Startups, and even major automakers, are turning their cars into mobile solar arrays. Hyundai’s 2019 Sonata (the solar version) uses an expansive roof-top solar panel to extend its electric range by 800 miles extra per year, assuming at least six hours of daily sunshine…

But physicists (and economists) argue that slapping solar panels on your car is not the most efficient way to procure electrons. Nor will it get you very far. For one thing, turning a vehicle’s body panels into power plants is pricey compared to buying solar power from the grid, even amortized over the life of the car, according to Jeremy Michalek, a professor of mechanical engineering at Carnegie Mellon University and director of its Vehicle Electrification Group. Nor are cars’ photovoltaic cells particularly efficient or well-positioned to capture sunlight. Even a best-case scenario would see less than 25% of solar energy converted into electricity.
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