The Severn Estuary Commission – will we see a tidal lagoon in the Severn?

Peter Kydd BSc CEng FICE, former SWIP chair and board member for both SWIP and the Great South West’s Energy Security Programme, has been advising on tidal power for over 30 years. But, he asks, have the UK’s tidal power aspirations been too ambitious in the past, resulting in too much paper and no energy?

What is the Severn Estuary Commission?

The Severn Estuary Commission was established in March 2024 by the Western Gateway Pan Regional Partnership – comprising two governments and 28 local authorities – to assess the feasibility of using the Severn Estuary’s large tidal range to generate renewable, clean and predictable energy. 

This followed a year-long assessment – see Severn Estuary Evidence Base and Framework (external PDF download 3.3MB) – undertaken by Western Gateway of the previous work undertaken, lessons learned and understanding the changed circumstances that prevail today.

The Commission was chaired by Dr Andrew Garrad CBE, FREng, one of the pioneers of the UK wind industry.  Instead of being chosen for direct experience in tidal range power development, he and the other commissioners were chosen specifically because of the best-practice expertise they brought from fields relevant to tidal power. More information on these commissioners is available here.

The Commission started work in March 2024, and engaged with more than 500 experts and stakeholders, supported by specialist consultancies, before issuing its final report in March 2025 at the Institution of Civil Engineers in London.

The Commission’s starting point was recognising what has changed since the last strategic consideration of tidal power in 2010 – see Severn tidal power: feasibility study conclusions (external link).

The UK’s rapidly growing demand for electricity, the war in Ukraine and associated widespread geo-political instability, and the rate at which climate change is impacting the planet all represent an urgent need to reduce our dependence on imported energy whilst accelerating production of clean, homegrown energy.

The UK has abundant natural renewable energy resources – particularly wind and tidal. Indeed, the UK has the third largest tidal range in the world.  

However, the Commission faced a challenge – how to balance the local environmental impact of a project with its broader environmental and economic benefit. Finding this compromise was key in their conclusions.

What has the SEC concluded?

The Commission found that developing tidal range power generation in the Severn was both feasible and supportive of the UK’s Net Zero and energy security goals.  While it was not in their remit to recommend any specific projects, they concluded that tidal lagoons are feasible and preferable to tidal barrages due to their low environmental impact.

The Commission’s detailed study also revealed several important conclusions:

• Mature technology: The technology is established and ready to deploy.

• Environmental considerations: The Estuary is highly protected and recognised as a wetland area of international importance. However, climate change is already impacting the Estuary, with rising sea levels and changing habitats. There are significant gaps in environmental data, so better monitoring is needed to guide decisions. Addressing these gaps is crucial to ensure that any development complies with environmental regulations and make sure any loss habitats are replaced or protected.

• Economic benefits: The clean energy industry, which includes tidal power and floating offshore wind, is one of eight growth-driving sectors identified in the UK Government’s Modern Industrial Strategy 2025 (external link). The Commission’s assessment of a range of example tidal lagoon projects shows that they have the potential to create between 30,000 and 220,000 job years and will contribute between £1.6 and 12 billion during the construction phase.

The Severn Estuary area could support new supply chains and has skilled workers available after Hinkley Point C. Tidal projects could also help generate some of the more deprived areas in South Wales.

• Smart Energy Solutions: Building a tidal lagoon is a good alternative to a barrage. They can generate reliable, low-carbon electricity every day using natural rise and fall of rides. Unlike barrages, lagoons cause less environmental damage and can be built in more locations, avoiding rivers or shipping routes.

Moreover, unlike the mainstream renewables such as wind and solar, tidal range energy is highly predictable and available everyday.

Funding approach

The Regulated Asset Base (RAB) model (as proposed for Sizewell C and used for the construction of the Thames Tideway Tunnel) presents the most effective funding approach for tidal range projects, balancing investor confidence and consumer protection.  Consumers would be expected to save significantly over the project’s lifetime compared with other financing methods.

Government support is needed at first to reduce risks and attract private investment. If the first project succeeds, it will help build investor trust and encourage more tidal projects across the UK.

The Commissioners have made seven recommendations based on these positive conclusions:

1. Governments must recognise the role of tidal range energy in the UK’s future electricity supply and support its development as an industry
2. Develop a Commercial Demonstration Project to demonstrate potential and evaluate environmental effects
3. Create a regional plan to enable the better management of the Severn Estuary
4. Develop funding and financing framework to unlock private investment
5. Take a public sector led initial development approach – a Project Delivery Vehicle
6. Invest in research and monitoring to address current gaps in the environmental data and evidence 
7. Take a strategic approach to mitigation and compensation delivery

Will their recommendations be adopted?

The recommendations put forward by the Commission are designed to ensure progress in making the UK a generator of tidal power.  They address the two biggest challenges that tidal power has previously faced, namely the environment, and cost. 

A step-by-step approach

The Commission proposes moving forward at a manageable pace. One example is the idea of building a commercially viable tidal lagoon in an area that is less sensitive environmentally. This approach would:

• Deliver affordable and predictable clean energy
• Be developed in conjunction with the environmental community
• Help fill important gaps in environmental data
• Enable the supply chain to develop and increase the confidence of potential investors

Boost potential investor confidence in tidal energy

A key requirement is for the UK Government to formally recognise the role that tidal power can play in the energy transition to net zero. This means:

• Adopting a National Policy Statement that supports tidal energy
• Creating a better system for managing shared areas like Severn Estuary.

What happens next?

With the UK Parliament’s Environmental Audit Committee formally requesting the Government’s position on tidal range energy in the Severn Estuary, the tide may finally be turning for one of the UK’s longest-running renewable energy debates.

Bill Esterson, Chair of the Energy Security and Net Zero Committee, has welcomed a clear Government position on both the Severn Estuary Commission’s proposals and the wider role of tidal energy in the UK’s future electricity mix.

The Commission’s final report, launched earlier this year, made a case for commercial demonstration tidal lagoon to explore real-world feasibility and environmental impact – recognising the need for a strategic, evidence-led approach to clean, predictable energy from the Severn.

Now, attention is turning to next steps and further work is now planned to convert these recommendations mentioned from the Commission into actions. This includes:

• Discussion with key UK and Welsh Government Departments
• Engaging with key other relevant parties such as The Crown Estate and British Energy and the organisations involved with the Severn Estuary’s various spatial management activities. 
• Develop the business case for a commercially viable tidal lagoon demonstration project and establish the appropriate project delivery vehicle.

Keep an eye out for further updates – more announcements on progress can be tracked on the Severn Estuary Commission News and Blogs page (external link).

What role can SWIP contributors play?

If you haven’t already, read the Commission’s Final Report (external link). It is a short summary report but is underpinned by more expansive technical reports which should provide a valuable technical resource summarising the Severn’s environment and its likely changes due to climate change, the intricacies of the national grid and its market characteristics, the socioeconomic considerations from a large infrastructure project, the engineering of tidal power and the funding and financing options potentially available.

Although tidal power has come in and out of fashion at regular intervals over time, as this year’s ICE State of the Nation report identifies, tidal power may be very relevant as the UK progresses to net zero by 2050.  It could also play a role in adaptation by limiting the impacts of sea level rise. 

A large tidal power project in the Severn Estuary could also build upon Hinkley Point C’s construction legacy and its associated socio-economic benefits.   However, there are relatively few professionals with any experience in tidal power and if a tidal lagoon demonstration project proceeds as proposed, there will be a need to expand the limited skills pool we currently have. 

So if you are involved in coastal engineering, hydropower, marine structures, power systems, environmental assessment, flood defence, finance and consenting, or want to become involved, read up and assimilate!  The next opportunity may be just round the corner!