40 vs 48 amp EV charger: your car sets the ceiling

Seven in ten residential installs by Qmerit, which calls itself North America's leading EV charger installation provider, are 48 amp units. Emporia tells its own buyers that many popular EVs max out at 32 or 40 amps anyway.

Most of the decision sits in the gap between those two sentences.

Choosing between a 40 vs 48 amp EV charger reads like a speed decision and is really three of them stacked: what the car will accept, what the panel will give up, and how much of the night you actually have. Only the first is fixed. It is also the one nobody checks before adding a charger to a cart, and it takes two minutes.

How many amps can your car actually take?

Whatever its onboard charger is built for. That figure lives in the owner's manual. The wall never shows it. Qmerit, the installation network behind more than 770,000 charging stations, puts the range at 32 to 48 amps of AC power at 240 volts, roughly 7.7 to 11.5 kW, and states the rule that governs everything below: the vehicle onboard charger ultimately limits how much power it can accept. A charger cannot push current a car declines to take.

Emporia sends buyers to that manual too, and adds the finding that makes this whole comparison smaller than it looks: many popular EVs max out at 32 or 40 amps anyway, which means the hardwire speed advantage does not apply to their vehicle. The Department of Energy gives the same instruction from the other direction and tells owners to consult vehicle manufacturer guidance where possible and learn the specifications before buying equipment or electrical services.

Do that one lookup before anything else.

What 40 vs 48 amp EV charger really trades

Qmerit publishes the conversion, so the trade is arithmetic. A 40 amp charger delivers about 9.6 kW and adds 20 to 30 miles of range an hour. A 48 amp charger delivers about 11.5 kW and adds 25 to 35, on their note that most EVs achieve 3 to 4 miles per kWh, larger trucks and SUVs possibly less. The whole case for the larger unit is 1.9 kW.

Emporia works the same sum on its help page and lands somewhere useful: an 80 kWh battery taken to 80 percent at 40 amps needs roughly 6.6 hours. A large pack, nearly empty, finished before anyone is awake. The 7.5-hour charge in the FAQ below is a different scenario: Emporia's own framing across many EVs, not one 80 kWh pack taken to 80 percent, so the two figures are not meant to reconcile. Faster is better on a truck battery that lands home close to empty most nights. It is invisible on a commuter car that arrives with two thirds of its range still in it.

The circuit is the difference, not the charger

Here is where the amps actually cost something. NEC 625.42 designates electric vehicle charging as a continuous load, and a continuing education course on that section puts the consequence as 80 percent of the branch circuit rating not to be exceeded. Qmerit states the same rule generally. Emporia's help page spells out the common case, that NEMA 14-50 circuits are rated for 50 amps but must be derated to 80 percent for continuous loads, limiting the output to 40 amps.

That sets the ladder. A 32 amp unit wants a 40 amp circuit, a 40 amp unit wants 50, and a 48 amp unit wants 60. Emporia lists that last pairing for its own hardwired install. The same step forces the install method too, because under that rule a NEMA 14-50 on a 50 amp circuit stops at 40 amps. Emporia states it that way, and ChargePoint builds it into both of its plug configurations. Choosing 48 amps therefore means choosing a hardwired install too, whether or not you meant to.

The bigger circuit also changes which ground fault rule can reach the install. NEC 210.8(F), new in the 2020 code, covers outdoor outlets for dwellings on single phase branch circuits at 150 volts to ground or less and 50 amperes or less. That source is explicit that an outlet includes a hardwired connection and not only a receptacle. So an outdoor hardwired unit on a 50 amp circuit sits inside it, and a 48 amp unit on the 60 amp circuit Emporia pairs it with sits above the ampere limit. Reading that section as reaching a charger is our inference; no code or manufacturer source prints it. Two members of a Tesla Motors Club thread on cheap outlets get to the same place, and a third says flatly that no ground fault rule reaches a hardwired unit indoors or out, so treat it as contested.

None of which exempts the plug in path, at any amperage. NEC 625.54 puts ground fault protection on a receptacle installed for EV charging wherever the receptacle sits, indoors included, which Leviton reprints with permission from NFPA. So the 40 amp plug in default takes that breaker in a garage the same as on a wall outside. A hardwired 40 amp unit has no receptacle for 625.54 to attach to, though that alone does not clear it of 210.8(F) above. TIA 17-2, the tentative interim amendment that introduced 625.54 against the 2017 code, scoped it to single phase receptacles at 150 volts to ground or less and 50 amperes or less. The 2020 text carries no such scope. We read that off the two documents side by side; neither one prints it. The 40 amp default comes out the same, because a 40 amp charger on a 50 amp circuit sits inside the 2017 band anyway. Adoption runs state by state, so an older jurisdiction may require none of it. Ask the electrician pulling the permit.

Then the panel has to have it. Emporia notes that most homes built after 1960 carry 100 to 200 amp service and that a level 2 charger typically wants a dedicated 40 to 50 amp circuit from it. On an older board, that bites. When there is nothing spare, load management is the documented answer: NEC 625.42(A) lets an energy management system set the maximum equipment load on a service and feeder, a subsection the 2023 edition added out of language the 2020 text already carried. Qmerit says a load calculation or smart load management often removes the need for a panel upgrade entirely. Sizing any of this is a licensed electrician's job, and permits may be required by the local building authority.

Which one to buy

Buy 40 amps. It is the default for a car that accepts 40, a house with a 50 amp circuit to spare, and a commute that ends with range left over. A 32 amp EV charger is the right answer more often than it gets picked, and Qmerit's table runs lower still, to 24 amps and even 16, so level 2 charger amperage has more rungs than the shelf suggests.

Buy 48 amps when three things line up: the car accepts it, the panel carries a 60 amp circuit, and the battery is big enough that the difference matters. Those three conditions make a narrower set than Qmerit's 70 percent of installs implies. Both ceilings sit on the level 2 charger shortlist, where the plug picks stop at 40 amps and the hardwired ones reach 48 or 50.

Know the escape hatch before you settle what size EV charger to order. NEC 625.42(B) permits equipment with restricted access to an ampere adjusting means, so an adjustable unit separates what you own from what it draws. The 2023 edition gave that its own subsection, and the 2020 text already permitted it for equipment fixed in place, a restriction the 2023 revision deleted. Emporia lists its charge rate as settable in single amp increments from 6 up to 48 on a hardwired install. Buy the larger unit, have it commissioned at the current the circuit and the car support, and the sizing stops being permanent. The permission turns on access to the adjustment being restricted, not on an app slider, and the electrician makes that call.

The same reasoning makes the connector question smaller than it looks. It is also why what this page had to clear is a list of documents and not a house style. The rest of the board gets read the same way.