European Energy Commissioner Gunther Oettinger joined Irish Prime Minister Enda Kenny at a ceremony to inaugurate of the 159-mile interconnector, a first for the region.
"This good example of cross-border integration of energy markets is a milestone in the continued efforts by Ireland to develop its electricity grid and to respond to changing markets and opportunities," he said in a statement.
The interconnector runs between north Wales and the Irish coast. It can carry as much as 500 megawatts of electricity and can integrate offshore wind energy in the region.
Oettinger said Ireland has tripled its renewable energy production in the past decade and is on pace to become a net electricity exporter.
"The combined pressures of climate change, dwindling fossil fuel production, global demand growth and changing geopolitics are taking their toll," said Oettinger. "I believe that the only way to deal with these global challenges is through a more Europeanized energy policy."