Day-ahead electricity prices across much of Central and Southeast Europe fell to zero or negative levels during Sunday’s solar peak before rebounding above €225/MWh in the evening, highlighting a widening shortage of flexibility.
Hungary, Romania, Slovenia and Croatia all posted negative prices around midday, while Bulgaria and Greece traded around zero for several hours as strong renewable output met lower weekend demand.
Hungarian power averaged about €113.8/MWh, falling to around -€1.5/MWh at 13:00 before rising to roughly €227.7/MWh at 20:00.
Romania followed a similar curve, dropping to around -€1/MWh before reaching about €227.7/MWh in the evening. Slovenia fell to -€1.18/MWh and Croatia to around -€0.93/MWh, while Bulgaria and Greece later climbed to roughly €225-227/MWh.
The simultaneous move shows that solar-driven oversupply is becoming a regional rather than isolated national event.
Interconnectors can redistribute excess generation, but their ability to absorb it falls when neighbouring markets are oversupplied at the same time.
The reverse occurs after sunset.
Solar output declines across the region simultaneously, increasing demand for hydro, gas, nuclear generation, batteries and imports and pushing competing markets toward the same limited pool of flexible supply.
The resulting intraday spreads strengthen the economics of battery storage and reservoir hydro while increasing price cannibalisation for standalone solar.
Electricity worth zero around midday was worth more than €225/MWh several hours later in some markets.
Serbia remained the main outlier.
SEEPEX averaged about €60.2/MWh, down roughly 47% day on day, with an evening peak near €134/MWh, substantially below Central and eastern SEE markets.
The divergence highlights continuing congestion and differences in national supply balances despite broader regional coupling.
The Sept. 6 session reinforces a structural shift already visible across Southeast Europe: additional solar capacity is increasingly creating cheap daytime electricity without eliminating expensive evening scarcity.
For investors, the relevant signal is therefore moving away from the daily baseload price toward the value of flexibility.
The region is increasingly producing enough renewable electricity, but still lacks sufficient storage, flexible demand and dispatchable capacity to move that energy into the hours when it is most valuable.