The amount of power you could pull from a single square metre of solar on the roof wouldn’t increase your range meaningfully.

What it would do, is that you could possibly keep your starter-battery from going dead-flat if you left your car alone for a 1/2 month, in the summer ( snow would cover it, obviously ), & since bringing a lead-acid battery to dead-flat permanently-damages it, this would prevent costly problems for the car-owners.

( this happened to a friend with a Prius: had to replace the battery, and the damned thing was inside the rear wheel-well??? in a little compartment.

Origami-engineering’s … simultaneously incredible & stupidly-frustrating )

I’ve held for years that they should be doing it to keep the starter-battery trickle-charging, but … why make the customers have fewer costly/frustrating problems?