People don't seem to talk about Watt hours per mile much but when you're generating the power yourself it really matters. Tesla's model 3 is AFAIK one of the more efficient EVs and gets ~260 Watt hours per mile. With solar a good rule of thumb is to take the nominal rating for the panels you can point south and multiply it by 4 to get the approximate daily energy you'll generate in watt hours. If you could optimally park a car and let's assume you could cover it in a couple 100 Watt panels that would give you about four extra miles of daily range.

Maybe it's interesting if you live in a city and drive once a week.