Recent commentary has suggested that Greece exports surplus renewable electricity to Bulgaria during the middle of the day, when solar PV output peaks and wholesale electricity prices are low, only for Bulgaria to store part of this electricity and sell it back to Greece at a higher price after sunset.
While this narrative has gained traction, analysis of the available data tell a different story.
Bulgaria is indeed the main destination for Greece’s electricity exports. According to the latest data published by the Independent Power Transmission Operator (IPTO), net electricity exports exceeded 3.5 TWh during the first four months of 2026. Nearly 2.1 TWh, or around 60%, was exported to Bulgaria, making it by far Greece’s largest export market. North Macedonia and Italy followed with net imports of approximately 1 TWh and 0.84 TWh, respectively.
The growing attention to Greece’s electricity exports is also justified by their rapid increase. In just the first four months of 2026, net exports had already surpassed the total recorded during the whole of 2025 (around 3 TWh).
Greece exports electricity to Bulgaria throughout the day
Hourly ENTSO-E data, however, paint a markedly different picture from that presented in much of the recent public debate.
During the first half of 2026 (up to 27 June), Greece was a net exporter of electricity to Bulgaria for 3,601 hours, equivalent to 84% of all hours during the period.
As shown in Figure 1, average net exports remain remarkably stable throughout the day, ranging from 325 MW between 01:00–02:00 to 402 MW between 23:00–00:00.
Perhaps more importantly, exports are not concentrated around midday, when solar PV generation reaches its peak. Instead, the highest average net exports occur during the evening, between 21:00 and midnight, averaging 398 MW. During the solar peak hours (12:00–15:00), average net exports are slightly lower, at around 386 MW.
The data therefore do not support the view that Bulgaria imports Greek electricity only because abundant midday solar generation temporarily depresses prices. Rather, Bulgaria imports electricity from Greece consistently throughout the day. Nor do the data support the claim that Bulgaria systematically exports electricity back to Greece during the evening. Even after sunset, electricity flows remain overwhelmingly in Greece’s favour, with exports substantially exceeding imports.
Figure 1. Average hourly electricity generation in Greece by technology and average net electricity exports to Bulgaria during the first half of 2026.
Greek electricity exports are not exclusively renewable
Figure 1 also sheds light on another widespread misconception. Greece does not export only renewable electricity to Bulgaria. A substantial share of exported electricity is generated by fossil gas-fired power plants.
The evening hours provide a striking example. Between 21:00 and 22:00, when average net exports to Bulgaria reach approximately 400 MW, fossil gas-fired plants generate an average of 3,423 MW, accounting for 49.4% of Greece’s total electricity generation. This exceeds the combined output of wind (1,557 MW) and hydropower (1,599 MW) over the same period.
The broader picture is equally revealing. An analysis of ENTSO-E’s hourly data shows that during the 3,601 hours when Greece was a net exporter to Bulgaria, the energy-weighted average generation mix consisted of 37.4% fossil gas, 24.8% wind, 17.7% solar PV, 15.1% hydropower, and 5.1% lignite (Figure 2)
Figure 2: Greece’s electricity mix during the hours that Greece is a net exporter of electricity to Bulgaria
These figures make clear that Greece’s electricity exports to Bulgaria cannot be characterised as exports of renewable electricity alone. Throughout most export hours, a significant share of the exported electricity is generated from fossil gas.
Why Did Greece Become a Net Electricity Exporter to Bulgaria?
The shift in electricity trade flows between Greece and Bulgaria in 2026 is closely linked to changes in wholesale electricity prices. Electricity in interconnected markets naturally flows from lower-priced to higher-priced bidding zones. It is therefore no coincidence that Greece recorded lower average wholesale electricity prices than Bulgaria throughout every hour of the day during the first half of 2026, as shown in Figure 3.
Figure 3. Comparison of average wholesale electricity prices in Greece and Bulgaria during the first half of 2025 and 2026.
What is particularly striking, however, is how dramatically the situation changed compared with the previous year. During the first half of 2025, wholesale electricity prices in Greece were significantly higher than in 2026 and exceeded Bulgarian prices for roughly half of the day, including the midday hours when solar PV generation peaked. As a result, Greece was a net importer of electricity from Bulgaria during more than half of all hours in the first half of 2025, including the period between 13:00 and 16:00, despite the strong contribution of solar generation (Figure 4). Overall, up to 27 June 2025, Greece imported more electricity from Bulgaria than it exported. Specifically, Bulgaria was a net exporter to Greece for 2,266 hours, while Greece was a net exporter for 1,999 hours. One year later, the pattern had completely reversed. During the first half of 2026, Greece became a net exporter for 3,601 hours, reflecting the equally dramatic reversal in the price relationship between the two markets.
In other words, the sharp increase in electricity exports to Bulgaria was not the result of Bulgaria charging its storage facilities with cheap Greek solar power during the day. Rather, it was driven by the fact that electricity became consistently cheaper in Greece than in Bulgaria, making exports economically attractive for most hours of the day.
Figure 4. Average hourly electricity generation in Greece by technology and average net electricity exports to Bulgaria during the first half of 2025.
What Drove the Decline in Greek Wholesale Electricity Prices?
A comparison of Greece’s electricity generation mix in the first halves of 2025 and 2026 provides an important insight.
Contrary to what might be expected, fossil gas-fired generation changed very little overall. Output remained broadly stable during the morning and evening hours and declined only around midday, when renewable generation was highest. Across the entire six-month period, electricity generation from fossil gas fell only marginally—from 10.23 TWh in the first half of 2025 to 9.86 TWh during the same period in 2026.
The key change therefore lay elsewhere.
Analysis of IPTO’s day-ahead market forecasts (ISP2 and ISP3) shows that fossil gas-fired and lignite-fired power plants set the wholesale market clearing price much less frequently in 2026.
As illustrated in Figure 5, fossil gas was the marginal technology for 2,262.75 hours during the first half of 2026, equivalent to 52.7% of all hours. This represents a reduction of 593.25 hours compared with the same period in 2025, when fossil gas determined the Day-Ahead Market (DAM) clearing price during nearly two-thirds of all hours (66.5%). The contribution of lignite as the marginal technology also declined, albeit from a much lower level, falling from 81 hours in the first half of 2025 to 56 hours in 2026. At the same time, hydropower and renewables increasingly became the technologies setting the market clearing price, exerting downward pressure on wholesale electricity prices.
The relationship between marginal pricing and wholesale prices is particularly evident in February. During that month, the number of hours in which fossil gas set the market price fell by 43%, from 542.5 hours in 2025 to 309.5 hours in 2026. Over the same period, the average monthly wholesale electricity price almost halved, dropping from €154.1/MWh to €78.3/MWh.
This was not a coincidence. It reflected a fundamental shift in the composition of Greece’s electricity generation mix.According to ENTSO-E data, electricity generation during the first half of 2026 increased by 155.8% from hydropower, 31.7% from wind and 6.6% from solar PV compared with the same period in 2025.
The rapid expansion of clean electricity generation substantially reduced the number of hours during which expensive fossil-fuel plants acted as the marginal generators. Overall, the combined number of hours in which fossil gas and lignite determined the wholesale market price fell by 21%, contributing to a 15% decline in Greece’s average day-ahead wholesale electricity price—from €108.4/MWh in the first half of 2025 to €92.1/MWh during the corresponding period of 2026.
The decline in wholesale prices was therefore driven not by a sharp reduction in fossil gas generation, but by the fact that renewables and hydropower increasingly displaced fossil fuels from the price-setting position in the market.
Figure 5. Comparison between the first halves of 2025 and 2026 in the number of hours during which fossil gas-fired power plants set the wholesale market clearing price.
Policy Implications
The analysis challenges the increasingly common narrative that Greece exports surplus renewable electricity to Bulgaria during the day only to import it back at higher prices in the evening.
The data show that Greece exports electricity to Bulgaria throughout the day, not just during periods of peak solar generation. Moreover, these exports are not exclusively renewables. During the first half of 2026, fossil gas accounted for 37.4% of Greece’s electricity generation during the hours of net exports to Bulgaria, highlighting the significant contribution of fossil gas-fired power plants to cross-border electricity trade.
The sharp increase in exports however, was driven by the rapid expansion of renewable electricity and hydropower generation, which substantially reduced the number of hours during which expensive fossil-fuel plants set wholesale electricity prices. Lower wholesale prices widened the price differential between Greece and neighbouring markets, making Greek electricity increasingly competitive and leading to a dramatic increase in exports to Bulgaria.
At the same time, however, the growing penetration of renewables exposed an important weakness in the current market design.
The increasing number of zero and negative price hours (778), together with rising renewable energy curtailments (1.56 TWh by 27 June), reduced revenues for renewable generators despite record levels of clean electricity production.
Paradoxically, the principal beneficiaries of these lower wholesale prices were not renewable generators but fossil gas-fired power plants. By taking advantage of lower market prices created by abundant renewable generation, they were able to increase electricity production and supply neighbouring markets. In effect, the price-suppressing effect of renewables improved the competitiveness of fossil gas generation while reducing the revenues of renewable producers—an example of renewable energy cannibalisation. This distortion is particularly problematic at a time when fossil gas prices remain elevated due to geopolitical tensions affecting global energy markets.
Accelerating the deployment of electricity storage is therefore essential.
Greater storage capacity would reduce renewable energy curtailments, improve the utilisation of low-cost renewable electricity and reduce reliance on fossil gas during evening demand peaks. It would also place further downward pressure on wholesale electricity prices.
Because wholesale and retail electricity prices remain closely linked in Greece, these benefits would ultimately be passed on to consumers through lower retail electricity bills.
At the same time, maintaining a competitive wholesale price advantage over neighbouring markets—particularly those that continue to rely heavily on expensive fossil fuels, such as Bulgaria, Italy and North Macedonia—would help sustain Greece’s position as a net electricity exporter.
Unlike today, however, those exports would increasingly be supported by clean electricity rather than fossil gas. The result would be a lower-carbon electricity system, lower costs for Greek consumers and stronger competitiveness for Greece’s energy-intensive industries and the wider economy.
