A proposed 400 kV interconnection between Montenegro and Bosnia and Herzegovina is advancing as a Western Balkan transmission investment. The Brezna–Sarajevo corridor is intended to reinforce a regional grid area where hydropower, new renewable development, ageing 220 kV infrastructure and access to the Italian electricity market intersect.
The project was nominated in the 2026 Projects of Energy Community Interest (PECI) process. It would connect the planned 400/110/35 kV Brezna substation in Montenegro with the Sarajevo 20 substation in Bosnia and Herzegovina. The scope also includes a new 400/220 kV Piva’s Mountain substation, strengthening connections around the existing Piva hydropower complex and transmission routes between northern Montenegro and eastern Bosnia and Herzegovina.
Project promoters, scope and planned commissioning
The promoters are CGES, Montenegro’s transmission system operator, and NOSBiH/Elektroprijenos BiH, working with relevant energy authorities. Preliminary project documentation points to commissioning around 2032. The stated CAPEX is approximately €70 million in Montenegro and €6.7 million in Bosnia and Herzegovina, for an initial combined envelope of about €76.7 million.
The configuration is planned in two phases. Phase one covers construction of the Piva’s Mountain substation, a new 400 kV overhead line towards the Buk Bijela area in Bosnia and Herzegovina, use of the existing high-capacity continuation towards Sarajevo 20, and a stronger connection between the Piva hydropower plant and the new substation. Phase two would extend the 400 kV line from Brezna to Piva’s Mountain.
Interfaces with other regional transmission projects
The phased approach is designed to allow incremental grid reinforcement rather than waiting for completion of the full corridor. It also creates interfaces with several other regional investments, including a proposed Gacko–Brezna 400 kV line, the Bajina Bašta–Višegrad–Pljevlja Trans-Balkan Corridor, and rehabilitation of the existing Trebinje–Perućica–Podgorica–Vau Dejës 220 kV route.
Taken together, these investments could affect electricity flows among Serbia, Bosnia and Herzegovina, Montenegro and Albania. They would also strengthen the inland network feeding Montenegro’s submarine electricity connection with Italy.
Link to Italy via HVDC capacity constraints
The existing Montenegro–Italy HVDC link provides a direct physical route into one of Europe’s larger electricity markets. Its initial operational pole provides approximately 600 MW. The commercial value of the cable depends on conditions in networks behind it, since congestion, voltage limitations or security constraints can restrict flows inside Montenegro and neighbouring systems.
A submarine interconnector cannot continuously absorb broader Balkan exports when internal constraints limit transfer capability. In that context, Brezna–Sarajevo is positioned as more than a bilateral link, with potential to contribute to a wider transmission spine connecting hydropower and renewable production in Bosnia and Herzegovina, Montenegro and Serbia with demand and trading opportunities in Italy.
Regional value estimates from grid optimisation
The regional investment plan estimates that a more fully optimised 2040 grid could reduce the marginal-cost difference across the Italy–Montenegro interface by approximately €20–30/MWh. The calculation reflects a package of reinforcements rather than Brezna–Sarajevo alone. It is presented as an indicator of economic value constrained by transmission bottlenecks.
The same analysis suggests that an optimised Continental Southeast European grid could reduce renewable-energy surplus by approximately 5 TWh, avoid around 10 million tonnes of CO₂, and lower regional electricity costs by roughly €7/MWh. These benefits are described as system-level outcomes that do not automatically translate into revenue for an individual TSO. Financing arrangements are therefore expected to convert part of that value into regulated cost recovery, cross-border cost allocation or grant support.
CAPEX range and bankability considerations
The original combined CAPEX estimate of about €76.7 million is described as a promoter-level planning figure rather than a final bankable budget. A 400 kV corridor through mountainous terrain can involve substantial costs tied to geotechnical conditions, access roads, foundations, conductors, substations, land acquisition and environmental mitigation. Inflation in transformers, switchgear and other high-voltage equipment has also increased costs for European transmission projects.
A more conservative development envelope could reach €90 million–€120 million, depending on detailed surveys, contingencies, owner’s costs, environmental mitigation, compensation levels, financing costs and schedule risks. The final figure would depend on how much new line length is required, whether existing corridors can be reused, and the technical scope of the Piva’s Mountain substation.
Cost allocation across borders under PECI status
The split between Montenegro and Bosnia and Herzegovina is identified as another bankability issue. Montenegro carries most of the stated investment while regional benefits extend beyond domestic consumers. Without grant funding or cross-border cost allocation, CGES customers could bear a disproportionate share of an asset supporting Bosnia and Herzegovina, Serbia, Albania and electricity trading with Italy.
Peci consultation process for environmental permitting
The environmental and social process is described as central because the corridor crosses mountainous areas with potentially sensitive habitats, forests, water resources and local communities. Civil-society concerns around the Brezna area have already entered the PECI consultation process. These concerns are not treated as issues that can be addressed only after route selection.
Early routing is expected to examine biodiversity, bird and bat interactions, protected areas, landscape impacts, cultural heritage, forestry impacts, erosion risks and cumulative effects from connected hydropower, renewable generation and transmission projects. Alternatives analysis must show how selected routing balances system needs with environmental and social effects.
Cadastral work timing for land acquisition and construction schedule
Land acquisition could become a critical path because overhead lines run along long corridors containing numerous parcels and rights holders. The legal right to construct towers and maintain conductors does not remove compensation disputes or local resistance risks. A credible schedule requires cadastral verification, access planning, stakeholder engagement and grievance management before an EPC contractor mobilises.
2032 target depends on approvals across both countries
The planned commissioning date around 2032 leaves an estimated six-year development and construction window for a cross-border 400 kV investment. That timeframe is described as reasonable but offers limited room for institutional delay. Intergovernmental agreements, regulatory approvals, environmental permits, spatial plans, expropriation processes, financing arrangements, procurement steps and cross-border technical coordination must progress in parallel.
Tight schedule risk from inflation during construction delays
A delay of 12–18 months would increase interest during construction by extending exposure to equipment inflation while postponing congestion benefits. For regulated TSOs this differs from impacts faced by merchant renewable projects: equity returns may be protected through regulatory asset base mechanisms. Timing mismatches can still affect cash flow pressure during debt drawdowns and tariff recovery periods.
Voltage stability studies for long 400 kV lines
The technical design must address long-standing voltage-management challenges across the region. Long 400 kV lines can generate reactive power during lightly loaded periods and may require shunt reactors or other compensation equipment. The Balkan system also experiences significant seasonal and hourly flow changes driven by hydrology, tourism demand, thermal availability and exports towards Italy.
Network-wide contingency planning after 2024 blackout experience
The 2024 regional blackout demonstrated how quickly voltage deterioration can spread across multiple systems when operators lack complete visibility and corrective measures. Brezna–Sarajevo is expected to strengthen system security while also changing regional power-flow patterns. Coordinated dynamic studies covering the wider network are therefore required rather than analysis limited only to terminal substations.
