EV Charger Load Calculator for New Hampshire
NEC 2020 ev charger load math for EV charger installers working in New Hampshire.
Sizing an EV charger circuit in New Hampshire starts with NEC 2020 Article 625 — the EVSE branch must be sized to 125% of the continuous load. Hot-climate mild-band states like New Hampshire (87°F design ambient) also force a 0.88× ampacity correction at 75°C terminations.
Worked example for New Hampshire
For a 40 A Level 2 charger on a 240 V single-phase circuit, the OCPD is sized to 50 A (40 × 1.25 = 50.0 A, rounded up to the next standard breaker). The conductor must carry 50 A after New Hampshire's 0.88× correction — that typically lands at #8 AWG copper THWN-2 for a residential garage run, with conduit fill checked separately if you're stacking multiple home runs.
Code & Utilities
New Hampshire currently enforces the NEC 2020 edition, adopted in 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.
New Hampshire's primary EV-relevant utilities are Eversource New Hampshire, Unitil, New Hampshire Electric Cooperative. Each has its own service-upgrade timeline, EV rebate availability, and metering rules — confirm them before quoting commercial work.
Climate & Ampacity
New Hampshire's representative summer design ambient is around 87°F, which yields a 0.88× ampacity correction factor at 75°C terminations per NEC 310.15(B)(1). 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.
New Hampshire takeaway
Always cross-check the EVSE manufacturer's listed maximum overcurrent rating; Eversource New Hampshire may also have specific service-upgrade or load-management requirements you'll need to coordinate before final inspection.