Interconnectors are high-voltage electricity cables that connect neighbouring countries, allowing power to flow in both directions across land and under the sea. They help countries trade electricity to secure more affordable electricity from other markets, improve energy security, reduce costs, and support the transition to cleaner energy.

They make an important contribution to the stability of power in a countries transmission system by balancing supply and demand across international borders, increasing security of supply while at the same time supporting the use of renewable energies more efficiently.

A central advantage of interconnectors lies in their ability to handle load peaks or overcapacity flexibly, avoiding energy wastage. If individual countries temporarily produce more electricity than they themselves consume, the surplus can be traded and exported via interconnectors — and vice versa. This helps maximise the use of clean energy, lower carbon emissions, and improve the efficiency of the electricity system.

Interconnectors consist of high-voltage lines that can run both on land and underwater. For connections across large bodies of water — for example, between the European mainland and the UK or Ireland — high-capacity submarine cables are used. Submarine interconnectors mostly use High Voltage Direct Current (HVDC) cables to minimise losses over long distances. This requires converter stations at each endpoint, where electricity is converted from the High Voltage Alternating Current (HVAC) used in national grids, to HVDC for transmission; and vice versa.

The proposed Tarchon Interconnector Project (Tarchon project) will create a direct power link between the UK and Germany, through the British, Dutch and German North Sea. By connecting the two energy markets, it will increase energy security and reliability, reduce CO₂ emissions and help to reduce energy costs.

The project proposes to connect the two countries’ energy markets and increase the security and reliability of their electrical systems and energy supply. If one country has a surplus of energy and the other has a shortage, this energy can be transferred through the interconnector to help meet the power demand during this time; and vice versa, rather than curtailing and wasting this power it can be traded to the benefit of the country’s economy. In this way, Tarchon contributes to balancing regional and national generation fluctuations, facilitating the efficient use of renewable energies and strengthening the energy supply in the UK and Germany in the long term.

The interconnector will be a combination of land and subsea cables around 760km in length and will allow up to 1.8GW of electricity to move in either direction.

National Grid has proposed a new East Anglia Connection Node (EACN) 400 kV substation in Tendring, where Tarchon has been offered a grid connection.

In November 2024, Ofgem confirmed its support for the Tarchon project to proceed and participate in the regulatory process, noting that it is in the interest of Great Britain’s consumers.

The Tarchon project has been created to strengthen energy security, enhance grid resilience, and support the transition to a low-carbon energy system in Europe. By linking the UK and German electricity transmission networks, the project facilitates the efficient exchange of electricity, optimising the use of renewable energy resources and contributing to a more integrated and flexible European energy market and creating a strong, self-sufficient energy network in the UK.

It will also enhance renewable energy integration by facilitating the export and import of renewable power, reducing curtailment (where a power generator may be requested to reduce generating capacity due to the inability for the grid to absorb this), and ensuring that valuable renewable resources are better utilised in both the UK and Germany.

Tarchon comprises of both onshore and offshore infrastructure. The offshore project elements include approximately 620km of subsea cabling, which will traverse UK, Dutch and German waters; with approximately 120 km of onshore cabling in Germany (in comparison to approximately 20 km onshore in the UK). The Tarchon converter station will then connect with approximately 5 km of underground cable to the proposed National Grid East Anglia Connection Node (EACN) substation. In this way, a direct, high-capacity electricity connection is created between two important European energy markets.

Between the UK and Germany, the Tarchon interconnector crosses Dutch territorial waters.

In Germany, the cable runs through the Exclusive Economic Zone (EEZ) of the Federal Republic, then through the 12-nautical-mile zone and finally beneath the island of Langeoog through the Wadden Sea.

In 2019, Tarchon submitted a Grid Connection application to National Grid Electricity System Operator (NGESO), now referred to as NESO. As a result of this application, Tarchon was allocated the East Anglia Connection Node (EACN) as the connection point for the project. Consequently, project infrastructure must be sited in close proximity to the EACN grid connection point, requiring a landfall, onshore cable route and onshore converter station within the Tendring district to facilitate the connection.

Interconnectors are high-voltage electricity cables that connect neighbouring countries, allowing power to flow in both directions across land and under the sea. They help countries share electricity, improve energy security, reduce costs, and support the transition to cleaner energy. The key benefits of the Tarchon Interconnector are:

Improved energy security – Interconnectors strengthen energy security. The more connected a country’s energy system is, the less vulnerable it becomes to energy shortages, supply disruptions, or volatility in global fossil fuel markets. This creates a more resilient and reliable energy system for consumers and businesses.

Lower energy costs – Interconnectors allow electricity to flow from areas where it is more abundant or less expensive to areas where demand is higher. By increasing access to available power and improving competition between energy markets, they help reduce overall system costs and support more affordable electricity for consumers.

Supporting renewable energy – Interconnectors enable excess renewable electricity, such as wind power, to be exported instead of wasted. This reduces the need for curtailment (when renewable generation is reduced because there is insufficient demand or network capacity), helping maximise the use of clean energy, lower carbon emissions, and improve the efficiency of the electricity system.

Reduced reliance on fossil fuels – Greater international connectivity helps reduce dependence on imported oil and gas.