Renewables ranked first in electricity generation and reached a 9-month high in May with 2,573 GWh, despite significant curtailments (418 GWh, or 14% of RES generation) and the comparatively higher absorption by the first batteries (9.5 GWh, accounting for just 2.2% of RES curtailments). In addition, there was an increase in production from fossil gas and lignite compared to the previous month, resulting in the average monthly price on the day-ahead market remaining the same as in April at 89 €/MWh. Cumulatively, the first five months of 2026 saw record levels for both RES generation (11,930 GWh) and RES curtailments (1.3 TWh), as well as for net exports (4,484 GWh).
This analysis concerns electricity production across the entire territory of Greece and is based on the latest available monthly data from the Independent Power Transmission Operator (IPTO) for the interconnected grid (May 2026) and from the Hellenic Electricity Distribution Network Operator (HEDNO) for the non-interconnected islands (April 2026). In addition, we use data from HEDNO for low and medium voltage, as well as for the installed capacity of self-production systems (April 2026). Data from the Renewable Energy Special Account bulletin of the Renewable Energy Sources & Guarantees of Origin Operator (DAPEEP) (February 2026) are used to calculate more accurately CHP production at low and medium voltage, as well as for the PV utilization factors needed to estimate self-production. Finally, for the wholesale electricity market we use price data of the Day-Ahead Market from ENTSO-E. You can read in more detail about our methodology here.
May
In May 2026, RES increased by 20.8% compared to April, reaching 2,573 GWh and a 9-month high, ranking first in electricity generation for the fifth consecutive month. Compared to May of last year, RES increased by 16.3%.
Fossil gas ranked second with 1,528 GWh, up 13.9% from the previous month. Compared to May 2025, fossil gas fired generation increased by 4.9%.
Large hydro plants ranked third with 470 GWh, marking the highest electricity generation for the month of May in the last decade. Compared to April, large hydro plants increased by 39.3%, while compared to May of last year, they increased by 83%.
Lignite ranked fourth with 207 GWh. During the final month of operation of the Agios Dimitrios power plant, lignite generation increased by 4.9% compared to the previous month, while it was more than double the output from May of last year (79 GWh).
Oil followed for the non-interconnected islands at 166 GWh, up 18.8% compared to April but down 42.9% compared to May 2025.
Finally, large-scale battery storage systems absorbed a total of 9.5 GWh, while feeding 8 GWh back into the grid—more than double the amounts recorded in April.
Total domestic demand in May was 4,063 GWh, up 2.3% from April but down by the same percentage compared to May 2025. Total domestic electricity generation was 4,953 GWh, up 19.4% compared to the previous month
In terms of the interconnection balance, the country recorded net exports of 890 GWh, nearly five times the exports in April and returning to levels close to those of March (1,061 GWh), as maintenance work on the interconnections with Italy and Albania was completed[1]. Compared to last May, when the country was once again a net exporter, net exports were more than six times higher.
The average price on the wholesale energy market (day-ahead market) in May stood at 89 €/MWh, remaining at the same level as in April, thanks to high levels of electricity generation from RES and the relatively moderate increase in fossil gas and lignite.
Historical comparison – first five months of the year
When comparing the first five months of 2026 with previous years, RES ranked first with 11,930 GWh, setting a record for electricity generation.
Fossil gas ranked second with 8,853 GWh and the second-highest electricity generation for this period of the year, while it was just 20 GWh below last year’s record (8,873 GWh).
Large hydro plants ranked third, with a record electricity generation of 3,332 GWh for the first five months of the year.
Lignite followed with 1,276 GWh, marking a historic low, while oil, at 720 GWh, also recorded a historic low for this period of the year.
Energy injected from storage systems totaled 11 GWh after two months of operation.
For the first five months of 2026, domestic demand reached 21,621 GWh, representing a 1.4% decrease compared to 2025, while total electricity generation reached 26,130 GWh, an increase of 16.2% compared to 2025.
In terms of the interconnection balance, the country recorded a record 4,484 GWh in net exports for the first five months, nearly 50% more than the total net exports for the entire year of 2025.
Changes in the shares of energy sources in demand coverage
Comparing the first five months of 2026 with the first five months of 2025, it is clear that the three fossil fuels (lignite, fossil gas, and oil) decreased by a total of 601 GWh, with the largest decrease coming from oil (-510 GWh) due to the completion of the Crete interconnector. This amount, combined with a 310 GWh increase in domestic demand, resulted in a total of 911 GWh that was more than offset by the increase in renewables (+2,002 GWh). Thus, a large portion of the increase in RES, as well as the even greater increase in large hydro (+2,221 GWh), went toward electricity exports to neighboring countries, as these rose by 3,919 GWh compared to the same period in 2025.
As for renewables, the increase during this period of the year appears to be driven by both wind and solar power. As an indication of this upward trend, wind power generation at high voltage reached 5,295 GWh (+31% compared to 2025), while solar power generation at high voltage reached 1,902 GWh (+36.6% compared to 2025).
The corresponding year-on-year percentage changes for the first five months of 2026, compared to 2025, were:
Lignite: -5.2%
Fossil gas: -0.2%
Oil: -41.5%
Renewables: +20.2%
Large hydro: +200%
Net exports: +693.3%
Demand: -1.4%
Comparison of clean energy with fossil fuels
In the first five months of 2026, clean energy sources (wind, solar, hydroelectric, biomass, self-production) with a total output of 15,262 GWh, reached an all-time high, surpassing fossil fuels (lignite, fossil gas, oil), which totaled 10,848 GWh. The difference between the two stood at 4,414 GWh.
Compared to the same period in 2025, clean energy sources saw a 38.3% increase, while fossil fuels, by contrast, decreased by 5.3%. Thus, clean energy reversed the trend seen in 2025 for the first five months of the year, taking the lead in meeting domestic demand with a 70.6% share, and in electricity generation with a 58.4% share.
Energy curtailment from RES
Based on the combination of forecasts shown in the ISP2 and ISP3 solutions of the consolidated planning process of the IPTO, RES curtailments in May are estimated at 418 GWh (or 14% of RES generation), down 12% compared to April, but up 9% compared to the RES curtailments in May 2025. Cumulatively for the first five months, total curtailments are estimated at 1,303 GWh (9.9% of total RES production), marginally like the total curtailments in the first half of 2025 (1,327 GWh).
The day with the highest curtailments was Saturday, May 2, 2026, with curtailments of 35.9 GWh (or 8.6% of the month’s total curtailments). Most curtailments in May occurred between 9 a.m. and 3 p.m.
Energy storage
The status of the system’s first batteries remained unchanged throughout May, as the first seven units continue to operate with a total installed absorption capacity of 210 MW and an injection capacity of 201.28 MW[2]. According to IPTO’s ISP2 and ISP3 forecasts, the batteries absorbed energy in May primarily between 8:00 a.m. and 3:00 p.m. and secondarily between 1:00 a.m. and 2:00 a.m., while they discharged energy primarily between 4:00 PM and 11:00 PM and secondarily between 4:00 AM and 7:00 AM.
Overall for the month of May, according to IPTO’s ISP2 and ISP3 forecasts, the batteries absorbed 10.24 GWh and supplied 8.83 GWh to the system[3]. However, the same forecasts indicate that 0.91 GWh was absorbed during hours when there were no RES curtailments. Given that total curtailments in April amounted to 418 GWh, it follows that the installed batteries prevented 2.2% of RES curtailments, while the 8.83 GWh injection reduced gas consumption by just 0.6% during the same month. These figures highlight the need to accelerate the installation of more batteries that already have connection permits (1,418.9 MW)2 in order to prevent far more curtailments and reduce gas consumption during evening peak hours to a much greater extent.
Accelerating the deployment of storage systems was also the subject of the trilateral agreement signed at the Energy Council on June 26, 2026, highlighting the need to install 200 GW of storage capacity by 2030 to support the energy system[4].
Hours with near-zero or negative prices
As for hours with near-zero or negative prices[5] on the wholesale electricity market, May 2026 saw 218 hours, 35 hours more than the previous month and 162 hours more than May 2025. In total, during the first five months of 2026, there were 642 hours with zero or negative prices, while during the same period in 2025, this occurred for only 124 hours — that is, just 19.3% of the total hours with negative or near-zero values in 2026.
[1] However, there were unplanned works for two days during May which affected interconnections with Albania, North Macedonia and Bulgaria https://bit.ly/3TbOJRj
[2] Based on the latest available data from IPTO (April 2026)
[3] However, based on IPTO’s Monthly Report for April, batteries consumed 9.53 GWh and they injected 8.04 GWh into the system, both at lower levels than predicted in ISP2 and ISP3 solutions.
[4] First-ever EU tripartite agreement signed to boost energy storage: https://ec.europa.eu/commission/presscorner/detail/en/ip_26_1426
[5] We consider as near-zero all prices below 0.05 €/MWh.
