Transformer Sizing Calculator for Mississippi
NEC 2020 transformer sizing math for EV charger installers working in Mississippi.
DCFC and large workplace EV deployments in Mississippi 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 Mississippi
A 150 kW DC fast charger draws roughly 180 A at 480 V three-phase. Applying the 125% continuous-load factor (150 × 1.25 ≈ 188 kVA), then rounding up to the next standard transformer rating gives a 200 kVA minimum. Mississippi's 95°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
Mississippi currently enforces the NEC 2020 edition, adopted in 2023. 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 Mississippi, you'll most often interconnect with Entergy Mississippi, Mississippi Power, Tennessee Valley Authority. Each has its own service-upgrade timeline, EV rebate availability, and metering rules — confirm them before quoting commercial work.
Climate & Ampacity
In Mississippi, the 95°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.
Mississippi takeaway
Coordinate primary-side voltage, impedance, and fault-current specs with Entergy Mississippi early — interconnection lead times for new pad-mounts in Mississippi can run 6-12 months on commercial DCFC sites.