Battery storage is expanding rapidly across Southeast Europe, narrowing the volatility-driven trading opportunity that initially attracted investment. As more batteries enter the market, price differences can shrink, making conservative long-term forecasts essential 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 2026, an increase of about 668 MW. Hungary’s observable capacity grew from 197 MW in January 2026 to 778 MW by July 2026 and continued above 1 GW later in 2026.
Early battery investors can earn scarcity rents that later projects may find difficult to reproduce. But projecting those early returns across the full operating life of every new battery risks assuming competitors will not respond. That assumption is particularly consequential when a battery is assessed over a 15-year period.
A stronger valuation model treats storage penetration as an endogenous variable, so anticipated market entry affects projected returns. A 15-year valuation based on today’s highest spreads effectively assumes competitors never respond, despite the build-out changing market conditions.
As storage capacity rises, ordinary arbitrage margins compress and balancing markets become more competitive. Current spreads therefore should not automatically be treated as lasting throughout a battery’s operating life. As the market matures, value shifts toward location, duration, contract structure and portfolio integration.
Some batteries can still outperform if they are located behind constraints or have access to higher-value services. The investment case increasingly depends on those characteristics and revenue options, rather than volatility alone. Hungary’s capacity above 1 GW later in 2026 reflects the scale of the regional expansion.
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 initially attracted investment.