Parking (Electric) meters
It's easy to have a section of the parking garage on controlled access - a gate, and every space in that section is fitted with a charger. As a minimal solution, every car that accesses that section is assumed to take one standard charge, and pays the daily rate for that.
In Sweden, street parking stations have small electric plug-ins to connect an engine-block heater to stop the engine freezong in the winter. Something similar can be done in the future but with higher power output, and linked to paid-parking time.
technology is easy, given time...