The quick answer
Most home Level 2 chargers land on 6 AWG copper. The exact size follows the charger's amp setting, not the car:
| Charger output | Breaker | Copper wire |
|---|---|---|
| 32 A | 40 A | 8 AWG |
| 40 A (NEMA 14-50) | 50 A | 6 AWG |
| 48 A (hardwired) | 60 A | 6 AWG * |
| 60 A | 75 A | 4 AWG |
* At 48 amps the wire type matters — 6 AWG only makes 60 amps as conduit wire, covered below. The two big decisions are your charger's amps and whether you plug in or hardwire, and everything else follows from those.
The rule that sets it: NEC 625.42 (the 125% rule)
An EV charger is a continuous load — it can pull its full current for hours. NEC 625.42 requires the circuit to be sized at 125% of the charger's output, which is the same as saying the charger only draws 80% of the breaker.
That one rule explains every row in the table:
- A 40 A charger × 1.25 = 50 A breaker → 6 AWG copper.
- A 48 A charger × 1.25 = 60 A breaker → 6 AWG copper (in conduit).
- A 32 A charger × 1.25 = 40 A breaker → 8 AWG copper.
It's why you can't put a 48 amp charger on a 50 amp circuit, and why "just use 50 amps for everything" is wrong for the bigger units.
40A plug vs 48A hardwired: the real decision
Almost every EV wiring choice comes down to one fork: a plug-in 14-50 outlet or a hardwired unit.
| NEMA 14-50 plug | Hardwired | |
|---|---|---|
| Charging rate | 40 A max | 48 A (or more) |
| Circuit | 50 A | 60 A |
| Wire (copper) | 6 AWG (6/3) | 6 AWG in conduit (6/2) |
| GFCI breaker | Required | Not required |
| Portable? | Yes, unplugs | No, fixed |
A 14-50 outlet is flexible — you can unplug the charger and take it — and it's the most common home setup. Hardwiring gives you the full 48 amps, skips the GFCI headache below, and removes the plug as a failure point. If your charger and panel both support 48 amps, hardwiring is usually the better install. (A 14-50 is just a 50 amp circuit under the hood.)
The 48A trap: 6 AWG only works in conduit
Here's the mistake that shows up on real installs. A 48 amp charger needs a 60 amp circuit, and 6 AWG copper is only rated for 60 amps as a 75°C wire — THHN or THWN pulled through conduit (65 A).
NM-B "Romex" is limited to the 60°C column, where 6 AWG is only 55 amps — under the 60 amp breaker. So a 48 amp hardwired run in Romex has to use 4 AWG, or you switch to 6 AWG THHN in conduit. Most hardwired EV installs use conduit for exactly this reason.
The 40 amp / 50 amp setup doesn't have this problem — 6 AWG is 55 amps even in Romex, comfortably above 50. The conduit rule only bites at 48 amps and up.
Does an EV charger need a GFCI breaker?
If you install a NEMA 14-50 receptacle, yes — NEC 210.8 requires GFCI protection for that outlet, which usually means a GFCI breaker. The catch is that many EV chargers have their own internal ground-fault protection, and the two can fight, causing nuisance trips that stop your car charging overnight.
A hardwired charger does not require a GFCI breaker, because the unit provides its own protection. Avoiding those nuisance trips is one of the top reasons electricians recommend hardwiring the 48 amp units. Either way, confirm what your local AHJ requires before you buy the breaker.
This tightened up with the 2020 NEC, which expanded the GFCI requirement to cover 240-volt dwelling receptacles like the 14-50 — so a plug-in EV outlet installed today almost always needs a GFCI breaker, and that breaker costs noticeably more than a standard one. If you've read about EV outlets tripping for no obvious reason, this double-protection clash is usually why. The clean fix is to hardwire, which sidesteps the requirement entirely; if you want the flexibility of a plug, use a GFCI breaker the charger manufacturer lists as compatible.
6/3 or 6/2 for an EV charger?
It depends on whether there's a receptacle. A 14-50 outlet has a neutral slot, so it's wired with 6/3 with ground — two hots, a neutral, and a ground — even though most chargers never use the neutral. A hardwired charger is a straight 240-volt connection with no neutral, so it takes 6/2 with ground (or individual THHN conductors in conduit). Match the cable to the connection and you won't over- or under-buy.
Tesla Wall Connector and other 48A units
The Tesla Wall Connector and most premium wall chargers can deliver up to 48 amps, so out of the box they want a 60 amp circuit and 6 AWG conduit wire, hardwired. The nice part is they're adjustable: you can set the charger down to, say, 40 amps to match a 50 amp circuit and 6 AWG, or lower on an older panel.
Always size the wire to the breaker, and set the charger to the circuit — never the other way around. A charger dialed to 40 amps on a 50 amp circuit is perfect; a 48 amp charger on a 50 amp circuit is a code violation and a fire risk.
Do you actually need 48 amps?
Before you pull the bigger wire, it's worth asking whether you need the speed — because your charger's amps decide everything downstream. On a 240-volt Level 2 circuit, power is simply volts times amps: a 40 amp charger delivers about 9.6 kW, and a 48 amp charger about 11.5 kW. For a typical EV that's roughly 30–37 miles of range per hour at 40 amps versus 37–45 at 48 amps (it varies by vehicle).
Here's the practical part: most people drive around 40 miles a day and charge overnight. Even a 32 amp charger adds well over 200 miles across an 8-hour night, so for the vast majority of drivers a 40 amp setup on 6 AWG is more than enough — and it keeps you on the simpler 50 amp circuit. The 48 amp jump earns its extra wire and conduit mainly for high-mileage drivers, big-battery trucks, or short charging windows. Deciding this first tells you exactly which row of the table you're wiring for.
Aluminum and long runs
Aluminum is an option at these sizes — step up one size (for example, 4 AWG aluminum in place of 6 AWG copper on a 50 amp circuit) and use aluminum-rated lugs with antioxidant. It's common on longer garage runs where the cost savings add up.
Speaking of long runs: a detached garage is a classic EV location, and voltage drop matters over distance. At a 3% target on 240 volts, 6 AWG copper is good to about 183 ft at 40 amps, or about 153 ft at 48 amps; past that, size up. The Voltage Drop Calculator checks your exact run, and the AWG ampacity chart has the full numbers behind all of this.
Common EV charger wiring mistakes
The classic one is running 6 AWG Romex on a 60 amp circuit for a 48 amp charger — it's only rated 55 amps, so it's undersized. Close behind is sizing to the charger's amps without the 125% bump, landing a 48 amp unit on a 50 amp breaker. Then come the cable mix-ups — wiring a 14-50 with 6/2 (it needs the neutral in 6/3), or skipping the GFCI on a plug-in outlet — and the dangerous one: setting the charger higher than the circuit can carry. As always, EV circuits are permit-and-inspection work in most places, so confirm with your AHJ.
Frequently asked questions
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This guide is for general information based on the National Electrical Code. Local codes and your authority having jurisdiction (AHJ) may differ, and EV circuits are usually permit-and-inspection work. Range-per-hour figures are approximate and vary by vehicle. Electrical work can be dangerous, so when in doubt, hire a licensed electrician.