Research Wind repowering United Kingdom

Weather-adjusted screening flags 30 UK onshore wind assets for repowering review

Separating genuine underperformance from a bad wind year across 102 sub-12MW assets

19 September 2026 Manni Truong

Why raw capacity factor is the wrong screen

A site with low output in 2023 might just have had a quiet year - or it might be a turbine quietly underperforming its own long-term normal. Telling these apart means asking what a site *should* have produced given that month's actual wind, not comparing it to a fleet average or its own multi-year mean, both of which blur the two causes together.

A fleet-wide weather benchmark

We pool every asset-month together - not asset-year, which cancels out most of the real month-to-month weather signal before a model ever sees it - and fit expected capacity factor from four things: the site's long-term wind resource, how that month's wind compared to the site's own long-term average for that same calendar month, the turbine platform, and shared seasonal and year effects across the fleet. No site gets its own fixed effect, so a persistently underperforming site can't quietly absorb its own shortfall into the model - it shows up as a gap instead.

30 of 102 assets show a persistent gap

Most assets track their weather-adjusted benchmark closely - a strong wind month lifts output, a weak one lowers it, roughly as the model predicts. Thirty assets don't: their output falls short of the benchmark persistently, across enough months and years that it isn't explained by any single bad season.

Click a point, or a row below, to inspect that asset.

Hover over or select a point to show details.

Every modelled asset: long-term wind resource against its mean weather-adjusted performance gap.

Mean performance gap against years until ROC subsidy ends - bottom-left is where a technical problem and a financial trigger arrive together.

Same assets, on the map.

What the data can and can't tell you

A persistent gap is a screen for investigation, not a diagnosis. It's consistent with several distinct causes - mechanical underperformance, wake effects from neighbouring turbines, grid or commercial curtailment - that monthly generation and weather data alone can't separate. Flagged assets are candidates for a closer, site-specific look, not confirmed underperformers.

All 102 modelled assets, ranked by mean performance gap

Asset	Flag	Mean performance gap	Resource percentile	Turbine platform	Years of data
Westmill Wind Farm	priority repowering investigation	-0.0873	24.5098	Siemens SWT-1.3	11
Galsworthy Wind Park	priority repowering investigation	-0.0809	77.451	Enercon E70	11
Loscar Farm	priority repowering investigation	-0.0776	54.902	Other / rare	11
High Haswell Wind Farm	priority repowering investigation	-0.0765	49.5098	Vestas V80	11
Torrance Farm Wind Park Extension	priority repowering investigation	-0.0726	2.451	Other / rare	11
Haddo	priority repowering investigation	-0.0625	64.2157	Other / rare	11
Stonish Hill (Bilsthorpe)	priority repowering investigation	-0.061	41.1765	REpower/Senvion MM82	11
Goonhilly Downs Wind Farm Repower	priority repowering investigation	-0.0579	94.1176	Vestas V90	11
South Sharpley Wind Farm (Revised)	priority repowering investigation	-0.053	49.5098	Vestas V80	11
Westfield	priority repowering investigation	-0.05	7.8431	Nordex N90	11
Park Spring Wind Farm	priority repowering investigation	-0.0496	37.2549	GE 2.85	11
Phase 1 Bettyhill Wind Farm	priority repowering investigation	-0.0473	88.2353	Enercon E82	11
Hill of Fiddes	priority repowering investigation	-0.0433	80.3922	Enercon E70	11
Avonmouth Wind Power	priority repowering investigation	-0.0397	17.6471	REpower/Senvion MM92	11
Burnt House Farm	priority repowering investigation	-0.0337	31.8627	Other / rare	11
Burgar Hill	strong resource, normal performance	-0.033	97.549	Nordex N80	11
Lochhead Farm	priority repowering investigation	-0.0281	15.6863	REpower/Senvion MM82	11
Loftsome Bridge	priority repowering investigation	-0.0259	29.4118	Nordex N60	11
Langley Moor	priority repowering investigation	-0.0244	27.451	REpower/Senvion MM82	11
Tilbury Docks	priority repowering investigation	-0.0232	20.5882	Siemens SWT-2.3	10
Lindhurst Wind Farm	priority repowering investigation	-0.0227	53.9216	Unknown	11
Michelin Tyre Co Ltd - Dundee	priority repowering investigation	-0.0224	4.4118	Enercon E70	10
Achairn	strong resource, normal performance	-0.022	92.1569	REpower/Senvion MM82	11
Marr Windfarm	priority repowering investigation	-0.0211	35.7843	REpower/Senvion MM92	11
North Pickenham Airfield	priority repowering investigation	-0.0201	61.7647	Vestas V90	11
Delabole (Repowering)	strong resource, normal performance	-0.0187	82.3529	Enercon E70	11
M1 Wind Farm	priority repowering investigation	-0.0154	42.1569	Enercon E48	11
Roskrow Wind Turbines	strong resource, normal performance	-0.0151	84.3137	Other / rare	11
Darracott Moor	strong resource, normal performance	-0.0145	69.6078	Gamesa G52	11
Lairg Wind Farm	priority repowering investigation	-0.0142	5.8824	Nordex N80	11
Penrhys Wind Farm/Ferndale Power Factory	priority repowering investigation	-0.013	14.7059	Enercon E48	11
Mynydd Portref	priority repowering investigation	-0.0124	56.8627	Gamesa G52	11
Trimdon Grange	priority repowering investigation	-0.0114	49.5098	Nordex N60	11
Barlockhart Moor	priority repowering investigation	-0.0111	95.098	REpower/Senvion MM92	11
Barmoor South Wind Farm	priority repowering investigation	-0.0108	78.4314	Unknown	11
Hampole Wind Farm	weak-resource site	-0.0107	35.7843	REpower/Senvion MM92	11
Sober Hill Wind Farm	strong resource, normal performance	-0.0103	58.3333	Unknown	11
Skelmonae Wind Farm	strong resource, normal performance	-0.0093	64.2157	Enercon E48	11
Sancton Hill	strong resource, normal performance	-0.0089	58.3333	Vestas V80	11
Tod Hill Farm Wind Turbines	weak-resource site	-0.0063	2.451	GE 2.85	11
West Knock Wind Cluster	strong resource, normal performance	-0.0058	74.0196	Enercon E48	11
The Hollies	strong resource, normal performance	-0.0054	83.3333	Nordex N60	11
High Hedley Hope 2 (Extension)	weak-resource site	-0.0052	27.451	Nordex N60	11
Haswell Moor	weak-resource site	-0.0043	49.5098	REpower/Senvion MM82	11
Arnish Moor	strong resource, normal performance	-0.0041	86.7647	Nordex N60	11
Strath of Brydock	strong resource, normal performance	-0.004	96.0784	Enercon E70	11
Jacksbank Wind Farm (Glenbervie)	weak-resource site	-0.004	13.7255	Other / rare	11
Ardoch and Over Enoch Wind Farm (Ardoch)	weak-resource site	-0.0032	9.3137	Siemens SWT-2.3	11
Upper Ardgrain Wind Farm	strong resource, normal performance	-0.0025	74.0196	Enercon E48	11
St John's Well	strong resource, normal performance	-0.0017	64.2157	Enercon E48	12
Seamer Wind Farm - Hambleton	strong resource, normal performance	-0.0004	60.7843	REpower/Senvion MM92	11
St. Johns Hill	strong resource, normal performance	0.0008	67.1569	Other / rare	11
Wear Point	strong resource, normal performance	0.0017	90.1961	REpower/Senvion MM82	11
Wern Ddu Wind Farm	weak-resource site	0.0024	6.8627	Enercon E70	11
Mossmorran Wind Farm	weak-resource site	0.0028	23.5294	Enercon E82	11
St. Breock Re-Power	strong resource, normal performance	0.0033	70.5882	Vestas V80	11
Carsington Pasture	weak-resource site	0.0034	46.0784	REpower/Senvion MM82	11
Point Wind / Beinn Ghrideag Farm	strong resource, normal performance	0.0037	86.7647	Enercon E82	11
High Sharpley Wind Farm	strong resource, normal performance	0.0046	68.6275	Nordex N60	11
Earl's Hall	strong resource, normal performance	0.0053	71.5686	REpower/Senvion MM92	11
Torrance Farm	weak-resource site	0.0054	18.6275	Other / rare	11
Blyth Harbour Wind Farm (re-power)	strong resource, normal performance	0.0067	76.4706	Other / rare	12
Ark Hill	weak-resource site	0.0079	4.4118	Enercon E48	11
Hammar's Hill	strong resource, normal performance	0.0083	99.0196	Other / rare	11
Whittlesey Wind Farm	weak-resource site	0.0131	39.2157	Vestas V90	11
Spurness Wind Farm Repowering	strong resource, normal performance	0.0131	100.0	Vestas V80	11
Low Spinney Wind Farm	strong resource, normal performance	0.0136	52.451	REpower/Senvion MM92	11
Craig Wind Farm	weak-resource site	0.0141	12.7451	Nordex N80	11
Ramsey Wind Farm Extension	weak-resource site	0.0148	31.8627	Vestas V90	11
Cairnmore Farm	weak-resource site	0.0154	10.7843	Other / rare	11
Watford Lodge	weak-resource site	0.0154	47.0588	Unknown	11
Broom Hill Farm	weak-resource site	0.0157	27.451	REpower/Senvion MM82	11
Bilbster Wind Farm	strong resource, normal performance	0.0166	92.1569	Nordex N60	11
NEILSTON WIND FARM	weak-resource site	0.0178	19.6078	Nordex N90	11
Land at Overside and Greenwellheads Farms	strong resource, normal performance	0.0204	74.0196	Enercon E70	12
Middleton Wind Farm	weak-resource site	0.0221	9.3137	Other / rare	11
Carcant Windfarm	weak-resource site	0.0229	38.2353	Siemens SWT-2.3	12
Wathegar wind farm	strong resource, normal performance	0.0234	92.1569	REpower/Senvion MM82	11
MSD Cramlington	strong resource, normal performance	0.0264	59.8039	REpower/Senvion MM92	11
Meikle Carewe	strong resource, normal performance	0.0268	67.1569	Gamesa G52	11
Burgar Hill (land Near), Evie	strong resource, normal performance	0.0269	97.549	Enercon E70	11
Spicer Hill Wind Farm	weak-resource site	0.0276	44.1176	Enercon E70	11
Muirhall	weak-resource site	0.028	22.0588	Unknown	11
Braich Ddu	weak-resource site	0.0283	11.7647	Nordex N60	11
Denzell Downs Wind Farm	strong resource, normal performance	0.0306	79.4118	Vestas V80	11
Tedder Hill Wind cluster	strong resource, normal performance	0.0323	85.2941	Nordex N90	11
Blackstone Edge	weak-resource site	0.0323	44.1176	Nordex N80	11
Greendykeside	weak-resource site	0.0345	0.9804	REpower/Senvion MM82	11
Forss Wind Farm (Extension)	strong resource, normal performance	0.0368	89.2157	Siemens SWT-1.3	11
Boardinghouse Wind Farm	weak-resource site	0.0377	31.8627	REpower/Senvion MM92	11
Greenhill Croft	strong resource, normal performance	0.0399	64.2157	Enercon E82	11
House O'Hill	strong resource, normal performance	0.04	74.0196	Enercon E48	11
Shielburn Farm	strong resource, normal performance	0.0424	55.8824	Enercon E70	11
Lilbourne Wind Farm	strong resource, normal performance	0.0432	52.451	Other / rare	11
Shooters Bottom Wind Park	weak-resource site	0.0486	25.4902	Enercon E70	11
Moel Maelogen A Phase 2	weak-resource site	0.0498	16.6667	Siemens SWT-1.3	11
Ramsey 1	weak-resource site	0.0506	31.8627	Vestas V90	11
Chelveston Renewable Energy Park Wind Farm (Bedford)	weak-resource site	0.0554	40.1961	GE 2.85	11
Hazlehead	weak-resource site	0.061	44.1176	REpower/Senvion MM82	11
Muirhall Extension	weak-resource site	0.0664	22.0588	Other / rare	11
Srondoire Community Wind Farm	strong resource, normal performance	0.0906	81.3725	Vestas V80	11
Woolley Hill Wind Farm	weak-resource site	0.0965	34.3137	Other / rare	11

Source: Ofgem, Companies House, ned2

Where this leaves investors

Flagged assets span the resource spectrum - their mean resource percentile (44) sits close to the cohort median, not concentrated among either the strongest or weakest wind sites. That's consistent with what the method is designed to do: separate a site's underlying wind resource from its weather-adjusted performance, so the flag reflects a persistent delivery gap on its own terms, not a proxy for site quality. A flagged asset at a strong-resource site and one at an average site warrant the same kind of investigation, for different reasons.