What the C-10 Electrical Contractor License Covers in California
A C-10 Electrical Contractor license in California authorizes you to install, modify, and service any electrical wiring or equipment from 12 volts to 12,000+ volts — residential, commercial, and industrial. Per CSLB Code of Regulations Section 832.10, the scope covers wires, fixtures, appliances, raceways, conduits, solar photovoltaic cells, and any related equipment used to transmit electrical current. To qualify you need 4 years of journey-level experience verified by a current licensee, a passing score (≥72%) on both the CSLB Law & Business exam and the C-10 trade exam, a $25,000 contractor’s bond, and roughly $330 in CSLB application fees.
The classification covers residential, commercial, and industrial work. It includes service entrances, panels and subpanels, branch circuits, lighting (interior, exterior, and landscape), motors and motor controls, generators, transfer switches, EV charging equipment, solar PV interconnection, low-voltage where it is incidental to the line-voltage scope, and the line-voltage portions of HVAC, fire alarm, and security systems. The C-10 is also the contractor of record for most utility-side work performed under PG&E, SMUD, or municipal utility coordination agreements.
California is in the middle of the largest sustained electrical work boom in modern history. Title 24 mandates electric-readiness for new construction, the EV transition is driving a residential charger installation backlog estimated in the hundreds of thousands of units, and Silicon Valley AI data center buildouts are absorbing C-10 capacity at every level. If you are deciding which classification to pursue, the C-10 is one of the safest bets for the next decade.
What the C-10 Does NOT Cover
Two boundary areas confuse a lot of candidates. First, certain low-voltage limited-energy work falls under the C-7 (Low Voltage Systems) classification: communications cabling, alarm systems, audio-video, and similar low-voltage installations as a primary scope. A C-10 can do low-voltage work that is incidental to a line-voltage project, but cannot pull permits for standalone low-voltage scopes.
Second, solar photovoltaic work has overlap. A C-10 can do residential and commercial solar PV, including the panels, inverters, and grid interconnection. The C-46 (Solar) classification is a separate contractor type, and a C-46 can install active solar systems but has limits on associated electrical work outside the solar scope. Most California solar contractors hold both C-10 and C-46.
The full scope rules are published by CSLB and you should read Section 832 carefully before committing to a classification path. Our team can walk you through the right choice for your business plan; talk to a licensing specialist if you are weighing C-10 against C-7, C-46, or a B general license.
Eligibility Requirements for the C-10 License
Per Business and Professions Code Section 7068, every C-10 applicant must meet these baseline requirements:
- At least 18 years old.
- Have a valid Social Security Number or Individual Taxpayer Identification Number.
- Have at least four full years of journey-level experience in the C-10 trade within the last ten years. Journey-level means you worked as a fully qualified worker, foreman, supervising employee, contractor, or owner-builder. Apprentice and helper time does not count toward the four years, although a CSLB-recognized apprenticeship completion can substitute for some of the experience.
- Have your experience certified by a qualified individual (a current or former employer, a journeyman who supervised you, a fellow contractor, or a building official) who can verify your work in writing.
- Pass a LiveScan background check. Felonies and certain misdemeanors require disclosure and may require additional review.
- Pass two written exams: Law and Business, and the C-10 Trade exam.
- Post a $25,000 contractor surety bond and, if you have employees, carry workers’ compensation insurance.
Educational substitutions are allowed: certain apprenticeship completions, technical training programs, and college coursework can credit up to three of the required four years of experience, but you must always have at least one year of practical journey-level experience. Read CSLB Section 7068.1 for the specifics.
The C-10 Trade Exam: Structure and Domain Breakdown
The C-10 trade exam is administered by PSI testing services at locations throughout California. Current format:
- Number of questions: 115
- Time limit: 3 hours, 30 minutes
- Format: Multiple choice, computer-based, closed-book
- Passing score: 73 percent (CSLB does not publicly confirm the exact passing score and it can shift slightly between exam forms; plan to score 80 percent or better in practice to give yourself margin)
- Cost: $60 application fee plus $50 examination fee at the time of writing; verify current fees on the CSLB website before applying
The exam is built around six knowledge domains. CSLB publishes the official Examination Study Guide for the C-10 with the exact percentage weight of each domain; download it from cslb.ca.gov before you start studying. The general topic areas, in the order CSLB tests them:
- Planning and Estimating: blueprint reading, takeoffs, scope of work definition, scheduling, cost estimating.
- Service and Distribution: service entrance sizing, transformers, switchboards, panelboards, grounding electrode systems, main bonding jumper, service disconnect rules.
- Branch Circuits, Feeders, and Wiring Methods: conductor sizing and ampacity, voltage drop, conduit fill, raceway selection, box sizing, derating, OCPD selection.
- Equipment Installation: motors, generators, transformers, control equipment, lighting fixtures, appliances, EV charging equipment.
- Low-Voltage and Communication Systems: Class 2 and Class 3 circuits, fire alarm, signaling, basic communication wiring as it relates to line-voltage installations.
- Safety: OSHA Subpart S, lockout/tagout, PPE, working clearances (NEC 110.26), arc flash awareness, ladders and lift safety.
The Law and Business exam is the same 115-question, 3.5-hour format and covers business organization, employment requirements, safety, mechanic’s liens, contracts, public works, and the Contractors State License Law. You can sit for both exams in the same day, although most candidates prefer to schedule them a week or two apart to focus.
The Reference Codes You Must Master
The C-10 exam is heavily code-based. You should be familiar with:
- California Electrical Code (CEC), Title 24 Part 3. The CEC is the National Electrical Code (currently NEC 2023) with California amendments. Know your way around Articles 100, 110, 210, 215, 220, 230, 240, 250, 300, 310, 358, 408, 430, 440, 480, 690 (PV), and 695.
- California Energy Code, Title 24 Part 6. Lighting power density, controls, EV-readiness, electric-readiness for new construction, demand response.
- Cal/OSHA Title 8, Subpart S (Electrical Safety) and Article 110 (Working Clearances).
- NFPA 70E for arc flash and shock hazard awareness.
- Local utility interconnection rules (PG&E Electric Rule 21 for solar interconnection is the most-cited).
The exam will ask you to apply these codes to scenario questions, not just recall numbers. Practice working through ampacity tables, raceway fill calculations, and grounding scenarios until you can do them without thinking.
The Topics That Trip Up the Most Candidates
Based on aggregated data from our question bank of more than 11,000 CSLB practice questions, these are the C-10 topic areas where candidates most often get stuck:
- Conductor sizing and ampacity (Article 310). Get comfortable with Table 310.16, ambient temperature corrections, and adjustment factors for more than three current-carrying conductors in a raceway. Voltage drop calculations are a classic stumble point.
- Grounding and bonding (Article 250). The single most failed topic. Know the difference between grounding electrode conductor, equipment grounding conductor, main bonding jumper, and supply-side bonding jumper. Know the table for grounding electrode conductor size (250.66) and equipment grounding conductor size (250.122).
- Motor circuits (Article 430). Motor branch circuit short-circuit and ground-fault protection, overload protection, conductor sizing for motors, and motor controller sizing all use specific tables and rules that differ from general branch circuits.
- Service calculations (Article 220). Standard versus optional method for residential, demand factors, neutral calculations, EV charger and PV adjustments.
- GFCI and AFCI requirements (210.8 and 210.12). The locations where each is required have expanded significantly in recent code cycles. Memorize the current list.
- Working clearances and dedicated equipment space (110.26). Easy points if you know the table; easy losses if you do not.
If you find yourself missing questions in any of these areas during practice, slow down and rebuild the fundamentals before moving on. Our CSLB exam prep courses for the C-10 are organized exactly around these high-failure topics.
A Six- to Eight-Week Study Plan That Works
Most successful C-10 candidates we coach follow a similar arc. Here is the plan we recommend:
- Weeks 1 to 2: Foundations. Read the CSLB Examination Study Guide cover to cover. Buy a current California Electrical Code book (the spiral-bound Mike Holt edition is popular for its tabs and indexing). Spend each evening reading one or two articles and taking notes.
- Weeks 3 to 4: High-frequency topics. Drill Article 250 (grounding and bonding) and Article 430 (motors) until they are second nature. These two articles are tested heavily and trip up the most people.
- Weeks 5 to 6: Practice exams. Take a full 115-question practice exam every two to three days, under timed conditions. Review every wrong answer back to the code section.
- Week 7: Law and Business focus. Most candidates underestimate how much memorization the Law and Business exam requires. Spend a full week on contracts, mechanic’s liens, license law, and workers’ comp.
- Week 8: Mock exam week and rest. Take two full timed practice exams, identify the last weak areas, and rest the day before your scheduled exam.
Common Reasons C-10 Candidates Fail and How to Avoid Them
- Misreading load calculation questions. Slow down and write down what is given. Use the standard method unless the question specifically invokes the optional method.
- Weak Article 250 fundamentals. If you cannot draw a complete grounding system from utility transformer through service to a downstream subpanel from memory, you are not ready.
- Running out of time. 115 questions in 210 minutes gives you 110 seconds per question. Practice pacing. Flag and skip rather than burning four minutes on a single calculation.
- Treating the Law and Business exam as an afterthought. A surprising number of C-10 candidates pass the trade exam and fail Law and Business because they did not study it.
- Showing up under-rested. A 3.5-hour computer-based exam on top of a stressful drive to the testing center will drain you. Sleep well, eat lightly before, and bring a water bottle.
Bonding, Insurance, and What Comes After You Pass
Passing the exams is not the finish line. Before CSLB issues your active license, you must:
- Post a $25,000 contractor surety bond (annual premium typically $200 to $600 depending on credit).
- Provide proof of workers’ compensation insurance if you have employees, or a signed exemption if you have none.
- Pay the initial license fee.
Once your license is active, plan on annual renewal at the two-year mark, continuing education on California-specific topics, and good record-keeping for the four-year statute of limitations on construction defect claims.
Earnings and Demand Outlook for Licensed C-10 Contractors
Industry data and California Employment Development Department reporting both place California licensed electrical contractors among the highest-earning skilled trades. Self-employed C-10 contractors in the Bay Area and Los Angeles markets routinely build six-figure businesses within two to three years of licensure, particularly those who specialize in EV charger installations, residential solar PV, and panel upgrade work tied to electric-readiness retrofits.
Demand projections through 2030 are extraordinarily strong. The combination of EV adoption, electric-readiness mandates, data center buildout, and aging panel infrastructure across California’s housing stock means there is significantly more demand than the existing licensed workforce can meet. If you are weighing classifications, you can browse all classifications and compare scope, demand, and exam difficulty before you commit.
Frequently Asked Questions
How long does it take to get a C-10 license from start to finish?
If you have your four years of qualifying experience documented, plan on 8 to 12 weeks total: 2 to 4 weeks for application processing and LiveScan, 2 to 4 weeks waiting for an exam date, plus your study time. The exams themselves are taken on a single day each. Bond and insurance come after passing.
Can I take the Law and Business exam and the C-10 trade exam on the same day?
Yes, PSI allows back-to-back scheduling. Most candidates choose to space them out by one or two weeks to focus their preparation; doing both in one day is exhausting but legal.
What is the passing score on the C-10 exam?
CSLB does not publish an exact passing score and the cut score can shift slightly between exam forms. Plan to score 80 percent or better consistently in practice to give yourself a margin. The historical pass rate for the C-10 trade exam hovers in the 50 to 65 percent range, so this is not an exam you can take cold.
Can a C-10 install residential solar systems?
Yes. The C-10 covers residential and commercial solar PV including panels, inverters, conduit, and grid interconnection. The C-46 solar classification is a separate option that focuses on solar specifically. Many California solar contractors hold both classifications.
What happens if I fail the C-10 exam?
You can retake either exam after a 21-day waiting period for an additional examination fee. There is no limit on retakes within the application window (typically one year from initial filing). Most candidates who fail do so on Article 250 grounding or motor circuit calculations; targeted study on those topics dramatically improves second-attempt scores.
Do I need a C-10 to install EV chargers?
For permitted residential or commercial Level 2 or DC fast-charging installations connected to the line-voltage electrical system, yes, you need a C-10 (or a B general acting within general scope rules). Plug-in Level 1 from an existing outlet does not require a contractor.
Ready to get started?
The C-10 is one of the highest-leverage licenses in California right now, but the exam does not reward casual preparation. Whether you are studying for your first attempt or retaking after a near-miss, we can help. Explore our CSLB exam prep courses, browse our other classification options, or talk to a licensing specialist to map the fastest legal path from where you are to a bonded, licensed C-10 contractor.