Charge at Home / Installing a Level 2 circuit
Charger amps and breaker size: the 80 percent rule
A charger may draw 80 percent of its breaker. That one rule sets every number on the quote.
EV charging runs for hours at a steady current, so the National Electrical Code treats it as a continuous load, and a continuous load may use only 80 percent of the breaker that protects it. Said the other way, the breaker must be rated at 125 percent of the charger's draw.
| Breaker | Most a charger may draw | Power at 240 V | Miles per hour |
|---|---|---|---|
| 15 A | 12 A | 2.9 kW | 8.4 |
| 20 A | 16 A | 3.8 kW | 11.3 |
| 30 A | 24 A | 5.8 kW | 16.9 |
| 40 A | 32 A | 7.7 kW | 22.5 |
| 50 A | 40 A | 9.6 kW | 28.2 |
| 60 A | 48 A | 11.5 kW | 33.8 |
| 70 A | 56 A | 13.4 kW | 39.4 |
| 80 A | 64 A | 15.4 kW | 45.1 |
| 100 A | 80 A | 19.2 kW | 56.3 |
Range figures assume a car that uses 30 kWh per 100 miles and loses 12 percent of the energy between the wall and the battery. Your car's figure is on its fueleconomy.gov label; the calculator takes yours.
What this means on a quote
- A charger set to 32 amps needs a 40-amp circuit.
- A charger set to 40 amps needs a 50-amp circuit.
- A charger set to 48 amps needs a 60-amp circuit, and at that size it is usually hardwired (see plug-in or hardwired).
Most Level 2 chargers let the installer set the maximum current to match the circuit. That setting is the safety-critical part: a charger set higher than its circuit allows will run the wiring past its rating for hours.
Bigger is not always better
Every step up costs heavier wire and more of your panel's capacity, and the car's onboard charger may not use it. Size the circuit to the miles you need back overnight and to what the car accepts, not to the biggest charger on the shelf. Wire gauge, breaker type and ground-fault protection are your electrician's call under the code edition your town has adopted.
Sources
- NFPA 70, National Electrical Code (Article 625 covers EV charging equipment) (accessed 2026-10-23)
- U.S. DOE Alternative Fuels Data Center: Charging Plug-In Electric Vehicles at Home (accessed 2026-10-23)
This page was drafted with a language model from the sources listed above and published under the quality gate; the editor samples pages after publication. Every number on it is computed by the site's calculator code, not typed.
General information for planning, not electrical, tax or legal advice. A licensed electrician and your local code decide what is safe in your home.
Found an error? See Corrections.