You know what would be 10x better for society? Not have a society where half of every city is compromised of parking lots.

The car and parking lots problem is a huge part issue in the US in particular. Not only is the whole concept incredibly bad environmentally, in terms of CO2 of course, but also emissions and other problems like cities being hotter and causing water management issues.

These parking lots are also a huge economic problem a symptom of the reason why so many towns are functionally broke. Encouraging cheap building for box stores or fast food restaurants with huge parking lots represents and incredibly uneconomic proposition and is losing cities money. Lots of infrastructure cost for very little in terms of property tax.

Not to mention that such a development pattern makes city centers less attractive, and that is exactly the place where cities could be making actual money. Often is actually the poorer denser areas of the city that financially support the sprawl of the richer part of the city.

So instead of plastering solar panels all over parking-lots ever effort should be made to eliminate the parking lots themselves. Infill development has to be done, and the city needs to support it with by relaxing their often borderline sociopathic zoning orders (along with a host of other harmful regulation).

Changing the development pattern would save far more energy then plastering parking lots with solar panels will ever do.

And not only will it help for the environment, things like the housing crisis in the Bay Area (and other places could be solved or at least massively impacted). Talking all the under utilized commercial zone property in the Bay Area and zoning it for mixed-use could potentially add 1000000s of housing units in the 'missing middle' segment.

See this talk on the Bay Area by City designer Peter Calthorpe: https://www.youtube.com/watch?v=fUtdFbK4YG4

The organization 'Strong Towns' has made this one of its central issues: https://www.youtube.com/watch?v=Em7nqDqQ8oM

For some more details on the economics Joe Minicozzi: The Cash Flow of Urbanism:https://www.youtube.com/watch?v=pFC_Q4WQKVk

So what I end up with is that inside of cities you shouldn't have parking lots hardly at all, and outside of the urban environment you might as well just put them onto some empty space. Putting solar panels on parking lots will just make those parking lots an even more persistent and harder to remove in the future.

So remove the parking lot, don't buy the solar panels, invest that money in a trolley bus instead. It will be better for the environment and the city.