Question is, do they really have to be? We all know ISPs oversell their backhaul, for example. That gigabit connection won't be a gigabit if everybody in the area is trying to download at full speed at the same time.
Same deal with charging EVs, I think. Put more chargers in, preferably capable of full speed individually, but what are the odds that you'd get 80 cars in during the exact same 15 minutes? That every single one of them would be properly preconditioned for a full speed charge?
If you have a few cars that have been there for 10-15 minutes already, their charging rate slows down naturally, the station can coordinate with the cars and driver's plans to ensure that the power is divided up in a equitable fashion.
As for the solar panels over the parking - I know it's not going to make a huge dent in providing all the necessary energy for charging the cars, but putting a structure over the top to shield them from the sun and rain is still very nice, at which point they might as well be solar panels.
A station that has 80 charging spots but normally only sees 3 of them being used at a time might still be able to satisfy most of their demand via the solar panels.
I have to agree with thegarbz - I think it is highly unlikely for a supercharger station to experience perfectly steady demand. At this point Tesla should have plenty of multiple yearlong examples to figure out likely usage patterns.
I'd expect, given food establishment (but no breakfast?) to see peaks around lunch and dinner periods: 11 am to 2 pm, 5 pm to 8 pm. A trickle of cars otherwise. Add good breakfast, add a peak at 6 am to 9 am. (8am would be when the retirees mostly show up).