Grounding Conductor Calculator for Hawaii
NEC 2020 grounding conductor math for EV charger installers working in Hawaii.
EGC sizing in Hawaii follows NEC 2020 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 Hawaii
For a 100 A EVSE branch, Table 250.122 calls for a minimum #8 Cu equipment grounding conductor. If you upsize the phase conductors for voltage drop in Hawaii's long runs, NEC 250.122(B) requires the EGC to be upsized proportionally.
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
On DCFC sites with parallel feeder sets, each parallel raceway needs its own full-size EGC — a detail inspectors in Hawaii catch frequently on commercial submittals.