Wire Size Calculator for Texas
NEC 2020 wire size math for EV charger installers working in Texas.
Wire sizing in Texas is governed by NEC 2020 Table 310.16, with the state's 101°F summer ambient driving a 0.82× correction factor at 75°C terminations per Table 310.15(B)(1).
Worked example for Texas
A 50 A continuous EV branch needs a conductor whose corrected ampacity meets or exceeds 50 A. In Texas's 0.82× correction, that means picking a conductor whose 30°C-rated ampacity is at least 61 A. For copper THWN-2 in EMT, that typically lands at #6 AWG; aluminum requires one to two sizes larger.
Code & Utilities
The applicable code in Texas is the NEC 2020, which the state 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 Texas, you'll most often interconnect with Oncor Electric Delivery, CenterPoint Energy, AEP Texas, Austin Energy, CPS Energy. Their make-ready, time-of-use, and demand-charge structures vary widely; pull the specific tariff before sizing service equipment.
Climate & Ampacity
Texas's representative summer design ambient is around 101°F, which yields a 0.82× 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.
Texas takeaway
Don't forget conduit-fill derating per NEC 310.15(C)(1) when more than three current-carrying conductors share a raceway — a common condition on multifamily and workplace EVSE home-run racks in Texas.