Europe’s Future Grid Is Being Built Under the Sea

Bay of Biscay and UK’s Eastern Green Link 4 lead a surge in subsea energy projects

2 Oct 2025

Europe is laying cables beneath its seas at unusual speed. Once seen as optional extras, subsea power lines are now treated as urgent tools to steady electricity supply and smooth the path to cleaner energy. Recent blackouts and rising demand have made the case for urgency hard to ignore.

France, Spain and Portugal have pledged to accelerate the Bay of Biscay interconnector, a 400km line of which three-quarters will run under water. With €1.6bn in backing from the European Investment Bank, it is due to more than double capacity between Spain and France by 2028, lifting it to five gigawatts. The project gathered momentum after a region-wide outage in April exposed Iberia’s reliance on fragile domestic networks.

Britain, too, is pushing ahead. Grid operators have chosen Prysmian to supply Eastern Green Link 4, a subsea route intended to move renewable power from Scotland to England. It is part of a wider plan to build "electricity superhighways" down the east coast, a sign that cables beneath the seabed are now seen as critical to national resilience rather than marginal upgrades.

Delivering them, however, is another matter. Only a handful of companies, among them Prysmian and Siemens Energy, possess the factories, vessels and skilled workers to build such links. Governments are trying to secure finance and speed up permits, but supply chain bottlenecks and labour shortages loom large.

Still, politics favours progress. Cables are cast as more than infrastructure: they embody Europe’s resolve to bind its grids together and lower costs while cutting emissions. With the Bay of Biscay and Eastern Green Link 4 under way, Europe is wiring not just the seabed but the future of its energy system.