Transformer Sizing Calculator for New Jersey
NEC 2020 transformer sizing math for EV charger installers working in New Jersey.
DCFC and large workplace EV deployments in New Jersey typically need a dedicated 480 V three-phase service, which means sizing a pad-mount or dry-type transformer against the connected charger load plus the NEC 2020 continuous-load multiplier.
Worked example for New Jersey
A 240 kW DC fast charger draws roughly 289 A at 480 V three-phase. Applying the 125% continuous-load factor (240 × 1.25 ≈ 300 kVA), then rounding up to the next standard transformer rating gives a 300 kVA minimum. New Jersey's 91°F summer ambient does not directly derate the transformer, but it does push the secondary feeder ampacity down by 0.88× — so the secondary copper has to be sized accordingly.
Code & Utilities
New Jersey 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.
In New Jersey, you'll most often interconnect with PSE&G, Atlantic City Electric, JCP&L, Orange & Rockland. Always verify the applicable tariff and any utility-specific requirements (CT cabinets, metering enclosures, demand limiters) at design time.
Climate & Ampacity
New Jersey's representative summer design ambient is around 91°F, which yields a 0.88× ampacity correction factor at 75°C terminations per NEC 310.15(B)(1). 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.
New Jersey takeaway
Coordinate primary-side voltage, impedance, and fault-current specs with PSE&G early — interconnection lead times for new pad-mounts in New Jersey can run 6-12 months on commercial DCFC sites.