Covering around 24km2 area, the Nordsee Ost farm features 48 wind turbines, and will produce clean electricity required to serve around 320,000 households a year.
Built with an investment of more than €1bn, the wind farm project received €50m grants from the European Union.
Germany Economics Minister Sigmar Gabriel said: "Offshore wind energy is a strategically important element of Germany’s energy and climate policy and is key to the success of the energy transition.
"Thanks to its continuous input into the grid and its high electricity yields, offshore power generation makes a crucial contribution towards a diversified and reliable energy supply system."
An operating station owned by RWE on the island of Heligoland will manage the operations of the Nordsee Ost farm for the next 20 years.
RWE CEO Peter Terium said: "In only one month’s time, we will be commissioning another wind farm, Gwynt y Môr, located off the coast of Wales."
RWE Innogy CEO Hans Bünting said: "At the end of this year, 40% of our power generation from renewables will already come from offshore power production.
