Breaker Sizing Calculator for North Carolina
NEC 2017 breaker sizing math for EV charger installers working in North Carolina.
Every EVSE branch in North Carolina is treated as a continuous load per NEC 2017 Article 625 — the OCPD must be sized at 125% of the EVSE's listed maximum draw.
Worked example for North Carolina
A 40 A continuous EV load requires a breaker rated 50 A (40 × 1.25 = 50.0 A, rounded up to the next standard size). The conductor downstream must carry that 50 A after North Carolina's 0.88× ampacity correction.
Code & Utilities
EV installations in North Carolina are governed by the 2017 National Electrical Code, in force since 2018. That includes Article 625 EVSE rules and the 125% continuous-load factor on charging branch circuits, though some 2020-cycle changes (like expanded EMS provisions) are not yet enforced statewide.
Major electric utilities serving North Carolina include Duke Energy Carolinas, Duke Energy Progress, Dominion Energy NC. 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 92°F ambient in North Carolina — 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.
North Carolina takeaway
Use a 100%-rated breaker only when the panel and breaker are both listed for 100% continuous duty — otherwise the 125% rule applies. North Carolina inspectors enforce this rigorously on Article 625 work.