Wire Size Calculator for Vermont
NEC 2020 wire size math for EV charger installers working in Vermont.
Wire sizing in Vermont is governed by NEC 2020 Table 310.16, with the state's 84°F summer ambient driving a 0.94× correction factor at 75°C terminations per Table 310.15(B)(1).
Worked example for Vermont
A 70 A continuous EV branch needs a conductor whose corrected ampacity meets or exceeds 70 A. In Vermont's 0.94× correction, that means picking a conductor whose 30°C-rated ampacity is at least 75 A. For copper THWN-2 in EMT, that typically lands at #4 AWG; aluminum requires one to two sizes larger.
Code & Utilities
Vermont 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 Vermont, you'll most often interconnect with Green Mountain Power, Vermont Electric Cooperative, Burlington Electric Department. Each has its own service-upgrade timeline, EV rebate availability, and metering rules — confirm them before quoting commercial work.
Climate & Ampacity
In Vermont, the 84°F summer ambient drives a 0.94× 75°C ampacity correction. Bake this into every Level 2 and DCFC conductor pick before you commit to a wire size. The correction is mild but still NEC-required; document it on the load calc so your inspector sees that 310.15(B) was applied.
Vermont 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 Vermont.