Tomorrow’s electricity grids

The German electricity grid will have to adapt to the requirements of the energy transition. This means: needs-based expansion of the electricity grid and continuous development of grid operations.

Smart operating resources can purposefully optimise the current energy infrastructure, thus reducing necessary expansions to a manageable level.

Statistics & facts

Extra-high-voltage transmission grid
High-voltage distribution grid
Medium-voltage distribution grid
Low-voltage distribution grid
Electricity grids

Electricity grids in transition

Germany’s electricity grid is the main stage for the energy transition. The changing conditions present major challenges. It is dena’s role to support this transformation process.

How the energy transition is transforming grid operation

In order to assess which actions the energy transition requires, it is first necessary to understand the basic structure of the electricity grid. Like a road network extending from a motorway to a country lane, the electricity grid also has routes that can be assigned to different hierarchical levels, depending on their function. While the largely lossless transmission grid (high-voltage level) transports  the energy nationwide from the power stations to the major consumption centres, the distribution grid is responsible for carrying the electricity throughout the regions to the end users.  At least this is the traditional division of labour; but it is changing gradually as the energy transition progresses. Extra-high-voltage wires achieve values of up to kilovolts (kV), but high, medium and low-voltage lines will not manage more than 110 kV and 35 kV, i.e. 400 V.

The electricity grid is changing from a distribution to a “collection grid”.

The distribution grid in particular is required to handle new tasks in order to accommodate increasing quantities produced using decentralised and renewable energy sources. In some cases, generation can even exceed consumption in a grid section when large numbers of decentralised power generation units are connected to the distribution grid, turning the distribution grid into a “collection grid”. The electricity grid must then compensate fluctuations and maintain reliable supply, even in peak load times. Flexibility, i.e. the capability of the grid to balance out local fluctuations in generation and load, is key here.

Broadly speaking there are two ways to make the electricity grid more flexible and therefore efficient, and fortunately they are complementary: the grid can be optimised both by expanding it, as well as by introducing changes to its operation. The latter method takes a flexible approach, for instance by integrating energy storage systems that withhold electricity in times of low demand and then release it when energy requirements increase. Moreover, application of a smart demand side management (DSM) system allows companies and private households to deactivate some of their electrical devices at certain times. This flexible load displacement is an effective method of easing the strain on the grid.

dena studies help build momentum

In its Grid Study II, dena analysed the integration of renewable energy sources in the German electricity supply system for 2015 to 2020, including a forecast for 2025. It found that an additional 1,700 to 3,600 km of extra-high-voltage lines will have to be built, depending on which transmission technology is used – while at the same time optimising the current integrated grid. Grid Study II focused on the transmission grid. In contrast, the dena Distribution Grid Study deals with high, medium and low-voltage grids. The results confirm a significant need for enlargement by 2030. The dena Ancillary Services Study indicates not only that there are changes in the required expansion of electricity grids, but also in their operation. It shows that decentralised energy plants and grid operating resources can and must accept greater responsibility for the electricity system, as conventional power stations, which primarily meet our need for ancillary services today, will have far shorter operating hours in future. 

Grid expansion und ancillary services are necessary

In summary: A double-pronged strategy is recommended. This will require the expansion of the electricity grid wherever necessary, and secondly, the systematic exploitation of alternative, operational options. In other words, wherever possible the introduction of smart control to improve capacity utilisation of the existing grid. There is additional information on this topic on the website set up by dena at:

Our projects


Die dena-Verteilnetzstudie hat den Aus- und Umbaubedarf in den deutschen Stromverteilnetzen anhand zwei alternativer Ausbauszenarien für die erneuerbaren Energien detailliert untersucht. Die Ergebnisse belegen einen deutlichen Erweiterungsbedarf für die Hoch-, Mittel- und Niederspannungs- sowie zwischengelagerte Umspannebenen bis zum Jahr 2030.


  • Veröffentlichung: Dezember 2012
  • Partner der Studie: 17 Unternehmen (Schwerpunkt Netzbetrieb und Energieversorgung)
  • Beteiligung eine Fachbeirats aus Ministerien und Verbänden
  • Bearbeiter: dena, Technische Universität Dortmund/ ef. Ruhr GmbH, Prof. Dr. Gert Brunekreeft

Grid Flex Study

In its “Grid Flex Study", dena is investigating how storage facilities can be used to increase flexibility in the electricity grid. The aim is to identify operating models for storage facilities that are economically viable and which reduce the load on the electricity grid.


  • Project start: February 2016
  • Study duration: 12 months (until the end of January 2017)
  • The partners in the study are 23 companies from various industries (grid operators, energy providers, plant engineers and providers of storage facility solutions)

Grid Study I and II

With the help of Grid Studies I and II, dena presents the measures which will allow the German electricity grid to meet the challenges of the future: through targeted grid expansion and at the same time optimising the existing energy infrastructure.


  • Grid Study I: released in February 2005
  • Grid Study I: 17 partners from the industry (grid and installation operators as well as their associations) as well as the Federal Ministry for Economic Affairs and Energy (BMWi) and the Federal Ministry for the Environment, Nature Conservation, Building and Nuclear Safety (BMUB)
  • Grid Study II: released in November 2010
  • Grid Study II: 14 partners from the industry (grid and installation operators as well as their associations) as well as the Federal Ministry for Economic Affairs and Energy (BMWi) and the Federal Ministry for the Environment, Nature Conservation, Building and Nuclear Safety (BMUB)

Ancillary Services Platform

In the future, renewable energy, storage facilities and other alternative providers of ancillary services can and must make a greater contribution towards the security and stability of our electricity system. With the aim of creating the necessary framework conditions in a swift and timely manner, the dena Ancillary Services Platform pools the results of individual activities in the field of future ancillary services, identifies areas in which action is required and promotes exchange between and communication with experts.


  • Project duration: September 2014 to September 2017 (36 months)
  • Partners of the platform: 22 companies from various industries (system operators, energy suppliers, system manufacturers) as well as politicians and associations