There are some doubts out there about whether on-vehicle solar can make sense.

And I do not only mean petrol heads from the anti-EV club, but also people who value solar energy and EVs in general, but just have doubts that it can make sense on a vehicle.

Is the energy output of on-car panels high enough?

I’ll do some (simplified) computations with well-known parameters as published by Aptera and other sources. I live in Germany, so numbers are for here and for 2023.

Aptera “full solar variant” solar panels output power: 700Wp = 0.7 kWp

Yearly energy yield in Germany: 1000 kWh/kWp (practically seen from rooftop solar)

(Germany is not a very sunny region, there are better and worse places than here.)

Yearly energy yield for the Aptera panel: 0.7 kWp * 1000 kWh/kWp = 700 kWh

Aptera range: 40 kWh battery is for 400 miles (644 km) range.

Aptera consumption: 40 kWh / 644 km = 0.062 kWh/km (or 40 kWh / 400 mi = 0.1 kWh/mi)

Yearly range just from on-car solar panels:

700 kWh / 0.062 kWh/km = 11270 km (7000 mi)

Yearly savings:

0.5 EUR/kWh * 700 kWh = 350 EUR (compared to electricity from grid)

Take this with a grain of salt!

In practice, it might be less than that, so better read that as “up to 11270 km per year” and “up to 350 EUR”.

Technical / environmental reasons:

• panels might be oriented in a worse angle to the sun compared to rooftop solar
• conversion losses in electronics or battery (*)
• climate (e.g. cold) and terrain (e.g. hilly) might be less than optimal (*)