Bulgarian Electricity System Operator EAD (ESO) was established on 4 April 2007 as a subsidiary of the National Electricity Company (NEK). On 4 February 2014, the unbundling of ESO from NEK went through its last stage in line with the Third Liberalization Package. This has been the final step needed to reach compliance with Directive 2009/72/EC and the national legislative provisions. ESO is responsible for the common operational planning, coordination and control of the Bulgarian power system and its parallel synchronous operation with neighbouring systems. Its purviews also include transmission grid operation, maintenance and reliable functioning, auxiliary network servicing, as well as maintenance and repair services in the energy sector. It also manages the power transit through the national grid and runs the electricity market.

In performing parallel synchronous operation with ENTSO-E, ESO, being a key partner in the Balkan region, constantly strives to achieve higher transmission efficiency and asset management performance by introducing and using the newest methods of planning, maintenance, monitoring and control. The company has deployed an asset management system (SAP/R3), Supervisory Control and Data Acquisition System (SCADA) and Energy Management System (EMS), and Geographic Information System (GIS).