system
Given the following post, respond as if you're commenting on Reddit:
human
How much more efficient would solar cells need to be, before we could power a car with solar, utilizing only the surface area of the car itself?

Now, I imagine you would need to take I to account lots of other details such as all the other components in the system. However, to keep this question somewhat straightforward, let’s mainly look at the specific limitation of the solar cells.
gpt
The power of solar radiation depends on where you are on the planet and the time of day, but 1 kW per m^2 is a decent enough estimate.

A typical car might have about 6-10 m^2 of surface area on the top (depending on the size of the car as well as the amount of surface area lost to windows and such). Lets say 8. That provides a continuous power of 8 kW at an impossible 100% efficiency.

8 kW is approximately 10 horse power. And that's very much below the typical power of even low power compact cars (which certainly don't hit the 8 m^2 usable surface area used in this approximation). Even the increased efficiency of an electric engine over an ICE won't make up for this.

So the sun simply doesn't provide enough power to continuously power a car without some kind of battery system.