Service upgrades and panel changes: 100 to 200 amps, the meter and main, utility coordination, working clearance, and the two panel brands you will be asked to replace
In one paragraph
The service upgrade is the most common large residential job a new C-10 sells, and it is a coordination job as much as an electrical one: the load calculation that justifies it, the utility's service planning process and the disconnect and reconnect appointment, the meter-main or meter socket and panel combination the utility will accept, the 2/0 copper or 4/0 aluminum conductors the code requires for 200 amperes, the outdoor emergency disconnect now required on one- and two-family dwellings, the working clearance that fails more inspections than any wiring error, the grounding electrode system you almost always rebuild, and the California rules that ban reconditioned panelboards and, on new work, set the busbar at 225 amperes for battery-ready homes. It closes with the two panel brands, Federal Pacific Stab-Lok and Zinsco, that customers will ask you about and how to answer honestly.
The rule
A 200-ampere single-phase dwelling service needs conductors of at least 83 percent of the rating, 2/0 copper or 4/0 aluminum (2025 CEC 310.12); one- and two-family dwellings need an emergency disconnect in a readily accessible outdoor location marked as the code requires (230.85); the service equipment needs 3 feet of depth, 30 inches of width and 6.5 feet of height of clear working space, with an exception that lets existing dwellings keep panelboards up to 200 amperes where the height is less (110.26(A)); reconditioned panelboards are prohibited in California (408.2(A)); and single-family panelboards must carry the Energy Code readiness spaces (408.2(B)).
Why it matters
A service upgrade sells for thousands and fails for inches: the panel that ends up 27 inches from the water heater, the meter the utility will not set, the drop that is 9 feet over the driveway. Every one of those is knowable at the site visit, and the customer who hears about it then, in the estimate, trusts you; the customer who hears about it from the inspector does not.