The final weeks of December 2025 and the opening month of January 2026 marked a clear inflection point for electricity trading across South-East Europe. After several years in which bilateral contracting, administrative interventions, and risk aversion dominated regional behavior, organized power markets re-asserted themselves as the primary arena for price discovery, arbitrage, and risk management. What emerged during this winter window was not a crisis-driven spike, but a structurally more mature trading environment: higher liquidity, more active cross-border flows, and price signals increasingly shaped by regional fundamentals rather than isolated national constraints.
For traders, utilities, and industrial consumers, this period offered a rare combination of volatility and depth. Prices moved sharply within weeks, yet volumes did not collapse. Instead, exchanges across the region—from Hungary and Romania to Serbia and Bulgaria—demonstrated that South-East Europe is no longer a peripheral market reacting passively to Central Europe, but a set of interconnected hubs where spreads, congestion, and flow patterns can be monetized in real time.
At the center of this evolution stood four exchanges that now define the regional trading map: HUPX, OPCOM, SEEPEX, and BELEN. Their interaction during the winter of 2025–2026 provides a revealing snapshot of where SEE power trading is heading.
A winter defined by liquidity, not fear
The defining feature of December 2025 and January 2026 was the return of liquidity to organized markets. This matters more than headline prices. In previous winters, high prices often coincided with thinning order books as participants withdrew to bilateral cover. In contrast, winter 2025–2026 showed that elevated prices could coexist with rising traded volumes, a hallmark of a market transitioning from defensive behavior to active trading.
Nowhere was this clearer than in Serbia. On SEEPEX, January trading volumes consistently ranged between 12.9 and 16.5 GWh per day, implying total monthly traded volumes of approximately 420–450 GWh. This represented a material year-on-year increase and, more importantly, confirmed that Serbian generators, traders, and large consumers were increasingly willing to expose positions to day-ahead price formation rather than relying exclusively on fixed bilateral contracts.
Price behavior reinforced this point. During January 2026, day-ahead clearing prices on SEEPEX fluctuated from lows near €67/MWh during mild, hydro-supported days to highs above €125/MWh during colder periods with tighter system margins. Crucially, high prices did not deter participation. Volumes remained robust even on peak-price days, signaling confidence in market mechanisms and risk management strategies.
This shift has structural implications. Once participants accept that volatility is tradable rather than something to be avoided, liquidity tends to compound. That dynamic was visible across the region, not just in Serbia.
HUPX as the regional gravity center
Hungary’s HUPX continued to function as the gravitational center of SEE power trading. With average daily day-ahead volumes typically in the 70–80 GWh range, HUPX remains an order of magnitude more liquid than most neighboring exchanges. That depth matters. It anchors regional price expectations, absorbs shocks, and provides a reference point for forward hedging and bilateral indexation.
In December 2025, average Hungarian day-ahead prices hovered around €110–120/MWh, reflecting a classic winter premium driven by higher demand, carbon costs, and marginal thermal dispatch. While these price levels were elevated compared to historical averages, they were notably lower than crisis-era extremes and displayed smoother intraday profiles.
For traders across South-East Europe, HUPX was the primary benchmark against which spreads on smaller exchanges were evaluated. When Serbian or Bulgarian prices diverged from Hungary, the question was no longer whether arbitrage was theoretically possible, but whether cross-border capacity and congestion pricing justified the trade. This is a fundamental change from earlier periods when physical constraints and regulatory frictions often rendered such comparisons academic.
Romania’s dual role: Volume and directionality
Romania’s OPCOM occupied a unique position during this winter. As both a large domestic market and a key transit node between Central and South-East Europe, Romania displayed highly active bidirectional trading with Hungary and Bulgaria. December 2025 average day-ahead prices on OPCOM clustered around €115–120/MWh, broadly aligned with Hungary but with episodic divergences reflecting domestic generation and cross-border constraints.
What stood out in December was not price level but flow directionality. Romania exported and imported electricity with Hungary in alternating patterns, sometimes within the same week. This bidirectional behavior is a strong indicator of market integration. It suggests that price differences were sufficiently narrow—and transmission sufficiently available—that traders could respond dynamically to short-term fundamentals rather than being locked into structural export or import roles.
For SEE traders, Romania increasingly functioned as a liquidity bridge. Positions taken on OPCOM could be offset against HUPX or BELEN, allowing for more sophisticated spread strategies. This reinforces Romania’s status as a regional trading hub rather than merely a large domestic market.
Bulgaria and BELEN: From peripheral to participatory
Bulgaria’s BELEN has historically been viewed as less liquid than its northern neighbors. Winter 2025–2026 did not change that ranking overnight, but it did demonstrate a clear trend toward deeper participation. Prices on BELEN tracked regional movements closely, with winter averages broadly aligned with Romania and Serbia, albeit with higher volatility during periods of domestic constraint.
For traders, BELEN’s growing relevance lies less in absolute volume and more in its role as a gateway between the Balkan markets and Greece, as well as its interaction with Romanian flows. As interconnector utilization improved, BELEN prices increasingly reflected regional supply-demand balances rather than isolated Bulgarian conditions. This enhances its usefulness for cross-border strategies, particularly when congestion premiums emerge.
Cross-border flows as the real price signal
If one theme defined winter 2025–2026, it was the centrality of cross-border flows to price formation. The SEE region no longer behaves as a set of semi-isolated national markets. Instead, price signals propagate rapidly along the Hungary–Romania–Serbia–Bulgaria corridors, moderated by available transfer capacity and congestion rents.
During December 2025, utilization of interconnectors between Hungary and Romania was consistently high, with flows reversing direction depending on relative price spreads. Serbia’s position was particularly sensitive. When SEEPEX prices traded below HUPX, exports toward Hungary became attractive; when Hungarian prices softened or Serbian prices spiked, imports flowed the other way.
This flow-driven behavior has two important consequences. First, it accelerates price convergence across the region, reducing extreme local deviations. Second, it shifts the focus of trading strategy from absolute price forecasting to relative price positioning and congestion management. Traders who understand when and why capacity binds are increasingly able to monetize short-lived spreads that would have persisted longer in a less integrated system.
Volatility with structure, not chaos
Volatility was unmistakable during January 2026, but it was structured volatility. Price swings were tied to identifiable drivers: cold spells increasing demand, variations in hydro availability, and the marginal role of thermal generation influenced by fuel and carbon costs. This contrasts with earlier crisis periods when prices were driven by panic, regulatory shocks, or extreme scarcity.
In practical terms, this meant that intraday and day-ahead markets rewarded active management. Industrial consumers with flexible load could adjust consumption during high-price hours. Generators optimized dispatch against short-term price signals. Traders deployed intraday strategies to capture swings between forecast and realized conditions.
The presence of volatility without systemic stress is a sign of market health. It indicates that participants trust the clearing mechanism and that liquidity is sufficient to absorb shocks without triggering withdrawal.
The trading implications for SEE participants
For professional market participants, the winter of 2025–2026 confirmed several strategic realities. First, organized exchanges in SEE are now indispensable for price discovery and risk management. Second, cross-border awareness is no longer optional; it is the primary determinant of trading profitability. Third, liquidity is deep enough in core hubs to support increasingly sophisticated strategies, including spread trading, shape optimization, and portfolio hedging.
Industrial consumers are also adapting. Rather than treating exchange prices as a threat, many are beginning to use them as reference points for procurement decisions and contract renegotiation. This behavioral shift feeds back into liquidity, reinforcing the role of exchanges as central infrastructure rather than marginal platforms.
From Regional To Integrated Markets
The dynamics observed in December 2025 and January 2026 point toward a clear trajectory. As South-East Europe moves closer to full integration with the EU internal electricity market, the distinction between “regional” and “core” European trading hubs will continue to blur. Market coupling initiatives, improved capacity calculation, and regulatory alignment are likely to further compress spreads and increase volumes.
For traders, this does not mean the end of opportunity. On the contrary, it means that value will increasingly lie in speed, information, and operational excellence rather than simple geographic arbitrage. Congestion will not disappear; it will simply become more transient and more tradable.
The winter of 2025–2026 should therefore be seen not as an anomaly, but as a preview. South-East Europe’s power markets are entering a phase where volatility, liquidity, and integration coexist. For those positioned to trade rather than retreat, it is a market environment rich with opportunity.
By virtu.energy
