Southeast European electricity prices are likely to remain fragmented through September and October as transmission constraints prevent cheaper Central European power from fully reaching Hungary, Romania and the Balkans during tight hours.
Summer trading repeatedly showed that additional generation alone does not guarantee price convergence.
Hungary traded almost €91/MWh above Germany on Sept. 4 even as west-to-east imports increased, while Serbia, Bulgaria and Greece frequently formed separate price zones depending on renewable availability and border capacity.
ACER has identified insufficient cross-zonal capacity and evening flexibility as the main structural causes of previous SEE price spikes and has urged grid operators to implement the EU requirement to make at least 70% of transmission capacity available for cross-border trade.
The issue should become more visible in autumn.
September will still produce strong solar output and occasional regional surpluses, but October brings shorter daylight hours and an earlier evening ramp.
Hungary is likely to remain the main regional optimisation hub, absorbing electricity from Austria, Slovakia and Romania before redistributing supply toward Serbia, Croatia and Slovenia.
Romania’s position will depend heavily on nuclear and hydro availability.
Bulgaria should retain greater export potential when Kozloduy operates normally, while Croatia and Slovenia remain structurally more dependent on imports during periods of weak hydro.
Serbia can move between importer and exporter within days, making the SEEPEX-HUPX spread particularly volatile.
The main autumn trading risk is therefore not a lack of electricity across Europe.
It is insufficient capacity to move lower-priced electricity into SEE during the hours when the region needs it most.
