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The transmission system operators

The transmission system operators – responsibility for system stability and modernisation

The transmission system operators have an obligation towards society. This responsibility is laid out in Section 11 of the German Energy Management Act (Energiewirtschaftsgesetz or EnWG), defined as “operating and maintaining a stable, reliable and efficient power supply network in an unbiased manner, optimizing, enhancing and expanding this in line with demand.”

The TSOs are therefore responsible for the security and stability of the German power supply system. This means that they must guarantee the uninterrupted exchange of electricity across all regions using their power lines and also ensure that generation and consumption levels are balanced at all times. The extra-high voltage grids currently face big challenges, particularly in light of the turnaround in German energy policy that was decided upon in 2011; with this Energiewende sustainable changes are being made to the current energy infrastructure. As the proportion of renewable energy sources used in electricity generation grows, so too do the demands on the extra-high voltage network. In some regions of Germany the amount of energy produced from wind-powered plants already exceeds the network’s capacity. Over the coming decades, the main task of the transmission system operators will therefore be to establish an infrastructure for the German energy supply that is fit for the future and equipped with up to date, efficient and environmentally friendly technology.

© 50Hertz

Company portraits

In Germany, there are four transmission system operators (TSOs) who are responsible for the nationwide supply and transmission of electricity at extra-high voltage: 50Hertz, Amprion, TenneT TSO and TransnetBW.


Over 40% of Germany’s installed wind energy output comes from the 50Hertz network region. This means that the company is not only responsible for providing electricity to 18 million people, but also for one of the largest energy export regions in Europe; it is a world leader in the integration of energy from renewable sources.

At 50Hertz, eight locations with around 800 members of staff are kept busy ensuring a constant electricity supply to their region. 50Hertz’s network area comprises around 109,360 km², covering Berlin, Brandenburg, Hamburg, Mecklenburg-Vorpommern, Saxony, Saxony-Anhalt and Thuringia. The 9750 kilometre-long network is managed and monitored from the Transmission Control Center in Neuenhagen, near Berlin. Company headquarters are located in Berlin.

Since May 2010 the Belgian transmission system operator Elia and the Australian infrastructure fund Industry Funds Management (IFM) have been shareholders in the company. 50Hertz is also a member of the international Elia Group.

Furthermore, 50Hertz is responsible for connecting the offshore wind farms in the Baltic Sea to the national grid. EnBW Baltic 1, the first commercial offshore wind farm in the Baltic Sea, has officially been in operation since May 2011.


At 11,000 km long, running through seven German states – from Lower Saxony to the Saarland and all the way to the Austrian and Swiss borders – Amprion operates Germany’s longest extra-high voltage network from its company headquarters in Dortmund. In a network covering 73,100 km², Amprion supplies 27 million people with energy – almost 1000 members of staff work around the clock to guarantee a stable, secure and economically viable electricity supply.

Amprion plans to invest almost 10 billion euro in its transmission network by 2025. The main shareholders are German financial investors from the insurance and pension fund industry. RWE AG holds a minority share.

Amprion has a very important position in the electricity market thanks to its central geographic location. Amprion also plays a key role beyond the borders of its own region – from its company headquarters in Dortmund and Brauweiler near Cologne, the company carries out vital tasks in the coordination of Germany’s four control areas as well as in the field of international energy transport. Amprion maintains interconnecting lines to nine foreign transmission system operators and can thus fulfil the demands of European electricity traders with the highest levels of safety during transport. These capacities will continue to grow over the coming years.

TenneT TSO

From the Danish border to the Alps; covering 140,000 km² – about 40% of Germany’s total area – more than 20 million people rely on the electricity supply from TenneT TSO GmbH. The TenneT company consolidates the knowledge and innovation of two countries – in October 2010 TenneT TSO GmbH was established as the German subsidiary company of the Dutch transmission system operator TenneT. As the first cross-border transmission system operator in Europe, the company connects power lines between Germany and the Netherlands and does a lot of work in international cooperation and transfer of expertise, particularly in the offshore sector.

10,700 kilometres of extra-high voltage network are operated, maintained and developed by TenneT TSO and its more than 1000 employees. The network region reaches all the way from Schleswig-Holstein in the north, though Lower Saxony and Hesse down to Bavaria in the south of the country. The company management operates from Bayreuth, other key centres of operation are located in Lehrte near Hanover and in Bamberg. The energy grid is monitored from the control centres established in Lehrte and Dachau, near Munich where load flow and power system security calculations are made as well as forecasts of electricity demand; these form the foundation of the secure transport of energy throughout Germany and are key to maintaining a stable grid frequency.

TenneT Offshore GmbH, an associate company, deals with all matters concerning connection lines at sea, whilst TenneT TSO handles transmission on land.


The 340 employees of TransnetBW GmbH watch over the 3200 km of extra-high voltage grid in their 34,600 km² region. TransnetBW GmbH operates the transmission network in Baden-Württemberg, which is connected to the national and European integrated network at a number of cross-border transfer points. At the borders of its control area, it is directly connected not only to networks within Germany, but also to those in France, Austria and Switzerland.

The company’s headquarters are located in Stuttgart, however, the true core of the company lies in Wendlingen, just outside Stuttgart. TransnetBW’s system control centre is one of the most state-of-the-art in Europe; from here the company carries out nationwide load offsetting for energy generated from combined heat and power stations.

The limited liability company under German law (GmbH) is run as an Independent Transmission Operator and is part of EnBW Energie Baden-Württemberg AG.