Panel Load Calculation Calculator for Texas
NEC 2020 panel load calculation math for EV charger installers working in Texas.
Adding EV chargers to an existing Texas service triggers an NEC 220 load calculation under 2020. The good news: NEC 220.83 and 220.87 both allow you to use the existing service's measured demand, but the EV load enters at 100% of its 125%-sized branch.
Worked example for Texas
On a typical 320 A single-family or small-commercial service in Texas, the existing demand plus a new 48 A Level 2 charger (60 A continuous-rated branch) fits comfortably under the service rating in most cases. When you add a second EVSE or a 19.2 kW charger, you usually need either a service upgrade or an NEC 625.42 energy-management system.
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
Oncor Electric Delivery's service-upgrade timeline is the long-pole item here in Texas — running the panel-load math early lets you decide between an EMS-managed shared circuit and a full upgrade before you're past the point of no return.