Greece is increasingly sending electricity to Bulgaria when the sun is producing cheap power, only to receive electricity back from its northern neighbour when demand and prices rise in the evening.
The unusual reversal is being driven by Bulgaria’s rapid expansion of solar generation and battery storage, according to a European Commission analysis published in October.
In other words, Greece supplies the daytime electricity. Bulgaria stores it. Bulgaria sends electricity back when the sun goes home.
The European Commission compared electricity flows between the two countries in August 2024 and August 2026 and found a striking reversal.
In August 2024:
- Bulgaria exported as much as about 800 MW per hour to Greece during daytime periods.
- Bulgaria generally imported electricity during evening peak hours.
In August 2026:
- Bulgaria imported up to 750 MW from Greece around midday.
- Bulgaria exported approximately 700 MW to Greece around 8 pm.
The reason is increasingly straightforward: Bulgarian batteries charge during hours when solar generation pushes electricity prices down, then discharge when demand rises.
The Commission says the shift allows Bulgaria to benefit from the difference between cheap daytime electricity and more expensive evening power, while also helping neighbouring electricity systems manage peak demand.
Bulgaria Built the Battery. Greece Supplied the Electrons.
Bulgaria’s solar expansion has been dramatic. Solar accounted for around 4% of Bulgarian electricity production in 2021. By 2026, that share had reached approximately 21%.
Installed photovoltaic capacity increased from:
- 1.3 GW in 2021
- 7.2 GW in 2026
European Union Recovery and Resilience funding supported a major part of this expansion. A 3.2 GW programme combined renewable generation with storage, while EU-backed investments helped push Bulgarian battery storage above 16 GWh.
At peak periods, batteries can now supply up to 30% of Bulgaria’s electricity generation, according to the Commission.
That storage changes the economics of solar power. Instead of having cheap electricity disappear when daytime production exceeds demand, Bulgaria can keep it and sell it later.
And some of that cheap daytime electricity is coming from Greece.
Greece Is Now Buying Back in the Evening
The consequences are becoming visible in Greece’s electricity trade. A recent analysis by Energiabook found that Greece exported electricity throughout the first half of 2026, particularly to Bulgaria. By the third quarter, the pattern had changed during evening peak hours, with Greece becoming a net importer and Bulgaria supplying much of that electricity.
The financial swing is striking. Greece recorded an electricity trade surplus of almost €290 million with Bulgaria during the first half of 2026.
In July–September, that relationship moved to a €58.3 million deficit.
The reason is simple enough to explain over coffee: Greece sells electricity when it is cheap and buys electricity when it is expensive.
Bulgaria’s Batteries Are also Helping Greece
There is another side to the story. When evening demand rises and solar production falls, electricity systems need another source of power. Bulgarian battery storage can supply part of that gap without relying entirely on fossil-fuel generation.
The Commission says the new cross-border pattern has helped stabilize electricity systems in the region, while stronger interconnections between Bulgaria, Greece and Romania allow power to move where it is needed.
Bulgaria also exported roughly 1 GW more electricity to Romania during August 2026 peak periods than two years earlier, after reduced output from Romania’s Cernavodă nuclear plant increased the need for imports.
Greece Is Building its Own Storage
The Energy Ministry reported 831 applications representing 12,319 MW for grid connection terms under a call covering battery projects of up to 4,700 MW.
The country has also added more than 7.5 GW of new renewable capacity through its Recovery and Resilience Plan, according to the European Commission.
The question is whether Greece can build enough storage quickly enough to keep more of the value created by its expanding renewable generation at home.