When the wind doesn't blow (above), Germany uses coal plants which are antiquated and run inefficiently
When the wind is good (below) German power is mainly renewable.

Chart showing EROI at link:
When oil was easy to extract and refine it had high EROI, perhaps as high as 50.
Now it's 4 or 5 for the heavier oil like tar sands.
Solar is 6 but that will gradually improve wih advances in technology.
Wind is 20 but can't improve much (always need a lot of steel and concrete)
But we need energy to make the panels, so energy EROI is paramount.