The Normandie 1, one of Jersey's three undersea power cables stretching to France, replaces its predecessor EDF1 which failed in June 2012.
The failure of the original power link to France forced Jersey and Guernsey Electricity to produce more energy by burning fossil fuels.
The new 27km-long (16.7-mile) cable has taken just over a week to install by a 4,000-tonne boat.
A spokeswoman for Jersey Electricity said it had been quicker to install than the Normandie 3 power cable because it was fixed on the seabed rather than under it.
The power cable will also provide electricity to Guernsey, via Jersey.
Guernsey Electricity chief executive officer Alan Bates said: "Once up and running, N1 will allow us to import around 95% of our electricity requirements.
"The remaining demand will be met on-island using our diesel generators, which also serve as a back-up to the cable network."
The cable, which joins Archirondel in Jersey with Surville on the north coast of France, has been jointly funded by Jersey Electricity and Guernsey Electricity and is due to come online at the start of 2017.
Undersea cable timeline
A £40m undersea electricity cable has been laid between Jersey and France.