Seaway Seven nears completion of all 95 monopile foundations at ScottishPower's 1.4 GW East Anglia Three

The foundation installation campaign at ScottishPower Renewables' 1.4 GW East Anglia Three (EA3) offshore wind farm in the southern North Sea is approaching completion, with the project on track for full commissioning by the end of 2026^[1].

Foundation scope and contractors

Seaway Seven, part of the Subsea7 Group, holds the contract for the transport and installation of all 95 monopile foundations, associated seabed preparation and scour protection, and the engineering, supply and installation of the 95 inter-array cables^[1]. The offshore construction phase began in April 2025 when the first monopile was driven into the seabed by the jack-up vessel Seaway Ventus.

The monopiles range from 67 to 85 metres in length, up to 10.6 metres in diameter, and weigh between 1,200 and 1,800 tonnes. The first foundation set a European record at the time as the largest monopile installed from a jack-up vessel. Two fabricators split the supply: the joint venture Navantia Seanergies Windar Renovables (JVNW) produced 45 of the 95 structures, with the remaining 50 manufactured by Haizea. Transition pieces - each 20 metres high and weighing more than 400 tonnes - were supplied and installed by Windar Renovables.

Turbine installation running in parallel

With the foundation campaign winding down, turbine installation is already underway. Cadeler's jack-up vessels Wind Osprey and Wind Pace mobilised from the Port of Esbjerg, Denmark, around 18 March 2026, with the first of the 95 Siemens Gamesa SG 14-236 DD turbines erected on 21 April 2026. Wind turbine installation is expected to be completed in the third or fourth quarter of 2026.

The turbines each carry a nameplate capacity of 14.7 MW and stand approximately 262 metres from seabed to blade tip. All 285 blades for the project are manufactured at Siemens Gamesa's factory in Hull, where the company employs more than 1,400 people. At 115 metres, the blades are the longest ever fitted to a UK offshore wind project.

Project structure and ownership

East Anglia Three is owned by ScottishPower Renewables, Iberdrola's UK subsidiary, and Abu Dhabi clean-energy company Masdar, with ScottishPower Renewables leading development, construction and operations. The project sits 69 km off the Suffolk coast and covers up to 305 km² of the southern North Sea.

EA3 is the anchor project of Iberdrola's East Anglia Hub, a three-farm macro-complex that also includes the planned East Anglia One North and East Anglia Two developments:

• East Anglia Three - 1.4 GW, under construction, commissioning targeted end-2026
• East Anglia Two - 900 MW, in planning
• East Anglia One North - 800 MW, in planning

The hub carries a total investment of £6.5 billion and a combined target capacity of around 3.1 GW. Once operational, EA3 alone is projected to supply the equivalent of 1.3 million UK homes.

The offshore converter station jacket - a 3,700-tonne, 59-metre-tall four-legged structure - was installed in August 2025 by Heerema Marine Contractors' SSCV Sleipnir in 36 metres of water. The onshore converter station at Bramford in Suffolk will connect the wind farm to the National Grid via underground cables running more than 37 km from the landfall point at Bawdsey.

What to watch

The critical path now runs through Cadeler's two-vessel turbine installation campaign. With the foundation work effectively done, any schedule risk shifts to the Q3/Q4 turbine completion window and the subsequent commissioning of the HVDC export system. Iberdrola has flagged EA3 as the largest project in its global offshore wind portfolio; a year-end first power would mark a significant milestone for the company's UK pipeline and for the UK government's 50 GW offshore wind target.