Week 08 of 2026 marks a decisive illustration of a structural shift underway in South-East Europe’s electricity system: price formation is no longer primarily dictated by fuel costs or thermal marginality, but by the availability and timing of flexible renewable and hydro resources. The data from the SEE Electricity & Gas Market Analysis confirms that both variable renewables and hydropower expanded materially during the week, directly compressing wholesale prices, displacing gas-fired generation and redefining system equilibrium .
Variable renewable generation across SEE increased by +25.5% week-on-week to 3,951 GWh, driven by a +19.0% rise in wind output and a remarkable +44.4% surge in solar generation . This scale of increase is not marginal. It represents nearly a full terawatt-hour of additional energy entering the system in a single week, fundamentally altering the merit order and reducing reliance on dispatchable thermal units.
Italy was the principal driver of this expansion, contributing +449 GWh of additional variable renewable output, supported by wind growth of +33.2% and solar growth of +57.4%. This dramatic shift reshaped Italy’s supply stack and directly influenced cross-border flows throughout the region. When a system of Italy’s scale increases renewable output by nearly half a terawatt-hour in a single week, the impact extends far beyond national borders.
Türkiye followed with a substantial contribution, increasing total variable RES generation by +19.7%, supported by wind growth of +16.8% and solar rebound of +56.7%. Greece recorded a +15.1% rise, Romania +25.6%, and Bulgaria delivered the strongest proportional increase among smaller markets at +35.7%, largely due to solar expansion of +46.0%. These synchronized gains confirm that renewable strengthening was region-wide rather than isolated.
For transmission system operators, this expansion of renewable output must be interpreted as a direct intervention in price formation. In Week 08, wholesale prices fell sharply across the region, with Greece declining -29.35%, Serbia -27.80%, Croatia -21.39%, and Hungary -11.57% . These declines coincided precisely with renewable and hydro gains. The causal chain is clear: renewables expanded, thermal units retreated, marginal costs fell, and prices compressed.
Hydropower played an equally critical role. Regional hydro generation rose by +15.05% week-on-week to 3,785 GWh, adding nearly 500 GWh of additional supply . Türkiye alone increased hydro output by +216 GWh (+10.79%), while Greece posted +21.68%, Romania +14.80%, and Italy +7.87%. Croatia recorded an extraordinary proportional surge of +683%, albeit from a low base.
Hydro differs from wind and solar in that it is dispatchable within operational limits. For TSOs, this flexibility is critical. While solar output depresses midday prices, hydro can respond to evening ramps and congestion events. In Week 08, hydro’s rebound effectively neutralized what might otherwise have been ramp-driven price spikes. This explains why, despite rising demand in Hungary (+5.86%) and Croatia (+5.22%), wholesale prices still declined .
The displacement of thermal generation confirms the dominance of flexibility. Total thermal output fell by -20.40% to 6,079 GWh, with gas-fired generation collapsing by -28.44% (-1,258 GWh) and coal declining by -9.33% (-300 GWh) . Gas units were the first to exit the stack, demonstrating that they now serve as balancing assets rather than price-setting baseload resources.
This shift has profound implications for market structure. When gas sets the marginal price, electricity prices track fuel and carbon benchmarks. When hydro and renewables dominate, prices track weather and reservoir conditions. Week 08 demonstrates that SEE has entered the latter regime. Wholesale prices became a function of wind speed, solar irradiation and water inflows rather than TTF volatility.
The spatial distribution of renewable growth also matters. Italy’s expansion reduced southbound import pressure and freed cross-border capacity. Bulgaria’s solar surge altered its trade balance, contributing to a dramatic shift in cross-border flows. Romania’s renewable strength supported its transition from net importer to marginal exporter, recording -7 GWh of net exports . These changes illustrate how renewable expansion reconfigures regional flow patterns.
For TSOs, the operational burden of this transition lies in ramp management and congestion mitigation. Solar’s +44.4%increase implies deeper midday demand netting and steeper evening ramps. Wind’s variability introduces additional uncertainty. Hydro’s flexibility mitigates these effects, but only within reservoir constraints. The system functioned smoothly in Week 08 because hydro recovery coincided with renewable growth. Without hydro support, the same renewable surge could have produced greater volatility.
Another structural insight from Week 08 is the asymmetric performance of renewable systems. Serbia experienced a -32.4% contraction in variable RES output due to weaker wind conditions . This highlights a critical reality: renewable strength is rarely uniform. Regional averages can conceal local weakness, requiring cross-border balancing to compensate.
Wholesale prices ranging from €29.54/MWh in Türkiye to €107.17/MWh in Hungary during Week 08 reflect both renewable abundance and structural constraints . Hungary remained the highest-priced market despite regional flexibility gains, indicating that renewable and hydro expansion cannot fully offset congestion and import dependence in tightly coupled systems.
The growing dominance of flexibility also reshapes forward-looking risk. As hydro and renewable output increasingly determine price direction, seasonal and meteorological forecasting becomes more economically significant than fuel hedging. For TSOs, coordination between market monitoring and meteorological modeling becomes indispensable.
Week 08 demonstrates that SEE electricity markets are transitioning toward a flexibility-led equilibrium. When hydro and renewables expand simultaneously, prices fall quickly and thermal units retreat. When either weakens, stress re-emerges rapidly. The system is therefore not fuel-anchored but weather-anchored.
For transmission system operators, the strategic takeaway is clear. The future of price stability and grid reliability in SEE will depend less on marginal fuel supply and more on how effectively renewable variability and hydro flexibility are integrated, forecasted and balanced across borders. The market is no longer reacting to fuel; it is reacting to flexibility.
In this new structure, hydro and renewables are not merely contributors to the mix. They are the market makers.
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