I looked at a job yesterday to bring power to a detached garage. Also to finish electrical rough but that wouldn't be a problem.
There are two choices, first to bring power from the house but that would require a lot of trenching to get around to the back of the house and the panel doesn't have correct working clearance (inspector may not like that), don't think there would be capacity for future charger and county may have them install smoke detectors in the house if it's considered a major addition.
The other choice is a seperate service that would be kind of easy and would provide power for future charger and the inspector would never get inside the house. There is a minimum charge just to have a meter for the seperate stucture each month and this would be more than power used.
I'm thinking that a seperate service may be the way to go even though I normally wouldn't. It would certainly look like over kill to have a seperate service for a couple door openers and a few lights and receptacles but with all the electric vehicles these days.
Do most of you offer a seperate service as an option for cases like this. Be easy as the transformer and pole are really close. Simple overhead, little 100 amp. Who knows they many end up with more in that detached garge than they are willing to admit now. It's kind of a large structure for a 2 car garage.