Something not explicitly stated in this thread:
Because car chargers draw continuously, code requires EVSE loads to be a maximum of 80% of the circuit's breaker, e.g. a 50 Amp breaker may only use a 40 Amp connector (the "charger" is actually built into the car; the box with a cable you hang in your garage is properly called a "connector" because all it does is allow the 240V, whatever Amperage, AC electricity to flow into the car, whose internal charger then converts the juice to DC and directs it into the big battery). As others have said, just because you have a 40 amp connector doesn't mean your car can or will pull that much; it pulls what its internal charger is able to pull or, in some cars with the feature, what the user sets the draw to be.
If your house supports it, I recommend a 60 Amp breaker, which could then supply up to 48 Amps. That is the draw of most Teslas, so it is, IMO, the de facto standard for high performance home charging. Plus, if your car's charger pulls less than 48 Amps (like the SE's, which pulls up to 32A), you've got even more headroom before wires get hot, etc.
Assuming your house wiring can support a 60A breaker, the material cost difference between installing and wiring for a 60A circuit and, say, a 30A circuit would probably be $100.
by itself.
having a 50A circuit available doesn't mean it's going to force 50A upon the charger... nay nay... think of amperage as the amount of power that can be safely pulled by the device attached... voltage is the force at which it is able to be applied... so, plugging a 16A or 32A device into a 50A plug/service, is perfectly acceptable... so long as the device in question or local regulations don't require a more closely matched circuit protection level. (always over-size your wiring whenever possible, e.g. run wires expecting the worst that circuit will ever see for a constant load, and life is good)
