Fixed versus floating offshore wind

Difference between fixed and floating offshore wind

At the end of 2021 cumulative installed global offshore wind capacity was approximately 57 GW. Only approximately 140 MW of this is floating, with the rest fixed to the sea bed. Fixed offshore wind projects generally use one of two basic designs for foundations. These are the:


  • A hollow steel tube driven into sea bed.
  • Lowest-cost foundation available at depths up to 50 m, depending on ground conditions.
Examples of monopile foundations.
Figure 10 Examples of monopile foundations.


  • A lattice structure with three or four legs, typically fixed to the sea bed using pin piles or suction buckets.
  • More expensive than monopiles to fabricate and install in waters generally less than 60 m, less expensive in deeper waters and where challenging ground and load conditions would otherwise make monopiles too expensive.

Fixed offshore wind foundations are generally the cheapest way of building offshore wind farms, but they are limited to shallow water depths. Fixed foundations have been installed in waters up to 55 m, and future fixed projects off Scotland are planned in waters up to 75 m deep.

Examples of jacket foundations being transported.
Figure 11 Examples of jacket foundations being transported.

Why use floating offshore wind?

Floating substructures allow the development of offshore wind in new areas with higher water depths where it is not possible to develop fixed offshore wind projects. This brings five main advantages:

Allowing offshore wind to be used in new markets

  • Almost all constructed offshore wind capacity is fixed and located in markets where there are large, shallow continental shelves, such as in Northern Europe.
  • Floating substructures allow projects to be developed in areas that don’t have as much shallow water available such as the west coast of the US, Japan and South Korea.

Increasing the offshore wind capacity of existing markets

  • By opening new areas of the sea bed for development, floating offshore wind can reduce the need to develop sea bed that is already constrained by competition with other human use cases, such as defence, fisheries, the harvesting of marine aggregates, tourism and conservation.
  • Projects less in constrained areas can be developed with more certainty than those that have clear conflicts of interest. Historically, legal challenges have slowed or prevented developers from realising projects in these areas.
  • Floating offshore wind may also be preferable in areas where the sea bed conditions create challenges for installing fixed foundations, for example where hard sediments require foundations to be drilled into the sea bed, or in areas where soft sea bed conditions require deep piling to achieve stability.

Reducing emissions from oil and gas production

  • Floating offshore wind farms can provide power to offshore oil and gas production facilities which might otherwise use large quantities of fossil fuels and are too deep to be partially powered by arrays of fixed offshore wind turbines.
  • For example, Equinor’s 88 MW Hywind Tampen project will meet around 35% of the power needs of five Norwegian platforms in the Gullfaks and Snorre fields, which are in waters 300 m deep.

Capturing more energy

  • Around 80% of the total ocean area is too deep for fixed foundations.
  • Many deep-water areas are also located far offshore, where wind resources are stronger than fixed offshore wind locations.
  • For example, the average capacity factor of a UK fixed offshore wind farm in 2020 was 45%.[1] This means the projects produced slightly less than half of the theoretical maximum amount that could have been produced if there were consistently strong winds offshore. For the UK’s first floating offshore wind farm the capacity factor over the same 12-month period was 57.1% – the highest in the UK[2].
  • s to areas already developed with fixed offshore wind projects, producing power at different times of the year or day as they belong to different wind regimes. This could make floating projects complementary to fixed offshore wind projects within the broader energy system.

Providing local economic benefits

  • Fixed offshore wind foundations are usually manufactured at specialist facilities around the world, providing few economic benefits to the area local to the offshore wind farm.
  • Floating substructures are generally larger and heavier structures than fixed foundations making storing and transporting them over large distances difficult. This means that floating substructures will need to be produced, either from scratch or using prefabricated components, in ports close to future floating offshore wind farms.
  • This will drive significant investment and create jobs in ports close to floating offshore wind farms.

[1]The Crown Estate, ‘Offshore Wind Report’, 2021, available online at , last accessed July 2022

[2]Equinor, ‘Hywind Scotland remains the UK’s best performing offshore wind farm, March 23 2021, available online at, last accessed July 2022

Barriers to floating offshore wind growth

The market for floating offshore wind will grow significantly over the next decade. The rate of growth for floating offshore wind projects will largely be determined by how quickly these three barriers can be overcome.

Higher costs

  • At present the cost per MWh of floating offshore wind energy is higher than the costs for fixed offshore wind projects. This means floating offshore wind farms are reliant on price support schemes run by governments.
  • One of the drivers of higher costs is the fact that floating offshore wind is a new and largely unproven technology which increases project finance and insurance costs for developers.
  • We expect the cost of floating offshore wind to fall as developers, suppliers and the wider industry gain experience, and projects increase in size allowing economies of scale to be realised.

Supply chain

  • At present there are not enough ports in the UK with the right combination of quayside length, water depth and storage space to support the simultaneous development of GW-scale floating offshore wind projects.
  • Manufacturing facilities for the mass production of floating substructures need to be established to ensure the UK supply chain has the capacity to support the buildout of projects at scale.
  • A competitive and capable UK supply chain is essential to securing significant cost reductions and fully capturing the economic benefits of floating offshore wind.

Technological challenge areas

  • Component specific issues need solving. These include the design and fabrication of new technology such as floating substations, dynamic export cables and optimising existing technology such as mooring systems.
  • Refining installation methodologies is critical. At present the largest floating offshore wind project (Hywind Tampen) contains just 11 turbines and will require a two-season installation campaign. Installing a project that has 60 turbines in a single season represents a significant challenge. Current difficulties include storing constructed floating substructures and finding suitable weather windows to tow floating offshore wind turbines into position.
  • Establishing ways of maintaining and servicing floating offshore wind turbines is essential. It is undesirable to tow floating offshore wind turbines to shore for repairs so new tooling and technology is required to fix issues offshore to limited downtime when problems occur.
  • In the UK the Carbon Trust and the Offshore Renewable Energy Catapult actively support innovation around particular floating technological challenge areas.

Guide to a floating offshore wind farm