In an initial message to the Nordic electricity exchange Nord Pool on Thursday, the state-owned energy group Vattenfall wrote that the date would be extended to June 5; a few hours later it was extended to June 12.
Ringhals 4 will now run at half power until then.
There is a leak in the generator, and troubleshooting is currently underway, says Elisabeth Rehn, communications officer at Vattenfall.
The problems occur at the same time as Ringhals 3 has been shut down for a month for maintenance work. In addition, Oskarshamn 3 and Forsmark 2 are shut down for inspection and maintenance.
It is difficult to say how long it may take to find the faults, but as it stands we expect to produce at half power until June 12, says Elisabeth Rehn.
The problems could cause electricity prices to increase further. In electricity area 4, which covers southernmost Sweden, today's average price is 119.12 öre per kilowatt hour, according to Nord Pool.
These are prices that are not common, says Patrik Södersten, electricity price expert at the energy company Fortum.
"There are extremely high prices for electricity consumers in southern Sweden. It is a consequence of the Ringhals problem, the cold and dry winter and the crisis in the Strait of Hormuz," he says.
Corrected: In a previous version, the interviewee had the wrong name.
