I don't have a Tesla so I'm not familiar with the superchargers specifically but I have a plug-in hybrid and I have seen a combination of both time and energy a

I don't have a Tesla so I'm not familiar with the superchargers specifically but I have a plug-in hybrid and I have seen a combination of both time and energy at various charging stations. For example, some have a flat $/kWh + $/hour "parking" after the first hour. I think that it makes a lot of sense to have some incentive for people to not just leave their cars there forever. But it is true that charging rates vary including a taper off in charging rate towards the end of charge if you are getting it "topped off" so to speak. So from that perspective basing it just off time does become a little disingenuous, and I like the hybrid approach of $/kWh + $/time that kicks in after some amount of time.