Celtic Interconnector

Brexit turned the Celtic Interconnector from an option into a priority. Ireland’s existing links all ran to Great Britain, and by 2019, with trading rules across those cables in doubt, planning for a direct route to France had accelerated. The cable will give Ireland a connection to the EU’s internal electricity market that does not pass through the UK.

The route is 575 km long. It starts at the Knockraha substation in County Cork, where a converter station is being built at Ballyadam near Carrigtwohill, and reaches the sea at Claycastle Beach in Youghal. From there about 500 km of cable crosses Irish, British and French waters in the Celtic Sea to landfall in Finistère, then runs inland to La Martyre. Capacity is 700 MW, which EirGrid says is enough for 450,000 homes.

Brussels pays a large share. The European Commission agreed a €520 million grant in December 2020, after €4 million of earlier funding for studies, and the European Investment Bank gave preliminary approval to €530 million of loans in 2018. The price rose all the same: an estimate of €1 billion in 2016 had become €1.6 billion by November 2022, per the Celtic Interconnector article.

Offshore cable laying began in August 2025. By June 2026 EirGrid reported the first 84 km section of subsea cable laid, with burial work continuing, and on land the DC cable route stood at phase 1 complete, phase 2 70% and phase 3 40%. Four transformers had been installed at Ballyadam by December 2025. Siemens Energy builds the converters and Nexans the cable.

The finish date has moved more than once. The original target was 2026; EirGrid now expects commissioning in spring 2028 after delays in submarine cable manufacturing, while RTE’s project page still showed the older schedule when checked. The last slip came from the cable factory, not from the sea. For how such cables are laid, see subsea power cables; for the other Irish links, Greenlink.