Electricity.Trade’s May 2026 analysis identifies hydrological conditions as a key factor shaping the Southeast Europe electricity market. The report describes a divide between countries with stronger hydro generation and those seeing declining output. It also notes that the region did not experience uniformly wet or dry conditions, with variations in hydroelectric production affecting trade flows and import needs.
May hydro increases in exporter markets
Hydro generation rose month-on-month in several markets during May. Greece recorded the strongest increase, with hydro output up 40.80%. Italy followed with a 12.45% rise, while Bulgaria reported a 7.30% gain.
The improved hydro availability supported domestic supply and reduced dependence on thermal generation. It also supported cross-border electricity exports. Greece became a major net exporter with 874.20 GWh of net exports, while Bulgaria exported 258.65 GWh.
Italy remained a net importer despite the stronger hydro and renewable generation contribution. Its electricity imports fell 16.41% to 3,706.01 GWh. The change reflected lower import volumes alongside improved generation conditions.
Hydro declines raise import requirements
Hydro production weakened across several other Southeast European markets during May. Serbia saw the sharpest decline, with hydro output down 31.68%. Hungary followed at 29.10%, Croatia at 21.17%, and Romania at 6.96%.
The fall in hydro generation translated into higher import needs in each market. Serbia imported 422.97 GWh of electricity during the month. Croatia’s net imports increased to 583.90 GWh, while Hungary remained heavily dependent on imports at 1,076.31 GWh.
Romania recorded net imports of 440.59 GWh. Across these markets, reduced hydro output aligned with increased reliance on external supply to cover demand and balance the system.
Hydropower’s role amid expanding renewables
The analysis links hydropower to both electricity generation and system flexibility in the region. Strong hydro output can reduce reliance on fossil-fuel generation and support electricity exports. It also enables power systems to respond efficiently to fluctuations in demand and renewable generation.
As solar and wind capacity continues to expand across Southeast Europe, hydropower’s balancing role becomes more prominent for grid stability. Electricity.Trade highlights that hydrological variability can affect trade flows and market balances when water availability changes within monthly timeframes.
Country-level examples from Serbia and Croatia
Serbia illustrates how weaker hydro can coincide with higher import needs even when other fuels remain significant in the generation mix. Coal and lignite accounted for 56.99% of Serbia’s electricity generation mix in May, while weaker hydro production combined with higher electricity demand increased the need for imports.
Croatia faced a different balance between generation sources and cross-border supply. Net imports represented 43.78% of Croatia’s electricity mix, while hydro accounted for 22.83% of generation in May.
The decline in Croatia’s hydro output increased reliance on neighbouring electricity markets, aligning with the broader pattern of hydrological variation influencing import requirements across Southeast Europe.
Interconnected river basins and market sensitivity
The report attributes regional sensitivity to hydrology to the structure of interconnected river basins across Southeast Europe . It says monthly hydrological conditions vary significantly, so changes in water availability can rapidly alter electricity trade flows and import requirements.
