Bulgaria is leading Southeast Europe’s shift towards using batteries to move solar electricity from midday to later hours. The country had around 7.2 GW of installed solar capacity by October, and photovoltaic generation reached 1,165 GWh in August 2026. Its battery fleet exceeds 6 GW, creating a large structural source of demand during solar-generation hours. As a result, some surplus solar power is being stored instead of generating little or no value when produced.
Battery operators can buy electricity in the middle of the day, absorb losses from battery inefficiency and sell the remaining power later, when it is more valuable to the system. They are emerging as buyers alongside industrial consumers and exporters, using storage to shift electricity between hours.
Serbia records negative day-ahead prices
SEEPEX began allowing negative prices in Serbia in May 2026, and the first negative day-ahead price hour occurred on 10 May. Such prices can give storage operators a potentially negative acquisition cost for surplus electricity. However, these hours should not be treated as a permanent feature of project economics.
Growing battery demand is expected to put a floor under some of the steepest solar-price collapses. Renewable developers can also capture value by co-locating storage with generation, keeping the time-shifting margin rather than selling the cheapest-hour electricity to an external storage operator.
