Battery storage is adding a timing dimension to power trading in Southeast Europe, requiring traders to consider when to sell electricity as well as where to sell it and the battery’s state of charge. Bulgaria’s battery fleet has exceeded 6.2 GW of storage power, while capacity is also growing in Romania and Greece. Romania had 1.162 GW of storage on 1 October, and two battery projects were commissioned in Greece in October.
The Greek projects were a 330 MW / 790 MWh battery in Thessaly and a separate 100 MW / 200 MWh HELLENiQ battery project. Traditionally, power trading has focused on generation, consumption and cross-border transmission. Storage adds time as a fourth dimension, allowing electricity to be sold at a different time from when it was generated or imported and adding another option to traders’ portfolios.
Battery fleets can absorb and release energy at volumes comparable with major interconnector flows. Traders are increasingly weighing whether to transmit electricity immediately or store it for a later sale, rather than looking only at where power is cheapest. Storage can carry energy through a congested period, reduce imbalance or allow a portfolio to wait for a better intraday price.
Storage changes the timing of cross-border trade
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 later-day electricity supply, where batteries can retain some low-value midday solar electricity and export it later. Shifting exports from midday to later in the day can alter the price signal seen by neighbouring countries and reduce the value of some traditional cross-border strategies.
Southeast Europe’s leading trading platforms will need to optimise location, timing and state of charge simultaneously.