I ordered the $450 Tesla home charger to be installed next week and my electrician just asked me if this is a 60amp charger. I recall reading when I ordered it that it was up to 60 amps. To double check before I responded to him I went to confirm 60 but I read the following which only says 48 amp. What is the correct answer?
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Tesla Home Charger - 48 or 60 amp?
- Thread starter rcm1201
- Start date
fholbert
Active Member
Yes, 60amp max at the breaker. Amps will downgrade 20% at the car giving you 48amps.
I’m not a sparky but IIRC the downgrade is due to continuous draw, unlike an electric motor (pool pump) which uses a lot of power to start then it reduces the power required to operate.
Last edited:
GHammer
Dark Star
The answer is both. In order to receive the full 48 amp output it needs to be connected to a 60 amp breaker. Code only allows for an 80% continuous output of the breaker rating.
Snowball316
Member
Correct and confirm 60 amp breaker for 48amp charger. Make sure your install uses the right size gauge cables (6 gauge Romex I believe) or you may not be able to utilize all current. Your installer should know or if anyone here could chime in to confirm.
And this business about getting the correct gauge wire is a biggie that electricians who don’t do EVs often do mess up. Just so we’re clear on this: The NEC says that a circuit that runs at a heavy load (hello, Tesla!) has to be derated by 20%.
This is all about the heat: power dissipated in wire goes as P=A^2 x R, where R is the resistance of the wire. Note the squared term in there.
Next, the temperature of the wire goes as
T-Tambient = PxTheta, where Theta is the thermal resistance between the wire and the ambient temperature. That ambient temp is usually the outside air temp; but theta is the sums of the thermal resistance of the wire insulation, any insulation in the wall, air trapped in the wall, thermal resistance of the drywall, and so on.
The idea is to keep the wire temperature below the level at which the insulation starts to degrade. Which is a bad thing if it happens and causes house fires, not joking.
So, there are charts out there for wire types, AWG, and so on. Don’t let that electrician say, “Well, it’s only drawing 48A, so I can use this far cheaper, thinner copper wire that’s rated for 48A that I can find easily at Home Depot, rather than this much more expensive 70A wire that I have to go to an electrical supply house for.”
Right. And when the house burns down in ten years and this clown is over the horizon, it’ll be you taking the hit, not the clown.
Electrical Inspectors are your friends in this. Make sure the work is permitted.
Eric33432
Member
In the US, use #6 MC or THHN/THWN in conduit, or #4 NM-B (Romex) cable for 60 amp breaker / 48 amp charging. If the circuit is really long, you might need to upgrade. Use a voltage drop calculator if the circuit is longer than 150 or so feet.
Right.
...which is not that. That only has a 55A rating, so cannot be used for a 60A circuit.
We see that mistake really often.
el-guapin
Trust no One
Snowball316
Member
That is correct I used #4, just confirmed after reviewing my docs and notes.
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