The maritime installation works started in January 2014, and electricity feed-in from the first turbine began in April 2015, the company said.
The operation and service station for the wind farm is located on the island of Helgoland, about 40 kilometres from the project site in the North Sea.
It uses 80 Siemens 3.6MW turbines and is connected to the German grid via the HelWin2 transmission link, which Siemens also commissioned in June.
Amrumbank West is E.on's second offshore project to be completed this year. In August, the 219MW Humber Gateway was also made fully operational.
The UK North Sea development comprises 73 Vestas V112-3MW turbines.