Every home charger job starts with the same question from us. What do you drive?
It sounds like small talk. It is not. Your car sets the top speed, no matter what the box on the wall claims it can do. Buy the wrong circuit for it and you either waste money or waste charging speed.
The car is the ceiling, not the charger
Every EV has a part called the onboard charger. It takes the AC power from your wall and turns it into DC for the battery. That part has a limit, and the limit is baked into the car.
Here is where three popular cars land.
Tesla
The Tesla Wall Connector can push up to 48 amps. To run at that speed it has to be wired in, not plugged in, on a 60 amp breaker with 6 gauge copper wire.
Rivian
The Rivian Wall Charger also tops out at 48 amps, about 11.5 kW. Same circuit as the Tesla. If you have an R1T or R1S and a big battery, this is where the wired-in install pays for itself.
Kia EV6
The EV6 takes 10.9 kW on AC, which is close to 48 amps. Both the rear drive and all wheel drive versions use the same part. So a 48 amp charger is fully used here, and anything faster on the wall does nothing.
Plenty of other EVs cap at 7.7 kW, or 32 amps. For those a 40 amp circuit is not a compromise. It is the whole car.
Why a plug caps you at 40 amps
This is the part that surprises people. A 14-50 outlet in the garage sits on a 50 amp breaker. You would think that means 50 amps of charging. It does not.
Charging a car is what code calls a continuous load. It runs for hours at full pull. So the rule is that the circuit has to be rated 25 percent above the load it carries. Run that backwards and a 50 amp circuit gives you 40 amps of steady charging.
Same math going the other way. A 48 amp charger needs a 60 amp circuit, because 48 plus 25 percent is 60. There is no plug rated for that in a house, which is why 48 amp units are wired in.
Plug-in installs have a second quirk. Code requires ground fault protection on the outlet, and the charger has its own protection built in. Stack the two and some cars trip the breaker for no real reason. Wiring the unit in removes that problem entirely.
What 40 amps actually gets you
Before you spend more, look at the real numbers. A 40 amp circuit delivers about 9.6 kW. For most EVs that is roughly 30 miles of range per hour.
Park at six in the evening and leave at seven in the morning. That is 13 hours, or close to 390 miles of range. The average driver does not put 390 miles on a car in a day.
Going to 48 amps buys you about 20 percent more speed. It matters if you drive long days, if two cars share one charger, or if you have a big truck battery and a short window at home. For a single commuter car it usually does not.
Wire it once
Here is the advice we give in every East Valley garage. Size the circuit for the house, not for the car sitting in it today.
A 60 amp circuit charges a 32 amp car perfectly well. The charger just pulls what the car asks for. But a 40 amp circuit can never feed a 48 amp car, and the fix is opening the wall a second time.
The extra cost up front is wire and a breaker. The cost later is the whole job again. Cars in your driveway change every few years. The wire in your wall should outlast all of them.
One thing does limit this, and it is your panel. A 60 amp circuit needs room and it needs capacity. In older Gilbert homes that often means a load management device, which lets the charger back off when the AC runs. In newer Queen Creek homes the panel is usually big enough but short on open slots.
Either way it starts with a load calculation, and that is a free conversation. Call (480) 283-5007 with your car and your panel size, and we can tell you most of the answer before we drive out.
