Rapid battery deployment across Southeast Europe is expected to narrow merchant-arbitrage spreads and lower prices for some balancing services, according to a regional outlook. The change raises the revenue hurdles for long-term projects, which need to remain viable if arbitrage and ancillary-service prices fall materially.
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 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 information does not say it has been commissioned.
Competition changes revenue assumptions
Batteries charge during low-price hours, increasing demand, and discharge during high-price hours, adding supply. At scale, this activity can make midday price troughs less deep and evening peaks less extreme, compressing the spread between solar-heavy midday hours and evening demand peaks. The regional fleet is developing quickly enough to change the price curve within a single investment cycle.
Balancing markets face a separate pressure: relatively small amounts of fast-response capacity can saturate high-value services and push clearing prices lower. A narrower spread does not necessarily make new storage uneconomic, but investors need to test whether revenues remain acceptable after a material reduction in both arbitrage capture and ancillary-service prices.
Project design and operating strategy can provide value beyond standalone arbitrage. Four- or five-hour batteries can compete in different time windows from one- or two-hour systems. Co-location with renewable generation can reduce curtailment and support shaped power purchase agreements, while industrial batteries can monetise demand optimisation and resilience. Portfolio batteries can also improve a trader’s imbalance position as standalone arbitrage margins shrink.
Projects entering service in 2028 or 2029 should not be valued using 2026 price spreads. The market is shifting from first-mover economics towards operating excellence, and long-term battery energy storage system models should assume that competing storage will erode part of the current arbitrage opportunity.
