The gap between commercial electricity schedules and physical flows widened across the Western Balkan network during the second quarter of 2026, creating a growing operational problem for transmission system operators.
The most striking example was the Bosnia and Herzegovina–Croatia border. Scheduled exports from Bosnia and Herzegovina to Croatia fell by around 43% year on year, to approximately 282 GWh. Physical flows in the same direction increased by roughly 270%, with more than 800 GWh actually crossing the border.
Physical electricity therefore moved at almost three times the level indicated by commercial schedules. The pattern had already appeared in the first quarter, but intensified during Q2.
The Albania–Greece border showed the opposite configuration. Scheduled Albanian exports remained close to their normal level, rising around 3%, while physical flows fell approximately 63%. Electricity commercially booked towards Greece appeared instead to travel north through Montenegro and Bosnia and Herzegovina.
The wider physical-flow data confirm a strengthening south-to-north route. Physical flows from Greece to North Macedonia rose by more than 200%, North Macedonia-to-Serbia by a similar magnitude and Montenegro-to-Bosnia and Herzegovina by more than 200%. The meshed network was carrying electricity towards Croatia and other EU borders regardless of where commercial transactions had been nominated.
For TSOs, schedules are a central input into security analysis. They help operators calculate expected loading, determine available margins and plan remedial actions. When physical electricity takes a different path, operators must maintain larger safety buffers and intervene more frequently through redispatch, countertrading and other corrective measures.
Those actions create costs. They may be initially borne by TSOs, but are ultimately reflected in network tariffs, congestion-management charges and reduced capacity available to market participants. The mismatch also weakens the locational logic of congestion income. Revenue can accrue at one border even though the physical congestion appears elsewhere in the network.
CBAM may be contributing indirectly by changing the commercial routes through which power is booked. Traders respond to national default factors, border-price spreads and eligibility rules, while physical electricity continues to follow the network’s laws. The larger the divergence between commercial incentives and electrical reality, the more pressure falls on grid operators.
The issue cannot be resolved by a single TSO. Coordinated capacity calculation, common network modelling and regional congestion management are needed across the Western Balkans and neighbouring EU systems. Greater transparency over loop flows and harmonised remedial-action cost sharing will also become increasingly important.
The regional market is being commercially reconfigured faster than the physical grid can adapt. That gap creates an infrastructure and regulatory cost that will eventually appear in tariffs, investment requirements and the amount of cross-border capacity available to traders.
