Home / The electricity interconnection across the Biscay Gulf

The electricity interconnection across the Biscay Gulf

400 km


4 cables


2 x 1,000 MW


Up to 5,000 MW


The electricity interconnection between  Gatika (Spain) and Cubnezais (France) will be the first fundamentally submarine interconnection between Spain and France.

This project will increase the exchange capacity from 2,800 to 5,000 MW,  improving the safety, stability and quality of electricity supply between the two countries and also with the rest of Europe.


Public participation

Each State will analyse and authorise the project based on its own procedures for electricity infrastructure. Besides prior consultation in each country based on their respective regulations, France and Spain must guarantee public participation and public access to information in accordance with European requirements for all Projects of Common Interest. These actions can be undertaken in a variety of ways but should at least have a website dedicated to the project, public meetings and a specific organisation capable of guaranteeing the collection of comments and responding to any type of question. This will ensure the population feels involved in the various stages to define the routes and technical specifications of the project.


Project managers

Etienne Serres
Project leader in France

Stéphanie Pajot
Consultation process manager in France

You will find all the documentation related to the process of public participation in France in the French webpage version.

You will find more documentation related to the process of public participation in Spain in the Spanish webpage version.

Project managers

Juan Prieto
Project leader in Spain

Antonio Miranda
Consultation process manager in Spain

Do you have any question? Contact us

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Project leaflet

Download all the information 

Biscay Gulf project leaflet
Download 2.51 MB

The route

The interconnection consists of four cables, two per link. This submarine and underground direct current dual connection will be almost 400 km in length, running between the Cubnezais substation (near Bordeaux, France) and the Gatika substation (near Bilbao, Spain). It will have two converter stations - one at each end of the link - that will convert the direct current to alternating current for connection to the electricity transmission grid of each country.

The submarine section

The link will be mainly underwater, with a length of approximately 300 km, from the Basque coast in Spain to the French Médoc coast, except for a short underground section needed to avoid the submarine Capbreton canyon.

The choice of route and placement of the cable on the sea floor will minimise the impact on maritime activities, especially fishing.

Submarine cable laying

The submarine cable

Each cable will be placed on the sea bed with the help of a cable-laying ship. Generally-speaking, the cables will be buried for protection except where the ground is too hard, where they will be covered.

Aerial/underground section

In Spain, the interconnection will be connected to the Gatika substation, located to the north-east of Bilbao and 10 km from the Basque coast. To do so, the plan is to install underground cables between the future Gatika converter station, which will be built alongside the existing Gatika electricity substation, to a point in the Urbieta-Lemóniz area, where the groundsea connection will be made.

In accordance with the Spanish procedure, an Environmental Impact Assessment will be presented. This will include regional and environmental diagnostics, the various alternatives for the station, the location and characteristics of the chosen project (alternative of least impact), and an analysis of the impacts and proposals in terms of preventive and corrective measures, as well as an environmental monitoring plan.

The link will be mainly underwater, with a length of approximately 300 km, from the Basque coast in Spain to the French Médoc coast, except for a short
underground section needed to avoid the submarine Capbreton canyon.

The link will connect to the Cubnezais electricity substation located to the north of Bordeaux. Hence, the underground section will run for 80 km, from the right bank of the River Dordogne, passing beneath this river and the Garonne to reach the Aquitaine coast, via the Médoc region to the commune of Le Porge. Its entirely underground route will respect the environment and human activity by using on existing infrastructure and the network of forest tracks.

Numerous factors must be considered in this coastal region, such as: environmental awareness, busy beaches, urban centres, awareness of coastline regression and the possibility of using infrastructures that already exist to sleave rapidly the coastline. The most suitable landfall points are located in the Médoc coast area.

The underground cable

The underground cable

Trench: Each trench will contain a pair of cables, and the two trenches will be separated by a minimum distance of 1 m Once work is completed, they will be covered over to hide them from sight.

Junctions: The underground cables will be installed in sections of approximately 1 km, each connected via a junction chamber. A similar, albeit slightly larger, device will be used to connect the submarine cables to the underground cables. These devices will be located far from the shore and will eventually be covered over because permanent access is not required, leaving them totally hidden from view.


Converter station

The connection will link two alternating current systems via a submarine direct current line.
At each end of the connection, the converter stations will convert the direct current into alternating current for connection to the transmission grids of Spain and France.

The converter stations cover an area of approximately 5 ha and will be approximately 20 m high.

Converter station



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2017 - 2021



Discovery of instability in the submarine canyon

2018 - 2021

Technical and environmental studies

2021 - 2023


2023 - 2027

Detail studies, supplies and construction

2027 - 2028

Testing and commisioning

Inelfe awards the main contracts for the electricity interconnection project across the Biscay Gulf

Inelfe, a joint venture company owned in equal parts by the Spanish transmission system operator Red Eléctrica and its French counterpart RTE, announces it has awarded the Engineering, Procurement and Construction (EPC) contracts for the Biscay Gulf electricity interconnection project.

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The Biscay Gulf Interconnection project enters the administrative authorisation phase in France and Spain

On the 1st of December, RTE officially submitted the applications for authorisation for the Biscay Gulf electricity interconnection project to the French authorities (Public Utility Declarations, Agreement for the Use of the Public Maritime Domain, Environmental Authorisation, etc.), 7 months after its counterpart, Red Electrica de España (REE), had done the same in Spain.

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In the absence of a viable crossing route, RTE and REE launch new studies to bypass the Capbreton Canyon

As part of the studies prior to the construction of the new interconnection between France and Spain via the Biscay Gulf, RTE and REE carried out geological studies of the seabed. They revealed ground instability along the edge of the Capbreton Canyon. Additional analyses conducted since June have not identified a route under the canyon that is guaranteed to be stable for the life of the power line.
RTE and REE are therefore forced to abandon this solution and define a new route around the canyon.

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RTE and REE perform additional analysis to secure the Biscay Gulf project

As part of the studies prior to the construction of the new interconnection between France and Spain via the Biscay Gulf, RTE and REE carried out extensive geological studies of the seabed. The latest studies, at the beginning of May, revealed soil instability very close to the Capbreton canyon, in French waters.

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Meeting with suppliers in Brussels

Inelfe organised a meeting with HVDC cable, converter station, submarine cable and drilling suppliers in Brussels. Held between 16 and 20 April, its goal was to explain the scope of the interconnection project between Spain and France via the Bay of Biscay and to exchange information on the best way to implement the project (technology, materials, implementation procedures, etc.).

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Supplier´s Event 2018

HVDC cables and converter stations for the Biscay Gulf electricity interconnection between France and Spain

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Frequently Asked Questions


An interconnected network will help achieve one of the goals of the Energy Union: to guarantee affordable, safe and sustainable energy compatible with growth and employment throughout the European Union.

  • Security of Supply, especially when consumption is high.
    Interconnectors allow a country to import electricity form another when needed, for instance in when consumption is high or in case of technical incident.
  • More renewable energies integration.
    Connecting national grids will allow renewable energies to flow across Europe and be available for European consumers.
  • The cheapest electricity to flow in Europe.
    Interconnectors allows the cheapest electricity to flow in Europe for the benefit of the consumer.

Link here for more information

The European Union (EU) strongly supports the project. Promoting interconnections between EU member States is one of the cornerstones of the EU energy policy. They will provide the European consumers with a more secure electricity, at the best cost. In addition, interconnections will increase the integration of renewable energy. EU, indeed, has included the project in the fourth existing lists of Projects of Common Interest (PCI)1.

The interconnection capacity between Spain and France is among the lowest of all the European countries and remains well below the 10% interconnection target for 2020 and 15% interconnection target for 2030.

1The 5th PCI list was published in the Official Journal of the European Union las 19th November 2021.

No, the rate of usage of the existing lines is very high, and they are saturated most hours of the year. In fact, in the last 3 years the Spain-France electric border was saturated 76% of the hours.


This solution is the best because it avoids building new high voltage overhead power lines (400kV). It allows us not to reinforce the existing grid.

This is the project with the least impact on the territory.

The line will be fully buried, both in land and offshore. In addition, most part of the line will be offshore. The start and end points of the line were considered the best solution because they avoid building new high voltage overhead power lines (400kV) for the interconnection itself, as well as for the neighbouring 400 kV network.

For instance, in France, should a 400 kV connection point be chosen closer to the border (Pyrénées Atlantiques, Landes), a new high voltage overhead power line would have been necessary to reach Cubnezais. The existing 400 kV overhead lines are not powerful enough to transmit 2000 MW of additional power.


The route


Yes, the information and public participation phase of the project was initiated in September 2017 according to the European requirements that establish that this type of process must be conducted in the initial planning stage of trans-European energy infrastructure (Regulation 347/2013 applied to the PCIs). This phase was concluded on 15 March 2018.

Link here for more information

Cada país tiene un proceso de consulta pública diferente en función de su propia reglamentación nacional.

Please link here for more info about the French public consultation process.

Please link here for more info about the Spanish public consultation process.

RTE and REE ensure the highest level of transparency possible, in accordance with national and European legislation. In this regard, public administrations, organisations and individuals may present arguments, at any time during the project’s permitting process. All arguments will be reviewed and answered, and those aspects that are considered viable and relevant from a technical and environmental point of view will be incorporated into the project.

All the necessary information regarding the project, including contact details or ways of participating in public consultations may be found on our website www.inelfe.eu, including several ways of contacting the project team.


The entire project, from Gatika substation to Cubnezais substation, was estimated at 1,95 billion euros when the applications for authorisation were submitted. The European Commission has allocated 578 million euros to the project through its Connecting Europe Facility (CEF) programme, of which 350 million will correspond to France and the remaining 228 to Spain.

The lower amount corresponding to Spain is offset by the benefits that this project entails for this country. In other words, the benefit of the interconnection is slightly superior for the Spanish consumer.

To date, this is the largest grant given by the EU for an energy project of common interest.

RTE and REE will share the investment on an equal basis: 975 million for each one of the two national transmission system operators.

This project is profitable, as both French and Spanish regulators have certified. Its potential benefits outweigh its cost. It will allow the European electrical system to be more efficient with lower costs.

The economic valuation of the actions for the development of the transmission grid has been calculated in accordance with a cost-benefit analysis (CBA) methodology taking into account a global perspective of the electricity system and, in particular, that of the final consumer.

Therefore, the benefit of the transmission grid development for society is evaluated by comparing the cost-benefit ratio associated with the scenarios that contemplate the planning and carrying out of a new action or a set of actions in the transmission grid versus the situation of the not carrying out any developments in the grid.

As required by Regulation (EU) n°347/2013, ENTSO-E has developped a cost-benfit analysis methodology for the evaluation of transport and storage infrastructure projects included in the Ten-Year Network Development Plan (TYNDP). The European Commission has approved this methodology which is the one used for the Bay of Biscay project.


The investment will come partially from the electricity bill, like all electric infrastructures, and partially from the European funds. As mentioned before, the project is profitable and its benefits will exceed its cost. It will help to make electric systems more efficient and it will allow the cheapest energy to circulate more easily. It is needed to invest today to get cleaner energy in the future.


The cable used for the project is designed with a shield, and therefore no electric fields are generated. In addition, the electrical line between France and Spain will be a direct current (DC) one. For this reason, the effects of the magnetic field are even smaller because they are static in nature (0 Hz), that is, with the same characteristic and similar effects as the Earth's magnetic field.

The future line will thus be under every European threshold in terms of EMF.

They will be very limited. The line will be buried in the seabed of the Biscay Gulf and in the land parts of the route, and therefore will have no visual impact. Only the converter stations, at both ends of the interconnection will be visible. That been said, these converter stations will be built close to the existing electricity 400 kV substations and studies are being carried out to achieve the best possible integration into the landscape.

From an economic perspective, INELFE helps major contractors’ needs for subcontracting to meet local companies’ offers as much as allowed by the regulations.

From a social perspective, INELFE will also insert social clauses in its contracts so as to favour social reintegration of long-term job seekers.

Furthermore, the projects undertaken by INELFE integrate themselves into the various areas they affect. INELFE helps highlight these areas through support for cultural, sports and public events.

For instance, the construction of the first electric line (though the Pyrenees) had a positif impact.

Direct local financial benefits in France (to the regional administrative scale in use at the project time Languedoc Roussillon) have been estimated to 37.8 M€. 95 people were employed from local human resources during every phase of the works, from a 3 to 36 months timespan, thanks to public authority’s involvement. 8 people have been hired with a permanent contract by one of the provider and 1 by RTE.

Yes !

The greenhouse gas emissions of interconnection projects are evaluated in a homogeneous way by ENTSOE, the European association of transmission system operators, according to a precise and transparent methodology. According to the latest evaluation based on 2030 scenario:

  • The volume of renewable energy curtailment avoided is estimated at 7,431 GWh/year.
  • The electrical losses generated by project, in the project itself as well as in the rest of the European network are estimated at 2,576 GWh/year.

Hence, the Greenhouse gases emission of the European electricity System is reduced by 4,855 GWh/year.


The sole responsibility of this publication lies with the author. The European Union is not responsible for any use that may be made of the information contained therein.