EV Charger Load Calculator for Massachusetts
NEC 2023 ev charger load math for EV charger installers working in Massachusetts.
Sizing an EV charger circuit in Massachusetts starts with NEC 2023 Article 625 — the EVSE branch must be sized to 125% of the continuous load. Hot-climate warm-band states like Massachusetts (88°F design ambient) also force a 0.88× ampacity correction at 75°C terminations.
Worked example for Massachusetts
For a 80 A Level 2 charger on a 240 V single-phase circuit, the OCPD is sized to 100 A (80 × 1.25 = 100.0 A, rounded up to the next standard breaker). The conductor must carry 100 A after Massachusetts's 0.88× correction — that typically lands at #6 AWG copper THWN-2 for a residential garage run, with conduit fill checked separately if you're stacking multiple home runs.
Code & Utilities
The applicable code in Massachusetts is the NEC 2023, which the state 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 Massachusetts include Eversource Energy, National Grid, Unitil Massachusetts. Each has its own service-upgrade timeline, EV rebate availability, and metering rules — confirm them before quoting commercial work.
Climate & Ampacity
Massachusetts's representative summer design ambient is around 88°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.
Massachusetts takeaway
Always cross-check the EVSE manufacturer's listed maximum overcurrent rating; Eversource Energy may also have specific service-upgrade or load-management requirements you'll need to coordinate before final inspection.