Siemens has secured a multi-million euro deal from Danish Dong Energy, which will see its wind turbine manufacturing subsidiary, Siemens Wind Power, install 97 turbines in Dong's new North Sea wind farms, Gode Wind 1 and 2.

The deal is for the largest turbine models ever installed – Siemens' new six megawatt turbines have a rotor diameter of 154 meters (168 yards). The wind farms have a total capacity of 582 megawatts (that's the annual consumption of about 600,000 German households) and are to be built 28 miles off Germany's North Sea coast at a total cost of €2.2bn (£1.84bn) – the company's largest investment to date. The contract includes full five-year services for the turbines.

Neither Siemens nor Dong have disclosed the value contract, but sources close to the discussions told Reuters that it amounted to about €1bn (£840m). “Being constructed in an area with good wind and soil conditions, relatively close to shore and in a cluster where we can harvest synergies, the Gode Wind projects provide a sound business case,” said Dong's vice president, Samuel Leipold, on the group's website.

Offshore wind farm projects in German territorial waters continue to be hampered by uncertainty around government policy and subsidies for wind power, along with vexing technical issues.

Dong said it would receive a fixed price per kilowatt hour of electricity produced for the first 10 years of operation. After that, it will have to sell its electricity at market price. In a bid to attract private investment for Germany's energy sector, the firm also called on the government to create a support framework for wind energy in the future.