Hydropower usually acts as one of Southeast Europe’s most important balancing cushions, especially during periods of high demand and volatile renewable output. In Week 26, that cushion weakened at regional level. Hydro generation fell by 2.8% to 3.51 TWh, with lower output in Türkiye and Bulgaria more than offsetting gains in Serbia, Croatia, Greece, Romania and Italy.
The decline was not evenly distributed, but its market effect was still significant. Türkiye, the region’s largest hydro producer, recorded a 5.9% weekly fall, removing 142 GWh from the regional hydro balance. Bulgaria experienced the sharpest relative drop, with hydro generation down 44.6%. In a week when demand rose sharply, weaker hydro output meant less low-marginal-cost flexibility was available to dampen prices.
Serbia and Croatia moved in the opposite direction. Serbia’s hydro generation rose 121.5%, while Croatia’s increased 93.8%. These are strong percentage gains, but they came from relatively low prior levels and did not fully offset the regional decline. Greece also recorded a 12.1% rise, while Romania and Italy posted moderate gains. The broader regional picture remained one of reduced hydro contribution during a week of higher system stress.
This matters because hydro is more than energy volume. It is dispatchable flexibility. During summer evenings, when solar output drops and cooling demand remains high, hydro can reduce the need for gas, coal, lignite or expensive imports. When hydro availability is weaker or unevenly located, the region becomes more exposed to thermal marginal pricing and cross-border congestion.
The Bulgarian case is particularly important because Bulgaria remained a significant net exporter despite lower hydro. That means other parts of the generation stack had to carry more of the export and domestic balancing role. For Greece, Romania and Serbia, hydro movements affected the degree to which each market could manage higher demand without excessive import dependence.
Hydro also influences trading expectations. In wet periods, Balkan markets can soften quickly, especially during off-peak and shoulder hours. In drier or constrained periods, the same systems can tighten sharply, particularly during summer heatwaves. Week 26 showed that even modest regional hydro declines can matter when demand is moving up by double digits.
The data point toward a summer in which hydro availability should be tracked as closely as gas prices. SEE’s price risk is not only about fuel and renewables. It is also about reservoir strategy, river flows, pumped-storage operation and the willingness of hydro operators to preserve water for higher-value peak hours.
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