Untangling UK Wind power production

Cross posted from Clive Best. Clive is a physicist of some distinction and a climate and energy blogger with coding skills that go beyond the norm. In this post he explains the portion of UK wind power generation that is metered by BM reports and that portion that is not. This is vital to the understanding of load factors, economics and the efficiency of UK wind power.

There are currently 6044 operational wind turbines in the UK with a total capacity of 12.133 GW. Do we know how much electrical power they generate? The answer is not simple. These 6044 turbines are installed in over 700 sites, some of which are very large while others are only a single turbine.  There are 3 ways to connect them to the Grid.

1. Direct transmission line to the Grid. This is suitable only for large wind farms especially off-shore. The output of such wind farms is metered through the ‘balancing mechanism’, from which Gridwatch and this site get their live updates. A full list of these directly connected wind farms are given below.

Wind Farm Capacity (MW)
Arecleogh 120
Clyde 462
Carraig Gheal 46
Crystal Rig 138
Greater Gabbard Offshore 501
Griffin Wind Farm 204
Gwynt y Mor offsgore 592
Hadyard Hill 130
Humber Offshore 220
Harestanes 126
London Array 720
Lincs Offshore 540
Ormonde 160
Sherringham Shoal Offshore 315
Thanet Offshore 300
West of Duddon Sands 382
Whitelee 511
Walney Offshore 369
Westermost Rough 205

Total Capacity = 7.1 GW

I had thought that these were all the ‘metered’ wind farms included in the Balancing Mechanism BM reports. However I later discovered that those in category 2 are also metered because they receive constraint payments.

2. Secondly there are wind farms that are registered  with the Balancing Mechanism, but are ‘BM embeded’ in the local distribution network. These large to medium wind farms are still visible to the Balancing Mechanism and their output is metered. We know this as they receive constraint paayments to disconnect when there is too much wind. This is the list of such wind farms

Baillie Wind Farm 52.5
BETHW-1 29.75
Braes of Doune 74
Berry Burn Wind Farm 66.7
Beinn An Tuirc 2 43.7
Burbo Offshore Wind 90
CLDRW-1 37
Clachan Flats 15
Dalswinton Windfarm 30
Gordonstown 13
Goole Fields Wind Farm 34.476
Glens of Foudland 26.7
Gunfleet Sands Demo 11.7
Great Yarmouth Power Limited 405
Hill of Towie 48
Minsca Wind Farm 36.8
E_RHEI-1 52
Tullo Extension 25

Total capacity = 1.1GW

Therefore the total metered capacity of wind farms within the BM system is simply the sum of category 1 and category 2.

Total Metered Capacity = 8.2 GW

The real-time output from category 1 and 2  wind farms is shown below:

3. Now there are about 600 smaller wind farms ranging from 1 up to to 40 turbines that have a connection to the regional Distribution Network Operator (DNO) and are paid ‘Feed-In Tariffs’ (FITS). These smaller wind farms are not part of the balancing mechanism and are therefore not metered centrally. Their net effect on the National Grid is to reduce demand slightly via the local distribution network. They must have an on-site transformer to convert generated DC to 3-phase AC and connect to the local DNO. They may also use generated energy locally and then get paid a discount because it is ‘green’. The exported electricity  is metered locally and receives the FIT as shown below.


The estimated total FIT capacity of these 600 farms =  3.8 GW (the difference of 12GW and the metered total).

Unfortunately the output from wind farms in category 3 is never made public. It is impossible to know the real-time power from these wind farms. What I originally set out to discover was  what percentage of  total wind power is measured by the Balancing Mechanism. It has been a headache to get all this information together, but I think we can now estimate the total output from all UK wind farms. To do this we can simply assume that the load capacity for the  feed-in wind farms is the same as that for the metered farms, (which may be optimisitic as the largest farms are off-shore). Under this assumption  the correction factor to be applied to the BM reports values is 12/8.2 = 1.46.  So the actual wind power  from all UK wind farms to electricity generation in the UK right now is:

Therefore I will in future increase the BM reports values for wind power output by this factor to better reflect the actual situation.


  1. UK Wind Energy Database (UKWED)
  2. Elexon
  3. Variable Pitch
  4. Renewable Energy Foundation


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17 Responses to Untangling UK Wind power production

  1. Leo Smith says:

    I considered doing this for gridwatch, but decided that would lay me open to charges of ‘guesstimating’

    In fact what is more accurate is to take annual figures which are recorded somewhere, and estimate the actual capacity factor as compared with metered farms. That gives a more realistic picture as the smaller farms are not nearly as good at getting their heads above the boundary layer as the big turbines are.

    • clivebest says:

      You’re right. The load capacity will be lower for the small wind farms. I don’t think the annual figures actually are available as that would tell you how much they get paid.

  2. Willem Post says:


    A better way would be to get the capacity factor of the smaller wind turbine installations that ARE metered and apply that CF to the ones that get FITs.

    Adding in the offshore wind turbine installations grossly overstates the UK energy production as their CFs is significantly higher than onshore.

    BTW, I NEVER call them farms, as that implies crops and animals, less noise, more bucolic, etc.

    • clivebest says:

      I agree. The capacity factor for the small wind “farms” is likely to be less than the big ones which are mainly located in Scotland and off-shore. I estimate the difference is likely to be of the order of ~0.8 (a guessed ratio of 0.23/0.28).

      That would reduces the compansation factor to ~1.2

      The problem is that the figures are not made public. David Mackay says he tried to get monthly figures published for each installation while at DEC. After all – this is what they get paid by us the consumers.

      Incidentally they get paid the same FITs price at night !

  3. bobski2014 says:

    I get confused with so many noughts, but at 13:46 on the 27th 2,800 MW divided by 6044 I calculate to be 0.46 MW. Considering that at least some offshore windmills are 5MW each that would confirm how lousy the idea is. If my simple arithmetic is accurate.
    Our neighbour’s irritating 50kw one has a CF of around 16% and is little more than an eyesore.

  4. Ed says:

    I wish people would talk about energy generated in a given year instead of peak power and load factors. Keep things simple.

    In 2013 onshore wind generated 17 TWh and offshore wind 11.4 TWh. Simple. If this is shared between 64.1 million people it gives us 1.21 kWh per day each. This is enough to light a 40W light bulb each, with a little left over. This is an average. On windy day we would be able to have a couple of 40W light bulbs on while on becalmed days, none at all.

  5. BillB says:

    Could someone here clarify how ‘parasitic consumption’ is recorded by the system.

    RWE Innogy publish interesting live data on the output of their wind turbine arrays and other renewables sites. This occasionally shows large wind installations to be recording a negative output, i.e. consuming substantial amounts of power.


    For example, at 00.35am on 24 April, 2015, Greater Gabbard, an offshore installation with a headline capacity of 509MW, was recorded as producing “-4,880kW”.

    • Euan Mearns says:

      This is a good question. I sometimes see windmills going round on days when there is zero wind, and so wonder if they are used as “spinning reserve”, a means to help balance the grid? We need Hugh, Leo or Clive to answer.

      • Euan

        Part of the answer is that the axles have to keep spinning otherwise they would distort under the weight of those enormous propellors.

      • A C Osborn says:

        Euan, as far as I am aware it is prevent Brinelling the bearings, which occurs if the weight of the system is left in one place for any length of time.
        During those periods the Wind Farm/Turbines will be drawing energy from Grid.
        I think you will also find they also have to heat the unit if the ambient temp drops below zero to prevent them from freezing and Brinelling.

  6. PhilH says:

    Doesn’t this article confuse the UK with GB? The National Grid and its Balancing Mechanism serves just GB – NI’s grid was separate, and is now (increasingly?) integrated with that of the RoI.

    According to the UK Wind Energy Database, GB currently has 5651 operational turbines, with a capacity of 11,528 MW. (NI having the difference from the article’s figures: 393 turbines of 606 MW capacity.)

    How does this alter the conclusions of this article?

  7. A more accurate way of accounting the unmetered (by NG thus BMRA) wind installations might be to group both them and the metered farms geographically and then use the metered farm output percentage of max in each group to estimate output on the unmetered farms in the same area. Would probably need a number of locations in Scotland as there is quite a spread in distance and terrain!!

    Note that the NG-BMRA figure for capacity of metered GB wind farms has been ‘stuck’ at 8403MW for some time!!

    National Grid have primary agreements for metering with Generation Licenced and Transmission connected stations. Basically anything over 50MW is supposed to be licensed but those embedded (distribution connected) farms up to 99MW usually get an exemption (they apply to DECC who issue a Statutory Instrument in Parliament).

    Thus (partly my efforts from the late 90’s to ensure adequate observability) NG also have separate agreements with embedded unlicensed generation stations. This came to a head with BETTA as In Scotland this is supposed to cover anything over 5MW (North Scotland) or 30MW (South Scotland) because the Transmission is only 132kV up there. In England the limit is 50MW. There are also some voluntary smaller participants.
    Hence list 2 on Clive’s post.

  8. David MacKay says:

    There is a paper by Staffell and Green that uses public NASA weather data and Renewable Obligation monthly data to deduce the hour-by-hour output of all wind farms in the UK, including the unmetered ones. It is a good paper and it resolves the answer to the “decline in performance of wind farms” question.

    • clivebest says:

      Thanks – that is a very interesting paper.

      A second impact is that more capacity will need to be installed to produce a given level of output. The UK has a target for energy production from renewable sources (15% of all final energy by 2020), as opposed to a target for peak capacity. If turbine build rates peak in the coming years, the average age of the UK’s wind farms will creep upwards, and so the output from a fixed capacity can be expected to decline. For every year the fleet ages, an additional 435 MW (4 large farms) would need to be brought online to maintain the original capacity of the UK’s anticipated 30 GW fleet.

      Modern nuclear plant has a load factor of 90% whereas even the aging UK AGR fleet still manages over 70%. If you properly fold in infrastrucure replacement costs ( 20y for Wind and 60y for Nuclear), then nuclear is far cheaper. Allways on nuclear power can also be used at night for all those future electric cars, and split water to H2.

    • Euan Mearns says:

      While detailed understanding of load factors and wind performance is important it misses the heard of elephants in the room and that is energy infrastructure multiplication and energy storage.

      We already have 8GW of wind in Scotland, and I’m persuaded to stop raging against the machine and to try and work with it. Spent the day looking at energy storage options and decided that the supernova has a long lead on pumped hydro storage.

      Click chart for a big version.

  9. Rob says:

    What effect does wind power have on the price of CCGT
    If we use gas as peaking or back up to wind surely this will
    distort or increase prices as wind power has greater market share
    Is there any evidence of increase price of gas turbines


    • Clive Best says:

      This has already happened in Germany where Gas is being priced out of the distorted green market. REW have mothballed a modern CCGT plant for exactly this reason.

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