The Gaza Strip's only functioning power plant ran out of fuel, leaving 2 million residents with only four to six hours of electricity per day, according to the Gaza Electricity Distribution Company.
A similar crisis in December was resolved by tax-free donations from Qatar and Turkey. But that ran out last week.
Samir Metir, head of Gaza's electricity provider, blamed a dispute between Gaza's electric authority and Fatah-led Palestinian Authority in the West Bank. Hamas seized power in Gaza in 2007 from Fatah, the party of Palestinian President Mahmoud Abbas.
Metir said the power plant cannot afford to pay the fuel taxes imposed by the PA. On Friday, the Hamas-controlled Energy Authority temporarily cut all sources of power in Gaza to protest "oppressive measures being taken" by the Palestinian Authority.
Demand for electricity in Gaza is about 450 to 500 megawatts per day, but it often gets less than half that. About 27 megawatts is imported from Egypt and 125 from Israel.
"Today we had about six hours of electricity at my house. Now it's off for the next 12 hours," Ezz Zanoun, a photographer in Gaza City, told Al Jazeera on Sunday. "Tomorrow it might be worse. We're expecting about four hours [of electricity] -- and from there the real problems start."