Breaker Sizing Calculator for Maryland
NEC 2020 breaker sizing math for EV charger installers working in Maryland.
Every EVSE branch in Maryland is treated as a continuous load per NEC 2020 Article 625 — the OCPD must be sized at 125% of the EVSE's listed maximum draw.
Worked example for Maryland
A 48 A continuous EV load requires a breaker rated 60 A (48 × 1.25 = 60.0 A, rounded up to the next standard size). The conductor downstream must carry that 60 A after Maryland's 0.88× ampacity correction.
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
Use a 100%-rated breaker only when the panel and breaker are both listed for 100% continuous duty — otherwise the 125% rule applies. Maryland inspectors enforce this rigorously on Article 625 work.