An EV charger (Level 2 EVSE) is a continuous load, so NEC Article 625 requires the circuit to be sized at 125% of the charging current: a 48 A charger needs a 60 A breaker and wire rated for 60 A; a 32 A charger needs a 40 A circuit. It must be a dedicated branch circuit (625.40), and if it's a plug-in unit on a receptacle, that receptacle needs GFCI protection (625.54). Hardwiring is required above 48 A. Most homes land on a 40 A or 60 A, 240 V circuit — but confirm your panel has the capacity before you add one.
Wiring a home charger? The EV charger circuit calculator sizes the breaker and wire from the EVSE's charging amps per Article 625 — free, no signup. This guide explains the 125% continuous-load rule, plug-in vs hardwired, and why the panel is often the real limit.
⚡ The 125% continuous-load rule
A load that runs for three hours or more is “continuous” in the NEC, and EV charging — often hours at a stretch — is the textbook case. The code requires the overcurrent device and conductors for a continuous load to be sized at 125% of the load (Article 625.41). So you take the charger's rated output current and multiply by 1.25.
- A 32 A charger → 40 A circuit (32 × 1.25 = 40).
- A 40 A charger → 50 A circuit.
- A 48 A charger → 60 A circuit — the most common maximum for a residential hardwired unit.
That's also why a “50 A” circuit charges at only 40 A: the continuous-load rule caps the charger at 80% of the breaker. Set the charger's output to match the circuit, not the other way around.
🔗 Dedicated circuit & GFCI
Article 625.40 requires the EVSE to be on its own dedicated branch circuit — no sharing with the garage lights or outlets. And if the charger plugs into a receptacle (typically a NEMA 14-50), that receptacle must have GFCI protection (625.54), which usually means a GFCI breaker.
Plug-in vs hardwired. A plug-in unit on a 14-50 is limited to a 40 A circuit (32 A charging) and needs the GFCI receptacle rule. Hardwiring lets you run up to 48 A (60 A circuit) or beyond, is generally more robust for daily use, and is required for units above 48 A. Many electricians prefer hardwiring for high-power chargers.
🧵 What wire the circuit needs
Once you know the circuit ampacity, the conductor follows Table 310.16 and the termination rules. Common results: a 40 A circuit takes 8 AWG copper; a 60 A circuit takes 6 AWG copper (THHN) — though NM-B (Romex) is rated at the 60°C column, so a 60 A run in NM-B steps up to 4 AWG. The wiring method matters, which is why the calculator asks.
For the exact gauge on your run and wiring method, the wire size calculator shows the full termination-rule math, and long garage runs are worth a voltage-drop check.
🏠 Can your panel handle it?
The wire is the easy part — the harder question is whether your service has room for a continuous 40–60 A load. Adding an EV charger to a panel that's already near capacity can push the total demand past the service rating.
Before you commit, run an electrical load calculation in existing-dwelling mode (NEC 220.83) to confirm your service can absorb the new load. If it can't, you're looking at a service upgrade — or a load-management device that throttles the charger when other big loads run. Note that EV-charger demand treatment is genuinely unsettled under the 2020/2023 codes (the 2026 NEC counts EVSE at 100%), so confirm with your AHJ.
✅ The bottom line
Size the EV circuit at 125% of the charging current, put it on a dedicated circuit, and add GFCI for a plug-in receptacle. Hardwire anything above 48 A. Pick the wire for your circuit size and wiring method, check long runs for voltage drop, and — most important — confirm your service has the capacity before you add the load.
This is a planning tool; adopted NEC editions and local amendments vary, and EVSE rules are actively changing. Size the circuit with the EV charger calculator, then have a licensed electrician confirm the install and your AHJ sign off.
Estimate your EV Charger Circuit materials
What wire and breaker does your EV charger need? Free NEC Article 625 calculator by EVSE amps — 125% rule, hardwire vs plug, GFCI, and run length.
Estimate with the EV Charger Circuit Calculator →