Battery investment and rising intraday trading are widening flexibility markets across Southeast Europe, creating more potential revenue for storage operators while intensifying competition. Bulgaria is the region’s most advanced market, with a battery fleet exceeding 6.2 GW of power capacity. The Independent Bulgarian Energy Exchange (IBEX) recorded 1.432 TWh of October trading on its intraday continuous market, its highest volume to date.
That scale allows storage operators to buy energy, rebalance positions and provide system services. Competition is also beginning to reduce the exceptional revenues available to the earliest battery projects.
Croatia commissioned the Šibenik battery energy storage system on 4 November. The system has 60 MW of power capacity and 120 MWh of energy capacity, is connected at 110 kV and is integrated into the Croatian Transmission System Operator’s (HOPS) automatic frequency restoration reserve framework. The project establishes a commercial and regulatory precedent for standalone storage in Croatia’s transmission system.
Romania is developing the region’s next large storage market, with about 1.16 GW of battery power capacity and 2.31 GWh of energy capacity reported for October. Its project pipeline exceeds 9 GW. Greece has around 800 MW of storage connected and is using it to reduce renewable energy curtailment.
As regional markets scale, cross-border balancing and intraday integration are expected to become more valuable. Local flexibility can be exported economically only when market rules and transmission capacity allow it. The European Union Agency for the Cooperation of Energy Regulators (ACER) said its 2026 market-integration work shows day-ahead markets have largely moved to 15-minute products, while access to cross-zonal capacity remains weaker in intraday and balancing timeframes.
Congestion-management costs reached 5.4 billion euros in 2025, strengthening the case for flexible assets and market rules that can move electricity across time and space. Battery financing should account for multiple accessible revenue sources and the risk of rising competition for each. Energy arbitrage, balancing, renewable optimisation and contracted services should be assessed against the same physical operating limits.