Tidal Lagoon Development
Cardiff Capital Region (CCR) is undertaking feasibility and initial development studies of a proposed tidal lagoon at Aberthaw, on the South Wales coast.
The project emerged from joint work undertaken by CCR and the West of England Mayoral Combined Authority (WECA) following the recommendations of the independent Severn Estuary Commission. That work examined potential locations across the entire Bristol Channel and Severn Estuary and identified Aberthaw as offering the best overall balance of energy potential and environmental, physical and infrastructure considerations.
Initial analysis indicates that a lagoon at Aberthaw could generate around 600MW of predictable renewable electricity – enough for approximately half a million homes – and operate for more than 100 years. Economic analysis estimates that its development and construction could generate around £3.5 billion in UK economic value and support thousands of jobs, creating significant opportunities for businesses and supply chains across South Wales, South West England and the wider UK.
This next stage will explore whether the project can be technically feasible, environmentally responsible, and commercially viable.
There is currently no fixed design for the lagoon and no decision has been made to construct it. The next phase will develop and assess potential options, with environmental evidence, engineering work and stakeholder input shaping the project from the outset.
The Severn Estuary
The Severn Estuary has one of the highest tidal ranges in the world, reaching up to 14.5 metres. This creates the potential to generate significant amounts of renewable electricity by harnessing the difference between high and low tides.
Tidal energy has an important advantage: the movement of the tides can be predicted many years in advance. It could therefore provide a reliable and predictable source of low-carbon electricity that complements other renewable technologies, such as wind and solar, while supporting the UK’s long-term energy security. The scale of this opportunity has been recognised for decades. Previous studies have considered a range of projects, from barrages spanning the Estuary to tidal lagoons located along its coastline.
The Severn Estuary and Bristol Channel is not simply an energy resource. It is also a unique and internationally important natural environment, supporting a wide range of habitats, fish and bird species. Large areas are protected through national and international environmental designations. The Estuary is also important for communities, ports, shipping, fishing, recreation and industry.
Exploring the potential for tidal energy and protecting the Estuary cannot be treated as separate activities: the environment must be central to deciding whether a project is possible and how it should be designed.
The Severn Estuary Commission
The independent Severn Estuary Commission was established in March 2024 to reassess the potential for tidal range energy in the Severn and identify a credible way forward.
The Commission engaged with more than 500 experts and stakeholders from over 200 organisations. These included environmental bodies, governments, regulators, local authorities, industry, investors, academics and community representatives. Its work examined environmental impacts, engineering, energy-system requirements, economic opportunities, funding and financing. It also considered lessons from previous tidal energy proposals that had not progressed.
The Commission concluded that tidal range energy in the Severn Estuary was feasible, but recommended a different approach from previous proposals. Rather than immediately pursuing one of the largest possible schemes, it recommended a staged programme beginning with a commercially viable but relatively smaller tidal lagoon.
This first scheme was described as a Commercial Demonstration Project to demonstrate that tidal range energy can be environmentally responsible, technically deliverable and commercially competitive. It could also build the knowledge, skills, supply chains and investor confidence required to inform decisions about any future projects.
The Commission recommended that environmental considerations should be integrated into the design process from the beginning, and that the early development stages should be publicly led.
The Commission’s reports, supporting evidence and recommendations can be found on the Severn Estuary Commission website.
Commercial Demonstration Project
Following the Commission’s recommendations, CCR and WECA worked together to identify a potential location for the Commercial Demonstration Project.
This was undertaken as a cross-border programme, recognising that the Severn Estuary and Bristol Channel are a shared natural asset and that the environmental, energy and economic implications extend across South Wales and South West England. The work began by examining potential development areas on both sides of the Estuary. Independent technical analysis was used to compare the opportunities and constraints associated with different locations.
This included spatial mapping of a wide range of environmental, physical and infrastructure considerations. Potential projects were then considered against the Commission’s criteria for a Commercial Demonstration Project. The project needed to be large enough to demonstrate tidal lagoon technology at a commercially meaningful scale, while remaining smaller and more manageable to minimise its environmental impact. It also needed to have the potential to operate as a viable standalone project and avoid, as far as possible, the most sensitive parts of the Estuary.
The work identified the coastal area around Aberthaw as offering the best overall balance. The area benefits from a strong tidal range, avoids major commercial shipping routes and is close to existing energy infrastructure and industrial land.
This does not mean that Aberthaw is free from environmental or technical challenges. The area includes important habitats and environmental designations, and more evidence is required to understand the potential effects of any project. Identifying Aberthaw establishes a preferred area for further investigation; it does not determine the lagoon’s final boundary, alignment, or design.
What happens next?
The next stage will undertake the initial feasibility work needed to improve our understanding of whether an environmentally credible and commercially viable lagoon can be developed at Aberthaw.
This will include outline engineering design, environmental studies, site surveys, hydrodynamic modelling and commercial assessment. It will examine how different potential designs could affect water movement, sediment, habitats, species, flood risk, navigation and other uses of the Estuary.
A central principle will be environmental and engineering co-design. The project will not begin with a predetermined engineering design and consider its environmental effects afterwards. Instead, environmental evidence will help determine the scale, location, alignment and operation of any emerging proposal.
Stakeholder engagement will be an important part of this process. CCR and WECA will work with local communities, environmental organisations, regulators, local authorities, ports, marine users, businesses, landowners, academic institutions and the Welsh and UK governments as the evidence and potential options develop.
Any future proposal would be subject to further assessment, consultation and the relevant planning and regulatory processes.
More information about the development programme, stakeholder engagement and opportunities to participate will be published as the work progresses.
Frequently Asked Questions
CCR is beginning the exploratory phase for a potential tidal lagoon at Aberthaw. This does not mean a lagoon has been approved or that construction will take place. The next phase will undertake the engineering, environmental, economic and commercial work needed to understand whether a viable project can be developed.
More FAQs will follow as the project develops; these new FAQs will often be more technical in nature. Come back for more updates.
Cardiff Capital Region is funding and leading the next phase of development at Aberthaw, building on work undertaken jointly with the West of England Mayoral Combined Authority following the recommendations of the independent Severn Estuary Commission.
The independent Severn Estuary Commission was established to examine whether tidal range energy could be developed in the Severn Estuary and, if so, how this could be done in a way that balances the opportunity for large-scale renewable energy generation with the estuary’s environmental, economic and social importance.
The Commission engaged with more than 200 organisations and 500 individuals and published its final report in 2025. It concluded that tidal range energy in the Severn is feasible and recommended beginning with a smaller Commercial Demonstration Project (CDP) tidal lagoon.
The Severn Estuary has significant potential for tidal range energy, but it is also an internationally important environment and supports communities, industries, ports and shipping.
The Severn Estuary Commission therefore recommended starting with a smaller Commercial Demonstration Project rather than immediately pursuing a much larger scheme. The CDP is intended to demonstrate that tidal range can be commercially viable while providing evidence on environmental effects, engineering, construction and operation that can inform decisions about whether further tidal lagoons should be developed in the future.
The Severn Estuary and Bristol Channel has one of the highest tidal ranges in the world and represents one of the UK’s largest potential sources of renewable energy. Unlike weather-dependent renewable generation, the tides are entirely predictable years in advance.
Tidal range could therefore complement technologies such as wind and solar by providing long-life, predictable renewable electricity. The wider Severn Estuary has the potential to provide renewable electricity at nationally significant scale, which is why the Severn Estuary Commission recommended further development work.
The current concept is for a lagoon of around 600MW, potentially generating approximately 1.3TWh of predictable renewable electricity each year – enough to meet the equivalent annual electricity needs of around half a million homes. These figures are indicative and will be refined as the design develops.
No. There is no final lagoon alignment or design at this stage. The next phase will develop and assess potential configurations, including the marine wall, turbine and sluice locations and landfall arrangements. Engineering and environmental considerations will be developed together rather than starting with a fixed design.
No. This is an early development phase, not a construction decision or planning application. Aberthaw has been identified as the preferred location to investigate further, but significant engineering, environmental, consenting and commercial work remains. The project could change substantially as evidence develops, or ultimately not proceed.
No decision has been made on how construction of the lagoon would be funded. Developing the commercial and financing approach will form part of the next stages of work.
The Severn Estuary Commission considered potential financing models for tidal range infrastructure, including a Regulated Asset Base (RAB) approach, which is already being used to support the delivery of other major UK energy infrastructure. Any future approach would require further development and engagement with the UK Government, regulators and potential investors.
If the project progresses towards a planning and consenting application, there would be formal statutory consultation as part of that process. Before then, CCR intends to engage with communities and stakeholders during the development phase so that issues and opportunities can be considered while the project is still being shaped.
Previous work indicates that a tidal lagoon of this scale could take around a decade to progress from early development to operation. Construction would only take place if the project successfully progresses through development, environmental assessment, consenting, financing and future investment decisions.
The next phase will develop the evidence needed to understand whether an Aberthaw tidal lagoon is technically, environmentally, commercially and economically viable. This will include engineering and environmental co-design, hydrodynamic modelling, surveys and investigations, environmental assessment, stakeholder engagement and development of the commercial and business case.
For more information please contact us at info@cardiffcapitalregion.gov.uk.