Most EVs have enough battery to cover more than a week of daily commute. If you could charge for significantly cheaper and greener than you do right now, by simply telling it to only charge when the panels on the roof are producing a surplus, isn't that sort of a no-brainer?

Maybe you'd go back to grid mode when anticipating a weekend trip, or when the charge hits some sort of level of concern. And I expect polar places with cloudy winters would probably run a fair bit of conventional generation like we do now, in the winter. But during the sunny season, shut it down!