Government ministers have warned of possible power outages in case of a gap between supply and demand, which they said would last no longer than two hours and be flagged in advance.
State-run utility EDF, a parent company of Enedis, is racing to get nuclear reactors hit by corrosion problems back on line.
The mayor of Paris Centre, Ariel Weil, confirmed the general breakdown on Twitter. "Power cuts have just taken place in the 4th and 5th arrondissements," he said.
Later, Weil added: "I confirm a general breakdown but @enedis confident of a rapid return to normal everywhere."