At least here in Germany, at the grid scale, there isn't a real surplus of renewable energy most of the time, especially if you subtract all coal and gas power

At least here in Germany, at the grid scale, there isn't a real surplus of renewable energy most of the time, especially if you subtract all coal and gas power going into the grid. Of course on smaller scales, batteries make much more sense. For example, it is profitable to combine your private solar generation with a battery, as you don't get much by feeding your surplus generated power to the grid.