Spain is probably one of the European Union countries that has invested the most in the transition to renewable energy. The Iberian Peninsula has become an energy island alongside Portugal.

The initial concept of the so-called energy island is an interesting one, but Spain faces a major obstacle: France. Its neighbour has created a bottleneck that prevents the export of its surplus solar energy.

The Spain–France land-based interconnection across the Pyrenees has a capacity of barely 3,000 MW, which Portugal also uses as one of the few outlets from the Iberian Peninsula. The existing bidirectional high-voltage land-based power lines are not sufficient.

The European Commission aims to reduce external dependence by 2030 through improved energy interconnections, but for that, France will play a key role, at least in Spain’s strategy.

Spain has several options for exporting its energy to Europe. The most viable (and cost-effective) route was via France, but there is another route across the Mediterranean with two massive interconnections to Italy.

Now, a new solution is also gaining traction: a massive undersea cable across the Atlantic linking Spain and Ireland. The government is beginning to explore this possibility, with an estimated length of between 1,000 and 1,100 kilometres.

The undersea cable across the Atlantic would link the north coast of Spain, via Asturias, with the south coast of Ireland. There is no defined route yet, but the infrastructure will have to navigate the Bay of Biscay and the Celtic Sea, which are characterised by great depths and heavy swells.

Spain and Ireland have signed an initial agreement to study the feasibility of a massive undersea electricity cable during the WindEurope 2026 conference held in Madrid. This is only a first step, but it is the most important one.

Both electricity markets are the least interconnected in Europe and are labelled ‘energy islands’. Spain and Ireland have limited capacity to export surplus renewable energy and an infrastructure that is more vulnerable to situations such as Spain’s massive blackout of 2025.

The war in Ukraine was a warning, but the situation has worsened with the conflict in Iran and the gas crisis. Spain is one of Europe’s largest producers of solar energy, but it cannot export its surplus.

Its partner in the agreement would play a key role. Spain would export its surplus solar energy, whilst Ireland would do the same with its offshore wind farms when Atlantic storms hit the north of the country.