For most drivers, yes. A 40 amp charger delivers 9.6 kW and adds roughly 30 to 40 miles of range per hour, so a typical day’s driving is replaced in about an hour of charging. It falls short mainly for high-mileage drivers, two-EV households sharing one charger, and very large batteries that must refill fully overnight.
Key Takeaways
- A 40 amp charger adds about 30 to 40 miles of range per hour — enough for typical daily driving in one to two hours.
- Judge by overnight headroom: 10 hours at 9.6 kW exceeds most batteries’ capacity.
- Step up to 48 amps for high mileage, two EVs or fast daytime top-ups.
- A 40 amp charger needs a 50 amp circuit under the NEC continuous-load rule.
Start with miles, not amps
Amps only matter through the range they buy back. Work backwards from your driving:
- Daily miles. The average U.S. driver covers roughly 30 to 40 miles a day. Your commute and errands set your real number.
- Hours plugged in. A car parked from 7 p.m. to 7 a.m. has about 12 hours available, far more than most sessions need.
- Miles per hour of charging. At 9.6 kW, expect about 30 to 40 miles per hour, depending on the car’s efficiency.
Multiply the hours by the miles per hour and compare the result with your daily miles. If it is two or three times your daily use, 40 amps is enough with room to spare.
What 9.6 kW does overnight
| Charging window | Energy added | Approx. range added |
|---|---|---|
| 3 hours | About 29 kWh | 90 to 115 miles |
| 6 hours | About 58 kWh | 175 to 230 miles |
| 10 hours | About 96 kWh | 290 to 380 miles |
Energy added is capped by the battery: a 60 kWh car cannot take 96 kWh in a night. The point of the table is headroom. A 40 amp charger can refill most batteries from near empty in a single overnight session, and ordinary daily use takes a fraction of that.
When 40 amps is not enough
- You drive 150 miles or more most days, and the car must be full again by morning.
- Two EVs share one charger, which halves each car’s plugged-in time.
- Your car’s onboard charger accepts more than 9.6 kW, and you regularly use that speed for daytime top-ups.
- You expect to add a second EV soon and want the circuit sized for the future.
In those cases a 48 amp charger adds about 20 percent more power. Our breaker size guide shows the circuit each charger size needs.
The circuit behind a “40 amp” charger
One point of confusion: a charger that outputs 40 amps needs a 50 amp circuit. EV charging is a continuous load under the National Electrical Code, so the breaker is sized at 125 percent of the charging current. That means 40 amps of charging needs a 50 amp breaker, while a 32 amp charger runs on a 40 amp breaker. Have a licensed electrician confirm your panel capacity before you choose.
A 40 amp option from EVDANCE
The EV-ACS4005T is a 40 amp portable charger with a NEMA 14-50 plug. Its current adjusts between 16 and 40 amps, so the same unit runs at reduced power on a smaller circuit and at full power on a 50 amp circuit. It is IP66 rated and comes with a 25 or 28 ft cable.
Frequently Asked Questions
Is 40 amps enough for a large-battery EV?
Yes, for overnight charging. Even a 100 kWh battery refills from 20 to 80 percent — about 60 kWh — in roughly six and a half hours at 9.6 kW.
Can I run a 40 amp charger on a 40 amp breaker?
No. Charging is a continuous load, so a 40 amp charger needs a 50 amp circuit. On a 40 amp circuit, set the charger to 32 amps or less.
Should I buy a 40 amp or 48 amp charger?
Buy 40 amps if your overnight math works with margin. Choose 48 amps for very high daily mileage, two EVs, or a second car planned soon.
Related Reading
- How Many Amps Does an EV Charger Need?
- What Size Breaker Do I Need for an EV Charger?
- How Many kW Is a Level 2 Charger?
- Is a Level 2 Charger Worth It?
