Serbia’s case should be read carefully. EMS has not technically “stopped all RES grid connections until 2030”; the practical effect is close to that for many new large wind and solar projects because the period for submitting applications for connection studies has been pushed to 1 September–31 December 2029. Existing projects that already obtained studies, approvals, guarantees or connection contracts can still move, but the next wave of merchant or early-stage RES is effectively pushed toward 2030+ grid access. That is why the market is treating Serbia as a de facto grid-capacity freeze for new large variable RES, even though legally it is framed as a delay in the connection-study procedure rather than a universal ban.
The same pressure exists across Southeast Europe, but the regulatory responses differ. Hungary is the closest to Serbia’s model: rapid solar growth strained the system, no new grid capacity was granted to solar or wind projects between 2022 and 2024, and the rules require rejection of generation projects that cannot be connected by 2030. A new competitive grid-capacity allocation regime is expected, with preference for projects offering batteries, balancing capacity, hybrid design and stronger financial guarantees.
Romania is not using a Serbian-style stop, but it is moving from a first-come, first-served queue toward competitive grid-capacity auctions and global solution studies. That is a market-based rationing mechanism: projects will compete for scarce capacity, and speculative connection requests should lose ground to bankable projects with financing, permits and grid-ready designs. The Romanian problem is not political reluctance to RES; it is the mismatch between a very large RES pipeline and the physical capacity of Transelectrica’s network.
Croatia has been constrained mainly by connection-cost and transmission-bottleneck uncertainty, not by a formal RES stop. The connection-fee problem delayed projects for more than three and a half years, and Croatia’s pipeline already exceeded its 2030 solar target on paper. The transmission system still has a large blocked capacity problem, including solar, wind, geothermal and standalone batteries awaiting grid solutions.
Montenegro is not frozen. CGES is still signing connection-infrastructure agreements, including a 70 MW solar connection agreement for the Tupan project, and earlier agreements covering nearly 1,500 MW of solar and wind capacity. The issue in Montenegro is different: the country has a small domestic load, a relatively narrow high-voltage backbone, a large investor pipeline and a strategic dependence on cross-border evacuation through Serbia, Bosnia and Herzegovina, Albania and the Italy submarine link.
Bosnia and Herzegovina is moving into the same grid-stability phase. The EBRD’s €46 million financing for variable shunt reactors is directly aimed at voltage stability, higher renewable integration and cross-border flows. That tells investors that the bottleneck is no longer only “is there enough line capacity?” but also reactive power, voltage control, operational security and the ability to handle dynamic RES injections.
Bulgaria is still connecting large volumes of RES, but it has introduced financial discipline. By the end of 2025, Bulgaria had nearly 7 GW of installed PV and wind, with another 1 GW expected in 2026. Investors must provide a deposit or bank guarantee of about €25,565 per MW during the connection process, which is designed to remove speculative projects. Bulgaria is also investing heavily in grid reinforcement, including the CARMEN project with Romania, four new 400/110 kV substations, more than 100 km of new 400 kV lines, and the GREENABLER upgrade programme.
North Macedonia, Kosovo and Albania are still in build-out mode, but their constraint is regional evacuation capacity. MEPSO and KOSTT signed a memorandum for the 400 kV Tetovo–Prizren interconnection, and MEPSO explicitly noted that Southeast Europe needs transmission capacity increases of at least two times, and in some cases more. That is one of the clearest official signals that the Western Balkans grid cannot absorb the RES pipeline without new cross-border infrastructure.
The congestion picture is therefore becoming clear. The region has three main congestion layers. The first is internal north–south and east–west transmission congestion, especially where solar is clustering in high-resource zones far from demand centres or export routes. The second is cross-border scarcity, where Serbia–Hungary, Serbia–Romania, Bulgaria–Romania, Bulgaria–Greece, Montenegro–Serbia/BiH and Albania–Kosovo/North Macedonia become price-setting borders in stressed hours. The third is system-flexibility congestion: even where wires exist, TSOs need batteries, pumped storage, voltage support, curative remedial action, dynamic line rating and better outage coordination to keep more capacity available to the market.
ACER’s 2026 assessment of Southeast Europe is especially important here. It found that the 2024 regional price spikes were driven by a lack of flexible resources during evening high-demand hours after solar output declined, combined with limited cross-border capacity and planned maintenance that constrained imports from lower-priced EU markets. ACER also estimated that many severe price spikes could have been avoided if the 70 per cent cross-zonal capacity target had been available, and it pointed to dynamic line rating, advanced conductors, better outage planning, remedial actions and market coupling as near-term tools to unlock capacity before new lines are completed.
The cross-border capacity build-out is real, but it is too slow for the RES pipeline. Serbia has already gained capacity on the Romania border: the second 400 kV Pančevo–Reșița system lifted Serbia–Romania cross-border capacity by 80 per cent, from 500 MW to 900 MW in each direction, with potential for additional daily capacity if Transelectrica agrees. That line is part of the wider Trans-Balkan Electricity Corridor linking Romania, Serbia, Bosnia and Herzegovina, Montenegro and Italy.
Serbia’s longer-term plan is broader. EMS has identified five major new interconnection corridors by 2035: the Trans-Balkan Corridor, a new Serbia–Croatia 400 kV connection, the Pannonian Corridor with Hungary, the North CSE Corridor toward Romania and the Central Balkan Corridor. These are not just export projects; they are the physical precondition for absorbing wind in Banat and eastern Serbia, solar in the south and east, and future battery-backed hybrid plants.
Montenegro and Bosnia are central to the Western Balkans grid solution. The Energy Community’s 2026 candidate PECI list includes the Gacko–Brezna 400 kV line, the double Pljevlja–Bajina Bašta–Višegrad 400 kV Trans-Balkan section, the Brezna–Sarajevo 20 400 kV project, and rehabilitation of the Trebinje–Perućica–Podgorica–Vau Dejes 220 kV corridor. These projects are explicitly framed around congestion reduction, renewable integration, cross-border exchange and stronger links toward Italy, Albania, Serbia and Bosnia and Herzegovina.
Further south, the most important capacity additions are the Fierza–Prizren 400 kV Albania–Kosovo reinforcement, the Prizren–Tetovo 400 kV Kosovo–North Macedonia line, and the already strengthened Greece–Bulgaria corridor. The second 400 kV Greece–Bulgaria interconnection increased exchange capability by 500 MW, bringing the maximum nominal exchange margin between the two countries to 1.7 GW, while a future 2 GW DC Greece–Bulgaria interconnection is already being discussed.
For investors, the conclusion is blunt: SEE is not closed to RES, but grid access has become the scarce asset. The winning projects before 2030 will be those with mature permits, bank guarantees, secured land, realistic connection studies, co-located batteries, curtailment-ready financial models, and proximity to high-voltage nodes included in TSO development plans. Pure merchant solar or wind projects sitting far from reinforced 400 kV corridors will face delayed connection, higher curtailment, weaker debt capacity and lower equity value. In the next investment cycle, the premium will shift from “who has the best irradiation or wind yield” to “who owns a credible grid position.”
