The proposed sub-sea electricity cable, which will connect Ireland and France, is estimated to generate 700MW of energy, enough to power 450,000 households.
The latest two-year phase will feature an in-depth economic assessment of the project; technical studies and initial technical design specifications.
It will also include environmental studies; and pre-consultation in preparation for permit granting procedures in both the countries.
Landing points will be assessed for a subsea cable and connection points to the electricity transmission grids in both the countries.
After completion of this two-year phase, EirGrid and RTE will decide whether to go ahead to the next phase of development.
A final decision will be taken to whether or not to proceed with construction of the project. If it progresses, the interconnector is expected to go live in 2025.
EirGrid chief executive Fintan Slye said the project would generate savings through more efficient use of the existing electricity grid in Ireland.
“It will improve security of supply on the island of Ireland and increase competition, driving down prices for customers.”
RTE board chairman François Brottes said: “This project shows the importance of the cooperation between transmission system operators for the success of the energy transition and for the development of the European Energy community.”
Image: The next stage of the Celtic Interconnector project has been launched. Photo: courtesy of EIRGRID PLC.