The two northern German power plants which Vattenfall’s German subsidiary operates jointly with E.ON have been disconnected from the grid since separate power supply incidents in June prompted the firm to conduct extensive inspections and maintenance work.
One plant, in the town of Brunsbüttel, went temporarily back on line in July for a brief period.
“There are ongoing discussions about when to restart the reactors, and the sooner this happens the better, but for now the end of February is the estimated time,” pokeswoman Maria Parent said.
Following the incidents, Vattenfall faced harsh criticism in the German media, with reports saying it had failed to inform the public sufficiently.
The firm denied a cover-up, but the scandal prompted the head of its Europe branch to quit, and caused an outcry in Germany, which is deeply divided over whether it should be using nuclear energy at all.
The country has begun a long-term phase-out of its nuclear energy programme and expects to mothball the last of its 17 plants sometime around 2020.