Grounding Conductor Calculator for California
NEC 2023 grounding conductor math for EV charger installers working in California.
EGC sizing in California follows NEC 2023 Table 250.122, indexed off the upstream OCPD rating, with parallel rules for parallel sets and increased-conductor adjustments under 250.122(B).
Worked example for California
For a 60 A EVSE branch, Table 250.122 calls for a minimum #10 Cu equipment grounding conductor. If you upsize the phase conductors for voltage drop in California's long runs, NEC 250.122(B) requires the EGC to be upsized proportionally.
Code & Utilities
California currently enforces the NEC 2023 edition, adopted in 2023. That includes Article 625 (Electric Vehicle Power Transfer System) requirements: 125% continuous-load sizing on EVSE branch circuits, GFCI protection at outdoor receptacles, and provisions for energy management systems on shared circuits.
Major electric utilities serving California include Pacific Gas & Electric (PG&E), Southern California Edison, San Diego Gas & Electric, LADWP, SMUD. Each has its own service-upgrade timeline, EV rebate availability, and metering rules — confirm them before quoting commercial work.
Climate & Ampacity
Plan EV feeders against a 95°F ambient in California — the resulting NEC 310.15(B) correction of 0.88× is what trims a #6 THWN-2 down to its true continuous rating. Because the correction is below 0.9, conductors that "look fine" on a 30°C ampacity table will not carry their nameplate current here — always derate explicitly.
California takeaway
On DCFC sites with parallel feeder sets, each parallel raceway needs its own full-size EGC — a detail inspectors in California catch frequently on commercial submittals.