North South Interconnector

Four hundred and seven pylons across five counties: that is the physical shape of the North South Interconnector, and the reason it has taken so long. The 138 km line would run from Woodland in County Meath through Cavan, Monaghan and Armagh to Turleenan in County Tyrone, with 306 of the pylons and about 100 km of the route in the Republic, on land belonging to roughly 400 landowners.

It is an alternating current line at 400 kV, not an HVDC cable, and it would link the two grids of the all-island single electricity market. EirGrid and SONI, the system operators north and south, say it would more than double the power that can move between the two jurisdictions. The Irish government has estimated savings for electricity consumers of around €100 million a year once it is running.

Opposition has lasted around 17 years, according to RTÉ’s report from March 2026. The North East Pylon Pressure Group, led by Pádraig O’Reilly, and Sinn Féin TD Darren O’Rourke want the line put underground; EirGrid has said that is not possible. O’Rourke has called for an independent comparison of overhead and underground options, including cost and technical limits. The compensation on offer is €50,000 per pylon and €160 per metre of overhead line.

When the project was cleared to move to construction in 2023, the Department of the Environment expected it to be finished by 2026. That did not happen. In Northern Ireland, NIE Networks has started work at 10 tower sites. In the Republic, construction had not begun as of March 2026 and was expected to start later in the year. The estimated completion date is now the end of 2031.

For a project that crosses no sea, it has spent longer in dispute than most subsea links take to build. The grid congestion guide explains what a missing line like this costs a system in the meantime. The 1,500 MW capacity given above comes from text attributed to EirGrid and should be treated as indicative until the operator publishes a firm figure.