EV Charger Load Calculator for Maryland
NEC 2020 ev charger load math for EV charger installers working in Maryland.
Sizing an EV charger circuit in Maryland starts with NEC 2020 Article 625 — the EVSE branch must be sized to 125% of the continuous load. Hot-climate warm-band states like Maryland (91°F design ambient) also force a 0.88× ampacity correction at 75°C terminations.
Worked example for Maryland
For a 40 A Level 2 charger on a 240 V single-phase circuit, the OCPD is sized to 50 A (40 × 1.25 = 50.0 A, rounded up to the next standard breaker). The conductor must carry 50 A after Maryland's 0.88× correction — that typically lands at #8 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 Maryland 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 Maryland, you'll most often interconnect with BGE, Pepco, Delmarva Power, Potomac Edison. Always verify the applicable tariff and any utility-specific requirements (CT cabinets, metering enclosures, demand limiters) at design time.
Climate & Ampacity
In Maryland, the 91°F summer ambient drives a 0.88× 75°C ampacity correction. Bake this into every Level 2 and DCFC conductor pick before you commit to a wire size. 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.
Maryland takeaway
Always cross-check the EVSE manufacturer's listed maximum overcurrent rating; BGE may also have specific service-upgrade or load-management requirements you'll need to coordinate before final inspection.