Comment by SideburnsOfDoom

> Maybe someday the price will get so low it will be a no-brainer.

The cost of solar panels is already low, that's why it's booming. This cost isn't the main constraint any more.

Panels on a vehicle have stronger requirements for low weight, and vibration tolerance than those on a fixed structure. They contribute to the complexity of the vehicle's power systems. They have to be designed with vehicle aerodynamics in mind.

And of course the limited surface area means that you do all of that, for a component that's it's barely able to keep the vehicles' aircon running. The physics of that will remain the same. Even of the total costs are low (and factors such as the vehicle weighing more are an unavoidable cost), the benefits are lower.

At any price point, including free solar panels, there are good arguments to put the panels on a fixed structure instead.

So maybe it will happen when we have run out of non-moving surfaces to put the panels on. i.e. don't hold your breath.