Lights out in Gaza as Israel cuts power supplies
The region is currently operating on around 140 megawatts of energy - less than a third of full capacity at 500 megawatts.
The GPA, which is run by the central authority Hamas, said Israel had cut its output from a previous 120 megawatts to 55.
The amount of power cut would be enough to light up more than 1.5 million 40 watt bulbs.
The decision to cut electricity supplies to the Gaza Strip was made after the Palestinian Authority (PA) cut its monthly payments for Gaza's electricity bills by 30 percent.
The PA, led by President Mahmoud Abbas, has committed to a number of punitive strategies to force Hamas' hand in ceding control over the besieged region.
Abbas dismissed more than 6,000 PA employees in the Gaza Strip on Tuesday, saying he was "taking steps" to end the split between the West Bank and Gaza.
Israel has repeatedly promised since April that it will cut off its power supply to Gaza over an unpaid fuel bill by Hamas.
"We regret the fact that it will be the civilians in Gaza who will pay the price for this," said Major General Yoav Mordechai.
Gaza has been blockaded by Israel for a decade while Egypt, the only other country the Palestinian enclave shares a border with, has mostly kept its crossing closed in recent years.
On Wednesday, Hamas leader Ismail Haniya said that Egypt was prepared to step in to help administer humanitarian assistance to Gaza.
The power shortage has caused power cuts throughout the Gaza Strip during the sweltering summer weather, leading to thousands of young people going to the beach to cool off.