By EV Charge Cost Editorial Team. Published September 28, 2026, updated October 26, 2026.
"How many amps" is really a question about how many miles you need to put back each night. Amps set the charging power, power sets the miles per hour, and your driving decides how many hours you have to fill. Here is how to size it without overbuying.
Amps, volts and kilowatts
Charging power in kilowatts is volts × amps ÷ 1000. An EV charger runs for hours, so the electrical code treats it as a continuous load: it may draw at most 80% of the breaker rating. That is why a 40 A circuit supports a 32 A charger, not a 40 A one.
The table shows what each common circuit delivers to a typical EV rated at 33.5 kWh per 100 miles. The EPA rating already includes charging losses, so these miles-per-hour figures are realistic at the wall.
| Circuit | Max continuous amps | Power | Miles of range per hour | Time to add 37 miles |
|---|---|---|---|---|
| ordinary household outlet (NEMA 5-15) | 12 A | 1.44 kW | 4 | 8 h 36 min |
| 120 V, 20 A circuit | 16 A | 1.92 kW | 6 | 6 h 27 min |
| 240 V, 20 A circuit | 16 A | 3.84 kW | 11 | 3 h 14 min |
| 240 V, 30 A circuit | 24 A | 5.76 kW | 17 | 2 h 9 min |
| 240 V, 40 A circuit | 32 A | 7.68 kW | 23 | 1 h 37 min |
| 240 V, 50 A circuit | 40 A | 9.60 kW | 29 | 1 h 17 min |
| 240 V, 60 A circuit | 48 A | 11.52 kW | 34 | 1 h 5 min |
The 37-mile figure is the average day at 13,500 miles a year. Most cars sit parked for far longer than that each night, which is why modest circuits work for so many people.
Match the amps to your daily miles
Start from your longest regular day, not your average one. The table shows the energy you need and the hours it takes at each Level 2 amperage.
| Daily miles | Energy from the wall | 16 A | 24 A | 32 A | 48 A |
|---|---|---|---|---|---|
| 20 | 6.7 kWh | 1 h 45 min | 1 h 10 min | 52 min | 35 min |
| 40 | 13.4 kWh | 3 h 29 min | 2 h 20 min | 1 h 45 min | 1 h 10 min |
| 60 | 20.1 kWh | 5 h 14 min | 3 h 29 min | 2 h 37 min | 1 h 45 min |
| 100 | 33.5 kWh | 8 h 43 min | 5 h 49 min | 4 h 22 min | 2 h 54 min |
| 150 | 50.3 kWh | 13 h 5 min | 8 h 43 min | 6 h 33 min | 4 h 22 min |
As an illustration, suppose you want every night's charge done within 8 hours. The smallest circuit that manages it:
- 20 miles a day: 16 A on a 20 A circuit (1 h 45 min)
- 40 miles a day: 16 A on a 20 A circuit (3 h 29 min)
- 60 miles a day: 16 A on a 20 A circuit (5 h 14 min)
- 100 miles a day: 24 A on a 30 A circuit (5 h 49 min)
- 150 miles a day: 32 A on a 40 A circuit (6 h 33 min)
A bigger vehicle shifts the answer. The Chevrolet Silverado EV (representative trim 49.6 kWh/100 mi) gains about 15 miles per hour at 32 A, versus 29 for the Tesla Model 3 (26.4 kWh/100 mi). Use your own car's figure from the vehicle pages.
When more amps actually help
- Large trucks and SUVs that use more energy per mile.
- Two EVs sharing one charging window. See charging two EVs at home.
- Short off-peak windows on a time-of-use plan, where every hour of cheap power counts.
- Frequent long days or unpredictable same-day trips.
When more amps are wasted
- Your car's onboard charger is the cap. A car that accepts 7.7 kW will not charge faster on a 11.5 kW unit. See onboard charger limits.
- Your panel may not have room. A larger circuit can trigger a panel or service upgrade that a smaller one avoids. See whether your panel can handle a charger.
- The electricity costs the same. You pay per kWh; a faster charger does not change the price of the energy.
Quick checklist
- Find your longest regular driving day and your car's kWh/100 mi.
- Check your car's maximum AC charging rate in the owner's manual.
- Pick the smallest amperage that refills that day inside your usual parked hours.
- Have a licensed electrician confirm panel capacity, size the wire and breaker, and pull the local permit.
- Install and configure the charger following the car and charger manufacturer's instructions.
For comparisons with a 120 V outlet, see Level 1 vs Level 2 charging, or test your own numbers in the charging time calculator.