Southeast Europe’s energy transition effort has evolved beyond an exclusive focus on renewable capacity additions, with success now hinging on how effectively power systems can integrate green electricity, according to Sofia-based business intelligence provider SeeNext. In its latest analysis published today, SeeNext focuses on the decisive role of flexibility.
SeeNext’s analysis, “Renewable Energy in Southeast Europe: Flexibility as the new capacity,” explores developments in the region’s five largest economies: Romania, Bulgaria, Croatia, Greece and Serbia. The study examines renewable energy targets, capacity growth across solar, wind and hydropower, the increasing importance of flexibility through battery storage, pumped hydro storage, grid consolidation and recent investment activity.
Green capacity
By the end of 2025, Greece remained the regional leader in installed renewable capacity with 21.11 GW, followed by Romania with 16.51 GW and Bulgaria with 9.15 GW. Croatia and Serbia reached 4.98 GW and 4.35 GW, respectively. Bulgaria recorded the fastest annual renewable capacity growth at 18.4%, followed by Romania at 17.1% and Greece at 15.6%.
Solar power remained the dominant driver of renewable capacity growth in 2025, accounting for between 88% and nearly all additions in four of the five markets. Serbia stood out as the only market where wind was the main contributor to renewable growth, accounting for 71% of annual additions.
Batteries step in
As solar deployment accelerated, signs of midday market saturation have begun to emerge in several countries, shifting attention toward system flexibility as a way to mitigate risks of curtailment and price volatility.
Bulgaria stood out as the region’s premier battery market in 2025 after installing 2.5 GWh of new grid-connected battery energy storage system (BESS) capacity, up from just 0.2 GWh a year earlier, making it the EU’s third-largest BESS market behind Germany and Italy. Romania also recorded sharp growth, reaching 914 MWh of BESS capacity in 2025, compared with 268 MWh in 2024.
Future battery deployment suggests strong momentum across the region. Bulgaria leads in this respect, projected to reach between 7 GWh and 10 GWh of installed batteries by the end of 2026. Romania’s publicly backed pipeline of 3.72 GWh already singlehandedly points beyond its official 2030 policy target of 2.4 GWh, while Serbia has a development pipeline exceeding 2 GW. In Greece, a 4.7-GW government call for standalone batteries underscores ambition, although financing conditions may limit implementation. Croatia’s policy ambitions are modest, but data suggests a pipeline of roughly 700 MW could materialise, should grid connection conditions improve.
Energy systems of the future
The analysis also finds varying levels of ambition towards the EU’s 2030 renewable energy target of at least 42.5% of final gross energy consumption. Greece and Croatia are the only two countries in the group to match or exceed the EU benchmark, targeting 43% and 42.5%, respectively. Meanwhile, Romania targets 38.3%, Bulgaria 35% and Serbia 33.6%.
The next phase of Southeast Europe’s energy transition will be defined by flexibility as storage and stronger grids are becoming essential to connect new renewable capacity, manage variability and create a more stable investment environment.
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