Breaker Sizing Calculator for Colorado
NEC 2023 breaker sizing math for EV charger installers working in Colorado.
Every EVSE branch in Colorado is treated as a continuous load per NEC 2023 Article 625 — the OCPD must be sized at 125% of the EVSE's listed maximum draw.
Worked example for Colorado
A 60 A continuous EV load requires a breaker rated 75 A (60 × 1.25 = 75.0 A, rounded up to the next standard size). The conductor downstream must carry that 75 A after Colorado's 0.88× ampacity correction.
Code & Utilities
The applicable code in Colorado is the NEC 2023, 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.
Colorado's primary EV-relevant utilities are Xcel Energy Colorado, Colorado Springs Utilities, Tri-State Generation. Each has its own service-upgrade timeline, EV rebate availability, and metering rules — confirm them before quoting commercial work.
Climate & Ampacity
In Colorado, the 90°F summer ambient drives a 0.88× 75°C ampacity correction. Bake this into every Level 2 and DCFC conductor pick before you commit to a wire size. 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.
Colorado takeaway
Use a 100%-rated breaker only when the panel and breaker are both listed for 100% continuous duty — otherwise the 125% rule applies. Colorado inspectors enforce this rigorously on Article 625 work.