The electricity trading landscape in South-East Europe experienced a significant transformation during the winter months of December 2025 and January 2026. This period marked a shift from reliance on bilateral contracts and administrative interventions to a more organized market structure that emphasizes price discovery, arbitrage opportunities, and effective risk management. The transition is characterized by increased liquidity, enhanced cross-border flows, and price signals that are increasingly influenced by regional fundamentals rather than isolated national factors.
This winter season provided a unique environment for traders, utilities, and industrial consumers, as markets demonstrated both volatility and depth. Despite sharp price fluctuations within weeks, trading volumes remained stable across various exchanges in the region, including Hungary, Romania, Serbia, and Bulgaria. This evolution indicates that South-East Europe is moving away from being a peripheral market to becoming an interconnected hub where market participants can actively engage in real-time monetization of spreads and congestion.
Central to this development are four key exchanges: HUPX in Hungary, OPCOM in Romania, SEEPEX in Serbia, and BELEN in Bulgaria. Their interactions during this winter period offer valuable insights into the future trajectory of power trading within the region.
A Return to Liquidity
The critical feature of the late 2025 to early 2026 period was the resurgence of liquidity in organized markets. In previous winters, high prices often coincided with decreased trading activity as participants opted for bilateral arrangements. However, this recent winter demonstrated that elevated prices could coexist with increased traded volumes—an indication of a market evolving from defensive tactics to proactive trading strategies.
In Serbia specifically, SEEPEX recorded daily trading volumes between 12.9 GWh and 16.5 GWh throughout January 2026, leading to total monthly volumes around 420–450 GWh. This represents a notable increase compared to previous years and highlights a growing willingness among Serbian market participants to engage with day-ahead price formation instead of solely relying on fixed contracts.
Price dynamics further illustrated this trend; day-ahead clearing prices on SEEPEX varied from approximately €67/MWh during milder days to over €125/MWh during colder periods. Significantly, even on days of peak pricing, participation remained strong—a clear sign of confidence in market mechanisms.
HUPX: The Core Trading Hub
Hungary’s HUPX has established itself as the central trading hub for South-East European power markets. With average daily day-ahead volumes consistently between 70 GWh and 80 GWh, it significantly surpasses the liquidity found on neighboring exchanges. This depth provides stability to regional price expectations and serves as a reference point for hedging strategies.
In December 2025, Hungarian day-ahead prices averaged between €110/MWh and €120/MWh due to increased demand and carbon costs; however, these levels were more manageable compared to past crises. Traders across South-East Europe now assess spreads against HUPX benchmarks rather than solely relying on theoretical arbitrage opportunities based on physical constraints or regulatory issues.
Romania’s Strategic Role
Romania’s OPCOM serves as both a significant domestic market and an essential transit point between Central and South-East Europe. In December 2025, average day-ahead prices on OPCOM ranged from €115/MWh to €120/MWh—generally aligning with Hungarian prices while reflecting local generation capabilities and cross-border constraints.
A noteworthy aspect of Romania’s trading behavior was its bidirectional electricity flows with Hungary—highlighting its role as an integrated market participant capable of dynamic responses based on short-term fundamentals rather than fixed export/import positions. This adaptability positions Romania as a vital liquidity bridge within the region.
Bulgaria’s Evolving Market Position
Bulgaria’s BELEN exchange has historically been perceived as less liquid compared to its northern counterparts; however, recent trends indicate deeper market participation. Prices on BELEN closely mirrored regional movements while exhibiting greater volatility during domestic supply constraints.
The exchange’s increasing relevance lies in its function as a gateway connecting Balkan markets with Greece alongside its interaction with Romanian flows. Enhanced interconnector utilization has allowed BELEN prices to reflect broader regional supply-demand dynamics rather than being confined to local conditions.
The Impact of Cross-Border Flows
A defining characteristic of the winter season was the importance of cross-border flows in shaping price formation across South-East Europe. The region no longer operates as semi-isolated national markets; instead, price signals rapidly disseminate along established corridors connecting Hungary, Romania, Serbia, and Bulgaria—adjusted for available transfer capacity.
Utilization rates for interconnectors between Hungary and Romania remained high throughout December 2025—with reverse flow patterns driven by relative price disparities indicating an adaptive trading environment responsive to immediate conditions.
A Structured Volatility Environment
The volatility observed during January 2026 was systematic rather than chaotic; it stemmed from identifiable factors such as weather-induced demand fluctuations and variations in hydroelectric generation capabilities influenced by fuel costs. This clarity allows industrial consumers flexibility in adjusting their consumption patterns based on real-time pricing signals while generators optimize dispatch accordingly.
Strategic Insights for Market Participants
The developments of winter 2025–2026 underscore several strategic realities for market participants: organized exchanges have become essential for effective price discovery; cross-border awareness is crucial for profitability; and sufficient liquidity supports advanced trading strategies including spread trading and portfolio hedging.
Industrial consumers are also evolving their approach by increasingly using exchange prices as benchmarks for procurement decisions instead of viewing them solely as threats—this shift enhances overall liquidity within these markets.
Toward Full Market Integration
The observed dynamics signal an ongoing trajectory toward greater integration within the EU internal electricity market framework. As regulatory alignment progresses alongside improved capacity calculations through market coupling initiatives, tighter spreads are anticipated alongside increased trade volumes across borders.
This evolution does not signify diminished opportunities; rather it suggests that competitive advantages will hinge more upon operational excellence than geographical arbitrage alone—congestion will persist but will likely become more transient.
The winter season should be regarded not merely as an anomaly but rather as indicative of South-East Europe’s power markets entering a new phase characterized by concurrent volatility, liquidity enhancement, and integration efforts.
