Time to repower
Why some ageing onshore wind assets make stronger repowering candidates than others
In this noteContents
By 2035, some 7GW of UK onshore wind capacity across 400+ projects will have reached 20 years of operation. Screening 102 sub-12MW assets identifies 29 potential repowering candidates, with four sites emerging where performance, resource and network conditions align particularly well.
The repowering opportunity
By the end of 2030, nearly 2.3GW of UK onshore wind capacity will have reached 20 years or more of operation, rising to more than 7GW across over 400 assets by 2035. This creates a growing pipeline of projects where owners will need to consider life extension, repowering, divestment or decommissioning.
In the context of the UK’s renewable targets, this fleet is strategically significant and presents further opportunities for value creation. Existing wind sites can offer advantages over greenfield development through established grid connections, known operating histories and sites already proven for wind generation. But repowering still requires fresh assessment of planning, grid, land rights and project economics.
So where do the stronger repowering opportunities sit?
By the end of 2030 nearly 2.3GW* of UK onshore wind capacity will have reached 20 years or more of operation.
Screening for stronger repowering opportunities
This analysis covers 102 assets commissioned between 2006 and 2015, each below 12MW, totalling some 700MW. These are old enough to warrant consideration for repowering. Using generation performance, wind resource, turbine data and local network conditions we identify sites with a stronger underlying case for repowering.
As generation varies with the weather, a low capacity factor does not necessarily indicate a poor performing asset. We therefore benchmark every asset against the wider cohort using monthly operating data over the past 10 years. The analysis accounts for the site’s long-term wind resource, monthly wind conditions, turbine platform and seasonal effects.
The performance gap then is the difference between an asset’s actual capacity factor and the capacity factor we would expect given the wind available to it. A negative gap means the asset is generating less than its wind conditions suggest it should; a positive gap means it is performing above expectations.
Assets are then flagged into three broad groups:
- Weaker wind site - performing broadly in line with or above expectations but located in a relatively weaker wind resource.
- Stronger wind - performing broadly in line with or above expectations and located in a relatively stronger wind resource.
- Potential repowering candidate - generating persistently less than would be expected given the wind resource available to it.
Use the dashboard below to explore the results for each asset.
Not all repowering candidates are equal
The potential repowering candidates are assets producing less than expected given the wind resource available to them. This makes them a reasonable starting point for further assessment, but not an investment conclusion.
An asset flagged in this group still requires further site-specific assessment to determine whether the repowering case is technically and commercially viable.
Narrowing the opportunity
Local grid conditions can materially affect how much value a repowered project is able to capture. Sites with available generation headroom may offer greater scope to accommodate additional capacity without substantial reinforcement work, and areas with growing electricity demand may be better placed to absorb locally generated power over time.
With this in mind, we overlay DNO generation and demand headroom data on the 29 assets flagged as potential repowering candidates. Focusing on sites with at least median wind resource and three or more turbines narrows the group to four assets.
- Goonhilly stands out for the quality of its wind resource, operating with 6 turbines and a strong demand growth forecast on the local network.
- Lindhurst combines supportive generation and demand headroom signals with a 5 turbine configuration.
- South Sharpley and Mynydd Portref show how more moderate-resource sites can still be interesting where turbine consolidation potential and network conditions align.
These four assets illustrate where the repowering case begins to strengthen: ageing, underperforming multi-turbine sites where the underlying resource and evolving network conditions may support a more productive second life.
Methodology
The analysis covers 102 operational UK onshore wind assets below 12MW, commissioned between 2006 and 2015. Monthly generation data is benchmarked against each site’s long-term wind resource, monthly wind conditions, turbine platform and seasonal effects to estimate the level of generation that would normally be expected.
For each asset-month, the performance gap is actual capacity factor minus this expected (benchmark) capacity factor. Everywhere else in this note, "performance gap" refers to an asset's mean performance gap across every month it has been modelled, not any single month.
Each asset is flagged into one of three groups:
- Potential repowering candidate - mean performance gap is negative and at least 60% of the asset's modelled months are individually negative. This persistence test is what separates a genuinely underperforming site from one that just had a few weak months.
- Stronger wind site - doesn't meet the persistence test above, and sits at or above the cohort's median long-term wind resource.
- Weaker wind site - doesn't meet the persistence test above, and sits below the cohort's median long-term wind resource.
We then combine the performance results with turbine configuration and DNO generation and demand headroom data to identify sites where resource quality, consolidation potential and local network conditions point to a stronger case for further repowering assessment.