A Test of Solar Panels' Ability to Capture Energy on Cloudy Days

In Bavaria the farm houses with large medium pitched roofs are well suited to a retrofit with solar panels. They don't detract from the neatness of the small villages, and appeal to the German penchant for thrift.
I'm used to seeing ubiquitous solar panel retrofits on Australia, where there's usually no shortage of sun.
I'd read somewhere that Germany generates more solar energy than some other much sunnier, larger place: Australia? USA? I don't remember exactly. The local German architectural norms are part of the reason this greening of the energy use patterns is possible.