Breaker Sizing Calculator for California
NEC 2023 breaker sizing math for EV charger installers working in California.
Every EVSE branch in California is treated as a continuous load per NEC 2023 Article 625 — the OCPD must be sized at 125% of the EVSE's listed maximum draw.
Worked example for California
A 80 A continuous EV load requires a breaker rated 100 A (80 × 1.25 = 100.0 A, rounded up to the next standard size). The conductor downstream must carry that 100 A after California's 0.88× ampacity correction.
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
Use a 100%-rated breaker only when the panel and breaker are both listed for 100% continuous duty — otherwise the 125% rule applies. California inspectors enforce this rigorously on Article 625 work.