Breaker Sizing Calculator for Texas
NEC 2020 breaker sizing math for EV charger installers working in Texas.
Every EVSE branch in Texas 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 Texas
A 40 A continuous EV load requires a breaker rated 50 A (40 × 1.25 = 50.0 A, rounded up to the next standard size). The conductor downstream must carry that 50 A after Texas's 0.82× ampacity correction.
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
Use a 100%-rated breaker only when the panel and breaker are both listed for 100% continuous duty — otherwise the 125% rule applies. Texas inspectors enforce this rigorously on Article 625 work.