Slovenia’s electricity system is being shaped by a weak hydrological year, with declining water availability reducing hydropower output in the opening months of 2026. Lower generation has increased the role of gas-fired plants to support domestic electricity demand.
April hydropower delivery falls sharply
Hydropower plants delivered 191.5 GWh of electricity to the transmission network in April. The figure was more than 49% lower than a year earlier, reflecting reduced river flows across the country.
The decline extended beyond April, with hydropower facilities on the Drava, Sava, and Soča rivers generating a combined 909.5 GWh over the first four months of 2026. This was 401.6 GWh less than in the same period of 2025, a drop of more than 30%.
Production also fell below levels projected in national generation plans during the same timeframe.
Domestic generation down; coal constrained
The hydropower shortfall affected overall electricity output. Between January and April, domestic generation totaled 4,055.8 GWh, down 9.2% year-on-year.
Coal-fired generation did not fully offset reduced hydro output. TPP Šoštanj operated under constraints tied to its role in ensuring district heating supply for the Šaleška Valley, limiting flexibility in electricity generation.
Gas plants increase output across Ljubljana and Brestanica
Natural gas plants took on a larger share of the generation mix as hydro output weakened. The biggest increase came from Ljubljana’s TE-TOL facility, where a new gas-fired unit boosted output.
During the first four months of 2026, TE-TOL produced 370.4 GWh, more than doubling generation compared with the same period in 2025.
Additional support came from TPP Brestanica, where electricity production rose by nearly 60% year-on-year to 15.4 GWh.
Hydrological weakness points to continued below-average hydro performance
The figures indicate that 2026 could become one of Slovenia’s weakest hydrological years in recent history. Early-year hydropower performance is often used as an indicator for annual output, and current trends point to continued below-average generation.
This would further increase reliance on alternative sources to maintain balance in Slovenia’s electricity system.
