You can actually get a pretty helpful trickle charge out of solar panels on cars, and their cost is so low that the slight convenience may be worth the expense.

You can actually get a pretty helpful trickle charge out of solar panels on cars, and their cost is so low that the slight convenience may be worth the expense. This particular Sono car was rated to get up to 21 miles per day under ideal conditions. Let's say these numbers are extremely ideal and we only get 5 or 10 miles a day. Let's say you go to the airport and park in the economy lot for a week, and you come back to your car having 35-70 miles of extra range than when you left. I think if someone was buying a Tesla or some other popular EV right now and they had the option to put some solar panels on the roof that charged the car enough to add one or two miles of range per day I'd still see a lot of people paying one or two thousand bucks for that option. That's a heck of a lot better than parking your car outside for a week and finding that the battery has slowly drained on you.