Battery storage is expanding rapidly across Southeast Europe, narrowing the volatility-driven trading opportunity that initially attracted investment. Hungary’s observable capacity exceeded 1 GW later in 2026, while more batteries trading can reduce price differences. The build-out is making conservative long-term forecasts important for assessing returns.
Bulgaria’s latest estimate put storage at more than 6.2 GW of power and 19 GWh of energy. Romania’s installed storage power rose from 494 MW at the start of 2026 to 1,162 MW by October, an increase of about 668 MW. In Hungary, observable capacity climbed from 197 MW in January 2026 to 778 MW by July and continued above 1 GW later in the year.
Early battery investors can earn scarcity rents that later projects may find difficult to reproduce. Capitalising those early returns over the full life of every new battery risks assuming competitors will not respond. A 15-year valuation based on today’s highest spreads effectively makes that assumption, even as storage capacity grows.
A stronger approach treats storage penetration as an endogenous variable, so expected market entry is reflected in projected returns. As capacity rises, ordinary arbitrage margins compress and balancing markets become more competitive. Current spreads therefore should not automatically be assumed to persist throughout a battery’s operating life.
As storage markets mature, value shifts toward location, duration, contract structure and portfolio integration. Batteries behind constraints or with access to higher-value services can still outperform. The investment case increasingly depends on assets’ ability to earn revenue beyond simple arbitrage, as well as on their position and service options.
The storage thesis remains intact, but the sector is expected to mature from a simple volatility trade into an infrastructure-and-optimisation business. The most successful batteries will remain useful after helping reduce the volatility that first attracted investment.