>Instead it can be argued that if it's calm in Hamburg it is still very likely that it is windy in many other parts of Germany

The industry way to capture this is with a portfolio benefit analysis.

I don't know how safe your assumption is in Germany.

I am far more familiar with wind regimes in the States. If you have a plant in northern Texas, another in Iowa, another in the Columbia River valley in Oregon, and the last in Tehachapi pass in Cali, you have a full portfolio benefit lol