German power utility Uniper's new Datteln 4 coal-fired power station will begin operating on May 30, it said on Tuesday.

The 1,050 megawatt (MW) plant that has cost Uniper 1.5 billion euros was granted an exemption from Germany's plan to exit coal power by 2038 after the company argued that it made more sense to shut old capacity with high CO2 emissions to clear the way for state-of-the-art Datteln to operate into the 2030s.

Environmentalists have criticised the compromise, saying the government lacked ambition and allowed coal operators to get off lightly.

"We confirm the commercial operation date of Datteln 4 on May 30," a Uniper spokesman said on Tuesday in reply to an enquiry, adding that the launch was in line with a previously envisaged timeframe.

Output notices under electricity wholesale market rules watched by traders had indicated the plant's impending synchronisation with the power grid.

The plant was meant to start production in 2011 but was held back by the environmental debate and by damages to its boiler during component tests.

(Reporting by Tom Kaeckenhoff and Vera Eckert; Editing by Michael Nienaber and David Goodman)