CSLB C-10 Electrical Exam Guide (2026): Fees, Format, Sections and Study Plan
Reviewed by Ken Pergeson, Permit Expediter & Code Compliance Consultant, Ventura County, CA ·
The CSLB C-10 Electrical exam is the California Contractors State License Board trade exam for electrical contractors, written against the 2025 California Electrical Code and Cal/OSHA safety orders. This guide covers the cost, format, pass score, open-book rules, retakes, experience, difficulty, how California differs from other states and a study plan, using only CSLB, Cal/OSHA and OSHA documents.
What Is the CSLB C-10 Electrical Contractor License?
The C-10 is the California contractor license class for electrical work. It is issued by the Contractors State License Board (CSLB) and lets a business contract for electrical projects in California. It is a contractor license, so it is about running and bidding jobs, not only wiring them. That is why CSLB makes the person qualifying the license pass two tests: the Law and Business exam and the C-10 trade exam.
The trade exam is the one this guide covers. CSLB's own C-10 Electrical study guide (form 13E-10, dated 03/2026, for exams on or after June 1, 2024) sets out what it tests. For the business half, see our CSLB Law and Business Exam Guide.
CSLB C-10 Exam Format at a Glance
| Item | CSLB C-10 rule |
|---|---|
| Question type | Multiple choice, four choices, one BEST answer |
| Open book | No. Closed book, no reference materials |
| Calculator | Provided by CSLB; some questions need math |
| Guessing penalty | None |
| Drawings | Most CSLB trade exams include questions on blueprints or drawing booklets |
| Passing score | Told to you at the test site |
| Vendor | PSI (scheduled through your PSI Exams account) |
| Question writers | Licensed contractors actively working in the trade |
CSLB's study guide does not print a question count or time limit, and we will not guess one. The guide does say "plenty of time is provided," and tells you to read every question and all four choices before picking an answer. Our full mock exam uses its own practice length and is labeled as unofficial.
The Five C-10 Exam Sections and Weights
The CSLB C-10 study guide splits the electrical trade exam into five sections. CSLB marks the percentages as approximate.
| Section | Weight | What CSLB lists |
|---|---|---|
| 1. Planning and Estimating | 28% | Existing system evaluation, plans and specs, electrical calculations, code requirements, material selection, energy production and storage planning |
| 2. Rough Wiring | 27% | System layout, clearance and accessibility, raceway and panel installation, wire and equipment, grounding and bonding |
| 3. Finish Wiring and Trim | 11% | Device placement, motor and equipment installation, labeling, trims and sealants |
| 4. Startup, Troubleshooting, and Maintenance | 16% | Energizing and testing, common problems, repairing inoperable components, choosing and using test equipment |
| 5. Safety | 18% | Lockout/tagout, PPE, tools and equipment, hazardous materials and job site environments |
One detail stands out. Every section ends with "energy production and storage" for photovoltaic, wind, generators, batteries and capacitors. Solar and battery work is not a side topic on the current C-10 exam. It runs through planning, rough-in, trim, startup and the final system performance checks.
Planning and Rough Wiring together make up 55% of the exam. If you have spent your career in the field and rarely bid jobs, Planning and Estimating is where you have the most to gain.
CSLB Sample Questions Explained
The study guide gives three sample questions, and they show the style well.
- PV bonding: solar modules, metal frames and mounting equipment on a roof array must be bonded and grounded. The wrong choices (weatherproof, wind resistant, anodized) all sound plausible but are not the electrical rule.
- Breaker replacement: choose a replacement breaker by frame type, AIC (interrupting) rating and ampacity. Upsizing the ampacity "to allow for arcing" is the trap.
- Estimating math: 13 receptacles at $3.56 with one free per 10 bought means paying for 12. 12 × $3.56 = $42.72, plus 7.25% tax, gives $45.82.
Notice the pattern: real field judgment, the "BEST" answer among close options, and simple business math. That last type is why CSLB hands you a calculator.
CSLB C-10 Cost: Application, License and Renewal Fees
CSLB's list of all fees shows these amounts. Exam fees are separate and paid to the testing vendor when you schedule.
| Fee | Amount |
|---|---|
| Original application (one classification) | $450 |
| Initial license fee, sole owner | $200 |
| Initial license fee, non-sole owner | $350 |
| Fingerprints: DOJ + FBI processing | $32 + $17 (plus the Live Scan site's own rolling fee) |
| C-10 active timely renewal, sole owner | $470 |
| C-10 active timely renewal, non-sole owner | $720 |
| C-10 active delinquent renewal, sole owner / non-sole owner | $695 / $1,070 |
| Additional classification on an existing license | $230 |
C-10 renewals cost $20 more than the standard rates, a surcharge the fee list shows only for C-10 contractors. The original license application adds that the initial license fee is sent separately after you pass, that eligible military applicants get those initial fees cut by 50%, and that the license needs a $25,000 contractor's bond.
C-10 Experience Requirements and Eligibility
To sit for the C-10, the qualifying individual needs at least four years of experience in the electrical classification within the last 10 years. CSLB's qualifying experience page only counts experience at journey level or as a foreman, supervising employee, contractor or owner-builder. A journeyman is "a fully qualified, experienced worker" who can work without supervision, or someone who finished an apprenticeship. Helper, laborer and apprentice time does not count toward the four years.
A qualified, responsible person must verify every claim. That can be an employer, a foreman, a fellow journeyman, a union representative, a building inspector or a homeowner, among others. Owner-builder experience only counts toward the B-General Building class, so it will not help you qualify for the C-10.
If CSLB returns your application as incomplete, you have 90 days to correct and resubmit it. A sloppy application can cost weeks or months, so it is worth checking it before you send it.
Pass Score, Retakes and Your 18-Month Window
CSLB's Studying for the Examination page says you will be told at the test site what percentage of correct answers you need. Do not trust any website that quotes a fixed C-10 passing score as official.
The application lays out the retake rules. Once your application is approved, you have 18 months to pass. In that window you may retake the exam as many times as needed within retesting guidelines, but you must wait 21 days after each attempt, and you pay the vendor again each time. You book the retake yourself in your PSI account. If you fail one or both exams, you pick the date, time and location for the next attempt in PSI.
How Hard Is the CSLB C-10 Exam?
CSLB does not publish pass rates on the pages we checked, so we will not invent one. What the study guide does show is why the C-10 trips up experienced electricians.
- It is closed book. No reference materials are allowed, so you must know the 2025 California Electrical Code rules cold.
- It is a contractor test. 28% is planning and estimating, including material takeoffs, plan reading and pricing math.
- Solar and storage are everywhere. PV, wind, generators, batteries and capacitors appear in all five sections.
- "BEST" answers. Several choices can be partly true. You need to pick the one CSLB considers best practice.
Safety: The Cal/OSHA Rules Behind 18% of the C-10 Exam
The study guide lists the Cal/OSHA General Industry, Construction and Electrical Safety Orders as references. Those are free to read, and several rules are worth knowing word for word:
- Title 8 §2320.2: work on exposed energized parts needs a supervision decision, trained staff and suitable PPE. Approved insulated gloves are required above 250 volts to ground. When connecting a dead line to a live circuit, attach to the de-energized part first. When disconnecting, remove the source end first.
- Title 8 §2320.4: before working on de-energized equipment, an authorized person notifies everyone involved, locks the disconnect open, tags it and blocks or dissipates stored energy such as capacitors.
- Title 8 §2340.16: working space must be at least 30 inches wide (or the equipment width), allow a 90° door opening, never be used for storage, and have 6 ft 6 in of headroom for installations built on or after May 5, 2008.
- 29 CFR 1926.404: on construction sites, 120-volt, 15- and 20-amp temporary receptacles need GFCIs, or the employer must run an assured equipment grounding conductor program with tests at least every 3 months.
How California Differs From Other States
California licenses electrical contractors through CSLB under the Business and Professions Code, so the C-10 qualifier takes the same Law and Business exam as every other contractor class. Rules in other states are set by their own boards, so check them directly rather than assuming they match. In California the code is the California Electrical Code, part of Title 24, which the Building Standards Commission publishes online at dgs.ca.gov/bsc. Safety is enforced by Cal/OSHA under Title 8 rather than only federal OSHA. The out-of-state waiver described in the CSLB application is for B-General Building applicants who passed the NASCLA exam, so an electrical contractor licensed elsewhere should plan on taking the C-10 trade exam.
Six-Week CSLB C-10 Study Plan
- Week 1, set up: download the C-10 study guide and get the reference list in order (2025 California Electrical Code, Ugly's, the Cal/OSHA orders). Take 25 questions in our CSLB C-10 Practice Test to find your weak sections.
- Week 2, Planning and Estimating (28%): load calculations, conductor and conduit sizing, plan symbols and takeoffs. Do a pricing math problem like the receptacle sample every day.
- Week 3, Rough Wiring (27%): working clearances, raceways, panels, grounding and bonding, and PV and battery rough-in.
- Week 4, Finish Wiring and Startup (27%): devices, motors, labeling, energizing and testing, and choosing the right meter for each test.
- Week 5, Safety (18%): read §2320.2, §2320.4 and §2340.16 in full, then OSHA 1926.404 and 1926.417. These are short and score well.
- Week 6, review: sit the CSLB C-10 Full Mock Exam with no books open, review every miss against its source, and study the Law and Business book in parallel.
Related guides: Journeyman Electrician Exam Guide and NABCEP PV Associate Exam Guide (2026): PVA Fees, Format, Domains and Study Plan.
Frequently Asked Questions
How much does the CSLB C-10 license cost?
CSLB charges a $450 application fee for one classification. After you pass, the initial license fee is $200 for a sole owner or $350 for a non-sole owner. Exam fees are paid separately to the testing vendor, PSI, when you schedule.
Is the CSLB C-10 exam open book?
No. The CSLB C-10 study guide says it is a closed-book exam and no reference materials may be used. A calculator is provided.
What is on the CSLB C-10 exam?
Five sections: Planning and Estimating (28%), Rough Wiring (27%), Finish Wiring and Trim (11%), Startup, Troubleshooting, and Maintenance (16%) and Safety (18%). The percentages are approximate.
What score do you need to pass the C-10 exam?
CSLB does not print a passing score in the study guide. Its Studying for the Examination page says you are told at the test site what percentage of correct answers you need.
How many times can you retake the CSLB C-10 exam?
As many times as needed within retesting guidelines during the 18 months after your application is approved. You must wait 21 days between attempts and pay the vendor fee each time.
How much experience do you need for a C-10 license?
At least four years of journey-level (or foreman, supervisor or contractor) experience in the electrical classification within the last 10 years, verified by a qualified person.
Do I also need to pass the Law and Business exam?
Yes. Every qualifying individual must pass the Law and Business exam plus the trade exam, unless they qualify for a waiver.
How much does it cost to renew a C-10 license?
C-10 contractors pay a little more than other classes: $470 for an active timely renewal as a sole owner or $720 as a non-sole owner, per the CSLB fee list.
Which code book does the C-10 exam use?
The current study guide lists the 2025 California Electrical Code (Title 24) plus the California Energy, Fire and Building Codes and Cal/OSHA safety orders.
TradeExamHub is independent and not affiliated with CSLB, PSI or Cal/OSHA. Our questions quote CSLB, Cal/OSHA and eCFR text and do not come from any actual CSLB exam.