This is a pretty late response, but even as "not too north" as Hamburg it gets close to 10%.

Hamburg is at 53.6 degrees North; Berlin is 52.5. Both are just farther north than Calgary, as a pretty reasonable comparison for the US.

To contrast, New York City is at 40.7 degrees, and Boston is at 42.3 degrees North.

In southernmost Sweden, just above Germany, solar production is only 5% in December compared to June. In northernmost Sweden the sun doesn't even rise above the horizon for most of December.