The turbines will be installed on RWE's 156MW Westereems project in the province of Gronigen. The project, which uses 3MW Enercon turbines, is the largest in the Netherlands.
The 6Ms will be installed by mid-2012. RWE said it will be used to gage its potential performance at its Nordsee Ost offshore wind farm.
RWE has acquired 48 6M turbines for Nordsee Ost. Installation is set for mid-2012.
Speaking about the decision, RWE head of offshore said: "The two 6M turbines are an ideal expansion of the existing wind farm Westereems. Furthermore, with operation of the plants we aim at gaining new insights for their employment on the high seas in the project Nordsee Ost."