EV Charger Load Calculator for Iowa
NEC 2020 ev charger load math for EV charger installers working in Iowa.
Sizing an EV charger circuit in Iowa starts with NEC 2020 Article 625 — the EVSE branch must be sized to 125% of the continuous load. Hot-climate warm-band states like Iowa (91°F design ambient) also force a 0.88× ampacity correction at 75°C terminations.
Worked example for Iowa
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 Iowa'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 Iowa are governed by the 2020 National Electrical Code, in force since 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.
Major electric utilities serving Iowa include MidAmerican Energy, Alliant Energy Iowa, Iowa Association of Municipal Utilities. 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 91°F ambient in Iowa — 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.
Iowa takeaway
Always cross-check the EVSE manufacturer's listed maximum overcurrent rating; MidAmerican Energy may also have specific service-upgrade or load-management requirements you'll need to coordinate before final inspection.