Rapid battery deployment across Southeast Europe is expected to narrow the price spreads behind merchant arbitrage and reduce prices for some balancing services. Investors in long-term storage projects will need to account for competition and test whether revenues remain acceptable after material declines in arbitrage capture and ancillary-service prices. Batteries competing with one another are a key long-term risk to returns.
Bulgaria’s storage fleet exceeds 6.2 GW of power capacity and 19 GWh of energy capacity, according to the latest estimates. Romania had 1,162 MW of storage power capacity and 2,312 MWh of storage energy capacity at 1 October; the year was not specified. Hungary has moved above 1 GW of grid-scale storage capacity.
Greece commissioned the 330 MW / 790 MWh Larissa battery energy storage system (BESS) in Thessaly in October 2026. A separate 100 MW / 200 MWh battery project is located at HELLENiQ ENERGY’s facilities in Thessaloniki; the available facts do not state that it has been commissioned.
Revenue models face changing price patterns
Batteries charge when prices are low, increasing demand, and discharge during high-price hours, adding supply. At scale, that shifts the price curve by making the midday trough less deep and evening peak less extreme. The first expected pressure is on arbitrage between solar-heavy midday hours and evening demand peaks, with the regional build-out developing quickly enough to change the curve within a single investment cycle.
Balancing markets face a separate risk. Relatively small amounts of fast-response capacity can saturate high-value services and push clearing prices lower. A narrower arbitrage spread does not necessarily make new storage uneconomic, but it changes the assumptions investors need to model.
Project timing matters: storage entering service in 2028 or 2029 should not be valued using 2026 price spreads. Long-term battery energy storage system models should assume that competing capacity will erode part of today’s arbitrage opportunity.
Investors can also assess value beyond standalone arbitrage. Four- or five-hour batteries can compete in different time windows from one- or two-hour systems, while batteries co-located with renewable generation can reduce curtailment and support shaped power purchase agreements. Industrial batteries can monetise demand optimisation and resilience; portfolio batteries can improve a trader’s imbalance position even as standalone arbitrage margins shrink. The market is shifting from first-mover economics toward operating excellence.