The reason is mainly that hydropower in several Norrland rivers must go down significantly in power, especially in Lule river, Skellefte river and Ume river, according to Per Larsson, responsible for production planning hydropower and nuclear power at Vattenfall.

When the cold sets in, the power producers want the ice to settle, which facilitates production for the rest of the winter.

And for that to happen, the water must be slowed down, flowing water freezes worse, which means less water through the power plants.

It happens every year, but what is possibly different is that it now happens in three rivers at the same time, according to Per Larsson.

Less hydropower production, weak with wind for wind power together with colder weather increasing consumption causes the price of electricity to rise.

The reduced hydropower production can last up to a week, according to a message to the power market, but can change depending on the weather.