Cover celtic interconnector
Cover celtic interconnector

Celtic Interconnector: interconnection project between France and Ireland


The purpose of the Celtic Interconnector Project, set up by RTE and its counterpart EirGrid, is to build an electrical link (HVDC), around 575 km in length (including 500 km off shore), for direct electricity exchange between France and Ireland. With capacity of 700 MW, this project aims to connect the north coast of Brittany to the south coast of Ireland.
This project for interconnection between France and Ireland meets the European target for energy transition and addressing climate change by facilitating development of renewable energies and transition to a low carbon energy mix. It also contributes to strengthening electrical solidarity between the two countries.

This project, with an estimated cost of €1 billion, is recognised as a project of common interest (PCI) by the European Union. Start-up is planned for 2026.


Key points :

  1. The first submarine electricity Interconnector between France and Ireland
  2. A project that speeds up European energy transition, by fostering the development of renewable energies
  3. A project that fits in with European electricity solidarity between Member States
  4. A project designated as a project of common interest by the European Union



What is the purpose oh the Interconnector between France and Ireland ?

The aim of the Celtic Interconnector is to link the Irish grid to the mainland European grid, with a continuous DC link, 575 km in length between Cork in Ireland and Brittany in France. The electrical link ensures power transmission in both directions: Ireland – France and France – Ireland.

This project will thus contribute to the European target for energy transition and addressing climate change. It will thus foster sustained development of wind power in Ireland and its integration in the European electricity system. In France, this new interconnection will ensure consumption of green electricity routed from Ireland. It thus constitutes a driver to support energy transition by facilitating change in the electricity mix.

The Celtic Interconnector Project will also contribute to strengthened security of power supply between the two countries, ensuring mutual support in the event of unforeseen circumstances (severe weather, technical incidents and peak consumption).

In broader terms, the project contributes to European electricity solidarity and shall enable Ireland to access the integrated European electricity without any curbs, within the context of Brexit.

Recognised as a project of common interest by the European Union in October 2013, with the label renewed in the 2017, the Celtic Interconnector Project fits in with the development of electricity interconnections – one of the drivers to support energy transition in France, Ireland and Europe.

    Cover video Celtic interconnector
    Celtic Interconnector - Financement Union Européenne

    700 MW
    of total exchange capacity
    the equivalent of supplying power to 450,000 homes
    575 km
    in length
    including 500 km for the submarine part
    930 M€
    of investments

    What does the Celtic Interconnector Project entail ?

    The Celtic Interconnector Project plans to link the Knockraha substation (Cork) to the La Martyre substation (Finistère), with a DC underground circuit, with capacity of 700 MW, over a distance of approximately 575 km, including 500 km off shore.

    In more concrete terms, the project is made up of:

    • A connection to the existing 400 kV substation in La Martyre
    • A converter station in France built in the immediate vicinity of the La Martyre substation. Installed on a plot of land of around 4 hectares, the buildings occupy approximately 5,000 m2 and are about 20 m in height. This station transforms DC into AC (and the other way round) to ensure connection to the French transmission grid.


    • A submarine circuit, approximately 500km in length placed on or beneath the seabed between France and Ireland
    • A landfall point where the submarine circuit comes onshore
    • A HVDC land circuit between the landfall and a converter station. As this will be HVDC, it is proposed to use an underground cable for this element
    • A converter station, to convert the electricity from HVDC to High Voltage Alternating Current (HVAC), which is used on the transmission grid. This station does not need to be in close proximity to the connection point on the grid
    • A HVAC land circuit between the converter station and the connection point to the grid. This circuit can be underground cable or overhead line. However as it is HVAC there are limits to the length of cable that can be installed underground
    • A connection point to an existing substation on the transmission grid


    What are the project stages ?


    The Interconnector is planned to go live in 2026. Since 2012, RTE and EirGrid have undertaken technical and environmental studies (especially concerning the maritime route), which confirm the technical feasibility of a DC submarine and land circuit between France and Ireland.

    In 2017 and 2018, RTE conducted preliminary consultation with the stakeholders, mainly local representatives, such as State Departments, parishes, elected officials and non-governmental organisations) affected by the circuit landfall point and land circuit. The purpose of these discussions is to be receptive to the territorial representatives, concerning their medium and long-term development and growth plans.

    The consultation was resumed in autumn 2018, in compliance with the provisions effective in France and the European Union Regulations for European energy infrastructure. Its purpose is to validate the study area and the lowest impact zone for the underground circuit in France. Large-scale consultation will also be run under the auspices of the two guarantors appointed by the National Public Hearings Commission (CNDP), based on referral by RTE.

    Provisional schedule:

    • Consultation: 2018-2019
    • Impact assessment and public inquiry: 2019-2020
    • Authorisations: 2022
    • Procurement and work: 2022-2025
    • Tests and commissioning: 2026

    Le projet Celtic Interconnector en vidéo


    1. Consultation

    Consultation: 2018-2019

    In 2017 and 2018, RTE held preliminary consultations with stakeholders essentially consisting of local players (State departments, municipalities, elected representatives, NGOs, etc.) potentially affected by the sub-marine and underground connection, as well as the future converter station. The purpose of these discussions was to get feedback from the regions about their medium and long-term infrastructure and development plans.

    In accordance with French legislation and with EU regulations governing European energy infrastructure, the consultation was extended in the autumn of 2018. It resulted in the agreement of a potential siting area. A broad public consultation was arranged under the aegis of the two sponsors appointed by the National Public Debate Commission (CNDP), on the basis of a court referral by RTE. The findings issued further to this consultation helped to determine the best possible siting for the electrical structures being built: the future submarine and underground electrical connection (identification of the "least disruptive" route), the landfall site for connection of the submarine and underground lines, as well as the converter station (substation for connecting the line to the existing network).

    Involving local players, the consultation (known as the "Fontaine" consultation) ended on Friday the 5th of July with a presentation of potential "least disruptive" routes to the stakeholders (State departments, elected representatives, municipalities, etc.). Gilbert Manciet, the Morlaix sub-prefect, agreed on the least disruptive siting corridor for the project’s terrestrial and maritime structures. This outcome was endorsed on the 25th of October by the Department of Energy and Climate Strategy, attached to the Ministry for Environmental Transition and Solidarity.

    France’s Energy Regulatory Commission (CRE) and Ireland’s Commission for Regulation of Utilities (CRU) passed a joint decision on the 25th of April 2019 for the funding of the Celtic Interconnector project.


    2. Impact study and public-opinion survey

    Impact study: 2019-2020

    Public-opinion survey: 2021

    Since the endorsement on the 25th of October – by the Ministry for Environmental Transition and Solidarity – of the least disruptive* siting corridor, RTE has continued to develop the project with the conduct of an economic and environmental impact study.

    The aim is to determine a more exact route while continuing to consult with local players. A public-opinion survey will be held in 2021.

    *Corridor within which, following detailed studies, the exact routes and locations of future electrical structures will be agreed.


    3. Licences

    Licences: 2022


    4. Supply chain and construction

    Supply chain and construction: 2022-2025


    5. Testing and commissioning

    Testing and commissioning: 2026

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