In 2025, Slovenia’s electricity generation saw a significant downturn, primarily due to adverse hydrological conditions impacting the country’s river-based hydropower facilities. The combined output from major plants along the Drava, Sava, and Soca rivers amounted to just over 3.8 TWh, representing a sharp decline of approximately 25% compared to the previous year, which had seen exceptionally high production levels. Despite this reduction, actual generation figures were only 2.4% below national forecasts.
According to data from the national environmental agency, river flows throughout Slovenia were consistently below average in 2025. Overall water volumes for the year fell more than 5% beneath the long-term averages established during the reference period of 1991–2020. Particularly concerning was the performance of the Mura and Drava rivers, which recorded their third-lowest average annual flow since records began in 1981.
The year began with relatively favorable hydrological conditions, with March noted as the wettest month and January also experiencing above-average water levels. However, from June onwards, river flows declined significantly. Although Slovenia avoided prolonged drought conditions, these fluctuations had a direct impact on hydropower generation. The most notable decrease was observed at Drava-based hydropower plants, where output plummeted by one-third year-on-year to 2,162.5 GWh. Similarly, production from Sava river facilities decreased by about 15%, totaling 875 GWh.
Conversely, hydropower plants situated on the Soca river experienced better conditions relative to their counterparts elsewhere. These facilities produced 793 GWh in 2025—an increase of 2.7% from the previous year—thereby surpassing initial production forecasts by around one-third.
Total domestic electricity supplied to Slovenia’s transmission network reached 11,786.4 GWh in 2025, marking a decrease of 14.7% compared to the prior year. This overall decline was significantly driven by reduced output at the Sostanj thermal power plant, which saw its generation drop by over 39%, falling from 3,021.4 GWh in 2024 to just 1,836.2 GWh.
To mitigate some of this shortfall at TPP Sostanj, there was an increase in electricity generation at the TE-TOL plant. The commissioning of a new gas-fired unit enabled TE-TOL’s output to nearly triple from 186.7 GWh to approximately 549.2 GWh year-on-year.
