SEE power markets rebound as wind drops, hydro weakens and nuclear availability tightens

South East Europe’s power market opened the week with a sharp rebound in spot prices across nearly all major regional exchanges, reversing the softer weekend tone and reintroducing tighter thermal-driven pricing conditions. For investors, the move matters because it highlights how quickly balance can tighten when wind underperforms and nuclear and hydro constraints reduce dependable supply.

Spot prices jump across the region

Day-ahead prices rose broadly. HUPX climbed to €138.68/MWh, Romania’s OPCOM reached €139.51/MWh, and Bulgaria’s IBEX advanced to €136.34/MWh. Most markets recorded daily gains above €35–42/MWh, while Greece remained structurally decoupled on the downside at €97.12/MWh, supported by stronger solar availability and lower regional tightness.

Renewables volatility tightens balance as demand rises

The price action was driven by a mix of falling wind generation, lower hydro contribution, nuclear maintenance pressure and sharply higher evening peak pricing structures. Regional consumption increased to 28.1 GW while total SEE generation fell to 21.7 GW, leaving the region in a net import position of roughly 2.16 GW.

Hydro generation declined by 615 MW day-on-day and wind production dropped by 725 MW—one of the key drivers behind the sudden tightening in balancing conditions. With hydro representing only 22% of the system mix and wind just 3%, coal and gas-fired generation moved back into the marginal pricing stack: coal output rose by 156 MW while gas-fired generation stayed elevated at 3.49 GW. Solar improved by 331 MW, but daytime strength was not enough to offset an evening scarcity premium visible across regional curves.

Thermal stress returns in hourly curves

Hourly trading confirmed a return to classic thermal stress pricing patterns. On HUPX, evening hours traded near or above €200/MWh, with the daily maximum reaching €200.9/MWh. Romania’s OPCOM peaked even higher at €212.2/MWh, while Bulgaria’s maximum hourly prices were near €177.6/MWh.

At the same time, minimum prices remained barely above zero during midday solar hours, illustrating a widening intraday spread that is becoming more pronounced as renewable penetration rises without sufficient storage depth.

Nuclear constraints add supply risk

The week’s bullish sentiment also reflected several simultaneous structural supply-side developments affecting nuclear availability.

Bulgaria’s Kozloduy began preparations for the scheduled maintenance outage of Unit 5 on 9 May, continuing toward mid-June. The maintenance includes reactor refueling using Westinghouse fuel assemblies as Bulgaria continues diversifying away from Russian nuclear fuel supply.

Romania extended the outage period for Cernavoda Unit 2 after a transformer-related technical fault forced automatic disconnection earlier this month. Replacement work on transformer systems and additional controlled shutdown procedures further tightened nuclear availability, while planned maintenance for Unit 1 also enters the schedule—raising concerns around Romanian export capacity in coming weeks.

In Slovenia, Krško reported reduced effective export capability due to low Sava river levels and thermal discharge limitations. Although the reactor continued operating at full power, environmental cooling constraints reduced exports to around 690 MW versus normal levels above 700 MW—pointing to broader climate-linked operational risks affecting cooling efficiency across Europe’s thermal and nuclear fleet.

Weather outlook could sustain pressure

Forecasts suggest additional pressure may persist into midweek as temperatures are expected to decline after 11 May across SEE and Hungary, particularly in Slovenia, Croatia, Bulgaria and Romania. That could support stronger thermal demand while uncertainty remains around wind normalization.

Forward prices firm; carbon supports coal economics pressure

Forward markets reflected a firmer short-term structure: Hungarian Week-20 power forwards rose to €126/MWh and Week-21 contracts reached €124.5/MWh. Carbon allowances strengthened further as EUA Dec-26 traded near €80/t, maintaining elevated pressure on coal and lignite generation economics across SEE.

Gas remains steadier; diversification talks continue

Gas markets were comparatively stable despite wider geopolitical uncertainty. Austrian CEGH gas traded near €45.5/MWh.

Turkey continued negotiations with Algeria regarding expanded LNG imports that could increase from about 4.4 bcm/year toward 6–6.5 bcm/year under a future long-term agreement. The talks also include potential LNG transit toward southeastern Europe via Bulgaria—an element described as strategically important for gas diversification and long-term balancing flexibility.

Renewables expand fast—but flexibility gaps are becoming clearer

Renewable investment momentum remains strong even as balancing stress rises.

North Macedonia confirmed solar capacity reached 962.6 MW, overtaking hydropower as the country’s second-largest installed generation technology after hydropower/solar ranking changes implied by that milestone (solar is now second). Solar generation rose by 27.7% year-on-year and renewables account for 46.4% of the national electricity mix; regulators also confirmed growing battery deployment activity tied to new storage licenses linked to solar projects.

Montenegro launched trial operation at its Gvozd wind farm near Nikšić—an €82 million project expected to generate about 150 GWh annually and supply around 25,000 households—financed by the EBRD and built by Nordex.

The market case for storage and grid upgrades strengthens

Still, the current daily market structure shows renewable expansion alone is no longer sufficient to stabilize SEE electricity markets as intraday spreads widen between midday lows and evening peaks alongside import dependency, tightening nuclear availability and volatile hydro performance.

The implication is that utilities and policymakers may need faster progress on utility-scale battery storage, flexible gas generation where available, cross-border interconnection upgrades and balancing market modernization—otherwise SEE could move into a more structurally volatile phase where high renewable penetration coexists with increasingly aggressive intraday pricing spikes during periods of weak wind output and constrained hydro availability.