The start of the 11/5 trading week in Southeast Europe brought a renewed tightening in power balances, pushing spot prices higher across most regional venues after a softer weekend tone. Day-ahead pricing jumped on HUPX to €138.68/MWh, while Romania’s OPCOM rose to €139.51/MWh and Bulgaria’s IBEX climbed to €136.34/MWh. Greece stood out for its downside decoupling at €97.12/MWh, supported by stronger solar availability and lower regional tightness.
Market conditions deteriorated as multiple system constraints aligned, with falling wind output and reduced hydro contribution coinciding with nuclear maintenance pressure. Regional consumption increased to 28.1 GW, while total SEE generation fell to 21.7 GW, leaving the area in a net import position of roughly 2.16 GW. Hydro output declined by 615 MW day-on-day, and wind production dropped by 725 MW, tightening balancing margins during the most price-sensitive hours.
The generation mix underlined how quickly the region can swing during renewable volatility. Hydro accounted for only 22% of the system mix, while wind contributed just 3%, limiting the ability of renewables to smooth supply swings. Coal generation increased by 156 MW and gas-fired output remained elevated at 3.49 GW as thermal units returned to the marginal pricing stack, while solar generation improved by 331 MW but did not prevent evening scarcity premiums from building.
Hourly prices confirmed a return to thermal stress dynamics, with evening hours again trading near or above €200/MWh on HUPX and a daily maximum reaching €200.9/MWh. Romania’s OPCOM peaked at €212.2/MWh, whereas Bulgaria recorded maximum hourly prices near €177.6/MWh. Minimum prices stayed barely above zero during midday solar hours, highlighting a widening intraday spread that reflects renewable penetration without sufficient flexibility depth.
Cross-border flows also pointed to continued north-to-south dependency within the import structure. Core imports from Austria and Slovakia into the Hungarian and SEE region remained extremely high at roughly 1.9 GW, while Italy continued absorbing regional export capacity. Greece remained a net importer at approximately 1.29 GW, and Hungary maintained heavy import reliance.
Nuclear availability emerged as a key driver behind the bullish tone, with several outages reducing effective baseload support across the region. Bulgaria’s Kozloduy began preparations for the scheduled maintenance outage of Unit 5, with shutdown activities starting on 9 May and continuing toward mid-June; the program includes reactor refueling using Westinghouse fuel assemblies as part of diversification away from Russian nuclear fuel supply.
Romania extended constraints on Cernavoda Unit 2 after a transformer-related fault triggered automatic disconnection from the grid earlier this month. Transformer replacement and additional controlled shutdown procedures further tightened nuclear availability, while Unit 1 is also entering planned maintenance, raising concerns around Romanian export capacity in the coming weeks.
Slovenia’s Krško plant reported reduced effective export capability linked to low Sava river levels and thermal discharge limitations. Even with the reactor operating at full power, environmental cooling constraints reduced exported electricity to around 690 MW compared with normal levels above 700 MW, adding to broader European risk around cooling system performance under hydrological stress.
Weather expectations suggest the market may remain supported by demand-side pressure into midweek as well. Temperatures across SEE and Hungary are expected to decline after 11 May, particularly in Slovenia, Croatia, Bulgaria and Romania, which could sustain stronger thermal demand while wind normalization remains uncertain.
Forward curves reinforced the short-term firmness seen in spot markets, with Hungarian Week-20 power forwards rising to €126/MWh and Week-21 contracts reaching €124.5/MWh. Carbon allowances strengthened further as EUA Dec-26 traded near €80/t, maintaining elevated pressure on coal and lignite generation economics throughout SEE.
Gas market signals were comparatively stable alongside these electricity moves. Austrian CEGH gas traded near €45.5/MWh, while Turkey continued negotiations with Algeria over expanded LNG imports that could rise from 4.4 bcm/year toward 6–6.5 bcm/year under a future long-term agreement; talks also include potential LNG transit toward southeastern Europe via Bulgaria for diversification and balancing flexibility.
Despite the near-term stress reflected in pricing spreads and balancing conditions, investment activity in renewables continues to build capacity across parts of the region. North Macedonia confirmed solar capacity reached 962.6 MW, overtaking hydropower as its second-largest installed technology, with solar generation up 27.7% year-on-year and renewables at 46.4% of the national electricity mix; the regulator also pointed to growing battery deployment activity through new storage licenses linked to solar projects.
Montenegro also moved forward on wind infrastructure by launching trial operation at the Gvozd wind farm near Nikšić, an 82 million euro project expected to generate about 150 GWh annually and supply around 25,000 households; it is financed by the EBRD and constructed by Nordex.
Taken together, the week’s price action shows that renewable expansion alone is no longer sufficient to stabilize Southeast Europe’s electricity market under conditions of constrained nuclear availability and weaker wind output combined with lower hydro performance. The widening gap between midday and evening pricing alongside persistent import dependence is increasing the relevance of utility-scale battery storage, flexible gas generation, cross-border interconnection upgrades and balancing market modernization.
Without additional flexibility infrastructure entering service at scale, the region faces a risk of structurally more volatile trading where high renewable penetration coexists with sharper intraday pricing spikes—particularly during periods when wind output weakens and hydro constraints tighten system balance.