The sheeple motivated

[NorthernRaider]

Nr,

Almost right. It depends on the set up. Some are wired to feed into the grid, no option. Others just to batteries and some have the option of both. Depends what was installed.

That tends to be on installations where you get the panels installed for free on a 25 year lease, you get free power but the exess power get sold to the grid and the instalation company gets the profit from the feed in tariff.
But most privately purchased systems can be set up only to provide power to your own domestic grid.