As winter settles across South-East Europe, the region’s electricity landscape enters a season shaped not by crisis but by structural interdependence. December 2025 finds the Balkan and Central-European power systems operating under a degree of cross-border coordination once unimaginable. The frantic volatility of 2022 has faded into the background; in its place stands a calmer regime where interconnectors, rather than domestic fuel swings or emergency interventions, define the pulse of the regional market. Prices still move sharply at times, but it is the availability of cross-border capacity—not national generation portfolios—that increasingly sets the conditions under which these movements unfold.
The defining feature of December 2025 is the absence of structural capacity reduction across major borders. Hungary, Romania and Bulgaria continue to release long-term rights through the Joint Allocation Office under stable technical conditions, while Greece’s interconnections with Bulgaria and Italy operate with a rhythm closer to Western European norms than to the ad-hoc patterns of a decade ago. Even Serbia, though outside the EU framework, now moves in parallel with this system. The updated Harmonised Allocation Rules for non-EU borders entering force in early 2026 show a deliberate tightening of Serbia’s integration with regional capacity allocation procedures. This legal alignment is not theoretical. As serbia-energy.eu has repeatedly highlighted throughout 2025, Serbia’s role as a physical and commercial transit node has expanded, and its cross-border coordination with Hungary, Romania, Bulgaria and Croatia now anchors its energy security more reliably than its ageing thermal fleet.
December’s power prices already reflect this emerging architecture. During the first days of the month, SEEPEX prices surged toward 160 to 170 euros per megawatt-hour amid a temporary tightening of Serbian lignite availability and cold weather across the Danube basin. The reaction in Montenegro was instantaneous, despite Montenegro not being the origin of the shock. Albania, entering winter with strong reservoir levels, still imported at elevated prices during those hours, tracking wholesale movements in Serbia and Bulgaria almost exactly. This near-perfect synchronisation is the product of cross-border capacities that remain broadly available, allowing price signals to propagate through the region rather than remaining trapped within national borders. It is also the direct consequence of a maturing market environment in which the daily auction signals published on platforms such as electricity.trade are now more regionally representative than ever before.
Romania’s situation illustrates the duality of constraint and convergence. Despite operating under a derogation from the EU’s 70 percent minimum capacity rule, Romania’s TSO has increased transparency and internal coordination, enabling more consistent export and import availability than in previous winters. New operational procedures adopted in late 2025 are already easing internal bottlenecks, and Romania’s ambition—reported through several updates on serbia-energy.eu—to double its cross-border exchange capability by mid-decade is now a central element of its energy planning. As December unfolds, Hungarian, Romanian and Serbian prices often move in lockstep, reflecting this steady improvement in grid fluidity. What once were three semi-independent markets have effectively merged into a single dynamic zone, driven by cross-border availability rather than national dispatch alone.
Bulgaria and Greece form the southern hinge of this system. Bulgaria’s mix of lignite, nuclear and hydro gives it a stabilising role, but historically this stability was undermined by sporadic export restrictions or internal grid congestion. In December 2025, by contrast, Bulgaria appears as a pillar of regional continuity. Prices at IBEX cluster tightly around those of Serbia and Romania, and the GR–BG interconnector remains the primary balancing channel between the gas-weighted Greek system and the lignite-nuclear core north of the Rhodopes. When Aegean winds surge and Greek production rises, exports move north; when Greek system marginal costs rise with gas, flows reverse. For the first time in years, this exchange pattern feels predictable. The transparency of commercial flows visible on electricity.trade reflects a region whose structural integration is finally catching up to its physical geography.
For Serbia, Montenegro and Albania, the stakes remain existential. Serbia’s system balance in winter depends on dependable import capability during hours when hydro inflows weaken and thermal units reach their operational limits. Montenegro, with its compact system, cannot absorb significant shocks without leaning on regional flows. Albania’s hydro dependence magnifies this vulnerability further. In dry winters, its only buffer is access to regional imports, and the price it pays reflects the tightness of neighbouring systems. Throughout December 2025, all three countries rely on available cross-border capacity to avoid supply stress, and the consistency of that capacity is the main reason none have faced acute market dislocation. Articles through serbia-energy.eu illustrate that this is no longer accidental resilience; it is the by-product of increasingly rigorous cross-border coordination between TSOs.
Looking toward the first quarter of 2026, the same structural forces appear poised to guide the region. Fuel markets remain benign, with gas prices sitting at multi-month lows; hydro reservoirs in Serbia, Montenegro, Albania and Bulgaria are at or above typical seasonal levels; and no major long-duration outages have been announced for the principal 400 kV corridors. Seasonal maintenance in January and February will temporarily curtail certain capacities, but these events are well-signalled and narrow in scope. The absence of structural de-rating means that the region will again behave as a coherent market, with Hungary, Romania, Serbia, Bulgaria and Greece forming the central price axis and Croatia, Montenegro and Albania oscillating tightly around it.
The real uncertainties lie not in capacity planning but in the volatility of generation conditions. A sharp cold spell across Central Europe could quickly test the HU–RO–RS–BG chain, while prolonged drought in the Western Balkans would expose Albania and Montenegro to the upper bands of regional pricing. Yet even these risks reinforce the central point: the more capacity remains available, the more shocks are diluted across the system rather than concentrated. December’s performance demonstrates that South-East Europe is entering a phase where interconnectors act not merely as commercial routes but as instruments of systemic stability. The data flows and auction results visible on electricity.trade, together with the operational narratives tracked through serbia-energy.eu, reveal a regional electricity system defined by transparency, alignment and shared vulnerability.
The winter of 2025–26 will likely confirm this transformation. Cross-border capacity has ceased to be a fragile constraint and has become the foundation of price formation and system security. December’s early patterns show a region moving as a single organism—sometimes stressed, sometimes calm, but always interconnected. The first quarter of 2026 will take this logic further, shaping a Balkan power system held together not by administrative integration, but by the physical reality of the lines between them.
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