Non-Technical Summary

MaresConnect is a proposed subsea and underground electricity interconnector system linking the existing electricity grids in Ireland and Great Britain, and the west of Ireland to Dublin.

Non-Technical Summary - MaresConnect

In Brief

Upon completion, MaresConnect will enable bi-directional flow of power, responding to the varying supply and demand dynamics between the two nations. The interconnector will have a nominal capacity of 750MW, equivalent to a large power station.

The demand for interconnector capacity across the Irish Sea is largely influenced by weather conditions, especially Atlantic depressions that typically move in a north-easterly direction across Ireland. During periods of high wind generation, wholesale prices tend to decrease, as renewable energy sources displace more expensive generation options. This causes the wholesale price differential between Ireland and Great Britain to widen for approximately four to six hours, resulting in power flows from Ireland to Great Britain. As the depression moves towards Great Britain, the power flows reverse direction.

The ability to transmit these renewable energy flows between Ireland and Great Britain provides a strong economic, environmental and security of supply argument for the building of interconnector capacity.

MaresConnect will consist of two converter stations – one located in the Greater Dublin Area and the other close to the Bodelwyddan 400kV substation in Denbighshire – connected by two High Voltage Direct Current (HVDC) cables under the Irish Sea.

Direct Current (DC) is often the preferred choice for transmitting electricity over long distances due to its lower losses and minimal heating effects, making it ideal for underground installation. As a result, there won’t be any overhead lines connecting the converter stations. Both onshore and offshore cables will be buried underground. Converter stations play a critical role in this process, as they convert electricity from Alternating Current (AC) to DC, and vice versa, ensuring the proper phasing of power flows into the national electricity systems.

MaresConnect is targeting operations in 2029

A large infrastructure project such as MaresConnect takes several years from concept to construction, including technical design, obtaining the relevant permits and consultation with a variety of stakeholders.

Identifying and thoroughly evaluating technical and environmental constraints is crucial for incorporating them into the final design of an infrastructure project. We plan to initiate comprehensive environmental and technical assessment surveys in 2023. At present, we are conducting desktop assessments, environmental scoping, and route alternative studies. Additionally, we are in ongoing consultations with statutory consultees and other stakeholders.

After finalizing the detailed proposal and design, we will need to obtain the necessary permits and licenses from various national and local authorities. In the UK, these authorities include Denbighshire County Council, Natural Resources Wales (NRW), and The Crown Estate. In Ireland, approvals will be required from An Bord Pleanála, the Department of Agriculture, Food and the Marine – Foreshore Unit, and the Commission for the Regulation of Utilities in Ireland.

Once all required permits and licenses are in place, we will proceed to the construction phase of the project, which is expected to last about three years.


The main permits required by MaresConnect are summarised as:

Interconnector systemWalesIreland

Converter stations

Town and Country Major Development - Outline (Denbighshire County Council)Strategic Infrastructure Development (An Bord Pleanála) - Authorisation to construct (Commission for the Regulation of Utilities)
Onshore cablesTown and Country Major Development - Detailed (Denbighshire County Council and Conwy Borough County Council)Strategic Infrastructure Development (An Bord Pleanála) - Consent to lay electricity lines (Commission for the Regulation of Utilities)
Offshore cable

Marine Licence (Natural Resources Wales) and Licence to use Seabed (The Crown Estate)

Strategic Infrastructure Development (An Bord Pleanála) and Maritime Area Consent (MAC)

Our Industry Collaborators

MaresConnect is working with some of the leading industry advisors and consultants in Ireland and the United Kingdom.