Bulgaria’s battery storage power capacity has surpassed 6.2 GW, while storage is also expanding in Romania and Greece. Romania had 1.162 GW of storage on 1 October. In Greece, a 330 MW / 790 MWh battery in Thessaly and a separate 100 MW / 200 MWh HELLENiQ battery project were commissioned in October.
Power trading has traditionally centred on generation, consumption and cross-border transmission. Storage adds a fourth dimension: time. It enables traders to sell electricity at a different time from when it was generated or imported, adding another option to their portfolios.
Battery fleets can absorb and release energy in volumes comparable to major interconnector flows. Traders increasingly have to choose whether to transmit electricity immediately or store it for a later sale, rather than focusing only on where power is cheapest. Storage can retain energy during a congested period, reduce imbalance or let a portfolio wait for a better intraday price.
Storage shifts power across time
This flexibility can make storage economically equivalent to a form of temporal transmission capacity. Its effects are expected to be strongest in markets with high solar penetration and constrained evening electricity supply, where batteries can hold some low-value midday solar output and export it later.
Moving exports from midday to later hours can alter the price signal in neighboring countries and reduce the value of some traditional cross-border strategies. Southeast Europe’s leading trading platforms will need to optimize location, timing and state of charge at the same time.
