a valid Social Security number or an ITIN;
- have four years of at least journey-level experience in the last 10 years in warm-air heating, ventilating and air-conditioning work: as a journeyperson, foreperson, supervising employee or contractor.
You can shorten the four years, but not all of it. CSLB may credit a completed apprenticeship, technical training or accredited education toward part of the experience, with certificates and transcripts sent in with the application. Every qualifier must still show at least one year of practical journey-level experience. A randomly selected share of applications is checked, so line up the people who can certify your warm-air heating, ventilating and air-conditioning experience before you apply.
The two exams: Law and Business and C-20
A first license takes two computer-based exams at a PSI test center: Law and Business, the same for every classification, and the C-20 trade exam. Both are closed book, multiple choice with four options and one best answer, and each allows 3½ hours. CSLB does not publish how many questions either exam has.
CSLB’s study guide splits the C-20 exam into 4 sections:
| Section / What it covers | Share |
|---|---|
| Planning and Estimating HVAC system design and evaluation; load and psychrometric calculations; duct system design and layout; job cost estimation. | 22% |
| Fabrication, Installation, and Startup Duct system fabrication; equipment installation; electrical and mechanical components; plumbing and refrigeration components; air distribution and duct systems; HVAC system startup. | 38% |
| Troubleshooting, Repair, and Maintenance HVAC system diagnostic tests and evaluation; HVAC system maintenance and repair. | 20% |
| Safety Personal protective equipment (PPE); job site safety requirements (Cal/OSHA); handling hazardous materials. | 20% |
CSLB License Examination Study Guide, Warm-Air Heating, Ventilating and Air-Conditioning (C-20), form 13E-20 (01-2026), for examinations scheduled on or after April 1, 2026. CSLB notes that the percentages are approximate.
Spanish: CSLB gives the C-20 exam in English only; it is not one of the exams translated into Spanish. You can ask for an approved translator with CSLB’s Translator Form, requested in advance. How the translator rules work.
How many pass the C-20 exam
CSLB reports every exam it gives. In 2022/23 46% of C-20 exams were passes (1,229 exams), against 57% for Law and Business. The counts include retakes: across all CSLB exams first attempts pass 71–76% of the time and retakes 37–40%, so the first attempt is the one to prepare for.
| Fiscal year | C-20 exams given | Passed | Law and Business passed |
|---|---|---|---|
| 2019/20 | 952 | 41% | 52% |
| 2020/21 | 1,181 | 50% | 58% |
| 2021/22 | 1,865 | 43% | 54% |
| 2022/23 | 1,229 | 46% | 57% |
Source: CSLB 2023 Sunset Review Report, Table 8 (Examination Data), pp. 50-56. More in CSLB pass rates.
Step by step
- Check you qualify. Four years of journey-level warm-air heating, ventilating and air-conditioning experience in the last 10 years, age 18+, an SSN or ITIN.
- Apply with $450. Send CSLB’s application for the C-20 classification with the non-refundable $450 processing fee. Do not send the bond or the license fee yet. Field 16 is where you ask for a Spanish exam or a translator.
- Fingerprints. Once CSLB accepts the application, every person listed on it submits fingerprints through a Live Scan site for the DOJ and FBI background check.
- Asbestos open book exam. Every applicant completes CSLB’s open book exam on asbestos abatement standards before a license can be issued. It is on the CSLB website.
- Book and pass both exams. After the Notice to Schedule an Examination, book Law and Business and the C-20 exam with PSI, $51.43 per exam for every attempt. You have 18 months from the day CSLB accepts the application, and 21 days to wait after a fail.
- Bond and workers’ compensation. File a $25,000 contractor’s bond (you pay a premium to a surety, not $25,000). C-20 contractors must carry workers’ compensation insurance even with no employees.
- License fee. Pay the initial license fee: $200 for a sole owner, $350 for any other business. The license is issued when CSLB has everything.
C-20 is on CSLB’s short list: C-20 contractors must carry workers’ compensation insurance, or a valid certificate of self-insurance, whether or not they have employees. Budget for the premium before you pay the license fee. CSLB workers’ compensation requirements.
What a C-20 license costs
The fees are the same for every classification. Here is what you pay to get from application to a C-20 license:
| Fee | Paid to | Amount |
|---|---|---|
| Application processing fee (non-refundable) | CSLB | $450 |
| Exam fee, Law and Business + C-20, first attempt | PSI | $102.86 |
| Fingerprints: Department of Justice + FBI | Live Scan site | $32 + $17 |
| Live Scan rolling fee | Live Scan site | varies |
| Initial license fee, sole owner (other businesses $350) | CSLB | $200 |
| $25,000 bond premium | Surety company | varies |
| Fixed fees, sole owner | $801.86 + … |
So plan on $801.86 in fixed fees ($951.86 for a business that is not a sole owner), plus the rolling fee and the bond premium. Each retake is another $51.43. The full table, with renewals: what a contractor license costs.
Sources: CSLB fee list, PSI candidate bulletins 2026, CSLB bond requirements.
How to study for the C-20 exam
CSLB publishes a free study guide for every exam, with the outline above and the list of references the C-20 questions are written from. Get it from CSLB’s study guides page. The references it lists for C-20:
- 2025 Building Energy Efficiency Standards for Residential and Nonresidential Buildings (California Energy Commission)
- 2025 California Building Code (California Code of Regulations, Title 24)
- 2025 California Electrical Code (California Code of Regulations, Title 24)
- 2025 California Energy Code (California Code of Regulations, Title 24)
- 2025 California Mechanical Code (California Code of Regulations, Title 24)
- 2025 California Plumbing Code (California Code of Regulations, Title 24)
- ASHRAE Handbooks: Fundamentals; HVAC Applications; HVAC Systems & Equipment; Pocket Guide (ASHRAE)
- Fundamentals of HVACR, C. Stanfield and D. Skaves (Pearson)
- HVAC Duct Construction Standards - Metal and Flexible (SMACNA)
- ACCA Manuals CS, D, H, J, N, P, Q, RS and S (Air Conditioning Contractors of America)
- Modern Refrigeration and Air Conditioning, Althouse et al. (Goodheart-Willcox)
- Refrigeration & Air Conditioning Technology, Johnson, Silberstein, Tomczyk and Whitman (Cengage Learning)
- Cal/OSHA General Industry, Construction and Electrical Safety Orders, 2026 (California Code of Regulations, Title 8)
Our C-20 course has 1,172 practice questions across the 4 sections, in English and Spanish, each answer with a plain explanation and its source, plus full-length practice exams of about 115 questions against the 3½-hour clock (CSLB does not publish the exact number). Start with the free 25-question C-20 test: it scores you section by section. Or read 10 C-20 exam questions with answers first.
Common questions
How many years of experience do I need for a C-20 license?
Four years of at least journey-level experience in the last 10 years, in warm-air heating, ventilating and air-conditioning work, as a journeyperson, foreperson, supervising employee or contractor. Apprenticeship, technical training or accredited education can count for part of it, but at least one year must be practical journey-level work.
Do I need the Law and Business exam for C-20?
For a first license, yes: CSLB requires Law and Business from almost every applicant in addition to the C-20 exam. If you already hold a license and are adding C-20, you take only the C-20 exam.
Can I take the C-20 exam in Spanish?
No. CSLB gives the C-20 exam in English only. You can ask CSLB in advance for an approved translator with its Translator Form.
What is the pass rate of the C-20 exam?
In 2022/23, 46% of the 1,229 C-20 exams given were passes, retakes included (CSLB 2023 Sunset Review Report, Table 8 (Examination Data), pp. 50-56). Law and Business passed 57% the same year.
How much does a C-20 license cost?
$801.86 in fixed fees for a sole owner: the $450 application, $51.43 per exam at PSI for Law and Business and C-20, $32 + $17 for fingerprints and the $200 initial license fee. Add the Live Scan rolling fee and the premium on the $25,000 bond. A business that is not a sole owner pays $350 for the license instead of $200.
Do I need workers' compensation insurance for C-20?
Yes, always. C-20 is one of the classifications CSLB requires to carry workers' compensation insurance, or a certificate of self-insurance, whether or not you have employees.
Last reviewed 14 October 2026 against CSLB’s Get Licensed to Build, the C-20 study guide, its Examinations FAQ, its fee list and the 2023 Sunset Review Report. Requirements change; confirm at cslb.ca.gov before acting. This is study guidance, not legal advice, and we are not affiliated with CSLB or PSI.