40 to 50% is the general expectation, depending on the area (and how conservative you are). German offshore should generally get 50% or more (the Areva 5000 at Alpha Ventus has a relatively small rotor at 116m; they are now selling the same model with a 135m rotor, which should increase the  capacity by several %

We posted the data from Denmark

The two big ones are at 40-45% (Nysted & Horns Rev) with old turbines (orns REn is in the North Sea, Nysted on the Baltic sea side)

Wind power