Wire Gauge Amp Chart for 240V Home EV Charging Circuits

The Short Answer

Wire size depends on the current a circuit carries, not on whether it runs at 120V or 240V. A 240V circuit uses the same ampacity chart as any other circuit. For EV charging, the deciding factors are the charger's continuous current, the breaker size that current requires, the type of cable or conductor, and the temperature rating used to size it. In common US residential practice under the National Electrical Code (NEC), a 50-amp EV circuit typically uses 6 AWG copper NM-B (Romex) or 8 AWG copper THHN in conduit, and a 60-amp circuit typically uses 4 AWG copper NM-B or 6 AWG copper THHN in conduit. Each of these depends on the conditions explained below.

This guide covers copper conductors on US residential circuits. Code editions, local amendments, and charger installation manuals can change the answer, so treat the figures as a starting point to confirm with your permitting authority or a licensed electrician.

Copper Wire Gauge Ampacity Chart

Ampacity is the maximum current a conductor can carry continuously without exceeding its temperature rating. The values below are the widely published NEC Table 310.16 figures for copper conductors with no more than three current-carrying conductors in a raceway or cable at a 30°C (86°F) ambient temperature. The column you may use depends on the insulation type and the temperature rating of the terminals on the breaker and charger.

Copper AWG | 60°C column (amps) | 75°C column (amps) | 90°C column (amps); 14 | 15 | 20 | 25; 12 | 20 | 25 | 30; 10 | 30 | 35 | 40; 8 | 40 | 50 | 55; 6 | 55 | 65 | 75; 4 | 70 | 85 | 95; 3 | 85 | 100 | 115; 2 | 95 | 115 | 130; 1 | 110 | 130 | 145

Small conductors carry an additional overcurrent protection limit. Regardless of the chart value, 14 AWG copper is generally limited to a 15-amp breaker, 12 AWG to 20 amps, and 10 AWG to 30 amps. The 90°C column is mainly used as a starting point for derating calculations. Final sizing is normally limited to the 60°C or 75°C rating of the terminals.

Why EV Circuits Need Extra Headroom

The NEC treats EV charging as a continuous load, meaning maximum current can last three hours or more. The breaker and conductors must be rated for at least 125 percent of the charger's continuous current. Put another way, a charger may draw no more than 80 percent of the circuit's rating.

Charger current | Minimum circuit (breaker) | Copper NM-B (Romex), 60°C | Copper THHN in conduit, 75°C terminals; 16A | 20A | 12 AWG | 12 AWG; 24A | 30A | 10 AWG | 10 AWG; 32A | 40A | 8 AWG | 8 AWG; 40A | 50A | 6 AWG | 8 AWG; 48A | 60A | 4 AWG | 6 AWG

These pairings assume short-to-moderate runs, normal ambient temperatures, no bundling derating, and terminals rated for the column used. Some chargers can be set to a lower current in software or with a dial. Matching that setting to the installed circuit is part of a correct installation. The supplied research did not include specific charger models or their documented ratings, so check your unit's manual for its required breaker size and conductor type.

Using Romex for a 240V Circuit

Romex is a common brand name for NM-B (non-metallic sheathed) cable. It is suitable for 240V circuits, but the NEC limits NM-B to the 60°C ampacity column even though the individual conductors carry a 90°C rating. This is why 6 AWG NM-B is commonly paired with a 50-amp breaker rather than a 60-amp breaker. A 60-amp EV circuit in Romex generally calls for 4 AWG.

Hardwired chargers usually need two hot conductors and a ground, so a two-conductor-with-ground cable (for example 6/2 with ground) is typical. Confirm this in the installation manual. A NEMA 14-50 receptacle needs two hots, a neutral and a ground, which requires a three-conductor-with-ground cable such as 6/3 with ground. A NEMA 6-50 receptacle needs two hots and a ground, without a neutral. NM-B is for dry locations. It is not permitted in wet or damp locations, including conduit run outdoors or underground, where individual conductors such as THWN-2 are used instead. Where NM-B is exposed to physical damage, such as low on a garage wall, it may need protection such as conduit or a raceway.

Conditions That Can Change the Wire Size

Long runs: The chart covers heat, not voltage drop. On long distances between the panel and the charger, an electrician may upsize the conductor to keep voltage drop reasonable. High ambient temperature: Attics and hot exterior walls can require derating, which may push the size up. Bundling: More than three current-carrying conductors together in a raceway, or cables bundled tightly over a distance, reduce allowable ampacity. Aluminum conductors: Aluminum has lower ampacity than copper at the same gauge and generally needs a larger size, along with terminals rated for aluminum. GFCI requirements: Recent NEC editions require ground-fault protection for EV charging receptacles and many 240V garage receptacles, which affects breaker selection. Panel capacity: A load calculation determines whether the existing service can support a new 40- to 60-amp circuit at all.

Next Steps

Start with the charger's rated current and the breaker size its manual specifies. Next, choose the cable type based on where it will run, then read the matching ampacity column. NEC adoption varies by jurisdiction and edition, and most areas require a permit and inspection for a new 240V circuit. A licensed electrician can confirm the conductor size, the protection requirements and the panel capacity before installation.