On 31 May 1999, Terna was established within the Enel Group, by way of implementation of Italian Legislative Decree No. 79/99^[5] which within the context of the process for the deregulation of the Italian electricity sector, sanctioned the separation between ownership and management of the national transmission grid.

On 23 June 2004, following the Prime Minister's Decree issued on 11 May of the same year, Terna was put on sale with an IPO on Borsa Italiana.

In 2010 Terna joined Desertec,^[6] a project aimed at producing and transmitting renewable energy in the Middle East and North Africa (MENA) to meet local needs and be assigned in part to the European interconnected grid.

In 2011, Terna Group adopted a new organizational structure. Through Terna Rete Italia^[7] safely manages the Italian electricity system with more than 63,500 kilometers of high voltage lines. Through Terna Plus manages new business opportunities and non-traditional activities, in Italy and abroad.

2011 was the 7th consecutive year of growth for the Group. A dividend of €21 was paid per share. The 2011 results were submitted by the CEO Flavio Cattaneo during the Terna Board of Administration meeting held to approve the Strategic Plan 2012–2016.

In 2012, Terna consolidated Revenues stood at 1,806 million euros, +10.4% compared to 2011, mainly due to the Grid Transmission Fee and to the results from Non Traditional Activities carried out by the Group.^[8]

On 31 January 2012, Terna presented the Development Plan of the National Electricity Transmission Grid^[9] for the decade 2012–2021. The plan is drafted and updated every year and, in 2012, it included investments for over 7 billion euro aimed at increasing efficiency for the electricity system, including the reduction of energy losses and the reduction of CO₂ emissions.

In 2013, Terna consolidated Revenues stood at 1,896 million euros, with an increase of 90.5 million euros (+5%) compared to 2012. Ebitda stood at 1,281 million euros (+6,5%), Group Net income at 514 million euro (+10,8%).^[10]

Terna is responsible for national electricity transmission management and development in Italy. Terna's assets include:^[1]

• 74,910 km of lines
• 901 transformation and switching stations
• 1 National Control Center (NCC)
• 3 Control centers
• 26 lines of interconnections with other countries (CTI)
• SA.PE.I. the longest underwater cable in the world (435 km), with a capacity of 1000 MW

To safeguard its assets, Terna has created an organization capable of protecting the company's physical and technological infrastructures, also through the prevention and management of episodes of corporate fraud. In this framework, in order to guarantee the maximum safeguarding of said infrastructures and investments, it has signed memoranda of understanding, first of its kind and type with the Ministry of the Interior, Carabinieri and Guardia di Finanza.

In 2010 the company invested €1.06 billion that financed the construction of 1000 km of new electrical lines and 48 new stations. Terna's transmission lines carried 326.16 billion kWh in 2010, of which:^[11]

• 286.53 billion generated by power plants in Italy
• 45.76 billion imported
• 1.81 billion exported
• 4.31 billion for pumping stations

In turn, 286.53 billion kWh were generated by:

• Thermoelectric power plants: 218.35 billion
• Hydroelectric power plants: 53.16 billion
• Wind power plants: 8.37 billion
• Geothermal power plants: 5.03 billion
• Photovoltaic power plants: 1.6 billion

Board members:^[12]

• Igor De Biasio - Chairman
• Giuseppina Di Foggia - Chief executive officer and General manager
• Francesco Renato Mele
• Qinjing Shen
• Regina Corradini D'Arienzo
• Angelica Krystle Donati
• Enrico Tommaso Cucchiani
• Gian Luca Gregori
• Simona Signoracci
• Marco Giorgino
• Karina Audrey Litvack
• Jean-Michel Aubertin
• Anna Chiara Svelto

Terna has been listed in the Italian Stock Exchange since 2004. Its major shareholder was Cassa Depositi e Prestiti, with 29.85% of shares. The remaining nearly 70% is held by other institutional and retail investors.^[13] Among the principal shareholders of the company: Romano Minozzi with 5.6%, Blackrock Inc. with 2.4% and Assicurazioni Generali with 2.0%.

According to the Edison Electric Institute, Terna is the best European company among utilities by total return of shares in 2010–2012.^[14] In these three years Terna's return stood at 24%, compared to average returns in the sector (DJ Stoxx-10%, Ftse Mib-21%). In 2010 Terna did receive the same recognition for the 2007–2009, as Terna's share return stood at +40%, achieving a net overperfomance (nearly 55%) compared to the European sector that registered -15%.

  Media related to Terna (TSO) at Wikimedia Commons

• ENTSO-E Transmission System Operators
• Corriere Economia