Project
Why the project is important
The Niederwil – Obfelden project is part of the capacity expansion of the line between Beznau (canton of Aargau) and Mettlen (canton of Lucerne) from 220 kilovolts to 380 kilovolts along its entire length. The section between the substations in Niederwil (canton of Aargau) and Obfelden (canton of Zurich), which is approximately 17 kilometres long, is already a source of congestion in the Swiss and European transmission grid. Its expansion will improve energy distribution in Central Switzerland, the supply of electricity to the greater Zurich area and electricity exchange between Switzerland and Europe. This is becoming increasingly important due to the growing expansion of renewable energies in Europe.
From the planning corridor to the actual line routing
For the Niederwil – Obfelden project, the Federal Council has approved a combination of an overhead line and around 4.5 kilometres of underground cabling under the protected Reuss landscape. Plans to lay the entire line underground were rejected after careful consideration of the interests involved. Further information on the decision regarding the corridor and the technology can be found in the Federal Council’s press release (available in German, French and Italian).
At the end of 2022, Swissgrid started the detailed planning of the construction project on the basis of this decision. The exact route of the line and the locations of the pylons and transitional structures were determined. These transitional structures connect the overhead line and underground cable sections. The construction project meets the requirements for regional planning and environmental and landscape protection. As far as possible, it takes into account the concerns of the population and remains technically and economically feasible.
An initial proposal for the routing of the line was examined by federal offices and the cantons. At the same time, Swissgrid set up a Project Advisory Council – consisting of representatives of the cantons of Aargau and Zurich, the affected municipalities and interest groups. The aim was to engage in constructive dialogue in order to find the most balanced compromise between the various demands placed on the project. Feedback from the Project Advisory Council and official statements were incorporated into the planning and led to the final construction project.
The future line route at a glance
The new 380 kilovolt line will be around 18.6 kilometres long, 4.4 kilometres of which will be laid as underground cables. The overall project can be divided into seven sections:
Overhead line and pylon design
The pylons will be made of steel mesh and be between 55 and 89 metres high. This height is necessary in order to comply with the cantonal regulations regarding the height of forest growth and to ensure that the necessary safety distance is observed between the treetops and sagging conductors. The «Donau» pylon design is used for forest spanning to allow installation at a lower height thanks to its wider lateral cantilevers.
Underground cable section
The power cables will run in cable conduit blocks – two adjacent conduits, each designed for 380,000 volts, with a distance of 1.5 metres between them. They will be covered by at least 1 metre of soil so that the area will remain usable for agriculture. Deep-rooted plants will only be permitted to the sides. The cables will cross underneath the Reuss using the horizontal directional drilling method – requiring a total of four bore holes.
Transitional structures
Transitional structures will connect the overhead line and underground cable sections. They will be located in the municipalities of Besenbüren and Jonen.
Why underground cables should only be used selectively
Laying new underground cables in the Swiss transmission grid only remains possible to a very limited extent. This is the result of the Swissgrid cable study, which shows that the physical properties of underground cables make stable grid operation and the rectification of disturbances much more difficult. An uncontrolled increase in the proportion of underground cables in the extra-high-voltage grid would have a negative impact on Switzerland’s security of supply. For future grid projects, the possibility of installing an underground cable should therefore be considered from an overall perspective. You can find out more about the cable study in our blog post «When physics sets limits for technology».
Illustration of the new line
Public consultation and next project steps
At the beginning of October, Swissgrid submitted the planning application – consisting of the planning approval dossier and the environmental impact report – to the Swiss Federal Inspectorate for Heavy Current Installations (ESTI). The public consultation of the project is planned between 23 February and 24 March 2026 for a duration of 30 days. Affected parties can consult the documents at the municipal administration offices and lodge an objection with the ESTI. If disagreements persist, the Swiss Federal Office of Energy will take over the negotiations. At the end of the planning approval phase, the authorities will either issue the construction permit or impose additional conditions. This decision can be contested by the authorities, associations or directly affected parties. The Federal Administrative Court and the Federal Supreme Court will then render a verdict.
Provided that no objections or legal proceedings delay the project, Swissgrid will be able to begin construction of the new line in mid-2028. The work will take around four years. Once the new 380 kV line has been commissioned, the existing 220 kV line can be dismantled. From 2032, the residents in Niederwil and Hermetschwil-Staffeln in particular will benefit from a much better situation. In the event of appeals and legal proceedings, commissioning may be delayed by several years.
Schedule
The following schedule is based on the current planning status and represents the best possible scenario, without taking into account potential legal proceedings.
Project Advisory Council
Swissgrid is responsible for drawing up the construction project on the basis of the planning corridor defined by the Federal Council. However, there is a certain degree of design latitude for every project. Swissgrid sets up a Project Advisory Council during the construction project phase to exchange information with stakeholders. This committee, initiated by Swissgrid, is made up of representatives of the cantons, municipalities, environmental associations and interest groups. The design latitude of a project can be applied to best effect when the members of the Project Advisory Council express their opinions candidly, point out options for action and introduce them constructively into the discussion. Swissgrid notifies the Project Advisory Council of the current status of the project and provides information about associated issues such as environmental measures, the route of the line and easements. In addition, Swissgrid accepts observations from the Project Advisory Council that enable the project to be optimised – for example to coordinate the line routing with the regional planning of the municipalities. The aim is to engage in dialogue with official bodies, municipalities and affected parties to find the best possible solution, taking into account the numerous demands placed on the project. The Project Advisory Council is a consultative forum which promotes mutual understanding and allows different concerns to be raised directly.
The following persons were members of the Niederwil – Obfelden Project Advisory Council:
Project Advisory Council meeting held on 25 January 2024
The first meeting of the Project Advisory Council took place in Niederwil on Thursday, 25 January 2024. After a brief introduction and discussion of organisational points regarding the tasks of the Project Advisory Council, Matthias Schmid, Head of Project Lines / Substations at Swissgrid, explained the project development to date. Project Manager Luis Mata then informed the members about the current planning status of the Niederwil – Obfelden grid project. He explained the procedure for developing the approximate route and showed examples of the various transmission technologies. You can find the full presentation of the meeting in the download area below.
Project Advisory Council meeting held on 26 June 2024
The second meeting of the Project Advisory Council took place in Niederwil on Wednesday, 26 June 2024. Project Manager Luis Mata informed the members about the current planning status of the Niederwil – Obfelden grid project and summarised what had been developed since the last Project Advisory Council meeting as part of the construction project. The main focus of the meeting was on the environmental impact assessment (EIA), which was explained by Simon Bohnenblust from Prona AG (spatial/environmental planner), as well as on the input from the authorities, cantons and municipalities in the preliminary EIA study and within the framework of the Project Advisory Council. The feedback and comments reveal a fundamental conflict of objectives in the routing of the line, which was discussed by the Project Advisory Council. Swissgrid is now analysing the feedback in greater depth and, where possible, incorporating it into the development of the construction project. The full presentation of the meeting can be found in the download area below.
Project Advisory Council meeting on 23 October 2024
The third meeting of the Project Advisory Council took place in Niederwil on Wednesday, 23 October 2024. Project Manager Luis Mata gave an update on the current planning status of the construction project. He also informed the members about the current schedule and the next milestones. The planning approval process is expected to start in mid-2025, at which point the project will go on public display. In dealing with the conflicting objectives highlighted at the last meeting (municipalities: greater distances to settlements; canton: fewer forest locations), Swissgrid is focussing on a specific weighing of interests for each pylon location. This focussed on the Niederwil and Hermetschwil-Staffeln areas. The concerns of the municipalities, cantons and landowners are incorporated into the detailed routing and planning, the latter particularly in the small-scale optimisation of the pylon sites. In addition to the Niederwil – Obfelden project, Swissgrid also provided an insight into a national topic at this Project Advisory Council meeting: Andrea Mäder, Head of Public Affairs, gave a short presentation on the so-called «Grid express» (consultation on the amendment of the Electricity Act) and explained Swissgrid's position. You can find the full presentation of the meeting in the download area below.
Project Advisory Council Meeting on 11 June 2025
On Wednesday, 11 June 2025, the fourth and final meeting of the Project Advisory Council took place in Niederwil. Project planner Christian Albanbauer (Axpo) reviewed the work completed since the last meeting in October 2024 together with the members and provided an update on the current project status. A key topic was the upcoming submission of the planning approval dossier, which is scheduled to take place in the coming weeks. Project manager Luis Mata outlined the key aspects of the procedure, time dependencies, and the contents of the project documents that will be made publicly available as part of the planning approval process. Simon Bohnenblust (environmental consultant, Prona) provided information on the field surveys for ecological assessment and the planned compensatory measures. Swissgrid asked the municipalities to already submit concrete project ideas for potential ecological compensation measures. Communications officer Sandra Bläuer explained the communication measures Swissgrid is planning in advance and how the public will be informed about the information events prior to the public participation phase. To conclude, the Project Advisory Board reflected on the collaboration. Swissgrid thanks the members for their committed participation and the valuable input that contributed to the development of the project. The full presentation from the meeting can be found below in the download section.
