Wire Size Calculator for Maine
NEC 2020 wire size math for EV charger installers working in Maine.
Wire sizing in Maine 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 Maine
A 60 A continuous EV branch needs a conductor whose corrected ampacity meets or exceeds 60 A. In Maine's 0.94× correction, that means picking a conductor whose 30°C-rated ampacity is at least 64 A. For copper THWN-2 in EMT, that typically lands at #6 AWG; aluminum requires one to two sizes larger.
Code & Utilities
The applicable code in Maine 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 Maine, you'll most often interconnect with Central Maine Power, Versant Power, Maine Public Utilities Commission Cooperatives. Each has its own service-upgrade timeline, EV rebate availability, and metering rules — confirm them before quoting commercial work.
Climate & Ampacity
Maine's representative summer design ambient is around 84°F, which yields a 0.94× ampacity correction factor at 75°C terminations per NEC 310.15(B)(1). The correction is mild but still NEC-required; document it on the load calc so your inspector sees that 310.15(B) was applied.
Maine 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 Maine.