In Week 25, regional hydroelectric generation fell by 4.7% to 3.57 TWh, tightening the overall electricity balance even as solar output increased across Southeast Europe. The hydro decline mattered for system conditions because hydropower provides flexibility, reserve capacity and support during evening hours. Solar strength did not offset the reduction in hydro availability.
Largest hydro declines across Italy, Bulgaria and Romania
The sharpest hydro decreases were reported in Italy, Bulgaria and Romania. Italy’s hydro generation dropped by 11.8%, increasing reliance on gas-fired power plants and imported electricity. Bulgaria recorded a 39.4% decline, while Romania saw a 9.8% decrease.
These changes affected regional price formation, particularly in systems where hydro availability typically supports stability when reservoirs are strong. When reservoir levels weaken, the same hydro-rich structure can contribute to tighter conditions. The combined impact of the declines was reflected in market outcomes during the week.
Serbia and Croatia see hydro recoveries but not enough to offset
Serbia and Croatia recorded hydro recoveries, with generation rising by 42.9% and 41.5%, respectively. The increases came from relatively low baseline levels and were not sufficient to counterbalance broader regional declines. Serbia’s improved hydro position supported a shift into a modest net export position.
Despite Serbia’s change in position, SEEPEX still increased by 9.6%. This reinforced that local hydro improvements alone did not fully insulate the market from wider regional scarcity pressures. The week’s price movement therefore aligned with the overall balance tightening.
Hydro value rises as solar penetration expands
The commercial relevance of hydropower is expected to increase further as solar penetration grows across Southeast Europe. Solar generation primarily reduces prices during midday hours, while hydropower contributes during the evening ramp and peak demand periods. Hydropower also supports system balancing intervals.
This shift places more emphasis on reservoir management, particularly during summer weeks with higher cooling demand and reduced wind availability. Under these conditions, timing differences between generation sources can influence how quickly supply-demand needs are met across the day.
Market focus shifts toward hydro metrics for trading and balancing
For traders, hydro metrics are becoming more important than headline renewable totals. A system combining high solar output with low hydro behaves differently from one with lower solar but strong hydro availability. Hydro provides dispatchable optionality, while solar contributes predictable but time-concentrated volume.
Wind, by comparison, adds diversification but remains weather-dependent and less controllable in real time. With these differing profiles, changes in hydro availability can alter intraday balancing requirements and price formation patterns.
Sensitivity to reservoir levels across regional markets
The investment case for storage technologies is linked to hydropower-driven volatility, including pumped-storage projects and battery systems alongside hybrid renewable portfolios. Markets identified as especially sensitive to hydro fluctuations include Serbia, Romania, Croatia, Greece and Montenegro. In these markets, reservoir levels affect export potential, balancing needs and price formation.
Week 25 highlights flexibility role of hydropower in SEE balances
Week 25 reinforced that hydropower remains a core flexibility asset within the Southeast Europe electricity system rather than a legacy component. When hydro availability declines, reliance on thermal generation and imports increases. When it recovers, market conditions ease and export opportunities expand.
The market is increasingly pricing this flexibility differential with greater precision and speed as conditions change across the region.