Voltage Drop Calculator for Idaho
NEC 2020 voltage drop math for EV charger installers working in Idaho.
Idaho 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 Idaho
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%. Idaho's 0.82× ampacity correction is independent of voltage drop but applies on the same conductor pick.
Code & Utilities
Idaho currently enforces the NEC 2020 edition, adopted in 2021. 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.
Idaho's primary EV-relevant utilities are Idaho Power, Avista Utilities, Rocky Mountain Power. Their make-ready, time-of-use, and demand-charge structures vary widely; pull the specific tariff before sizing service equipment.
Climate & Ampacity
Plan EV feeders against a 96°F ambient in Idaho — the resulting NEC 310.15(B) correction of 0.82× 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.
Idaho 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 Idaho will notice any drop above 5%.