The car park itself is going to generate the same money with or without the solar. Consider that irrelevant for this discussion.
Building the solar over the car park only really makes sense if you have absolutely nowhere else to put it. The land for solar is usually very cheap, compared to the cost of constructing a large gantry that is designed for vehicular impacts. If you need to do any repair, maintenance or replacement, you have to contend with all the cars in the carpark, or absolutely nothing in a field. You also need to do it at height (i.e., with a crane or lift), which is much more complex than just driving out with a van and doing it on the ground.
The only instances that I would recommend doing this are:
You are already building a gantry for shade.
You have a green target for the development and cannot achieve it with only rooftop solar on the buildings.
someguy3@lemmy.world 2 weeks ago
When over a parking lot, you can’t have supports columns every few feet. So now you’re spanning with a beam, then you need bigger columns, and bigger foundations. Construction of that is also more complicated requiring concrete, cranes, etc. It all adds up.
You could also be aggressive with the design in the field because if it tips over in a storm, who the fuck cares. You just pick it up and redo it.