The machine was fully commissioned near Bremerhaven in January following its first power generation in December.
The turbine is an upgrade of the company's existing 6.2MW offshore machine, but with a 152-metre rotor. The previous model's rotor is 126 metres.
Senvion claims the greater blade length means an increase in the swept area of about 50% and a 20% increase in yield at wind speeds of 9.5m/s. It also has a a design life of 25 instead of 20 years.
The manufacturer said it is ready to enter commercial production of the new model this year if orders are forthcoming.
The prototype has already been sold to German developer EWE, which also operates a 5MW Senvion prototype nearby.
Speaking to Windpower Monthly prior to the announcement of the new machine, Senvion vice-president for offshore development Norbert Giese said the company was planning to stick with the 6M platform until the end of the decade.
He said: "We firmly believe the 6MW platform will be the platform for this decade, We believe we can improve it to make it more efficient, but this will still be the right turbine for us for the next few years."