"The power plant in Gaza has stopped (working) due to the fuel shortage," said Mohammed Thabet, spokesman for the electricity company.
The power station has gone without fuel deliveries through Israel since the country shut its goods and people crossings with Gaza on Tuesday, the Arab Weekly reported.
The electricity supply is expected to plummet to just four hours a day, Thabet said.
Israel's closure of its crossings with Gaza came as the military braced for reprisals following the arrest of two senior Palestinian Islamic Jihad members in the occupied West Bank.
In a statement earlier on Saturday, Gaza's electricity company said the shutdown "will affect all public utilities and crucial installations and exacerbate the humanitarian situation".
The company called on "all parties to urgently intervene and allow the entrance of fuel deliveries for the power plant to work."
MA/PR