Southeast Europe’s renewable generators are set to face a different price pattern this autumn, with shorter daylight hours reducing extreme solar oversupply and increasing the value of electricity delivered after sunset. Summer 2026 saw repeated zero and negative-price periods across Greece, Bulgaria, Romania, Hungary, Croatia and Slovenia. The episodes were linked to solar generation expanding faster than storage and flexible demand.
Midday zero prices and evening price spikes in 2026
By early September, several markets were trading around or below zero during midday. Those same markets then moved above €225/MWh in the evening. The change is expected to start in October, when the seasonal balance between solar output and demand shifts.
Lower solar output combined with fewer daylight hours is expected to shorten the duration of zero-price periods. That shift should also improve the captured price achieved by photovoltaic projects. At the same time, reduced solar production is expected to remove cheap electricity from the late afternoon.
With less low-priced power available later in the day, the evening scarcity ramp is expected to move earlier. This timing change affects how quickly prices rise toward evening peaks. Wind generation is also expected to become relatively more valuable as solar cannibalisation eases.
Wind and hydro value under changing seasonal supply
Autumn conditions typically bring stronger wind and less dependence on daylight. This allows wind projects to produce outside the period when solar output is most heavily cannibalised. Hydro remains the most valuable renewable flexibility source where water is available.
Where reservoir resources exist, operators can preserve output during weak-price hours and dispatch into evening peaks. The market therefore points toward diversification rather than only adding more renewable megawatts. Solar-plus-storage configurations are expected to perform better than equivalent standalone PV during volatile days.
Wind and hydro are described as retaining stronger natural production profiles compared with solar under these seasonal dynamics. The key operational issue for batteries is whether deployment keeps pace with growing renewable surpluses. Romania already has more than 1 GW of operating BESS and 2.3 GWh, alongside a rapidly expanding pipeline.
BESS capacity growth versus regional flexibility needs
Even with that expansion, regional storage remains small relative to total peak demand. October is therefore expected to reduce solar cannibalisation without removing the underlying flexibility premium. The shift in price dynamics continues to be tied to how quickly batteries absorb surplus generation as autumn progresses.
