Southeast Europe’s electricity-price crisis is no longer explainable as a temporary fuel or weather shock. ACER’s 2026 assessment found that the price gap between SEE and Central Europe persisted through 2025 and into early 2026, pointing to structural weaknesses in flexibility, network use and market integration.
The regulator examined the extreme summer of 2024, when average peak electricity prices in the affected SEE markets reached about €350/MWh. The core problem emerged after sunset: solar generation fell quickly while demand remained high, and the region lacked enough flexible resources to replace it. Limited import capacity, including restrictions associated with planned network maintenance, prevented cheaper Central European electricity from fully easing the shortage.
ACER estimates that 147 of the most severe price spikes could have been avoided if the EU requirement to make at least 70% of relevant transmission capacity available for cross-zonal trade had been met. The finding does not mean that every line should operate at 70% of its thermal rating at all times. The legal calculation accounts for reliability margins and contingencies. It does mean that domestic congestion and uncoordinated operating decisions are leaving too little capacity for the integrated market.
The affected SEE group comprises Slovenia, Croatia, Hungary, Romania, Bulgaria and Greece, while Austria and Slovakia form the relevant Central European comparison. Power flows through this corridor are shaped by outages and constraints far from the national border where capacity is sold. That is why flow-based calculation and stronger regional coordination are necessary: bilateral capacity values cannot fully represent a meshed network.
ACER recommends improved outage planning, wider use of curative remedial actions, accelerated high-impact investment and full implementation of flow-based market coupling. It also urges grid-enhancing technologies such as dynamic line rating, which could increase available capacity by more than 50% on some constrained elements.
Interconnection alone is not enough. If every SEE country experiences the same evening solar ramp, neighbouring systems may all seek imports at once. Storage, demand response, flexible hydro and fast-starting generation are still required. Cross-border capacity reduces the cost of scarcity by pooling resources; it cannot create surplus energy when the entire region is tight.
The commercial implications are significant. Persistent price separation creates arbitrage opportunities for batteries and traders but raises costs for industrial consumers and weakens the promise that renewable expansion will deliver affordable power. It also changes the value of assets: a megawatt of flexible capacity near a congested border can be worth more than a megawatt in an unconstrained zone.
ACER’s report reframes the policy debate. SEE does not simply need more cables. It needs to use existing networks more efficiently, coordinate outages and apply common market rules. The fastest price relief may come from operational reform and flexibility while larger interconnectors are being built.
