EV Charger Load Calculator for Missouri
NEC 2020 ev charger load math for EV charger installers working in Missouri.
Sizing an EV charger circuit in Missouri starts with NEC 2020 Article 625 — the EVSE branch must be sized to 125% of the continuous load. Hot-climate hot-band states like Missouri (95°F design ambient) also force a 0.88× ampacity correction at 75°C terminations.
Worked example for Missouri
For a 48 A Level 2 charger on a 240 V single-phase circuit, the OCPD is sized to 60 A (48 × 1.25 = 60.0 A, rounded up to the next standard breaker). The conductor must carry 60 A after Missouri'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
Missouri 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.
Major electric utilities serving Missouri include Ameren Missouri, Evergy Missouri, Empire District Electric. Always verify the applicable tariff and any utility-specific requirements (CT cabinets, metering enclosures, demand limiters) at design time.
Climate & Ampacity
Plan EV feeders against a 95°F ambient in Missouri — the resulting NEC 310.15(B) correction of 0.88× 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.
Missouri takeaway
Always cross-check the EVSE manufacturer's listed maximum overcurrent rating; Ameren Missouri may also have specific service-upgrade or load-management requirements you'll need to coordinate before final inspection.