Celtic Interconnector

Around December 2025, EirGrid and RTE marked the milestone of two years since construction on the ground for the Celtic Interconnector commenced, highlighting project progress at the PCI Energy Days event in Brussels in discussions with European Commission energy officials and Irish and French representatives.

On 19 November 2025, EirGrid announced the successful delivery and installation of four large-scale power transformers, each weighing 240 tonnes, for the Celtic Interconnector project. The transformers were shipped from Rotterdam to Aghada Power Station in Cork and then transported by specialist 94‑metre-long vehicles to the Ballyadam converter station site near Carrigtwohill, marking a major equipment milestone for connecting the interconnector to the Irish transmission grid.

Offshore construction for the Celtic Interconnector commenced in summer 2025 with the start of marine cable‑laying operations off the Irish coast near Claycastle beach. The specialist vessel Calypso began installing the first 84 km of the HVDC submarine cable from around 10 km offshore, with additional vessels undertaking burial works, marking the first major offshore construction phase for the interconnector between east Cork and north‑west Brittany.

In early August 2025, as the Celtic Interconnector entered a new construction phase, civil works at the Ballyadam converter station near Carrigtwohill in Cork were reported as being near completion, with internal fit‑outs of the converter hall progressing well alongside the start of offshore cable‑laying operations.

Marine installation of the Celtic Interconnector’s HVDC submarine cable started in early August 2025, when the cable‑laying vessel Calypso, mobilised from Norway to the Port of Cork, began laying an initial 84 km section of the 500 km subsea route from near Claycastle beach. The cable is being laid on the seabed with concurrent burial operations by two additional vessels, initiating the offshore cable installation campaign for the 700 MW link between Ireland and France.

On 20 March 2025, Designer Group announced it had been awarded a contract on the Celtic Interconnector project, working in partnership with Siemens Energy. The Irish mechanical and electrical engineering firm will deliver complex electrical and mechanical infrastructure associated with the interconnector, supporting construction of the first direct electricity link between Ireland and France.

In March 2025, EirGrid achieved a major milestone on the Celtic Interconnector by successfully completing essential onshore cable ducting works at the beach section of Claycastle Beach in Youghal, finalising the duct route that prepares the Irish landfall to receive the subsea cable connection to France.

Preparatory maritime works at the Cléder landfall began, including installation of protective ducts to receive the submarine cables.

In November 2024, the Celtic Interconnector project marked a significant milestone by passing one year in construction, which EirGrid and project partners celebrated at the converter station site in Ballyadam near Carrigtwohill, East Cork, together with the French Ambassador to Ireland.

In a construction update marking one year of work on the Celtic Interconnector, EirGrid reported that marine preparatory works in Irish waters for the subsea interconnector were successfully completed during the first year of construction, representing a key offshore site preparation milestone for the project.

In May 2024, Nexans kicked off the installation of HVAC onshore cable on the Irish side of the Celtic Interconnector, marking the start of cable installation for the 575 km France-Ireland interconnector. The onshore segment spans 40 km on the Irish side, with completion scheduled for 2025.

On 19 March 2024, ACER Decision No 04/2024 took the Celtic Interconnector into account by including it in an electricity capacity calculation region (CCR), with the former Core Europe CCR to become the Central Europe CCR, integrating the future Ireland–France link into EU regional capacity calculation processes.

Construction on the Celtic Interconnector project began in November 2023, marking the start of onshore works for the 575 km, 700 MW HVDC link between east Cork and Brittany. Subsequent project communications note that by November 2024 the scheme had passed one year in construction and by December 2025 had reached two years since construction on the ground commenced, confirming this late‑2023 start of physical works.

By 2022, the Celtic Interconnector project had secured all necessary consents, permits and licences in France, Ireland and the UK, allowing the construction phase of the 700 MW interconnector to commence.

In November 2022, the Celtic Interconnector reached Final Investment Decision and financial close after the Irish and French regulators issued an updated cross‑border cost allocation decision, enabling the Celtic Board to approve the project and sign EPC contracts for the cables and converter stations. In parallel, EirGrid completed an €800 million debt financing package comprising two €300 million 30‑year term loans from the European Investment Bank and Danske Bank and a €200 million revolving credit facility provided by Barclays and BNP Paribas, securing the long‑term funding needed to move the interconnector into its construction phase from 2023.

On 25 November 2022, Nexans was awarded the Engineering, Procurement and Construction contract for the Celtic Interconnector’s cable systems by project developers EirGrid and RTE. Under this award, Nexans will manufacture and install approximately 1,000 km of subsea HVDC cables, 180 km of underground cables in France and Ireland, and a 10 km 400 kV HVAC connection to the Irish grid, using facilities in Norway, Belgium and Switzerland to deliver the 700 MW, 575 km interconnector.

In November 2022, following updated cross‑border cost allocation decisions and financial close, EirGrid and RTE signed Engineering, Procurement and Construction contracts for the Celtic Interconnector’s converter stations, selecting Siemens Energy to design and build the HVDC converter facilities. The contracts cover the converter stations required in Ireland and France to connect the 700 MW HVDC link to the respective AC transmission grids.

On 15 November 2022, the European Investment Bank signed loan agreements totalling EUR 300 million with EirGrid plc to co-finance the Celtic Interconnector project, providing long-term public lending support for the Ireland–France HVDC link.

In November 2022, the national regulatory authorities of Ireland and France issued an update to the Celtic Interconnector cross‑border cost allocation (CBCA) decision, refining the regulatory cost‑sharing framework and enabling the project board to proceed to Final Investment Decision and sign EPC contracts for cables and converter stations.

Overall statutory consents for the Celtic Interconnector were effectively achieved in 2022. An Bord Pleanála granted planning permission for the Irish onshore element in May 2022, and on 31 August 2022 EirGrid welcomed the Minister’s decision to grant the Irish foreshore licence for the offshore elements, meaning the main Irish planning and marine consents were then in place.

In August 2022, Ireland’s Department for Housing, Local Government and Heritage granted a foreshore licence for the Celtic Interconnector, providing a key permit for the undersea works in Irish waters.

In May 2022, An Bord Pleanála granted planning permission for the onshore portion of the Celtic Interconnector in Ireland, authorising construction of the land-based elements including cable routes and associated infrastructure.

RTE’s project schedule and the French prefecture of Finistère confirm that a statutory public-opinion survey (enquête publique unique) for the Celtic Interconnector took place in France, with the inquiry running from 29 November 2021 to 11 January 2022. This satisfies the planned 2021 public consultation milestone.

The planning application for the Irish onshore element of the Celtic Interconnector (case reference VA04.310798) was lodged with An Bord Pleanála on 9 July 2021, later than the original second‑half‑2020 target for submitting formal consents in Ireland and France.

Offshore consents for the Celtic Interconnector in Ireland were submitted as a Foreshore Licence Application in June 2021. The statutory application form and EIAR documentation are dated June 2021, indicating formal submission of the marine authorisations later than the originally anticipated mid‑2020 date.

In March 2021, EirGrid submitted an Environmental Impact Assessment Report for the Ireland offshore elements of the Celtic Interconnector as part of the foreshore licence application, providing a voluntary EIAR to assess the environmental effects of the proposed submarine cable and landfall.

An Environmental Impact Assessment Report titled "Celtic Interconnector Project – Environmental Impact Assessment Report supporting the Foreshore Licence Application" for the Ireland offshore section was prepared in March 2021, indicating submission of a foreshore licence application for the Celtic Interconnector’s offshore works in Irish waters.

In December 2020, EirGrid and RTE signed a funding agreement with the European Commission for approximately €530 million under the Connecting Europe Facility to support the construction of the 700 MW Celtic Interconnector between Ireland and France. This major EU grant, administered via CINEA, builds on earlier study-phase support and provides substantial non‑repayable co‑financing for the works phase of the project, reducing the costs borne by the Irish and French transmission system operators and their customers.

Following a public consultation that attracted more than 1,000 responses on converter station siting options near Knockraha in East Cork, EirGrid announced on 23 November 2020 that Ballyadam had been identified as the best-performing location for the Celtic Interconnector converter station, reflecting consultation feedback supporting this industrial area.

On 23 November 2020, EirGrid announced that Ballyadam in east Cork had been selected as the site for the Celtic Interconnector converter station, following assessment of Ballyadam and two alternative sites near Knockraha. The chosen location is about 10 km by road from the Knockraha substation, and the project design foresees HVDC cables coming ashore at Claycastle Beach, running underground to the Ballyadam converter station, and then onward by underground AC cables to Knockraha.

On 7 April 2020, RTE, the French transmission system operator, issued a 12‑month tender seeking a contractor to perform integrated nearshore geophysical, UXO and geotechnical surveys for the Celtic Interconnector at the French landfall. The procurement covers surface and subsurface geophysical investigations and nearshore geotechnical drilling in water depths from 0 to about 30 m LAT to characterise ground conditions for future horizontal directional drilling during cable installation.

A broad public consultation in France, known as the "Fontaine" consultation and overseen by guarantors appointed by the National Public Debate Commission (CNDP), concluded on 5 July with the presentation of least-disruptive route options for the Celtic Interconnector’s submarine and underground connection and converter station; following this, the Morlaix sub-prefect agreed the least disruptive siting corridor, later endorsed by the Ministry for Environmental Transition and Solidarity.

On 25 April 2019, France’s Energy Regulatory Commission (CRE) and Ireland’s Commission for Regulation of Utilities (CRU) issued a joint decision on the funding of the Celtic Interconnector, establishing the cross‑border cost allocation that set a 65–35 cost split between Ireland and France, with project costs above €1.18bn shared 50–50.

In 2018, project promoters EirGrid and Réseau de Transport d’Électricité (RTE) submitted a joint Investment Request to the Irish and French National Regulatory Authorities under Article 12 of the TEN‑E Regulation for the Celtic Interconnector. The submission included a detailed cost–benefit analysis and formed the formal application for regulated cross‑border cost allocation and associated revenue treatment, representing a key regulatory and financial milestone for the project.

By late 2018, the Celtic Interconnector had already received capital support from the EU’s Connecting Europe Facility (CEF), with more than €3.5 million granted for the project’s Feasibility Phase and a further €4 million allocated to the then‑current initial design and pre‑consultation phase. These early CEF grants co‑funded prefeasibility and initial design studies undertaken by EirGrid and RTE, helping to mature the project towards permitting, cost allocation and eventual construction.

In 2017 and 2018, RTE, the French transmission system operator and project promoter for the Celtic Interconnector, held preliminary consultations with local stakeholders potentially affected by the submarine and underground connection and the future converter station in Brittany, gathering feedback on regional development plans and project siting.

By 2018, extensive geophysical surveys along the entire offshore route and several nearshore approach options for the Celtic Interconnector had been completed as part of a wider marine survey campaign.

By 2018, geotechnical surveys across the full offshore route and multiple nearshore approaches for the Celtic Interconnector were completed, providing detailed seabed and subsurface data to support cable design and installation planning.

Benthic (seabed ecology) surveys covering the entire offshore route and several nearshore approaches for the Celtic Interconnector were completed by 2018 within a comprehensive marine survey campaign supporting environmental assessment and route optimisation.

EirGrid and Réseau de Transport d’Électricité (RTE) established a dedicated joint venture company, Celtic Interconnector DAC (CIDAC), to develop and deliver the 700 MW Celtic Interconnector between Ireland and France, with each transmission system operator owning 50% of the new company.

In May 2018, the Celtic Interconnector project was granted a foreshore licence to undertake marine surveys at potential Irish landing sites at Ballinwilling, Claycastle and Redbarn beaches in County Cork, enabling detailed nearshore investigations for route and landfall selection.

Between 2014 and 2016, EirGrid and RTE completed the Feasibility Phase of the Celtic Interconnector, carrying out marine route desktop studies, offshore marine surveys, onshore connection studies, economic and financial analysis, and cost assessment. Following completion of this phase in 2016, both promoters confirmed the project’s feasibility and agreed to progress it to the Initial Design and Pre‑Consultation phase.

The Celtic Interconnector was listed as Project 107 in ENTSO‑E’s 2016 Ten Year Network Development Plan (TYNDP), confirming its continued status as a planned interconnection of European significance between Ireland and France.

Between 2014 and 2016 the Feasibility Phase of the Celtic Interconnector was completed, confirming the project’s feasibility and securing approval from both the Irish and French governments to move forward into the Initial Design and Pre-Consultation phase.

The Preliminary Feasibility Phase of the Celtic Interconnector was completed in 2014, after which EirGrid and RTE agreed to proceed to a more detailed Feasibility Phase to further assess the technical, economic and environmental viability of the Ireland–France interconnector.

The Celtic Interconnector was included in the first Union List of Projects of Common Interest (PCIs) under the EU TEN‑E Regulation in 2013 and has remained on the PCI list through subsequent updates, recognising its strategic role in EU cross‑border electricity infrastructure.

The Celtic Interconnector was recognised as a project of pan‑European significance by being included in ENTSO‑E’s 2012 Ten Year Network Development Plan (TYNDP), and has retained this listing in subsequent biennial reviews.

Project development for the Celtic Interconnector began in 2011, with EirGrid and RTE initiating work to study high-level benefits, technology options and costs as part of a preliminary feasibility stage for the proposed Ireland–France HVDC link.