Presumably the car's solar panels are not getting any sun under a roof.

A car having anything remotely close to useful solar charging requires so many goldilocks conditions to be just right that it's not worth the complexity, and it's better to invest equivalent resources into more practical solutions.

Combustion Engines require so many goldilocks conditions that it is not worth the complexity. Better to invest in more practical solutions: one big engine dragging carriages is vastly more efficient.

Just to make my point really clear, This whole thread is generally arguing: Don't do innovative things, because there are other known (non-innovative) things you could do.

Cars that charge themselves in the sun is a no brainer, is it going to replace needing to ever charge them, not yet... But if we don't try we won't improve that technology.

That implies that all innovation is created equal and has equal payoffs.

The ICE brought about big gains for its use case even as a prototype; ICE cars don't produce poop and they wear out a lot less quickly than a horse. In comparison, flying cars or amphibious cars never really made it off the ground in a big way, because the "innovation" there resulted in a hybrid machine that did two jobs poorly and impractically, rather than having two specialized machines.

If it is really easy to point out inherent problems, like, say, the fact that most of the surface area on a car is not generally oriented at an angle to the sun conducive for generating electricity, and those aren't problems that would be solved by "innovation", why try to squeeze water from a stone?

Except that panel development has meant that more energy has been generated at wider angles. Battery tech had the advantage of advances in consumer electronics, Tesla (and everyone else) literally just connected laptop batteries together.

The same thing won't happen with solar, it needs active use in novel areas. Cars are out in the sun, why not collect it? Panels aren't exactly a super rare resource, we could and should make piles of these and stick them to everything, it's literally free electricity and basically 0 maintenance.

> Cars are out in the sun

Are they? Cars spend a fair amount of time under things that would block sunlight; there are garages in all sorts of buildings from your bare-bones detached house garage to multistory affairs, and even if they're outside they're often parked under trees, or in streets and lots shaded by buildings. So it makes already intermittent solar even more situational.

In fact, in hot climates, people take care to park their cars in shade, because the last thing people want is for their car to be baking in the sun.

Zoom in on any satellite shot of a city, or a road... count the cars vs the solar panels you see. Yes cars are out in the sun... lots of them, all the time. The fact the satellite can see it means there is solar energy in that spot, right when that photo was taken. Multiply that by "All the cars outside in the world" and it's a lot of energy. (Even if they are all still plugging in at their destinations as well).