How much does workers' compensation cost for California plumbers?

There is no single answer, because the premium is built from your own numbers: your payroll, how it is classified, your carrier's rate for each classification and, if you are experience rated, your X-Mod. Two plumbing companies with the same number of trucks can pay very different premiums.

What moves the cost, roughly in order of weight:

1. Plumbing payroll. Premium is charged per $100 of payroll, so the size of your field crew is the base.
2. Classification split. Plumbers paid at or above WCIRB's dual-wage threshold are rated in 5187 at a lower rate than 5183. Office staff who qualify for 8810 and outside sales who qualify for 8742 are rated far lower still. Each split must be supported by time and payroll records or it is lost at audit.
3. Your X-Mod. Above 1.00 it surcharges the whole plumbing premium; below 1.00 it discounts it. Claim frequency drives it more than any single large claim.
4. Carrier rate and appetite. California carriers file their own rates, and one that wants plumbing accounts prices them differently than one that does not. Quote more than one market.
5. Underwriting credits and debits. Years in business, a written safety program, return-to-work practices and the mix of service versus new construction or underground work influence scheduled credits.
6. Subcontractor exposure. Uninsured or unlicensed subs are charged as your payroll at audit.

The policy premium is an estimate; the final figure comes from the audit. A quote built on your actual payroll by employee and classification is the way to a real number.