The Electricity System Operator – ESO is a sole proprietorship joint stock company, which carries out the unified operational planning, coordination and control of the electricity system of the Republic of Bulgaria and its common operation with neighbouring countries. Electricity transmission operator guarantees the secure, reliable and continuous power supply of Bulgaria, manages the transit of electricity flows through the country and the parallel operation with power systems of the countries of synchronous zone Continental Europe.

ESO EAD is a key participant in the process of liberalization of the electricity market with a leading role in the market coupling with Bulgaria’s neighbouring countries in the intraday and day-ahead segments.

The electricity system operator is actively developing and modernizing Bulgaria’s electricity transmission infrastructure in line with European policies. The company manages the transmission of electricity from producers to end users in accordance with national and European regulatory standards for quality and security of electricity supply. Electricity System Operator applies high standards and measures in harmony with the current environmental guidelines with the introduction of the most modern methods for planning, management and monitoring.

In close cooperation with the neighbouring European transmission system operators, ESO coordinates and controls cross-border electricity flows and ensures sustainable long-term electricity supply as a member of the European Network of Transmission System Operators for Electricity (ENTSO-E).


IPTO (Independent Power Transmission Operator) is the transmission system operator of Greece, founded in 2011. It is responsible for the transmission system operations of Greece over 12000MV lines and cables.


The Terna Group was the first independent operator in Europe and is the seventh largest in the world in terms of number of kilometers of operated lines. This Italian TSO is also the primary owner of Italy’s National High Voltage Electricity Transmission Grid, with over 62,000 km of HV lines throughout Italy. Terna is responsible for nationwide energy transmission and dispatching and so for the safe management of energy flows across Italy, guaranteeing the balance between electricity supply and demand 24/7.


Transelectrica is the Romanian Transmission and System Operator (TSO) for electricity. Fully connected to the wider continental European power network, Transelectrica operates Romania's electricity cross-border links with its neighboring countries. In close cooperation with its peers in the region Transelectrica handles an increasing level of cross-border energy flows as the electricity markets become more integrated strenghtening regional security of supply, supporting sustainable economic growth across the region and thus delivering substantial benefits to society at large.

In its home country Transelectrica is fully unbundled from the market side of the electricity sector i.e. generation and trading, operates a 9000 km high-voltage transmission network and balances a generation fleet of more than 15000 MW active in its control area.