Why Don’t We Have Solar-Powered Cars?

Like a lot of things we’d like to have but can’t, it’s because of physics.

When the sun is high in the sky on a sunny day, each square meter of the Earth’s surface below receives about 1000 Watts (1 kiloWatt) of power. Suppose there are three square meters of solar PV on the car shown here, so that’s 3 kWs. If the solar panels are 30% efficient, that’s 900 Watts, a little over 1 horsepower, not even enough to filter a good-sized swimming pool.

Now, obviously, if the car has a big battery pack, you can leave it charging for a long period of time.  But even cheap little cars have 100-hp+ motors so they can achieve freeway speeds and get up hills.

Let’s suppose that, because of its sleek design, you can get away with 50 hp. You’ll be charging  it (in full sun) 50 times longer than you’ll be driving it.