The initial use of solar on the Prius was to power a ventilation fan while the car was parked, and the current version seems to specifically be designed to provide power to the air conditioner while driving. But, I also can't imagine the difference between cooling down the cabin is much different from parking in the sun or in the shade - you'd be running it continually to achieve "room temperature" during the entire drive either way.

You can't imagine that air conditioning power draw varies with the heat load that it is working against? As a heat-pump, it takes more energy to move more energy.

In the old days, they used duty cycle to adapt to the changing load. Modern ones do things like varying compressor displacement or compressor speed to adapt to the load. Variable frequency inverters are used to efficiently drive electric compressors.

The variable displacement trick is used in ones mechanically linked to internal combustion engines. It can vary the compression stroke to account for different load as well as different engine speed.

Watching power draw on my Leaf with LeafSpy, the AC seems to use between 500-1000W (maybe more sometimes, but that's just off the top of my head from a few times running it while driving).

At the low end maybe achievable with a full rooftop covered in solar panels, but probably not adequate at 1kW+.

> Does the extra 3-6 miles factor in the need to now run the AC much more aggressively because the car will be hot from sitting in the sun all day?

Most cars are already sitting in the sun all day.

Yah, it's a great point that the whole scheme is predicated on very questionable land use policy...

You are not getting the 3-6 mile per day boost if your car is parked in the shade.

That's his point. You won't get any reasonable charge because you (mostly avoid parking your car in direct sunlight

What kind of European cities are you talking about lol, no offence but I hate this generalisation of "European" anything as if Southern Spain has the same culture and architecture as Poland or Lithuania.

It is a somewhat fair generalisation of urban europe to have more innside parking or tall ish buildings that give shade.

To my thinking, the best use of a solar panel on a car is running a low power AC unit all the time whenever the car is in the sun. Parking in the shade often isn't possible.

I don’t think you’d have to run the AC any more aggressively with the solar panels than with a traditional steel roof?

If you’re suggesting it wouldn’t work in a garage, that’s obviously true (and another factor in whether car solar makes sense) but many (most?) people park their cars outside during the day anyway. I for one can’t remember the last time I parked under cover