Offshore transmission network review

This review looked into the way that the offshore transmission network is designed and delivered. It concluded in May 2023, and the organisations involved, including the Department for Energy Security and Net Zero, are now implementing its findings to deliver a coordinated offshore transmission regime for Great Britain.


Offshore wind generation plays a central role in decarbonising our energy system to reach net zero and to meet growing consumer demand.

The UK is aiming to generate 50GW of secure, home-grown offshore wind power by 2030. As we increase offshore wind generation, we will need to reinforce the onshore and offshore transmission network infrastructure to deliver the energy from wind farms at sea to consumers across Great Britain.

We launched the offshore transmission network review (OTNR) in 2020 to ensure that the transmission connections for offshore wind generation are delivered in the most appropriate way, and to find the appropriate balance between environmental, social and economic costs.

The review brought together key stakeholders involved in the timing, siting, design and delivery of offshore wind, to consider all aspects of the existing regime and how this influences the design and delivery of transmission infrastructure.

We have published the review outcomes in a summary report. We are now implementing the review’s findings. Project partners continue to deliver several outputs of the OTNR and we will continue to build on its findings in collaboration with them.

The transmission infrastructure and why we need more of it

To achieve our 2030 ambition, we need to transform Great Britain’s energy system. We are working to enable the most efficient and coordinated grid reinforcement to be delivered by relevant parties, keeping new developments to a minimum. However, the transition to net zero will need to be underpinned by new network infrastructure across GB, both onshore and offshore, to meet the scale and pace of demand, and to transport electricity where it is best placed to be generated, to where it is needed most.

Transmission infrastructure is required to transfer the electricity generated offshore, onshore. Overhead lines, underground cables (in designated areas), substations and sub-sea cables are key components of transmission infrastructure.

How the transmission infrastructure is developed and the government’s role

Development of new transmission infrastructure currently takes 11-13 years and is often on the critical path for connection of new generation. The 2022 British Energy Security Strategy (BESS) committed to significantly reduce timelines for delivering strategic onshore transmission network infrastructure, with an ambition to halve the duration of the end-to-end process by the mid-2020s. This is vital for our renewable energy generation ambition.

The process

  • Government works alongside other bodies such as ESO, NGET and Ofgem to deliver energy infrastructure
  • the Crown Estate and Crown Estate Scotland lease areas of seabed to private developers to design and deliver offshore generation
  • the Electricity Systems Operator (ESO) sets out the high-level design for the necessary transmission through independent, evidenced based assessment
  • developers, often transmission operators such as National Grid Electricity Transmission (NGET) or generator developers such as Orsted, can then make applications to build infrastructure. They must show that their proposals meet the nationally set criteria, and that they have considered alternatives and community views . Each project must hold statutory consultations to take into account community views
  • the government does not make planning applications or choose precise routes for energy infrastructure but does have a robust and independent planning process

Offshore Transmission Network Review (OTNR) closure

The following 2 documents mark the move to implementing the review findings:

Projects that have grid connection offers

The Early Opportunities workstream oversees advanced projects with existing connection agreements that were too far advanced to be included in the Holistic Network Design. The Early Opportunities workstream is working with developers on coordinating infrastructure, to deliver near-term benefits to communities and the environment.

To help achieve this, we launched the Pathfinder process. Pathfinder projects will use the enabling regulatory and policy changes to test processes and deliver benefits to communities and the environment by delivering coordinated solutions.

Read more about the first 4 Pathfinder projects and the projects in East Anglia that will enable coordination.

Offshore Coordination Support Scheme

We launched the Offshore Coordination Support Scheme (OCSS) in December 2022, a grant fund to enable successful late stage projects to develop feasible coordinated designs that could be put forward for planning application. The scheme closed in February 2023 and we plan to allocate funding by the end of June 2023.

Holistic Network Design (HND)

19 March 2024: The Holistic Network Design update (HND2)

In summer 2023, the Electricity System Operator (ESO) for Great Britain concluded an important phase of the Holistic Network Design Follow-Up Exercise, meeting the Terms of Reference set by the Offshore Transmission Network Review, a UK government led review. 

The ESO for Great Britain has now published the second Holistic Network Design (HND2) as part of its report Beyond 2030: A national blueprint for a decarbonised electricity system in Great Britain.

These projects are included in the July 2023 Holistic Network Design (HND) or the Holistic Network Design Follow Up Exercise (HND FUE), for which the Electricity Systems Operator (ESO) is responsible.

The HND and HND FUE are recommended designs for the connection of offshore wind farms. The recommendations cover both the on and offshore network, and show how the power should be transported from the wind farms to where it is needed. In some cases, the HND recommends that 2 or more wind farms should build coordinated connections. This means that the wind farms will share some of the infrastructure needed to transport the power generated by the wind farms.

See also:

What happens next for projects in the HND

The HND and the HND FUE will provide recommendations for how to connect offshore wind farms, but they are not fixed, detailed plans. For example, the HND can recommend that a wind farm connects to a specific existing substation, but it will not say exactly what route the cables should take between the wind farm and the substation.

The ‘project promoter’ is responsible for building the transmission projects included in the HND. Ofgem are responsible for deciding who is allowed to build which bits of the network. Ofgem published an update to their consultation for Pathway to 2030 projects.

The project promoter will be either:

  • the company that is building the wind farm
  • a company set up specifically to build the offshore transmission (known as an Offshore Transmission Owner, of OFTO), or
  • one of the 3 onshore transmission owners

The project promoter is responsible for undertaking consultation with communities and other stakeholders in accordance with the requirements under relevant legislation. For Development Consent Orders this includes the Planning Act 2008 and Environmental Impact Assessment regulations.

To have your say on the proposed projects, you should participate in the project promoter’s consultation. Project promoters will share information about proposed projects with affected communities.

9 August 2023: Holistic Network Design Follow Up Exercise phase update

The Electricity System Operator (ESO) for Great Britain has concluded an important phase of the Holistic Network Design Follow-Up Exercise, meeting the Terms of Reference set by the Offshore Transmission Network Review, a UK government led review.

The ESO will now work with Ofgem during their asset classification process, and with Transmission Owners and developers to:

  • determine wider grid reinforcements that will also be needed across the electricity system
  • develop connection agreements
  • agree delivery timescales

This will be published as part of the second Transitional Centralised Strategic Network Plan expected at the end of 2023, as we move towards a whole system approach to network planning that will be undertaken by the Future System Operator, once established.

Future Framework

The Future Framework workstream considers the long-term approach for developing and delivering offshore wind and associated transmission infrastructure for projects connecting from 2030.

In 2021 we consulted on proposals for a new, more strategic end-to-end approach to how offshore wind and associated transmission infrastructure is developed and delivered.

We have considered responses to the consultation and collaborated with OTNR delivery partners to develop 3 key recommendations for a Future Framework for the deployment of offshore wind and multi-purpose interconnectors. The government response to this consultation provides details of the recommendations and actions for implementation.

The key recommendations are:

1. DESNZ will work with project partners to develop a more strategic approach for the deployment of offshore wind and Multi-Purpose Interconnectors.

2. Adopt delivery models to maximise efficiency in terms of cost and risk.

3. Consider the timing of transmission design and delivery.

Initial changes will apply to projects due to become operational by the mid- to late-2030s. The Future Framework will be implemented in a transitional way, with different aspects put in place over time by relevant programmes or activity taken forward by project partners. In the longer-term, the approach will evolve for subsequent projects captured by future iterations of holistic, centralised network planning.

We have published a statement of support from project partners alongside the Future Framework publication, in which project partners confirm their commitment to delivery of the recommendations in line with their existing remits. We will work closely with the Scottish and Welsh Governments to ensure the Future Framework will be implemented in line with devolved functions in Scotland and Wales.

Community engagement

As part of a fair and just transition to net zero, the communities that are hosting future electricity transmission network projects must be recognised for the contribution they are making to support the delivery of cheaper, secure, low carbon energy. We are therefore consulting on community benefits for electricity transmission network infrastructure (closing 15 June 2023), which proposes to introduce voluntary guidance for industry and local communities on working with project developers to decide what benefits they want.

Any scheme will remain separate to the planning process. It will not be a material consideration in planning decisions, and won’t be secured through those decisions.

Delivery partners

The OTNR was led by the Department for Business, Energy and Industrial Strategy (BEIS) and its successor, Department for Energy Security and Net Zero (DESNZ), with support and collaboration from a range of government and industrial bodies. We will continue to work with the project partners as we proceed with implementation.

Expert Advisory Group members

The OTNR operated a multi-tiered governance structure at working and executive guidance levels to ensure it is being delivered in accordance with the Terms of Reference. A key part of this involved engaging with experts across industry, and this will continue into the implementation stage. This group will continue to convene as the OTNR’s findings are delivered following its closure. These experts are listed below :

Name Organisation Representing
Zoe Keeton Offshore Wind Industry Council Chair
Aileen McLeod SHE Transmission Onshore transmission owners
David Adam Scottish Power Energy Networks Onshore transmission owners
Joe Northwood National Grid Electricity Transmission Onshore transmission owners
John Tindal SSE plc Offshore wind developers
Marc Smeed Corio Generation Offshore wind developers
Nicola Crawford-Percival RWE renewables Offshore wind developers
Oyvind Bergvoll Equinor ASA Offshore wind developers
Bruce Turner Transmission Investment Offshore transmission owners
Gary Thornton Diamond Transmission Corporation Offshore transmission owners
Ruben Pastor-Vicedo National Grid Ventures Interconnector developers
Andrew Hiorns Independent consultant Technical expert
Robert Hull Riverswan Energy Advisory Industry expert
Xiao-Ping Zhang University of Birmingham Academia
Gilles Etienne ENTSO-E European partner
Tania Davey The Wildlife Trust Environmental group
Dai Richards Hitachi ABB Power Grids Supply chain
Nigel Platt Siemens Energy Supply chain

Documents and resources

Historic OTNR resources



Multi-purpose interconnector projects