A Note on UK Renewable Load Factors

I recently came across the excellent UK renewable energy data base maintained by the Renewable Energy Foundation (REF). The data base is highly detailed with over 630,000 small and large scale generators documented based on the subsidy records. The data affords the opportunity to estimate load factors for UK wind and solar. DECC also publishes data on UK load factors (dukes6_5) which are compared with those calculated from REF data.

In summary:

Solar PV UK (REF): 11.8%
Solar PV UK (DECC): 10.8%
Solar PV Scotland (REF): 9.0%
Solar PV England (REF): 11.9%

Onshore wind (REF): 26.3%
Onshore wind (DECC): 27.3%
Offshore wind (REF): 30.5%
Offshore wind (DECC): 37.3%

Generally there is good agreement between REF and DECC with the exception of offshore wind where the DECC number is significantly higher than REF. All the numbers are calculated the same way and so I simply do not understand this discrepancy. DECC and REF should seek to reconcile this.


Figures for installed capacity and production are provided for year end. What we don’t know (or at least don’t calculate) is the distribution of adding capacity with time over the year. DECC take the average of the capacity at the beginning and at the end of the year and I have done same. This is a potential source of bias. Installed capacity MW * 24 * 365 provides the maximum possible generation for the year. Actual generation / maximum possible generation provides the load factor.

The REF data are easily accessed from their web site. Click on the “Energy Data” tab. The data are archived under a number of different headings that allows the data to be interrogated in a number of different ways.


Figure 1 The REF load factors are biased higher than DECC but with no significant difference. REF = 11.8%, DECC = 10.8%.

Figure 2 As is to be expected, the load for Scottish solar is below English solar. Scotland = 9.0% and England = 11.9%.

Figure 3 As is to be expected, the load for onshore wind is lower than offshore wind. There is good agreement between REF and DECC for onshore wind; 26.3 and 27.3% respectively. But poor agreement for offshore wind; 30.5 and 37.3% respectively. 

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41 Responses to A Note on UK Renewable Load Factors

  1. Peter Lang says:


    Excellent post, thank you.

    For interest, the capacity factor for onshore wind in Australia’s National Electricity Market in 2014 was 29%.


    1. Is the output from solar PV actually metered or guessed? If measured, How?

    2. How do you know how much PV capacity is actually in service – as distinct from out of service (often without the owners knowing) or has been removed since it was installed?

    • Euan Mearns says:

      From REF:

      The data above gives the installed capacity in MW and electricity generated in GWh for UK renewable generators from 2002 to date. The data is sourced variously from Renewables Obligation Certificates, Renewable Energy Guarantees of Origin and in the case of some municipal waste generation, from Climate Change Levy Exemption Certificates. Output from small generators that are supported under the Feed-in-Tariff and that do not claim REGOs is estimated from the installed capacity provided in the FiT register.

      So the data are compiled from the documentation that attends subsidies which presumably includes installed capacity and annual generation. IMO, this REF data base is an extremely valuable resource.

      • Peter Lang says:


        Thank you. I am not clear on how the installed capacity of PV is estimated and how the electricity generated by PV is metered (or estimated) in the UK. Is the electricity generated by PV metered for all installations or is it estimated; e.g. from estimated capacity multiplied by solar isolation and factors to allow for less than optimal orientation, installation no longer in service or shaded, etc.?

        I wrote a longer comment yesterday explaining how it is done in Australia and explaining why both capacity and fleet average capacity factor are probably significantly overestimated (in Australia). But the comment didn’t get posted.

        • Euan Mearns says:

          Peter, I don’t know exactly how the subsidy system works in the UK. But I think the subsidy is paid for home use and power sold to the grid. So it must be metered and I’m guessing monthly paperwork and settlement. So this provides a simple means to monitor capacity and production. Check out this page at REF:


          They document 631404 FIT generators.

          But the comment didn’t get posted.

          Sorry about that. It is not awaiting moderation. Unfortunately sometimes comments disappear. Best to always copy before hitting the submit button.

          • Peter Lang says:

            Thank you. Will try to remember in future.

            The link is broken. However, don’t worry, because I suspect UK has the same issue as Australia – i.e. electricity generated by PV is not metered so not measured, and the estimates are probably unreliable.

        • PhilH says:

          If I understand it correctly, every generation system has a generation meter, on whose readings the FiT payment is made or ROC entitlement derived. So someone in the civil service knows how many kWh units have been generated from each installation of each technology (PV, wind, AD, small hydro, etc) each year, because they paid out for them. This is presumably where official gov’t statistics, eg DUKES, get their figures from. It looks like REF gather actual data for ROC systems, but just estimate it for FiT systems – another reason to use DECC’s data over REF’s.

          • Peter Lang says:

            PhilH,”Can you refer me to a link that explains how the generation data is collected from every PV installation? Is every PV installation in UK paind for actual gerneration or is the householder’s bill reduced by the amount of PV generation they generate and use themselves.

            In more technical terms, if UK does ‘net metering’ then I believe UK does not have metering of actual generation. However, if ‘gross metering’ is used for all installations, then perhaps actual generation is measured and reported.

          • Günter Weber says:

            Metering for renewables: http://www.fitariffs.co.uk/eligible/metering/
            (I assume this is valid for small scale installations).

  2. edmh says:

    Some additional information of Renewable capacity factors with data up to the end of 2014 give somewhat more pessimistic results. EurObservER actively supports the Renewable Energy industry.


    Plausible cost comparisons are have been clearly made by the US EIA
    US EIA electricity_generation.pdf 2015 Table 1

    For fuller illustrations from European experience see:

    Accounting for the capacity factors, (the actual electrical output as compared to the Nameplate capcity of the Renewable installation) that are actually reported by the Renewable industry, the overall capital cost of all European Renewable Energy installations averages out at about €27billion / Gigawatt, whereas the cost of a conventional gas-fired generation is about €1billion / Gigawatt.

    That overall value for Renewables at €29billion / Gigawatt is derived from the combination of
    Onshore Windpower €14.2 billion/GW
    Offshore Windpower €41.4 billion/GW
    On Grid Solar Power €48.5 billion/GW

    By 2014 European Union countries had invested approximately €1 trillion in large scale Renewable Energy installations. This may well be an underestimate.

    This has provided a nameplate electrical generating capacity of about 216 Gigawatts, nominally about ~22% of the total European generation needs of some 1000 Gigawatts.

    The actual measured output by 2014 from Renewable Industry sources has been 38 Gigawatts or 3.8% of Europe’s electricity requirement, at a capacity factor of ~18% overall.

    The whole 1000 Gigawatt fleet of European electricity generation installations could have been replaced with reliable, dispatchable, lower capital cost Gas-fired installations for the €1trillion of capital costs already expended on Renewable Energy in Europe.

    However Renewable Energy production is dependent on the seasons, local weather conditions and the rotation of the earth, day and night.

    So the Renewable Energy contribution to the electricity supply grid is inevitably erratic, intermittent and non-dispatchable. It is therefore much less useful than dispatchable sources of electricity, which can be engaged whenever necessary to match demand and maintain grid stability.

    That 3.8% Renewable Energy contribution to the grid is often not available when needed and obversely its mandatory use and feed-in obligations can cause major grid disruption if the Renewable Energy contribution is suddenly over abundant.

    The Renewable Energy industry could not exist without the Government mandated subsidies and preferential tariffs on which it depends. It is not a truly viable business proposition

    Viewed from the point of view of the engineering viability of a nation’s electrical grid, Renewable Energy would never be part of the generating mix without its Government mandate and Government market interference.

    So the Greens in their enthusiasm to save the world from an undefinable but probably minimal threat will destroy civilisation long before the world fails from excessive overheating from CO2 emissions.

    • A C Osborn says:


    • Peter Lang says:


      Could you please give me the source for the figures that total $1 trillion cost of RE in EU

      By 2014 European Union countries had invested approximately €1 trillion, €1000,000,000,000, in large scale Renewable Energy installations.

      Sorry if it’s there and I missed it.

    • PhilH says:

      It’s not clear to me how much of your alternative’s costings are for capital costs and how much are for fuel costs – this is vital as without fuel your proposed thermal power station alternative would be useless. The gold standard for comparing costs of electricity from different technologies seems to be the Levelised Cost of Electricity system – could you recast your numbers in this format so they can be properly compared with the various renewables’ costs, please?

      If the current coal-fired stations were replaced with stations running on gas, which is more expensive, wouldn’t this push up the whole system’s running costs?

      There also seems to be some confusion over capacity and average output in your calculations. If renewables produced an actual average output of 38GW, then that needs to be compared with the actual average output of the 1000GW (or whatever) capacity, which was about 370GW, to derive their contribution to the electricity supply, ie just over 10%, not 3.8% – surely?

      • edmh says:

        for Peter Lang
        The value of about 1000 GW for installed European generating capacity is provided by the EIA at

        for PhilH

        The comparative values of the fuel non-fuel costs for alternate generation means are also taken from the EIA
        Table 1. Estimated levelized cost of electricity (LCOE) for new generation resources, 2020

        This data is condensed as a chart (shown under data sources) showing comparative proportions of capital and variable costs / MWhr : fuel costs for gas firing amounts to about three times the capital cost of gas fired installations.

        These comparative figures are used to assess both the capital costs and running costs comparisons shown in


        The capacity figures are derived from EurObservER data in:

        This gives installed capacity of Solar and Onshore and Offshore wind power and the recorded output for Solar and combined Wind Power in GWhr per year which is easily converted to effective Gigawatts using David MacKay’s formula.

        This then gives the capacity factors achieved by each Nations Renewable Energy installations.

        Europe has an installed Renewable capacity of about 200GW but the eventual output is about 38GW ie an average capacity figure (wind and solar) of about 19% overall.

        The approximate costs for gas fired generation is ~€1 billion / GW this is probably an overestimate. The EIA data comparison is used to generate the approximate capital value of Renewable installations.

        I am happy to provide my trivial spreadsheet containing these data.
        I have been trying to get the orders of magnitude right, using credible RE published data: I would be pleased to hear of any enhancements or corrections.

        • PhilH says:

          Since you answered a different question to the one that Peter Lang asked, may I try to provide an answer: http://oi59.tinypic.com/8vyio3.jpg, from another recent EM post, shows Europe’s cumulative clean-energy investment from 2004 to date to be roughly US$800G = EUR700G.

  3. Leo Smth says:

    The BMreports data available to e.g. Gridwatch suggests the wind capacity factors are nothing like as high as claimed by DECC and renewable UK


    based on BM reports data showed a massive discrepancy between claims and reality.

    IIRC Gridwatch average for on and offshore was around 25-27%.

    • Euan Mearns says:

      This from renewables UK:

      The load factor is the actual output of a turbine benchmarked against its theoretical maximum output in a year. The load factor is calculated by RenewableUK as a rolling average of the past five years using data from the Digest of UK Energy Statistics published by the Department of Energy and Climate Change annually in July.

      • For onshore wind this is 25.74%
      • For offshore wind this is 34.88%

      The load factor for all wind (onshore + offshore) is 28.42%


    • PhilH says:

      The report linked to by Leo derives a LF from BM reports of:
      27.2% for 2009 and 21.1% for 2010.

      DECC’s DUKES 2012 gives a LF of:
      27.1% for 2009 and 23.7% for 2010.

      Given that there could be undetected partial dropouts in the BM data as well as the complete ones detected & adjusted for, and that new capacity comes online in the total fleet and is included in the BM non-linearly with time, BM was over-estimating in one year and underestimating in the other, and was catching in real-time for its subset of farms about 95% of what DECC tallies for all farms when all the dust has settled – this seems pretty good agreement to me.

  4. GeoffM says:

    Scottish Renewables put out a press release around December last year which, whilst it didn’t state the LF for Scottish solar, when one did the simple calculation involving capacity and production a LF of 4% was derived.

    The figure in the main article above of 9% LF for Scottish solar I take with a pinch of salt. I live in Scotland and we hardly see the sun; and most panels are not south-facing.

    I suspect that most data for UK solar is an estimate. If you go to the neta page of the bmreports website, under the Transparency Data tab, go down to Actual Generation, then across to “Actual or Estimated Wind and Solar Power Generation”, it doesn’t seem to specify which is estimated but I guess that it’s mainly the solar.

    Also, groups like WWF have put out press releases where they make big claims for solar generation in Scotland using phrases like “could have” (generated) instead of “did”. They admit using the website weatherenergy.co.uk to get their data, and this website admits that it uses a “software model” to gain the percentages and uses “virtual PV production points”. It also uses the phrase “could have” (been generated). It also admits to using “a number of statistical and technical assumptions” for example that panels sit “on a south-facing roof”.

    No doubt the modelling doesn’t take into account that panels become dustier and dustier over time (I’ve never seen anyone up on the roof cleaning the panels). They probably also don’t account for panels being covered in frost or snow (in my area they are thus covered for typically 2 months each winter).

  5. Last year I estimated a solar load factor of 10.1% for the UK and Ireland:


  6. Roberto says:

    It would be interesting to see a graph with the monthly PV production, just to see how little help is given by PV during the entire 4 months with shorter days, Nov through Feb.

  7. edmh says:

    You may find the example here from Germany gives a very clear idea of the Wind and Solar input to their energy structure.

    They report the bad news as if it is good news with characteristic efficiency.


  8. Roberto makes an interesting point about November through February being the months with the lowest solar PV output. Of course late autumn and winter is also the period when you would expect wind power output to be at its highest. Wind and solar are thus complementary, as can be seen from the following chart for German wind and solar for 2013.


    Incidentally this graph contains the information Roberto was asking for above.

    While wind production is mainly at night, the demand peak is typically during the day. Solar power thus fortuitously becomes available mainly during periods when power prices would otherwise be high. Here’s a chart of how provision of more solar caused “peak shaving” which reduced the peak summer power pricing over a period of seven years.


    So, sure, solar is not available 24 hours a day and 365 days per year. But when it is available it is very useful indeed in the German power grid.

    • Euan Mearns says:

      Germany has among the highest electricity prices in Europe. These dumped wholesale prices do not get passed on to consumers who have to pay the tariffs to renewables producers regardless. The low wholesale prices are breaking the back of the traditional generators – which is the whole point of the Green Dream – isn’t it?

  9. Here’s the information Roberto was looking for – solar by month for 2013, with wind by month thrown in as a bonus.


    Note how solar and wind are complementary, not just by month, but also by time of day. Wind power tends to be at its strongest when there is less solar power available.

    • Euan Mearns says:

      Its totally meaningless / pointless to plot electricity data with 30 day resolution. We are normally using 5 minute resolution – but that’s a lot of work. The Nat Grid data plotted below is at 30 minute resolution – still a lot of work.

    • GeoffM says:

      Not true Peter, as Euan says on his 5.35 pm comment. Look at the “Daily production solar and wind” bar chart for 2014 on this link:

      If my link doesn’t work, go to website ise.fraunhofer.de, on the left click on Renewable Energy Data, on the drop-down click Electricity Production Data, on the right scroll down to Electricity Production Data From Solar And Wind In 2014, when the document has downloaded go down to Daily Energies, look at the 4th bar chart down Daily Production Solar And Wind. You will see that it’s all over the place!

  10. Euan Mearns says:

    I have rediscovered another data mine in National Grid. The chart shows small-scale embedded wind and embedded solar – neither linked to the HV grid. National Grod sees this as negative demand.

  11. Euan Mearns says:

    Here’s solar on its own. It is model based, based on weather and capacity inputs. Click on charts for large copy.

  12. Euan Mearns says:

    And here’s same plotted at appropriate scale of 0-60 GW. Now lets be serious. If these panels were dirty, covered in bird sh*t, covered in snow and frost, pointing north, mounted upside down or left in their boxes, would anyone notice? And January is normally the highest demand month.


  13. Günter Weber says:

    Ending up with more or less the same number for offshore and onshore wind power installations is very strange.

      • gweberbv says:


        because on average you expect higher wind speeds on/near the sea than in the interior country.

        • It is not so much the higher wind speeds which correlate with higher average generation. Far more important is the consistency of the wind, within operating range of the generator. In the extreme, wind turbines are feathered or shut down completely during high winds.

          I believe that off shore winds are more reliable/constant than onshore, hence the difference.

          However, as Peter stated upthread, without reliable metering of output there cannot be reliable data – only guesses. Measuring energy returned to the grid (“negative demand”) is only part of the story. It ignores energy consumed on site and completely overlooks any renewables which are consumed off-grid.

          Currently, those two errors might be small, however if/when renewables, batteries and disconnection from the grid become increasingly common, then their influence will also be greater and, in all probability, not measurable and hence either overlooked or overestimated, according to the objectives of the observer.

  14. yt75 says:

    Thanks for that.
    A question : what are the reference “100%” for these load factors ?

    For solar is it something like “summer light at noon in summer 24/24” ?
    Or “typical sunny day” ?

    And for wind ?

  15. PhilH says:

    There are some curious details deep down in the REF data. Unfortunately the site seems to be down so I can’t check the latest values of the following figures.

    The Walney offshore wind farm is effectively in two halves, built simultaneously and adjacent. One half uses 51 Siemens SWT-3.6-107 turbines, the other uses 51 Siemens SWT-3.6-120 turbines; I’ve no idea what the difference is. When I last looked, REF gave the first a LF of 32%, and the other 45%. This is curious to say the least.

    Also Whitelee, the large onshore wind farm in Lanarkshire, had a very much lower LF (~12% ?) than Black Law (~20-25% ?), another large onshore wind farm in Lanarkshire, both built at a similar time with similar-sized turbines (~2MW).

    I guess the people who really know about wind farms’ LFs are the owners, who’d be keeping such info close to their chests for reasons of commercial confidence. The next most likely to know, and so be reliably accurate, would be DECC, who are the first in line to receive statistics about their actual generation and consequent subsidy payments. REF would be getting their info indirectly.

  16. I have another, sort of alternative energy question. When people talk about how much (industrial) energy is consumed within a country, they are including all industrial sources, from nuclear to oil to coal to solar, etc. But when they say that “country x gets 45 percent of its power from renewables” they are meaning that country x gets 45 percent of its electricity from solar, wind, etc. So I guess I have two questions. 1) Am I reading this correctly, that when they say “power” they mean electricity generation? and 2) Why would that be the case? I understand the definition of power as this: “In physics, the amount of energy put out or produced in a given amount of time. Power is often measured in watts or kilowatts.” But I also understand that “Power is nothing more than the rate at which energy is used. The familiar unit, the Watt, is simply Joules per second. A 100 W incandescent light bulb is spewing 100 J of energy per second in the form of light and heat. It does not make sense to talk of Watts per second or Watts per hour.” So why would someone talk about electricity in terms of power and oil and gas in terms of energy? Why are they seeming to mix those different measures? Or am I just being silly and missing something completely obvious?

    • PhilH says:

      You’re right, Michelle. ‘Power’ is often used informally to mean electricity, as well as its formal meaning of a flow or rate of change of energy. ‘Energy’ is often used informally to mean all forms of energy that we use (coal, oil, gas, electricity, etc), as well as its formal meaning of a quantity of useful work. I don’t know why the words have come to have these informal meanings – they’re not always used correctly.

  17. PhilH says:

    Table 1 in that link gives LCOE costs per MWh, not MW or GW capacity, with CCGT fuel costs being 4 times capital cost, not 3, making total costs 5 times what you keep using. I don’t have time to recast your capital cost calculations as LCOE, so just using your figures with corrections, the EUR700G would buy just 120GW of CCGT with fuel, not 1000GW.

    To what extent would using this capacity in your alternative scenario displace cheaper coal generation, lessening your alternative’s savings?

    You’ve not mentioned where you envisage the extra gas coming from – most likely Russia, much of that via Ukraine, or as LNG from the Middle East. That would further put Europe’s energy security at the goodwill of countries who have repeatedly used such dependence against other countries. How much is lessening this dependence worth as part of the support of the renewable alternative?

    The expenditure on renewables was not just to build generation capacity, it was explicitly to create new industries, with wider, longer-term paybacks, eg GreenIndusTree (http://www.greenindustree.de) being just one new, entirely export-oriented, German company that could not have existed otherwise. France has done the same with its investment in nuclear, now exporting that to Finland, China & the UK.

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