HTSO is a member of ENTSO-E (European Network of Transmission System Operators for Electricity) and participates in all of its Activities. More specifically, HTSO participates in all ENTSO-E Committees and Working Groups as follows,

• Market Committee
• Market Integration WG
• Ancillary Services WG
• Market Information & Transparency WG
• Electronic Data Interchange WG
• Renewable Energy Sources WG
• System Development Committee
• Ten-Year Network Development Plan WG
• System Adequacy and Market Modeling WG
• Continental South-East RG (presidency until 2011)
• System Operations Committee
• European Operational Standards WG
• Electronic Highway WG
• Continental Europe RG
•  Research and Development Committee 

            and also

• participates in consortia for the implementation of projects regarding the operation and development of the Networks of ENTSO-E
• holds the presidency of Project Group ‘Turkey’. This Project Group has undertaken the efforts to connect Turkey to the ENTSO-E Network.

HTSO also participates in the Southeast European Cooperative Initiative (SECI)