The project has been connected via the DolWin Alpha substation by networks specialist Tennet and is now producing power.
Borkum West II is using 40 Areva M5000 turbines 45 kilometers off the German coast in the North Sea.
The turbines will be progressively brought online with full commissioning expected in spring 2015.
Installation of the turbines and cabling was completed in August 2014, but Trianel said the "multiple displacement" of the transmission system meant a delay in the connection.
The developer was founded by municipal and regional utilities from Germany, Austria, Switzerland and the Netherlands, making Borkum West II the first offshore project to be developed in this way. It is also the first full-scale commercial site to feature Areva's 5MW turbine.
A second 200MW phase of the project is expected online in 2020.