Olkiluoto produced about a quarter of Finnish electricity in 2025
In 2025, a total of 23.41 TWh of electricity was produced at the Olkiluoto nuclear power plant. This equals about a quarter of the Finnish electricity consumption. The newest plant unit Olkiluoto 3 (OL3) produced electricity without any interruptions during the year.
Production at OL3 totalled 10.38 TWh last year. The year was the best so far for the plant unit in terms of both production and reliability: there were no unplanned interruptions and the availability factor of the plant unit was 82.6 %, the highest in the three-year operational history of the plant unit.
The plant unit was only out of production during the annual outage and even that was completed ahead of schedule.
The final acceptance of OL3 by TVO took place in June when the terms and conditions of the plant delivery contract were fulfilled. This was preceded by a two-year period of regular electricity production.
- The excellent reliability of OL3 was the greatest accomplishment during the year. It is exceptional for a new plant unit to operate for a full year without a single unplanned interruption. Our thanks for this strong performance go to our personnel says Marjo Mustonen who is the Senior Vice President for electricity production at TVO.
The next planned outage at OL3 will occur in the autumn of 2026 as the unit was last spring for the first time received fuel for an operating cycle of 18 months.
The year was strong in terms of production at all Olkiluoto units
Last year, Olkiluoto 1 (OL1) produced 7.49 TWh of electricity with an availability factor of 96.2 %. Apart from the annual outages, production was disrupted in May as a result of a damaged condenser tube. The disruption was a brief one keeping the unit off the grid for only about 25 hours.
The annual production of Olkiluoto 2 (OL2) was 5.55 TWh and the availability factor of the unit was 71.2 %. Production at OL2 was halted as a result of a generator rotor fault detected in April which caused an interruption of about three weeks in electricity production at the plant. The unit will be operated at a power output of 735 megawatts until the 2027 outage in order to minimise the risk of rotor failure.
The annual outage of OL2 was the only one among the Olkiluoto plant units outages whose duration exceeded the original schedule. Due to some technical issues, the outage took nine days longer.
- The past production year was quite a successful one and once again our organisation proved their high level of knowledge and excellent cooperation skills. A big thank you for this to both TVO’s own personnel and our cooperation partners, Marjo Mustonen says.
Annual production in Olkiluoto has increased significantly as a result of the completion of OL3 and the power uprates at OL1 and OL2. Electricity production in 2025 was about twice as high as the 11.68 TWh production 30 years ago in 1995.