Why we won't see solar-powered cars

It is a simple fact of physics: the sun drops about 1kW of energy on 1 sq m of Earth.

For petrol heads, 1kW is about 1hp.
If you are lucky, you will get up to 2.9 in Australia.
On average over a 24 hour day in the typical location you will get .25 kW/sq.m.
This is the total amount of energy landing on you, whatever the technology you have on hand.
See http://en.wikipedia.org/wiki/Insolation


  • If you live near the equator or it is summer
  • If the weather is fine and you have cleaned the car
  • If you are happy to leave your car outside all day
  • If you can find a spot that gets the sun all day
  • If your car is covered in 3 sq m of solar panels all oriented in the same direction
  • If those panels are 50% efficient in capturing sunlight (and the theoretical limit is 30%)
  • If you can store and retrieve power from batteries with minimal loss
  • If your electric motor is 100% efficient

Then you will get about .25 x 50% x 3 x 24 = 9 kWh of power a day from the cells.

The Toyota Prius uses about 100kW. i.e. if it was an entirely solar-powered entirely electric vehicle it would flatten the battery of a daily charge in about six minutes of hard running.

The performance of the Prius is truly awful. For a car that people are actually going to want to drive anywhere, you need 200-300 kW.

Unless you are prepared to classify a carbon-fibre enclosed bicycle with capacity for one passenger and no luggage as a "car", we aren't going to see solar powered cars.

Simple physics.