Panel Load Calculation Calculator for Arizona
NEC 2017 panel load calculation math for EV charger installers working in Arizona.
Adding EV chargers to an existing Arizona service triggers an NEC 220 load calculation under 2017. 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 Arizona
On a typical 400 A single-family or small-commercial service in Arizona, 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
EV installations in Arizona are governed by the 2017 National Electrical Code, in force since 2018. That includes Article 625 EVSE rules and the 125% continuous-load factor on charging branch circuits, though some 2020-cycle changes (like expanded EMS provisions) are not yet enforced statewide.
Major electric utilities serving Arizona include Arizona Public Service, Salt River Project, Tucson Electric Power. Each has its own service-upgrade timeline, EV rebate availability, and metering rules — confirm them before quoting commercial work.
Climate & Ampacity
Plan EV feeders against a 108°F ambient in Arizona — the resulting NEC 310.15(B) correction of 0.75× 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.
Arizona takeaway
Arizona Public Service's service-upgrade timeline is the long-pole item here in Arizona — 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.