South-East Europe’s electricity system is entering a decisive phase in which transmission infrastructure—rather than generation capacity—is becoming the primary constraint and the key determinant of value. Across Serbia, Bosnia and Herzegovina, Montenegro, Albania, and North Macedonia, a new wave of 400 kV interconnections, grid reinforcements, and storage-linked projects is reshaping the regional power system into a more integrated but unevenly investable network.
What is taking shape is not a simple expansion of capacity, but a structural reconfiguration of how electricity moves across the region. The traditional hierarchy—where national systems operated largely in isolation with limited cross-border exchange—is being replaced by a corridor-based architecture, anchored in high-voltage transmission and increasingly influenced by renewable generation patterns.
At the centre of this shift lies the Trans-Balkan electricity corridor, which is evolving into the backbone of the regional system. New project announcements across 2025–2026 confirm that this corridor is no longer a single project, but a multi-country infrastructure platform linking Serbia, Montenegro, Bosnia and Herzegovina, and further into EU markets.
The next phase of development is defined by a series of interconnected 400 kV investments. A double 400 kV overhead line linking Pljevlja (Montenegro), Bajina Bašta (Serbia), and Višegrad (Bosnia and Herzegovina) is designed to complete the core Trans-Balkan loop, significantly increasing cross-border transfer capacity and enabling larger electricity exchanges, including flows toward Italy through the existing submarine cable.
In parallel, new interconnections such as Gacko–Brezna (Bosnia and Herzegovina–Montenegro)and Brezna–Sarajevo 400 kV links are being advanced to reduce congestion and support renewable integration across western Balkan systems. These projects are explicitly designed to absorb rising volumes of wind and solar generation, particularly in mountainous and coastal regions where grid capacity has historically lagged development potential.
Further east, the Kosovo–North Macedonia 400 kV corridor is emerging as part of a broader east–west transmission axis, strengthening connectivity toward Albania and enabling a more balanced regional dispatch structure. At the same time, Albania itself is undertaking a significant grid transformation, including new 400 kV interconnections with Kosovo and Greece, as well as upgrades to existing substations such as Fierza, positioning the country as a future renewable export hub.
This expansion of the 400 kV layer is not occurring in isolation. It is closely tied to a parallel buildout of renewable generation and, increasingly, system flexibility. One of the most strategically significant projects in the region is the proposed Moglice pumped-storage expansion in Albania, with up to 1,620 MW of capacity and around 30 GWh of storage, which would provide balancing capability across multiple national systems.
The integration of such large-scale storage is a recognition that the region’s transmission buildout alone will not be sufficient. Renewable generation is expanding rapidly, but its variability requires both stronger interconnections and time-shifting capacity. Without both, transmission corridors risk becoming congested rather than enabling.
The link between transmission and renewables is becoming even more explicit in project design. In northeastern Albania, for example, new 400 kV infrastructure is being planned specifically to enable the integration of more than 1 GW of wind capacity, while also relieving pressure on existing 220 kV lines. Across the region, grid investments are no longer generic reinforcements but are directly tied to identifiable renewable pipelines.
Montenegro offers a parallel illustration of this trend. A developing partnership between EPCG and Masdar is targeting large-scale solar, wind, and hybrid projects, with the explicit objective of exporting green electricity through the country’s existing interconnection with Italy. This strategy effectively treats transmission capacity as a monetisation channel for renewable energy, rather than a passive infrastructure asset.
Serbia remains the central node within this evolving system. Its internal grid—particularly the 400 kV network linking Belgrade, Kragujevac, Kraljevo, and Niš—is being reinforced through investments estimated in the range of EUR 200–300 million, aimed at reducing internal bottlenecks and improving north–south transfer capacity. At the same time, new 400 kV lines such as Kragujevac–Kraljevo and Obrenovac–Bajina Bašta are being constructed to replace aging 220 kV infrastructure and strengthen the country’s role as a regional transit hub.
Yet, despite this acceleration at the highest voltage level, the broader system remains constrained by legacy infrastructure. The 220 kV network, still widely used across SEE, is increasingly being identified as a bottleneck. Projects such as the rehabilitation of the Trebinje–Perućica–Podgorica–Vau Dejës corridor highlight the need to upgrade existing assets simply to maintain system operability under higher load and renewable penetration.
At the 110 kV level, the challenge becomes even more acute. This is where most renewable projects physically connect, and where congestion, transformer limitations, and local network constraints often determine real output levels. Even as 400 kV capacity expands, insufficient reinforcement at lower voltage levels can prevent electricity from being effectively distributed, creating a structural disconnect between generation and transmission capability.
The emerging result is a three-speed grid. The 400 kV system is expanding and integrating, the 220 kV system is stabilising through selective rehabilitation, and the 110 kV system is under increasing stress from decentralised generation. This layered dynamic is shaping not only physical flows but also market behaviour.
Electricity markets across SEE are beginning to reflect these structural realities. Cross-border capacity expansions are increasing trading volumes and reducing price spreads in well-connected corridors, particularly between Serbia and Hungary or Romania. At the same time, congestion persists in less-developed parts of the network, creating persistent regional price divergence and arbitrage opportunities.
The introduction of negative pricing mechanisms and the expansion of balancing markets are accelerating this transition. Price signals are becoming more granular and more reflective of physical constraints, exposing weaknesses in the grid and rewarding flexibility. Storage, hybrid generation models, and proximity to strong transmission nodes are emerging as key determinants of project economics.
Looking toward 2030–2035, South-East Europe is unlikely to converge into a fully unified electricity market in the Western European sense. Instead, a more complex system is emerging—highly interconnected at the transmission level but still characterised by local bottlenecks and uneven investment conditions.
Three distinct investment geographies are beginning to take shape. The first is the northern and better-coupled belt, linking Hungary, Romania, and northern Serbia, where strong interconnections and higher liquidity create relatively stable conditions. The second is the transitional central layer, including Serbia’s internal grid and parts of Bosnia and Bulgaria, where reinforcement is ongoing but not yet complete. The third is the southern and western periphery, including Albania, Montenegro, and parts of North Macedonia, where large renewable potential is emerging alongside still-developing transmission infrastructure.
In this evolving landscape, transmission corridors are no longer just physical assets. They are becoming economic arteries, determining where capital flows, where projects are built, and how electricity is priced. The value of a renewable project in SEE is increasingly defined not by its installed capacity alone, but by its position within this network—its access to 400 kV corridors, its exposure to congestion, and its ability to integrate flexibility.
The transformation now underway suggests that South-East Europe is moving from a fragmented set of national systems toward a corridor-driven regional market, where transmission infrastructure, renewable generation, and storage capacity are tightly interlinked. The pace at which these elements align will determine whether the region becomes a fully functional extension of the European energy system or remains a partially integrated frontier market defined by structural inefficiencies and opportunity.
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