The Terna Group

Terna - Galbani HeadquartersTerna is the largest independent transmission system operator (TSO) in Europe and the seventh largest in the world in terms of kilometers of lines managed.

The Company’s headquarters is in Rome and it is the owner of the Italian National Transmission Grid (NTG)i, with more than 57,000 kilometers of high-voltage lines (more than 63,000 km of three-phase conductors), 431 transformation stations, and 22 lines interconnecting with foreign grids as of December 31, 2010.

The Company’s name comes from the set of three conductors or groups of conductors – in Italian, a terna – used to transport each of the three phases of the three-phase electric field in alternating-current grids.     

In Italy Terna is the government-licensed transmission system operator, responsible for transmitting and dispatching electric power throughout the country on the high- and ultra-high-voltage grid. Terna is also responsible for the planning, construction, and maintenance of the grid.    

The structure of Terna’s equity interests as of December 31, 2010 was as follows:

The structure of Terna’s equity interests

As of December 31, 2010, the consolidation boundary of the Terna Group included:

  • the directly controlled, 100%-owned Italian subsidiaries SunTergrid S.p.A. (formerly International S.p.A.) and TELAT S.r.l.
  • the Italian companies Rete Solare S.r.l and Rete Rinnovabile S.r.l. (RTR S.r.l.), indirectly controlled through SunTergrid S.p.A., which owns 100% of them. Rete Rinnovabile S.r.l. was sold on March 31, 2011 to Terra Firma Investments (GP) 3 Limited for 641 million euro.
  • the companies valued in the Consolidated Financial Statements by the equity method, in which Terna S.p.A. has an equity interest: CESI S.p.A., an affiliated company (39.91% equity stake) and ELMED ÉTUDES S.a.r.l., a jointly controlled company (50% equity stake).

CESI is the leading company in the market of testing and certifying electro-mechanical equipment and consultancy on electric systems. It covers all the stages of the life cycle of the electric system and offers companies therein (generation, transmission, and distribution), manufacturers of electrical and electronic equipment, large consumers of electricity, and local and national governments a complete range of services aimed at the solution of problems connected with the productive processes of the entire electricity industry.    

CORESO is a service company operating under Belgian law, with its headquarters in Brussels, in which Terna acquired an equity interest of 22.485% in November 2010. Shareholders of the company include the TSOs of France (RTE), Belgium (Elia), and Great Britain (National Grid), each with the same percentage of the share capital as Terna, as well as Germany’s (50Hertz Transmission), with 10%. CORESO develops daily forecasts and real-time analyses of power flows in Central and Western Europe, identifying potential problems and promptly informing the TSOs concerned. Terna’s stake in CORESO constitutes an equity investment in an affiliated company for the Group.

ELMED ÉTUDES is the company to which its joint owners, Terna and the Tunisian electricity company STEG, entrusted the feasibility study regarding the undersea Italy-Tunisia interconnection for the development of the Elmed Project, which provides for the production of electricity in Tunisia from both conventional and renewable sources and its connection with the Italian electricity market. Productioni will be awarded through an international competitive procedure to qualified generation companies.   

In order to make the best use of its resources and maximize the profitability of its assets, in 2009 Terna instructed its subsidiary SunTergrid to undertake the construction of photovoltaic plants on unused land adjacent to the transformation stations leased from the Parent Company. Absolutely negligible in 2009, the production of electricity actually began only in 2010. The power produced was withdrawn and exploited by GSE S.p.A., according to the dedicated withdrawal mechanism provided for by the Energy Account, thus ensuring Terna’s total neutrality with regard to the sale of electricity on the Electricity Market.

In December 2009, SunTergrid incorporated a new company, Rete Rinnovabile S.r.l. (RTR S.r.l.), which took over all the projects for photovoltaic production that became operational in 2010. The corporate structure of the company, which was then sold on March 31, 2011 to Terra Firma Investments (GP) 3 Limited, satisfied both the requirements of functional and accounting separation from the Parent Company and compatibility with Terna S.p.A.’s bylaws and license, as well as with the provisions of Legislative Decree 79/99 (the so-called “Bersani Decree”).

In October 2010, Rete Rinnovabile S.r.l. also acquired 98.5% (corresponding to 1,118,106.99 euro) of Valmontone Energia Srl from Troiani & Ciarrocchi S.r.l. and C.I.EL. S.p.A. The purpose of the company acquired by RTR is the design, construction, and management of the network of photovoltaic plants.  

In November 2010, Terna signed the definitive agreement for a strategic partnership with CrnoGorski Elektroprenosni Sistem AD (“CGES”), the TSO of Montenegro, and the government of Montenegro, which is its majority shareholder, to construct the new electrical interconnection between Italy and Montenegro. On January 25, 2011, Terna acquired 22% of CGES.

Today’s Terna is the result of the liberalization of the electricity industry begun in 1999, when the role of TSO was assigned to GRTN – Gestore della Rete di Trasmissionei Nazionale, a government-controlled company. In November 2005, Terna – which already owned almost all of the National Transmission Grid – acquired the role of TSO from the latter, with the related human and material resources, as established by the Prime Minister’s Decree of May 11, 2004. The reunification of the ownership of the grid, with the exception of a few segments, and its management coincided with Terna’s independence from the Enel Group, of which it had previously been a part. Terna now competes in the market with total strategic and managerial autonomy. It can count on the technical expertise acquired in the past.


Number of employees 3,468
Turnover in millions of euro 1589
Total capitalization in millions of euro
Km of three-phase conductors
Km of lines
     underwater cable