"The power station started reworking gradually after stopping for 50 days," spokesman Jamal Dirsawi told AFP.
The plant, which supplies some 30 per cent of the coastal enclave's electricity needs, fell silent on November 1 as the stocks of diesel to power it ran out.
"The first generator has started working, the second one will follow, and by this evening, the company should be able to generate around 60 megawatts of electricity," he said.
"This will give the Gaza Electricity Distribution Company (GEDCO) an opportunity to provide more hours of electricity to citizens."
The power station began operating after receiving a delivery of long-awaited fuel earlier in the day that had been purchased from Israel by the West Bank-based Palestinian Authority using funds donated by Qatar.
Raed Fatuh, the PA official in charge of transferring goods into Gaza, said 450,000 litres of fuel were being supplied to the plant on Sunday.
The PA is involved in helping coordinate the transfer of goods into Gaza via Israel, which Hamas does not recognize.
Gaza's Hamas rulers have blamed the fuel outage on Egypt's destruction of cross-border tunnels which had been used for bringing fuel into the blockaded Strip.
They have also accused the Palestinian Authority of charging too much for fuel.