The first unit at the UAE's Barakah nuclear plant is fully powered up.
The milestone takes Barakah a step closer to the start of commercial operations early next year, state news agency Wam reported.
At 100 per cent, Unit 1 is generating 1400 megawatts of electricity for the nation's grid.
Once Barakah's four reactors are online, the plant will deliver clean, efficient and reliable electricity for decades, providing about a quarter of the country's electricity and eliminating up to 21 million tonnes of carbon emissions annually.
That is comparable to taking 3.2 million cars off the roads each year.
The Emirates Nuclear Energy Corporation (Enec) announced the news on Monday, crediting Nawah, its operating subsidiary, for the achievement.
"We are proud to deliver on our commitment to power the growth of the UAE with safe, clean and abundant electricity," Mohamed Al Hammadi, chief executive of Enec, said.
"Unit 1 marks a new era for the power sector and the future of the clean carbon economy of the nation, with the largest source of electricity now being generated without any emissions," Mr Al Hammadi said.
"I am proud of our talented UAE nationals, working alongside international experts to deliver this clean electricity to the nation, in line with the highest standards of safety, security and quality."
Nawah has been responsible for safely and steadily raising the power levels at Unit 1 since start-up in July and connection to the grid in August.
Engineers will now carry out a series of tests before the reactor is safely shut down, examined again and prepared for full commercial operations.
"This is a key achievement for the UAE, as we safely work through the start-up process for Unit 1 of the Barakah plant," said Ali Al Hammadi, chief executive of Nawah.
Barakah, in Al Dhafra, is the cornerstone of the UAE's peaceful nuclear energy programme.
Construction began in 2012 and it was built in partnership with the Korea Electric Power Corporation.
Construction of Units 3 and 4 is in its final stages – 93 per cent and 87 per cent complete respectively – benefiting from lessons learnt during the construction of Units 1 and 2.
The Barakah complex as a whole is now more than 95 per cent complete.