Orsted has agreed to sell 50 per cent of the Hornsea Project One offshore windfarm currently under construction in the North Sea to Global Infrastructure Partners (GIP) for £4.46 billion.

The project is located 120km off the coast of Yorkshire and will feature 174 of Siemens Gamesa’s 7MW SWT154 turbines – giving it a total capacity of 1,218MW. It will become the world’s largest offshore windfarm when it is commissioned in 2020.

As part of the agreement, Orsted will complete the installation and provide operations and maintenance services from its base in Grimsby. The transaction is expected to be completed in the fourth quarter of 2018, with payments being made between then and 2020.

Ole Kjems Sorensen, executive vice president for mergers and acquisitions, partnerships and asset management at Orsted, said: “This is our third partnership with GIP, and we are delighted to have one of the world’s largest infrastructure funds as a partner, in what will be the world’s largest offshore windfarm.

“The Hornsea Project One farm down is a landmark transaction which will create substantial value for our shareholders and reduce single asset exposure.”

The project was awarded a contract for difference at a strike price of £140/MWh (2012 prices) through a one-off non-competitive process prior to the introduction of auctions.

It will be superseded as the world’s largest offshore windfarm when its sister scheme, Hornsea Project Two, becomes operational in 2022.

Hornsea Project Two was one of three offshore windfarms to secure a contract for difference in the latest auction in September 2017, and one of two to win a contract at a strike price of just £57.50/MWh (2012 prices) – the other being the Moray East project.

The windfarm will have a total capacity of 1,386MW provided by 165 of Siemens Gamesa’s 8MW SG167 turbines. Orsted placed an order for the turbines in June.

The company applied to the Planning Inspectorate in May for a development consent order for Hornsea Project Three which will have an even larger capacity of 2.4GW.

The title of the world’s largest offshore windfarm is currently held by the 659MW Walney Extension in the Irish Sea. The project was officially opened earlier this month at a ceremony in Cumbria.