Once exchange liquidity and cross-border capacity are understood, the decisive question in South-East Europe becomes operational rather than theoretical: who controls flows at the margin, on which borders, and during which hours. The answer is not uniform across the region. Dominance shifts by corridor, by time block, and by whether a market is deep enough to dilute physical control or thin enough to amplify it.
The Slovenia-centred corridors are the clearest example of trader-driven dominance rather than asset-driven dominance. On the Slovenia–Italy, Slovenia–Austria and Slovenia–Hungary interfaces, GEN-I is consistently one of the most influential participants. This is not because GEN-I controls generation, but because it controls access, speed and portfolio optionality. These corridors are characterised by relatively high coupling quality and sufficient interconnector capacity to allow arbitrage to work when prices diverge.
GEN-I’s dominance expresses itself most strongly in intraday and shoulder hours. When Italian prices spike relative to Central Europe, or when Austrian renewables overproduce relative to regional demand, GEN-I is often among the first to reposition. The result is that spreads on these borders tend to collapse quickly, often within one to two intraday trading intervals, provided physical capacity is available. This does not eliminate peak congestion rents, but it sharply limits their duration. For industrial consumers in Slovenia, northern Croatia and parts of Italy, this behaviour translates into lower time-weighted average prices, even if peak prices remain high.
On the Hungary-centric corridors, dominance is more distributed but still trader-led. The Hungary–Romania and Hungary–Serbia borders are characterised by high trader density, with participation from Axpo, MET Group, Statkraft, RWE Supply & Trading, Engie Trading, alongside regional desks and utility traders. No single actor dominates these corridors structurally. Instead, dominance rotates by hour depending on portfolio balance. During Romanian surplus hours, traders with nuclear-backed positions dominate exports into Hungary. During Serbian peak hours, traders with flexible access to Hungarian imports dominate flow in the opposite direction.
This multiplicity of actors is precisely why these corridors are among the most price-stabilising in SEE. Spreads rarely persist beyond €5–10/MWh unless physical capacity binds. For industry, this is the best-case scenario: congestion exists, but it is quickly arbitraged away when capacity opens.
The Western Balkans present a different picture entirely. On corridors involving Bosnia and Herzegovina, Montenegro and parts of Serbia, generation-anchored dominance becomes visible. Here, EFT plays a central role. EFT’s influence is strongest on Bosnia–Serbia, Bosnia–Croatia and Bosnia–Montenegro interfaces, particularly during peak winter and summer hours when hydrological conditions tighten or demand surges.
EFT’s dominance does not stem from trading speed but from control over exportable physical volume. In thin markets, the marginal export decision sets the price. When a single portfolio controls a large share of flexible output, that portfolio effectively determines whether neighbouring systems face scarcity or relief. This is why price spikes in Montenegro and parts of Bosnia can exceed €200/MWh during constrained hours, while prices in Hungary or Romania remain far lower at the same moment. The difference is not marginal cost; it is market depth.
Croatia sits at an intermediate position. On the Croatia–Slovenia and Croatia–Hungary borders, dominance is mixed. HEP plays a stabilising role through hydro optimisation, while regional traders and GEN-I-style optimisation desks exploit short-term spreads. During high hydro availability, Croatian exports can suppress regional prices. During dry periods, Croatia becomes a net importer, and dominance shifts to traders controlling access to Hungary or Slovenia.
The Serbia–Hungary corridor is one of the most dynamic in the region. Here, EPS interacts with international traders in a way that is increasingly market-driven. EPS no longer acts solely as a domestic supplier; it is an active participant in cross-border optimisation during surplus hydro hours. However, during Serbian peak demand periods, dominance shifts to traders controlling Hungarian imports. This alternating dominance is a hallmark of a market transitioning from administrative control to genuine price formation.
The Bulgaria-centred corridors demonstrate volume-driven dominance rather than player-driven dominance. On Bulgaria–Romania and Bulgaria–Serbia borders, the sheer scale of baseload nuclear output means no single trader can easily dictate prices. IBEX functions as a deep pool where arbitrage pressure is constant. Dominance rotates rapidly among traders depending on fuel spreads, carbon pricing and intraday forecast errors.
By contrast, the Bulgaria–Greece corridor exhibits persistent directional dominance. Greece’s gas-heavy marginal pricing and renewable volatility mean that imports are frequently required during peak hours. Traders with secured cross-border capacity into Greece capture sustained congestion rents. Here, both international houses and Greek-aligned traders such as PPC Trading play decisive roles. Price spreads of €7–12/MWh are common, and during extreme conditions spreads can widen significantly further. For Greek industry, this corridor is one of the most expensive structural bottlenecks in the region.
Albania and Kosovo, operating through ALPEX, remain largely importer-dominated. Dominance on their borders is episodic and highly dependent on hydrology. During wet periods, exports briefly emerge and local players dominate. During dry periods, dominance shifts to traders controlling imports from Greece or Bulgaria. The lack of depth means that price formation remains fragile, with limited arbitrage capacity to smooth volatility.
Montenegro represents the most extreme case of thin-market dominance. On borders linking Montenegro to Serbia and Bosnia, whoever controls marginal imports or exports in a given hour effectively sets the local price. With BELEN operating at daily volumes often below 1 GWh, even small trades can move prices dramatically. In such an environment, dominance is not continuous; it is episodic but powerful. For industrial consumers, this means pricing outcomes that bear little relation to regional averages.
When dominance patterns are mapped by time block, another layer emerges. Baseload hours in SEE are increasingly competitive and arbitraged, especially in coupled zones. Peak hours remain where dominance and pricing power concentrate. Evening peaks during winter and late summer are where generation-anchored traders exert the most influence, particularly in thin markets. Intraday correction windows are where optimisation traders dominate, compressing spreads when forecasts deviate.
The industrial implication is precise and measurable. Where corridors are dominated by multiple fast traders, delivered electricity prices typically carry a risk premium of €3–5/MWh. Where corridors are dominated by one or two physical portfolios, premiums rise to €8–15/MWh. For a 100 MW industrial consumer, that difference represents €4.4–13.1 million per year in electricity cost variance—purely from market structure, not energy efficiency or technology choice.
This is why trader composition matters as much as exchange design. A market with a well-designed exchange but thin participation will still price risk expensively. A market with active, competitive traders can absorb volatility even if generation costs are high. South-East Europe is now divided less by national borders than by liquidity regimes.
The structural winners are corridors where trader diversity is high, access is open and intraday depth exists. The structural losers are corridors where physical control substitutes for market depth. Until coupling deepens and participation broadens, those differences will remain embedded in industrial electricity prices across the region.
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