Why Sumitomo Sold 600 MW of Operating Belgian Offshore Wind and Bought Into Gwynt Glas

Sumitomo Corporation has acquired a 33.3 percent stake in Gwynt Glas, an offshore wind project of up to 1.5 GW located roughly 40 km off the west coast of the United Kingdom in the Celtic Sea. The sellers are EDF power solutions UK and Ireland and Electricity Supply Board, which previously held 50 percent each and will now each hold a third alongside Sumitomo. Terms were not disclosed. Watson Farley & Williams advised Sumitomo, describing the transaction as an investment in the floating offshore wind sector. Sumitomo's position in offshore wind has changed considerably this year, and this purchase is the other side of that change.

What did Sumitomo acquire in the Celtic Sea?

Sumitomo acquired a one-third equity interest in a single pre-construction offshore wind project with a stated capacity of up to 1.5 GW, giving it roughly 500 MW of attributable capacity if the project is built at full scale. The consideration was not disclosed. The ownership structure moves from a two-party joint venture split evenly between EDF power solutions and ESB to three equal thirds, so each incumbent has given up a third of its holding rather than one selling out. That matters, because it signals a capital-raising exercise rather than an exit: both original partners remain fully engaged, and the new shareholder brings balance sheet capacity to a project that will require several billion pounds of investment before it generates anything.

What is floating offshore wind, and why does the Celtic Sea need it?

Floating offshore wind mounts turbines on platforms moored to the seabed rather than fixed to it, which allows deployment in water too deep for conventional fixed-bottom foundations. The Celtic Sea was largely passed over during earlier UK offshore rounds precisely because its water depths ruled out fixed foundations, and floating technology is what has reopened it. The Crown Estate, which manages the seabed around England, Wales and Northern Ireland, has targeted 4.5 GW of floating capacity in the Celtic Sea by 2035, with a further 12 GW envisaged by 2045. At up to 1.5 GW, Gwynt Glas represents about a third of that first-phase target. The technology remains pre-commercial at this scale, which is why projects of this size attract multi-party ownership rather than single balance sheets.

Why is Sumitomo buying development-stage offshore wind now?

Because it has spent the year selling the operating kind. Enerdatics records two Sumitomo disposals of Belgian offshore wind in 2026 alone: 384 MW of operating capacity sold to JERA and BP in April, and a further 216 MW sold to Publiwind in July, 600 MW of producing assets released within three months. Alongside those, Enerdatics records Sumitomo acquiring a 694 MW UK battery portfolio in construction from Gresham House in May 2026 with TPK Holdings, and a 1,000 MW Estonian wind development position from Enefit Green in February 2025. The pattern across the record is consistent: operating assets out, development and construction-stage assets in. Sumitomo is not reducing its exposure to offshore wind, it is moving that exposure to the earliest and least contested end of the lifecycle.

Enerdatics' data shows how deliberate that rotation looks across the wider portfolio. Beyond the Belgian exits, Enerdatics records Sumitomo selling a 300 MW Australian wind development position to Wind With Purpose in April 2025 and a 1,500 MW US solar development portfolio to CEP Solar in October 2024, while buying into a 2,700 MW Indian solar development platform from Amp Energy alongside Intermediate Capital Group and the Asian Infrastructure Investment Bank for $250 million, or $0.09 million per MW, in 2023. The company recycles positions rather than accumulating them, taking early-stage risk, developing alongside partners and selling once assets are producing. For pricing context on offshore specifically, Enerdatics records Allianz Global Investors paying $1.32 million per MW for a 500 MW in-construction French offshore position from Ocean Winds in October 2025, and Aspiravi paying $1.43 million per MW for 216 MW of operating Belgian offshore wind in 2024.

What does the deal signal for floating offshore wind?

The deal signals that floating projects at gigawatt scale are being financed by syndication well before construction, and that trading houses are the natural third partners. Neither EDF power solutions nor ESB needed to sell, and neither did: they each diluted by a third to bring in a partner with the capacity to fund a project whose technology has no commercial track record at 1.5 GW. Expect further stake sales across Celtic Sea projects as they approach investment decisions, and expect the buyer list to feature Japanese and Korean industrial groups, which have been steadily building positions in European floating wind.

The counterpoint is that this is still a project with no turbines in the water. Floating wind's cost curve is unproven at scale, the Celtic Sea supply chain is being built from a low base, and the 4.5 GW target for 2035 depends on projects like this one reaching final investment decision on schedule. Buying a third of a development-stage floating project is a considerably longer-dated commitment than the operating Belgian assets Sumitomo has just sold. That is the trade being made, and it is a deliberate one.

Key takeaways

• Sumitomo Corporation acquired a 33.3 percent stake in Gwynt Glas, an offshore wind project of up to 1.5 GW in the Celtic Sea, from EDF power solutions UK and Ireland and ESB. Terms were not disclosed.
• Ownership moves from an even split between EDF power solutions and ESB to three equal thirds, so each incumbent diluted by a third rather than exiting, giving Sumitomo roughly 500 MW attributable.
• Enerdatics records Sumitomo selling 600 MW of operating Belgian offshore wind in 2026, 384 MW to JERA and BP in April and 216 MW to Publiwind in July.
• Over the same period Enerdatics records Sumitomo buying a 694 MW UK battery portfolio in construction from Gresham House and a 1,000 MW Estonian wind development position from Enefit Green.
• The Crown Estate targets 4.5 GW of floating capacity in the Celtic Sea by 2035, so Gwynt Glas at up to 1.5 GW represents roughly a third of that first-phase ambition.

Frequently asked questions

How much did Sumitomo pay for its Gwynt Glas stake?Terms were not disclosed. For offshore context, Enerdatics records Allianz Global Investors paying $1.32 million per MW for a 500 MW in-construction French offshore wind position in October 2025 and Aspiravi paying $1.43 million per MW for 216 MW of operating Belgian offshore wind in 2024, though a pre-construction floating project would be expected to price well below both.

What is floating offshore wind?Floating offshore wind places turbines on platforms moored to the seabed rather than fixed to it, allowing installation in water too deep for conventional foundations. It is what makes the Celtic Sea developable, since the region's depths ruled it out of earlier fixed-bottom UK offshore rounds.

Who owns the Gwynt Glas project now?Following the transaction, Gwynt Glas is owned in equal thirds by Sumitomo Corporation, EDF power solutions UK and Ireland, and Electricity Supply Board. It was previously held 50-50 by EDF power solutions and ESB, and is located approximately 40 km off the UK's west coast.

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