In Bulgaria, the battery fleet is estimated at more than 19 GWh, a scale that makes its potential impact on prices a regional issue. As battery deployment expands across Southeast Europe, evening premiums that have made storage commercially attractive are expected to narrow. A more stable price profile is expected, although occasional extreme events may still occur.
Solar generation pushes prices down around midday, then prices rise as solar output declines, demand stays high and flexible generation becomes scarce. In Serbia in August, midday prices were around EUR 66/MWh, while prices averaged roughly EUR 244/MWh around hour 20. Charging batteries before the evening demand ramp and discharging during it could raise the low-price trough and reduce the evening peak.
Batteries are not expected to eliminate the evening premium. Weather, hydrological conditions, thermal plant outages, interconnector congestion and demand can still cause scarcity events that batteries cannot address. Longer-duration storage could also sustain an evening premium later into the night, after two-hour systems have run out of stored energy.
Investment returns and revenue sources
The expected narrowing of the average evening premium could affect project returns. A project commissioned in 2028 should not be valued using the 2026 evening price curve. Developers are advised to model storage additions in every major neighbouring market before a project reaches mid-life.
The investment case is expected to change, not disappear: the premium remains investable but should be treated as a declining resource. Batteries may earn less from routine daily cycling and more by selecting the most valuable days. They can also provide balancing services and support portfolio optimisation.
