In 2025, Slovenia experienced a notable reduction in electricity generation, primarily driven by diminished output from its hydropower sector and thermal plants. The country’s major river-based hydropower facilities, located along the Drava, Sava, and Soca rivers, contributed just over 3.8 TWh to the national grid, marking a decline of nearly 25% compared to the previous year. Despite this downturn, production levels remained relatively close to national forecasts, falling short by only 2.4% from projections.
According to data from Slovenia’s national environmental agency, river flows were consistently below average throughout 2025. Overall water volumes were reported to be over 5% lower than the long-term average for the reference period of 1991–2020. The Mura and Drava rivers recorded their third-lowest average annual flows since 1981, indicating a concerning trend in hydrological conditions.
The early months of the year saw more favorable hydrological conditions, with March being particularly wet and January also experiencing above-average water levels. However, starting in June, river flows fell below average consistently, although Slovenia did not face severe droughts. This shift had a direct impact on hydropower output; the Drava River saw a significant year-on-year decrease with hydropower plants generating approximately 2,162.5 GWh—about one-third less than in 2024. Additionally, output from both upper and lower Sava plants decreased by around 15%, totaling 875 GWh.
In contrast, hydropower facilities along the Soca River managed to perform better than expected, producing 793 GWh—an increase of 2.7% from the previous year and surpassing initial forecasts by roughly one-third.
Overall electricity generation across all domestic sources reached 11,786.4 GWh in Slovenia for 2025, which represents a decline of 14.7% compared to the prior year. This significant drop was largely attributed to the Sostanj thermal power plant (TPP), where production plummeted by over 39%, decreasing from 3,021.4 GWh in 2024 to just 1,836.2 GWh.
To mitigate some of the losses from TPP Sostanj, generation at the TE-TOL plant increased significantly due to the introduction of a new gas-fired unit that nearly tripled its output—from 186.7 GWh to 549.2 GWh year-on-year.
