EV Charger Load Calculator for Illinois
NEC 2020 ev charger load math for EV charger installers working in Illinois.
Sizing an EV charger circuit in Illinois starts with NEC 2020 Article 625 — the EVSE branch must be sized to 125% of the continuous load. Hot-climate warm-band states like Illinois (91°F design ambient) also force a 0.88× ampacity correction at 75°C terminations.
Worked example for Illinois
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 Illinois'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
EV installations in Illinois 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.
In Illinois, you'll most often interconnect with ComEd, Ameren Illinois, MidAmerican Energy. Each has its own service-upgrade timeline, EV rebate availability, and metering rules — confirm them before quoting commercial work.
Climate & Ampacity
Illinois's representative summer design ambient is around 91°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.
Illinois takeaway
Always cross-check the EVSE manufacturer's listed maximum overcurrent rating; ComEd may also have specific service-upgrade or load-management requirements you'll need to coordinate before final inspection.