Ampacity Derating Calculator for South Carolina
NEC 2017 ampacity derating math for EV charger installers working in South Carolina.
South Carolina's 94°F design ambient drives a 0.88× NEC 310.15(B)(1) correction at 75°C terminations — the single most-overlooked derate on hot-climate EV installs.
Worked example for South Carolina
A conductor with a 30°C-rated ampacity of 130 A drops to roughly 114.4 A in South Carolina ambient conditions. Stack a 0.8× conduit-fill adjustment (NEC 310.15(C)(1)) on top and that same conductor is only good for 91.5 A.
Code & Utilities
The applicable code in South Carolina is the NEC 2017, which the state adopted in 2018. That includes Article 625 EVSE rules and the 125% continuous-load factor on charging branch circuits, though some 2020-cycle changes (like expanded EMS provisions) are not yet enforced statewide.
Major electric utilities serving South Carolina include Duke Energy Carolinas SC, Dominion Energy South Carolina, Santee Cooper. Their make-ready, time-of-use, and demand-charge structures vary widely; pull the specific tariff before sizing service equipment.
Climate & Ampacity
South Carolina's representative summer design ambient is around 94°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.
South Carolina takeaway
Never size off the 30°C column in NEC Table 310.16 for South Carolina work — always start with the temperature-corrected number, then apply any conduit-fill adjustment.