Sonomotors have an electric car, the Sion. They claim that this car use its own solar-cells to charge the batteries in one day sufficient to drive up to 34km.
Their information sheet says:
Thus, under ideal conditions, up to 34 kilometers of additional range per day can be achieved with pure solar energy - CO2 neutral and completely for free. [...] For solar integration, we use monocrystalline silicon cells that produce energy even under cloudy skies or in the shade. viSono generates up to 1.2 kilowatts at peak performance.
This comes with a graph showing the calculated additional range in day per kilometer, based on average meteorological data for Munich, Germany:
But note the disclaimer:
All details provided for Sono Motors’ products are preliminary. Information about the vehicle is based on the Sion prototype’s current planning and technology at the time of publication (of this document). [...]
Is this true?