To encourage adoption of plug in solar, at least in the US, it can offset your local consumption, but a smart meter doesn't credit power back that flows to the utility to your local distribution (as model legislation is currently written and being passed). Being credited for excess generation only applies with a traditional grid tie system, ground mount or roof mounted, with an interconnect agreement with the utility (with the exception being that if you already have residential solar, have an interconnect agreement, and add plug in or balcony solar, you would get credited for that excess generation, as the utility isn't going to know the difference with their smart meter).