And so it does: "If installing for maximum power, use minimum 6 AWG, 90° C-rated copper wire for conductors.", which is highly misleading for Tesla to put that in their freaking manual.
I don't want to get all code nazi on you, but here's a typical ampacity table showing the maximum ratings. NM-B (Romex) has a maximum ampacity rating of 55A on 6 gauge, unlike THHN wire pulled in a conduit. The problem is the construction of the romex wire bundle itself. It has a very thin vinyl outer cover which can melt and cause the potentially hot internal conductors to touch sawdust and combust. This electrical code page section, right at the top states that you have to use the 60 degree temperature rating for NM-B cables which results in the 55A rating with 6 gauge.
The other thing you are confused about is intermittent loads versus continuous loads. The 55A rating for 6 gauge NM-B is for intermittent loads. EVs are considered continuous loads since they stay on full blast for hours at a time. Continuous loads must themselves also be derated to 80%. So a circuit that can handle 60A with a 60A breaker can only draw 48A by an EV. For a 55A wire, that would be 44A maximum for an EV.
As far as "only charging at night" goes, well that'll work until you need to charge during the day once.
Look, do want you want, I'm just pointing out the safety concerns.
MANY MANY electricians screw this up, so don't feel like you did anything unusual. All this is one reason why I wrote a special page about DIY EVSE installs here on my site.
