Voltage Drop Calculator for Illinois
NEC 2020 voltage drop math for EV charger installers working in Illinois.
Illinois EV installs frequently push past 100 ft of conductor — detached garages, parking-lot DCFC pedestals, and multifamily carport runs all add distance. NEC 2020 recommends a 3% branch / 5% total voltage-drop ceiling.
Worked example for Illinois
A 48 A Level 2 charger at 320 ft on 240 V single-phase #6 Cu shows roughly 6.3% drop. That's above the 3% NEC recommendation, so you'd upsize to #4 or #2 AWG to land back under 3%. Illinois's 0.88× ampacity correction is independent of voltage drop but applies on the same conductor pick.
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
Voltage drop is a recommendation, not a hard NEC rule — but EVSEs throttle aggressively below ~228 V on a 240 V circuit, so customers in Illinois will notice any drop above 5%.