Breaker Sizing Calculator for Hawaii
NEC 2020 breaker sizing math for EV charger installers working in Hawaii.
Every EVSE branch in Hawaii is treated as a continuous load per NEC 2020 Article 625 — the OCPD must be sized at 125% of the EVSE's listed maximum draw.
Worked example for Hawaii
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 Hawaii's 0.88× ampacity correction.
Code & Utilities
EV installations in Hawaii are governed by the 2020 National Electrical Code, in force since 2022. 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.
Hawaii's primary EV-relevant utilities are Hawaiian Electric, Hawaii Electric Light, Maui Electric, Kauai Island Utility Cooperative. Always verify the applicable tariff and any utility-specific requirements (CT cabinets, metering enclosures, demand limiters) at design time.
Climate & Ampacity
Plan EV feeders against a 88°F ambient in Hawaii — 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.
Hawaii takeaway
Use a 100%-rated breaker only when the panel and breaker are both listed for 100% continuous duty — otherwise the 125% rule applies. Hawaii inspectors enforce this rigorously on Article 625 work.