Serbia’s transmission-system operator EMS has not technically stopped all renewable energy connections until 2030. The practical impact for many new large wind and solar projects is similar to a freeze because applications for connection studies must be submitted between 1 September and 31 December 2029. Projects that already hold connection studies, approvals, guarantees or connection contracts can still proceed. The market is therefore treating Serbia as a de facto grid-capacity freeze for new large variable renewables, even though the legal framing is a delay in the connection-study procedure rather than a universal ban.
Different regulatory approaches across the region
Hungary is described as the closest to Serbia’s model. After rapid solar growth strained the system, no new grid capacity was granted to solar or wind projects between 2022 and 2024. Rules also require rejection of generation projects that cannot be connected by 2030. A new competitive grid-capacity allocation regime is expected, with preference for projects that include batteries, balancing capacity, hybrid designs and stronger financial guarantees.
Romania is not using a Serbian-style stop, but it is shifting from a first-come, first-served queue toward competitive grid-capacity auctions and global solution studies. The approach is presented as market-based rationing for scarce capacity, with speculative connection requests expected to lose ground to bankable projects backed by financing, permits and grid-ready designs. The issue in Romania is described as a mismatch between a large renewables pipeline and the physical capacity of Transelectrica’s network.
Croatia’s constraints are linked mainly to connection costs and transmission bottleneck uncertainty rather than a formal renewables stop. A 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 faces blocked capacity issues affecting solar, wind, geothermal and standalone batteries awaiting grid solutions.
Country-specific bottlenecks: Montenegro, Bosnia and Bulgaria
Montenegro is not described as frozen. CGES continues to sign connection-infrastructure agreements, including a 70 MW solar connection agreement for the Tupan project. Earlier agreements cover nearly 1,500 MW of solar and wind capacity. The constraint in Montenegro is characterized as different: small domestic load, a relatively narrow high-voltage backbone, a large investor pipeline and reliance on cross-border evacuation through Serbia, Bosnia and Herzegovina, Albania and the Italy submarine link.
Bosnia and Herzegovina is moving into a grid-stability phase tied to operational requirements for renewables. The EBRD has provided €46 million financing for variable shunt reactors aimed at voltage stability, higher renewable integration and cross-border flows. The financing indicates that the bottleneck extends beyond line capacity to reactive power needs, voltage control, operational security and the ability to manage dynamic renewables injections.
Bulgaria continues connecting large volumes of renewables while adding financial discipline during the process. By the end of 2025, Bulgaria had nearly 7 GW of installed PV and wind, with another 1 GW expected in 2026. Investors are required to provide a deposit or bank guarantee of about €25,565 per MW. Bulgaria is also investing 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.
Evacuation limits and congestion layers in Western Balkans markets
North Macedonia, Kosovo and Albania remain in build-out mode with regional evacuation capacity identified as the constraint. MEPSO and KOSTT signed a memorandum for the 400 kV Tetovo–Prizren interconnection. MEPSO also noted that Southeast Europe needs transmission capacity increases of at least two times, and in some cases more. This is presented as an official signal that the Western Balkans grid cannot absorb the renewables pipeline without additional cross-border infrastructure.
The congestion picture is described in three layers. Internal north–south and east–west transmission congestion affects areas where solar clusters in high-resource zones far from demand centres or export routes. Cross-border scarcity makes borders such as Serbia–Hungary, Serbia–Romania, Bulgaria–Romania, Bulgaria–Greece, Montenegro–Serbia/BiH and Albania–Kosovo/North Macedonia price-setting points during stressed hours. A third layer involves system flexibility congestion requiring batteries, pumped storage, voltage support, curative remedial action, dynamic line rating and better outage coordination.
The ACER 2026 assessment attributes the region’s 2024 price spikes to limited flexible resources during evening high-demand hours after solar output declined. It also cites constrained cross-border capacity alongside planned maintenance limiting imports from lower-priced EU markets. ACER estimated that many severe spikes could have been avoided if the 70% cross-zonal capacity target had been available. It points to dynamic line rating, advanced conductors, improved outage planning, remedial actions and market coupling as near-term tools before new lines come online.
Interconnection upgrades: Serbia’s corridors and regional PECI projects
The cross-border build-out is described as real but too slow relative to the renewables pipeline timeline. On the Serbia–Romania border, a second 400 kV Pančevo–Reșița system increased cross-border capacity by 80%, from 500 MW to 900 MW in each direction. Additional daily capacity could be possible if Transelectrica agrees. The line forms part of the wider Trans-Balkan Electricity Corridor linking Romania, Serbia, Bosnia and Herzegovina, Montenegro and Italy.
Serbia’s longer-term plan includes 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 described as physical prerequisites for absorbing wind in Banat and eastern Serbia as well as solar in southern and eastern areas. They are also linked to future battery-backed hybrid plants.
The Energy Community’s 2026 candidate PECI list includes several projects framed around congestion reduction and renewables integration across Montenegro and Bosnia. These include the Gacko–Brezna 400 kV line; the double Pljevlja–Bajina Bašta–Višegrad 400 kV Trans-Balkan section; the Brezna–Sarajevo 20 x 400 kV; and rehabilitation of the Trebinje–Perućica–Podgorica–Vau Dejes 220 kV corridor. The list also references stronger links toward Italy, Albania, Serbia and Bosnia and Herzegovina.
Bilateral reinforcements further south: Albania-Kosovo-North Macedonia and Greece-Bulgaria
The most important additions further south are described as Albania–Kosovo reinforcement via Fierza–Prizren at 400 kV, plus a Prizren–Tetovo 400 kV Kosovo–North Macedonia line. The Greece–Bulgaria corridor has also been strengthened already. A second Greece–Bulgaria interconnection increased exchange capability by 500 MW, bringing maximum nominal exchange margin between the two countries to 1.7 GW.
A future 2 GW DC Greece–Bulgaria interconnection is also being discussed. For investors considering timing before 2030, projects with mature permits, bank guarantees, secured land and realistic connection studies are highlighted alongside co-located batteries and curtailment-ready financial models. Proximity to high-voltage nodes included in TSO development plans is also cited as relevant for grid access outcomes.
The constraints described point to delayed connection risks for merchant solar or wind projects located far from reinforced . In this context, emphasis shifts toward ownership of credible grid positions rather than solely resource yield characteristics.
