[egberts1]

I did take liberty here in saying 37A-ish (40A is code) because that's what some national fire marshalls are reporting about hot garage and reuse of range-type wiring for new purpose of EV charging.

It's the wire material and size issue in hot area.

[Kirby64]

But, if it supports 40A charging it'll charge at 40 amps unless you back off the charging rate (which nobody does, typically). You'd always assume 40 amps for circuit purposes.

[egberts1]

See @quickthrowman's comment for detailed breakdown on high-temperature and copper wire.