I wonder how that would change the safety profile of the car (for driver and outsiders) and insurance costs. Panels are fairly cheap but you'd be adding a bit of value there.

Why is that better than just putting the solar panel on the roof of your house and plugging the car in?

Your car is presumably not always at home. So, a solar panels on the roof of your house don’t increase the range of your car. At highway speeds assuming regular charges that’s mostly irrelevant. But if you’re camping or run out of charge it could become so.

Even relatively small solar arrays could keep a car from discharging at an airport parking lot etc. That could extend to running the climate controls when your shopping without concern for draining the battery.

PS: That said, the roof also has many advantages such as allowing you to park in a garage without issue.

I am not positive but I am guessing that solar panels as the roof would weight more than the regular car material?

I am not really an expert on electricity but there could also be additional equipment involved as well (inverters, transformers, etc).

The light collecting portion of solar panels is extremely light weight. https://www.amazon.com/dp/B082FCZ4MD/ref=emc_b_5_t?th=1

59.2 by 26.5 inches or ~1 square meter Weight: 6.2 lbs.

If you looking at 12 square meters of space that’s 75 pounds though an integrated system would have plenty of options to save weight.

Solar panels are DC as are batteries so you don’t need an inverter.