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"Wind theft is the term coined to describe the reduction in wind energy available to downstream wind turbines due to the 'wake effect' created by upstream wind turbines."
What is wind theft?
“Wind theft” is the term coined to describe the reduction in wind energy available to downstream wind turbines due to the “wake effect” created by upstream wind turbines. This “wake effect” means that wind passing through the upstream turbine slows down and becomes more turbulent, forming a “wake” that can extend for tens of kilometres, thus adversely affecting the output of downstream turbines.
Whilst the largest impact is between turbines in the same wind farm, wake effects originating in one wind farm can impact the output of other neighbouring wind farms.
Why now?
The concept of wind theft is not new, in fact it has been modelled by scientists and developers for years, but it has become a more pressing concern as the deployment of offshore wind accelerates and distances between wind farms decrease. The UK is at the forefront of this issue by virtue of being one of the world’s most mature offshore wind markets and where accelerated deployment is expected to meet government Net Zero goals.
Developers, faced with a potential loss of output that threatens their profitability, have been clashing over the issue. In fact, it is estimated that up to 20 GW of wind farms in UK waters are now affected by wind wake disputes.¹ One of the most high-profile of such disputes – between Ørsted and BP and EnBW – recently saw Energy Secretary Ed Miliband wade in, siding with Ørsted by requesting BP and EnBW assess how wake effects from their new offshore wind development will affect existing Ørsted sites in the Irish Sea.
This position echoes the recently published UK government consultation – which has acknowledged the issue of wind theft through proposed planning and policy updates that seek to encourage coordination among developers.
Proposed amendments to the energy National Policy Statements
On 24 April 2025, the Department for Energy Security and Net Zero (“DESNZ”) published a consultation in relation to the revised energy National Policy Statements (“NPS”) that support energy infrastructure, including EN-1 (overarching NPS for energy) and EN-3 (NPS for renewable energy infrastructure). The updates include new guidance on spatial planning for offshore wind farms that aim to minimise inter-farm interference, promote coordinated development of offshore wind clusters and ensure sustainable and efficient use of marine space.
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"There is no requirement for inter-project compensation where wake effects are present."
Under the new guidance, there is no expectation on developers to eliminate wake effects entirely, but they must carry out an assessment of inter-array wake effects between their proposed development and nearby offshore wind farms that are either planned, consented or operational. Following this assessment, developers must take “reasonable steps to minimise as far as possible the impact of wake effects”. Examples of steps that could be taken in mitigation include optimising the turbine layout to reduce downstream turbulence, changing the spacing of turbines to minimise wake overlap, coordinating with neighbouring developers to align layouts or share data, using advanced modelling tools to stimulate and reduce wake interactions and considering turbine types with lower wake effects.
Once an assessment and reasonable steps to mitigate have taken place, the developers can take their project to the planning phase and, crucially, even if residual wake effects remain, this is unlikely to carry more than limited weight against the project in the planning process.² There is no requirement for inter-project compensation where wake effects are present.
The consultation window closed on 29 May 2025, and feedback will now be considered before any further amendments to the energy NPS are made. While the current proposals certainly recognise the risks posed by wind theft to the UK’s growing offshore wind market, they have stopped short of adjudicating on who should shoulder the associated risks.
Risks
Wind wakes pose a significant threat to the predictability of wind farm revenues – not only is it challenging for developers in the planning stage to predict whether new wind farms will be built upstream or downstream of their proposed site, but the scale of the impact is also difficult to quantify. This is cause for concern when revenues are typically modelled over a 25–30-year period, with increasingly tight margins, meaning even a small reduction in projected revenue can have a huge impact on the viability of the project.
These kinds of question marks over future project revenue should be of increasing concern to developers in a market where wind farms are becoming larger and more expensive and thus more likely to be financed through external debt. Ultimately, a less predictable project revenue stream will likely lead to increased debt costs and less favourable financing terms.
Developers must also prepare for an increase in the number of wind wake disputes, in circumstances where, as yet, wind wakes and wind theft are undefined in English law, leading to uncertainty for the parties involved in such disputes (both in terms of the associated cost and the eventual outcome).
The adequacy of law and policy in this area is not the only problem in circumstances where some studies have indicated that wake effects can be felt for up to 100km,³ meaning future disputes could involve multiple jurisdictions, raising complex legal and diplomatic challenges.
Mitigations
Practically, developers can attempt to mitigate wake effects by reconfiguring the layout of their wind farms and considering the location of those wind farms in relation to others (as set out in the proposed amendments to the NPS set out above). However, this is widely considered to be an imperfect solution. In fact, thus far no method of mitigation modelled by independent academics or developers has been able to mitigate more than a small percentage of wake impacts.⁴ Some analysis goes even further, suggesting that building more, poorly configured wind farms in an attempt to mitigate potential wake effects may result in a net loss in generation for both the mitigating wind farm and downstream wind farm(s).⁵
As it stands, the Crown Estate and Crown Estate Scotland employ “buffer zones” between leased seabed areas, designed to manage various external impacts (including wake effects). Going forward, the size of these “buffer zones” may need to be revisited to ensure that they are properly accounting for wind wakes, as well as the ever-increasing size and power of turbines deployed. However, government figures will be keen to ensure that expanding buffer zones (and thus potentially decreasing the remaining area available for wind farm deployment) does not jeopardise the ability to meet wind deployment targets.
In terms of practical steps to consider, we expect that developers will need to lean on technical experts and wind wake modellers more to get the most accurate information they can whilst in the planning stages so that this can be factored in when seeking funding. From a scientific perspective, this is a highly complex issue – so this expertise will be crucial.
Developers can, and do, enter into wake effect agreements, but they are difficult to effect in practice, owing partly to the range of results produced by the different modelling techniques available. This uncertainty means the agreements often stop short of apportioning risk between developers or imposing payment obligations.
For lenders, the most important thing will be for them to consider the impact of potential wake effects in the context of contingency buffers and financial modelling – to ensure that the generation output (and therefore IRR) of the borrower’s project is not overestimated. Some potential mitigations which could be included in finance documentation include:
- increased due diligence: enhanced assessments and reporting as part of the upfront due diligence package;
- ongoing reporting: if it is known that there is, or there is the potential for, another project to be developed in the vicinity of a wind farm, the funders may request more regular reporting once their project is operational so they have greater monitoring and visibility over this specific issue (enabling them to take or require other steps more quickly if a negative impact arises rather than waiting for a financial covenant breach, for example); and
- mandatory prepayments/regearing event: to address a worst-case scenario, the funders could pre-emptively structure a regearing event if the impact of wind theft on the project revenues is significant (but, given the lack of consistency amongst wind wake models, this may be challenging to formulate in practice).
Concluding remarks and future developments
University of Manchester – POUNDS study
"For developers, collaboration may be the only viable way forward."
Whether the wake effects themselves can be mitigated, or just the financial implications, a concerted effort to better understand the concept of wind theft is required. The UK Government has recently announced an initiative in conjunction with the University of Manchester (and ORE Catapult, Arup, RWE, EDF, and The Crown Estate) to address the growing issue of wind theft. The POUNDS (Prediction of UnqualifieD losseS from offshore wind farm wakes) study is a 12-month national-scale research effort that was launched in March 2025. The project will use advanced mesoscale models to simulate and assess wake effects across UK waters with a view to optimising siting and reducing investment risk for the offshore wind market.
The POUNDS project indicates the UK Government’s commitment to addressing wind theft (and continuing to back offshore wind as a means of achieving its goal of Clean Power by 2030).
For developers – being both potential victims of as well as contributors to wind theft – collaboration may be the only viable way forward. The POUNDS initiative described above is certainly a step in the right direction – and it is encouraging to see the collaboration between some major industry players.
Given that this risk (1) will impact players across the market; (2) is difficult to effectively mitigate; and (3) is likely to prove increasingly contentious between project developers as wind farm deployment accelerates, thereby worsening the case for inter-project collaboration as an effective form of mitigation, it may well be that the most realistic mitigation comes in the form of increased government support, for example through adjustments to CfD revenue in future allocation rounds. However, this kind of support would only assist new wind farms under development. Other mitigations, such as the introduction of new industry regulations, may be necessary to address adverse impacts on wind farms already in operation arising from the wake effects of new, neighbouring wind farms.
[1] https://tamarindo.global/insight/analysis/uk-seeks-solutions-for-20gw-wake-effect-disputes/#:~:text=This%20work%20is%20due%20to,Bergen%20in%20Norway%20in%202022.
[2] https://assets.publishing.service.gov.uk/media/6809f0588c1316be7978e7cb/draft-nps-en-3.pdf, para. 2.8.316
[3] https://www.ft.com/content/5a824394-d7c8-4e65-8069-d7be1dd814b4
[4] https://uk.rwe.com/press-and-news/uk-statements-and-opinion/wind-turbine-wakes-and-wake-mitigation/
[5] https://uk.rwe.com/press-and-news/uk-statements-and-opinion/wind-turbine-wakes-and-wake-mitigation/
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