SSE Renewables said it started the third phase of construction at the world’s largest offshore wind farm at Dogger Bank, off the North-East coast of England.
Work has already started on phases one and two. This final phase, Dogger Bank C, will cost £3bn and bring the total investment to £9bn.
Dogger Bank C has a capacity of 1,200MW and will generate around 6,000GWh a year or enough to supply 5% of the UK's demand, equivalent to powering six million UK homes.
SSE is leading on construction across all three phases with partner Equinor set to operate the wind farm thereafter.
Earlier this month, Eni acquired a 20% stake in Dogger Bank C. On completion the ownership structure will be SSE Renewables (40%), Equinor (40%) and Eni (20%).
Alistair Philips-Davies, SSE chief executive, said: "It is a fantastic achievement to be reaching financial close on the third phase of the world's largest offshore wind project.
"Construction is well underway on the first two phases of Dogger Bank with work on the third phase already progressing and we look forward to this ramping up in the New Year.”
SSE added the goal is to deliver 25% of the UK's 2030 40GW offshore wind target.