The hydropower landscape in South-East Europe (SEE) has undergone significant changes as of the first quarter of 2026, shifting from a historically stable energy source to a more unpredictable and climate-sensitive variable. This transformation has profound implications for price dynamics, cross-border electricity flows, and the dispatch of thermal generation.
Throughout Q1 2026, hydrological conditions exhibited considerable variability, mirroring broader European trends of erratic precipitation and fluctuating reservoir levels. The data for Week 16 illustrates this fragmentation: total hydro generation experienced a week-on-week decline of 3.45%, with notable decreases in Romania (-15.79%) and Bulgaria (-25.68%). Conversely, Italy saw an increase of 17.8%, while Croatia reported a staggering rise of 270%, albeit from a low production base.
The crux of the issue lies not merely in the volume of hydroelectric output but rather its predictability. Traditionally viewed as a quasi-firm resource capable of providing flexibility and seasonal reliability, hydropower in Q1 2026 increasingly resembles a secondary renewable source subject to short-term weather fluctuations and longer-term climate patterns. This shift undermines its previous role as a reliable buffer against the intermittency of wind and solar energy sources.
The implications for power systems are significant. When hydropower availability is high, market prices can drop sharply as low-cost hydro generation displaces more expensive thermal units. However, during periods of underperformance—especially when combined with weak solar or inconsistent wind—the system becomes strained, leading to increased reliance on higher-cost gas, lignite, or imports. This trend exacerbates market volatility rather than alleviating it.
The interplay between hydro and wind generation is becoming increasingly critical. In Q1 2026, several markets faced simultaneous deficits in both resources, resulting in compound supply gaps that existing flexibility resources could not mitigate. Even modest demand spikes can lead to disproportionate price surges in these contexts, as evidenced by certain regions within SEE despite overall stable consumption levels.
Looking ahead to the remainder of 2026, hydropower is expected to continue functioning as a swing factor rather than a stabilizing force. While improved inflows in late spring and early summer could temporarily relieve system pressures and lessen dependence on thermal generation, the prevailing expectation is for ongoing variability in hydro output around historical averages, with potential for wider deviations.
In scenarios characterized by below-average inflows or extended dry spells, deficits in hydropower could become significant drivers of price spikes, particularly during periods of low renewable output. Such conditions would reinforce the necessity for thermal generation and heighten reliance on cross-border electricity imports.
For market participants, this evolving landscape necessitates a reevaluation of hydropower’s role within energy models—shifting from deterministic assumptions to probabilistic assessments regarding its contributions to system balance.
Thermal Generation: Evolving Backbone Amid Transition Pressures
In Q1 2026, thermal generation remains the backbone of SEE’s power systems but is undergoing rapid changes due to increasing renewable penetration, carbon pricing pressures, and demands for greater system flexibility. During Week 16, thermal output across the region was relatively stable at 4,300 GWh (+0.18%); however, internal shifts were notable: gas-fired generation rose by 3.31%, while coal and lignite outputs fell by 3.35%.
This trend highlights that thermal generation is not disappearing but rather being reallocated across various functions within the energy mix. Gas-fired plants are increasingly serving as flexibility providers that respond swiftly to short-term fluctuations in renewable output—an essential role especially evident in markets like Italy, Greece, and Hungary.
Conversely, coal and lignite continue to deliver baseload stability in regions with domestic resources. Serbia exemplifies this trend with lignite generation increasing nearly 20% during Week 16, underscoring its critical role in ensuring supply security.
Three distinct thermal archetypes are emerging across SEE: gas-led flexibility systems (Italy and Greece), coal/lignite-dominant systems (Serbia and parts of the Western Balkans), and hybrid systems (Romania and Bulgaria) that integrate gas, coal, hydro, and renewables for diversified balancing capabilities. This diversity reflects varying resource availability, policy frameworks, and levels of market integration across different countries.
Looking forward through 2026-2030, while thermal generation will remain vital for system stability, its utilization profile is set to evolve. Gas plants may operate at lower capacity factors but will capture higher marginal value by participating in balancing markets during price spikes. Meanwhile, coal and lignite facilities will face mounting economic pressures due to carbon costs but will continue operating where reliability demands dictate their presence.
A key risk remains the potential for a flexibility gap; as renewable energy sources proliferate, demand for quick-response generation increases while investments in new flexible capacity—particularly battery storage—have yet to achieve necessary scale to fully replace or complement existing thermal assets.
In baseline scenarios, thermal generation is expected to stabilize the system with gradual shifts toward gas utilization. However, tighter scenarios marked by hydropower deficits or renewable shortfalls may see increased output from coal and lignite sources—reinforcing their ongoing relevance within the regional energy landscape.
Nuclear Energy: Stable Baseload Amid Limited Expansion Prospects
Nuclear power continues to provide low-cost and low-carbon baseload stability across Europe during Q1 2026; however, its impact within SEE remains limited due to constrained capacity and slow expansion rates. In Western Europe, improved nuclear availability—especially from France—has bolstered overall system stability while reducing price volatility compared to previous years. This stability indirectly benefits SEE through market coupling effects that help moderate cross-border price dynamics.
Nuclear capacity within SEE is concentrated primarily in Romania (Cernavodă), Bulgaria (Kozloduy), and Slovenia (Krško). These facilities play crucial roles in providing baseload generation while supporting export capabilities—particularly notable in Bulgaria and Slovenia—but their overall contribution remains overshadowed by hydroelectricity and thermal sources.
The defining characteristic of nuclear energy is its stability; unlike variable renewables such as hydro or wind that are susceptible to weather conditions—and unlike gas which faces short-term fuel price volatility—nuclear provides a consistent anchor for system reliability and price stability.
However, nuclear power also has inherent limitations: it lacks short-term operational flexibility; requires lengthy development timelines; and involves substantial capital investments alongside regulatory complexities that can hinder rapid deployment.
This means nuclear cannot adequately respond to the swift changes now characterizing SEE power markets. Future developments will depend heavily on policy decisions regarding investment frameworks; life extensions for existing plants in Romania and Bulgaria appear likely but new projects face significant challenges related to financing timelines—suggesting little impact on regional generation mixes before the early 2030s.
