Tesla Charger


Senior Member
Retired EE
I am contemplating installing a Tesla charging station that will tie-in to my existing service panel. I’m thinking a charger for a Tesla Type 3 Model. . . the smaller Tesla compared to the sporty type.
I think (at least that’s what I intend to do) of just adding a Triplex Murray plug-in double pole 40 Amp breaker. The reason for the Triplex is, I want to keep the two 15 Amp single pole CB and provide space for my intended 40 Amp 2 pole CB.

My service is 150 Amp and equipped with a 125 Amp Main CB. It has a 2/0 underground service conductor to the meter. NEC says 2/0 aluminum copper clad is good for 150 Amps.

My guess is the electrician undersized the main breaker when the house was built.

The Tesla Type 3 charger draws 32 Amps. Will take at least three hours to charge for completely discharged battery.

I did crunch some numbers that include my existing load and I came up with numbers that will put me within a safe range of my service capability.

I’ve seen in my neighborhood with Tesla chargers, but they are served with 200 Amps service.

Maybe the homeowner is thinking of plugging-in two or three Teslas at a time. . . I don’t know.

I don’t want surprises from AHJ telling me I need 200 Amps simply because the neighbors have 200 Amps.

From your experience, have you ever encountered something like this?

I really hate to spend the money upgrading if I can get by with what I already have.


Not a DIY. . .will get a sparky to do this because of some wiring involved..


Senior Member

A couple AHJs I've worked with won't allow you to apply the 40% factor to an EV. So ideally your load calc comes in below 85A.


Chico, CA, USA
You can set your car to draw fewer amps on charging. Setting it to 20A on the charing setting on the car.

We just added a dryer plug and use the unit that came with the car. $30 instead of $500, + wire.

Dennis Alwon

Staff member
Chapel Hill, NC
Electrical Contractor
If you have 125 amp main breaker then your service is 125 amps not 150. So is the panel rated 150 amps with a 125 amp main? If so then it may be cheaper to just change to 200 amps. I suggest you talk to an ec and see what is going on. If the wiring to the meter base is utility owned then you don't size that the same as the NEC requires