The Transmission Network Development Plan of Bulgaria for the period 2025–2034 (the “Plan”) has been developed by a team of experts at ESO EAD. On 30 July 2025, a public consultation on the Plan was held. Below we present some of the key highlights of the Plan.
Key Quantitative Projections
As of now, it is projected that gross electricity consumption in the country will not exceed 41,600 GWh by 2034. The anticipated absolute maximum electrical load in 2034 is 7,680 MW, and the maximum load for an average working day is estimated at 6,800 MW. These projections serve as the basis for planning generation capacity and network infrastructure necessary to ensure reliable power supply.
New Generation Capacities: Dominance of RES
According to declared investment intentions and already signed grid connection agreements, a total of 23,008 MW of new electricity generation capacities are planned for construction during the 2025–2034 period, of which 21,528 MW are from renewable energy sources (RES), including solar, wind, hydro, and biomass installations. The remaining capacities include gas-fired and cogeneration plants, primarily for balancing purposes.
It is anticipated that by 2034, electricity generation from RES will exceed 50% of the projected gross electricity consumption in the country. In a scenario with lower demand, the share of RES in the energy mix may prove even higher.
Challenges for the Transmission Grid
The main risks for the Bulgarian power system, as identified in the draft ten-year plan of ESO, stem from the growing share of non-synchronous renewable energy sources (solar and wind power plants) and storage facilities, whose variable generation profiles make it more difficult to balance the system and maintain frequency, voltage, and system inertia. The decommissioning of conventional baseload generation such as coal-fired plants further limits the availability of regulation and reserve services.
The geographical mismatch between areas with available grid capacity and zones attracting the most investor interest in RES leads to the risk of local overloads, exhaustion of transformer capacities, and connection difficulties. Delays in the development of new grid infrastructure relative to the pace of RES expansion, as well as limited system restoration capabilities in case of failure, also represent significant systemic and investment risks.
Solutions
The draft Plan proposes several groups of technical and strategic solutions to address the main risks facing the power system:
- Grid development and reconstruction – construction of new 400 kV rings in Southeastern and Northeastern Bulgaria; reconstruction and expansion of existing 110 kV/MV substations and replacement of transformers with higher-capacity ones; new switching stations and power lines at 110 kV and 400 kV levels.
- Planned integration of balancing capacities – including gas-steam power plants (combined cycle gas turbines – CCGT) as a transitional measure, which provide regulating and reserve services and can be adapted for hydrogen fuel blends.
- Projects of common European interest – including the CARMEN project, which envisages digitalisation and physical modernisation of key infrastructure along the EU’s eastern border, with the aim of ensuring cross-border connectivity and enhanced reliability.
- ESO plans to install controllable shunt reactors with a range of 30…80 MVAr, which will be connected directly to the 110 kV grid. In the first phase, five reactors will be installed – at the substations Elhovo, Balkan, Obraztsov Chiflik, Arpezos and Bononia. The installation of two shunt reactors of 50 MVAr each is also planned on the tertiary winding of the 400/220 kV autotransformer at the Maritsa East substation.
Development of the RES sector
The development of the RES sector in Bulgaria is extremely dynamic, with a significant increase in the number of grid connection applications submitted to ESO by new RES producers and electricity storage facilities (BESS). This places considerable pressure on the transmission infrastructure, particularly on 110 kV/MV substations, whose reconstruction and expansion cannot be adequately addressed in ESO’s ten-year plans due to the constraints imposed by Ordinance No. 6. In cases of transformer capacity shortages, ESO prescribes equipment replacement and the construction of new facilities. However, in a number of substations even these measures are insufficient, and individual technical solutions, including new construction, are required.
A particularly acute challenge is the geographical mismatch between available grid capacity and the locations with the highest investor interest in RES, which hampers the timely development of new network infrastructure. There is also a systemic risk to the security of electricity supply in the event of an irreversible lead of RES projects over grid investments. According to ESO data, current applications for the construction of new RES park modules exceed the installed capacity of conventional power plants in the country by more than three times.
Given the exceptionally high investor interest in the construction of new RES capacities—exceeding more than three times the existing conventional generating capacity—ESO has proposed technical solutions for the development of the 400 kV and 110 kV transmission network and for the reconstruction of existing elements. The following is planned:
- Construction of a new 400 kV ring in the southeastern part of the country: Uzundzhovo substation – Lyubimets 2 substation – Asenovo substation;
- Construction of a new 400 kV ring in the northeastern part of the country: Varna substation – Dobrich 2 substation – General Toshevo 2 substation – Svoboda substation;
- Reconstruction of a large number of 110 kV transmission lines in all areas of the country where RES have been applied for and where the grid capacity has been exceeded;
- Gradual replacement of 400/110 kV autotransformers in system substations with higher-capacity units;
- Reconstruction and expansion of several 110 kV/MV substations and replacement of existing 110 kV/MV transformers with higher-capacity ones;
- Construction of new 110 kV and 400 kV switching stations and 110 kV/MV substations.
What is CARMEN?
The CARMEN project aims to strengthen cooperation along the eastern border of the EU through both physical and non-physical measures for optimized connectivity. By means of digitalization and physical upgrades to targeted energy infrastructure, the implementation of CARMEN will foster cross-border cooperation between Romania, Bulgaria, and other neighboring countries such as Hungary, Moldova, and Ukraine. The activities planned to be carried out in Bulgaria by ESO are divided into three work packages:
- Construction of four new 400/110 kV substations: Svoboda, General Toshevo 2, Dobrich 2, and Pleven 3;
- Reconstruction, expansion, and deployment of automated control systems in the substations Madara and Obraztsov Chiflik. Deployment of automated control systems in the substations Varna, Dobrudzha, Gorna Oryahovitsa, Balkan, and Mizia;
- Construction of new 400 kV transmission lines between the substations: Svoboda – General Toshevo 2; Dobrich 2 – General Toshevo 2; Dobrich 2 – Varna; Varna – Obraztsov Chiflik; Tsarevets – Obraztsov Chiflik; and Mizia – Tsarevets.
More information about the project is available at: https://carmen-smart-grid.eu/en/
The full text of the Plan (in Bulgarian) can be found here: https://www.dker.bg/uploads/_CGCalendar/2025/10_Year_Net_Dev_Plan_2025-2034_project.pdf
The news above is for information purposes only. It is not a (binding) legal advice. For a thorough understanding of the subjects covered and prior acting on any issue discussed we kindly recommend Readers consult Ilieva, Voutcheva & Co. Law Firm attorneys at law.
