Breaker Sizing Calculator for Oklahoma
NEC 2020 breaker sizing math for EV charger installers working in Oklahoma.
Every EVSE branch in Oklahoma 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 Oklahoma
A 80 A continuous EV load requires a breaker rated 100 A (80 × 1.25 = 100.0 A, rounded up to the next standard size). The conductor downstream must carry that 100 A after Oklahoma's 0.82× ampacity correction.
Code & Utilities
Oklahoma currently enforces the NEC 2020 edition, adopted in 2022. 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 Oklahoma, you'll most often interconnect with OG&E, Public Service Company of Oklahoma, Western Farmers Electric Cooperative. Their make-ready, time-of-use, and demand-charge structures vary widely; pull the specific tariff before sizing service equipment.
Climate & Ampacity
Plan EV feeders against a 99°F ambient in Oklahoma — the resulting NEC 310.15(B) correction of 0.82× is what trims a #6 THWN-2 down to its true continuous rating. 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.
Oklahoma takeaway
Use a 100%-rated breaker only when the panel and breaker are both listed for 100% continuous duty — otherwise the 125% rule applies. Oklahoma inspectors enforce this rigorously on Article 625 work.