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.
I think they only switched to Epik/Voxility for a few hours after being kicked off Cloudflare, but I'm not familiar with where they would have been hosted or what services they used 3-4 years ago.