Hydroelectric generation in Southeast Europe fell by 4.7% to 3.57 TWh in Week 25, tightening the regional electricity balance. The decline occurred alongside stronger solar output across the region. The reduction mattered for system operations because hydropower also provides flexibility, reserve capacity and evening-hour support.
Largest hydropower declines affect Italy, Bulgaria and Romania
The biggest 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 saw a 39.4% decline, while Romania recorded a 9.8% decrease.
These changes affected regional price formation. In systems with strong hydro availability, hydropower typically acts as a stabilising force, while weaker reservoir conditions can contribute to scarcity dynamics.
Serbia and Croatia see hydro recoveries
In contrast, Serbia and Croatia recorded hydro recoveries in Week 25. Serbia’s hydro generation rose by 42.9%, and Croatia’s increased by 41.5%. The increases came from relatively low baseline levels and did not offset the broader regional declines.
Serbia’s improved hydro position supported a shift into a modest net export position. However, SEEPEX still increased by 9.6%, indicating that local hydro improvements alone were not sufficient to prevent wider scarcity pressures.
Hydro value rises with solar penetration and summer conditions
The commercial relevance of hydropower is expected to increase as solar penetration expands across Southeast Europe. Solar generation primarily reduces prices during midday hours, while hydropower supports the evening ramp, peak demand periods and system balancing intervals.
This makes reservoir management more central during summer weeks marked by higher cooling demand and reduced wind availability.
Trading focus on hydro metrics alongside solar and wind
For market participants, hydro metrics are becoming more important than headline renewable totals. A system with high solar output and low hydro behaves differently from one with lower solar but stronger hydro availability.
Hydropower provides dispatchable optionality, while solar contributes predictable but time-concentrated volume. Wind adds diversification but remains more weather-dependent and less controllable in real time.
Pumped storage and batteries tied to hydro-driven volatility
From an investment perspective, hydropower-related volatility supports the case for pumped-storage projects, battery systems and hybrid renewable portfolios. Markets including Serbia, Romania, Croatia, Greece and Montenegro are described as especially sensitive to changes in hydro availability.
Reservoir level movements can influence export potential, balancing needs and price formation across these markets .
Week 25 highlights hydropower as a flexibility driver
Week 25 also reinforced that hydropower remains a core flexibility asset within the SEE 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 . Virtu.Energy
