Neither class is better on its own. A 32 amp charger runs on a 40 amp breaker and delivers about 7.7 kW; a 40 amp charger runs on a 50 amp breaker and delivers 9.6 kW. Three checks decide between them: the headroom your panel actually has, the most your car can accept, and whether your overnight window ever feels the difference.
Key Takeaways
- 32 A pairs with a 40 A breaker, 40 A with a 50 A — the 125% continuous-load rule decides.
- Your car’s stated AC limit can make the choice for you: a car capped at the lower class gains nothing.
- Overnight, both classes refill an ordinary day; the gap shows only in short windows.
- An adjustable charger covers both classes and can be reset if the circuit changes.
The Two Classes, Side by Side
| 32 amp charger | 40 amp charger | |
|---|---|---|
| Breaker (NEC continuous-load rule, 125%) | 40 A | 50 A |
| Session power at 240 V | About 7.7 kW | 9.6 kW |
| Range added per hour | Both sit in the Level 2 band of roughly 10–20 miles per hour (U.S. DOT); the 40 A class sits higher in it | |
| Energy in a 4-hour window | About 31 kWh | About 38 kWh |
The gap is real but narrow — about a quarter more power, not a different category of charging. That is why the decision is made by your constraints, not by the spec sheet. Our amps guide shows where each class fits in the wider ladder.
Check One: Your Panel’s Headroom
EV charging is a continuous load, so the breaker is sized at 125% of the charger’s current, as set out in NFPA 70, the National Electrical Code. Whether your panel can host a 40 A or a 50 A breaker for the charger is decided by a load calculation over everything else the house runs, not by free slots. If the calculation only leaves room for the smaller circuit, the 32 amp class is not a compromise — it is the correct size. A licensed electrician runs the calculation; our breaker size guide shows what it produces.
Check Two: Your Car’s Own Limit
On AC charging, the car’s onboard charger sets the ceiling, and it only takes what it is built to take. A car whose documents state an AC limit in the 32 amp class will charge at exactly the same speed on both chargers, every night, for as long as you own it. A car that accepts the full 40 amp class can use the difference. This check costs nothing: the figure is in your car’s specifications.
Check Three: Your Night, With Numbers
Worked example, assumptions stated so you can swap in your own: say a day’s driving uses about 15 kWh, and about 30 kWh on your heaviest days. At a steady 7.7 kW those refill in roughly 2 and 4 hours; at 9.6 kW, roughly 1.6 and 3.1. Parked 10 hours overnight, both finish with most of the night to spare. The 40 amp class only changes the outcome when the window shrinks — a late arrival and an early start, or two cars sharing one charger in turn.
The future-proofing argument — wire once for 40 amps against a faster car later — is a design conversation with your installer about conduit and circuit capacity, not a promise about your next car. And an adjustable charger dissolves much of the dilemma: set it to today’s circuit, and reset it if the circuit is upgraded.
Both Classes From EVDANCE
The EV-ACS4005T spans the whole question: 9.6 kW, NEMA 14-50P, adjustable at 16, 24, 32 and 40 A, IP66, with a 25 or 28 ft cable — one unit settable to either class as your circuit allows. The EV-ACS3210T is the dedicated 32 amp class: about 7.7 kW, NEMA 14-50P, 10–32 A in six steps, IP66. Pick by your panel’s answer and your car’s limit, in that order.
Frequently Asked Questions
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 breaker under the 125% rule. On a 40 amp breaker the correct charger setting is 32 amps — which is exactly what an adjustable unit is for.
Will a 40 amp charger charge my car faster than a 32 amp one?
Only if your car’s onboard charger accepts more than the 32 amp class. If the car’s stated AC limit is in that class, both chargers deliver the same session.
Is the price difference between the classes large?
The chargers themselves sit close in price; the bigger cost difference is the circuit — a 50 amp run can cost more than a 40 amp run depending on distance and panel work. That is an installer quote, not a catalogue figure.
Related Reading
- How Many Amps Does an EV Charger Need?
- What Size Breaker Do I Need for an EV Charger?
- Which Level 2 Charger Should I Buy? A Buyer’s Checklist
- How Many kW Is a Level 2 Charger?
