Quantifying CO2 savings from wind power



The graphic is from a writeup of a calculation which indicates that CO2 emissions reductions associated with wind power were 0.279 tCO2/MWh for the Irish electricity grid in 2011. Wind power met 17% of electricity demand that year. Such savings are a lot lower than have usually been assumed. Most grid operators do not publish official numbers on the effectiveness of wind power each year, despite the large investment going into this technology. Fortunately in the Irish case, the detailed data required to do the analysis is publicly available.

co2calc contains the details of the emissions model and the simple statistical analysis. It uses 1/2-hourly generation data compiled from market operator www.sem-o.com. Zipped data files can be downloaded below, although the script can also be run directly in an R terminal without downloading these files.








The European Wind Energy Association claims that wind power saves 0.696tCO2/MWh, while the British Wind Energy Association uses a figure of 0.43tCO2/MWh.

A 2012 report by the Institute for Public Policy Research, a UK think tank, entitled “Beyond the Bluster: Why Wind Power is an Effective Technology” claims that “every megawatt-hour (MWh) of electricity produced by wind power in Great Britain results in a minimum CO2 saving of around 350kg”.

(Paper submitted to Energy Policy, Elsevier November 2012)



  1. *Very* interesting. Which data exactly did you use on the http://www.sem-o.com site ? Is the data not yet up-to-date enough to get the complete 2012 values ? (I see the public weekly reports stop at 13/07/2012 for now, and the part that’s accessible after registration is not very easy to navigate)

    Your “metered generation file” separates by generation unit, and the generation one contains the total, right ?

  2. The semo site is indeed difficult to navigate. Also the data has to be downloaded one small piece at a time.

    After registration and login, go to “Market Data”. Select Report Type “Dynamic Reporting”, Report Group “Energy Data” and Report “Metered Generation by Unit”. You can find unit codes in various places. e.g.
    http://www.eirgrid.com/media/2011-2012%20ROI%20Market%20Participant%20TLAFs%20v3.0%20(13.07.12).pdf for example.

    Well worth repeating for 2012.

  3. Ireland 2013- Due to grid stability requirements wind is currently constrained to a maximum of 50% of instantaneous generation. When wind reaches 50% at times of high wind and low demand it can be noted that the CO2 intensity of the fossil generated electricity increases significantly, for example check the EirGrid website data for January 25th 2013; when wind hit 50% the CO2 intensity of fossil generated electricity increased by 66% over the level reported at the lowest wind period earlier that day. A 66% increase implies that 40% of the fuel burned at peak wind is wasted in order to facilitate 50% wind generation on the grid. This increased CO2 from fossil scenario happens frequently, just browse through the EirGrid data, many similar occurrences can be found.
    Ireland’s 2020 target of 37% of annual electricity generation from wind (out of a total of 40% renewable contribution) will require a grid capable of accommodating wind peaks of 75%. To achieve this objective billions of Euros must be spent on constructing new flexible gas fired CCGT power generating plants, pumped storage and other grid stabilization equipment such as rotary condensers (decommissioned generators can be converted for this purpose). Failure to install the required grid improvements will result in fuel wastage on a scale far greater than that seen to date as existing power plants which are no longer fit for purpose are inefficiently operated on low load so as to maintain grid stability as 75% of the load is generated by asynchronous grid destabilizing wind turbines. The Irish electricity consumer should be properly informed as to the costs associated with the dash for renewable energy, to date the costs are under reported while the benefits are exaggerated.
    In 2008 when the oil price was soaring the wind power industry stated that “the cost of wind power would break even with fossil power generation at an oil price of between 200 and250 per barrel”. Today WTI is 90 and Brent is105 implying a massive and increasing subsidy is paid to Irish wind power industry. The extent of this subsidy can be seen on your ESB bill where the PSO levy which covers a portion of the additional costs associated with renewable electricity generation is an approximately 45% levy on the cost of the renewable and turf portion of your bill. As renewable electricity increases from the current 15-18% to the planned 40% by 2020 expect this levy to increase considerably, unless fossil fuel doubles in cost. Ireland has decided in favor of wind power, the costs should be made public.

  4. Hi, this is probably a long time after the original posting. However, I wanted to thank you for a nice paper on the topic. It shows how the the true savings are system dependent. In the UK, we probably have a current situation similar to that presented for Ireland, i.e. mainly gas is modulated to match the demand (the biggest cause of variability) and the wind. Our average wind penetration is approaching 10%. 2 years ago, coal was much more expensive so it was usual to see both coal and gas varying together, so the higher fossil fuel network mix would have been the appropriate C02 saving. If we charged the low CO2 “levies” (insulation, wind and nuclear) to the carbon burners instead of directly to the customers, then the coal would be displaced.

    It’s all a matter of systems. By the way, the result that shows that gas turbine cycling only loses 3% of the CO2 saving is also very interesting.

    Thanks again,

  5. Hi, again,

    I was just looking at recent utilisation in the UK, and realised that another feature needs to be accounted.

    Wind only displaces gas when the gas is above the minimum level allowed in the system. On many nights, wind is actually displacing coal, so we need the full time history analysis to assess the actual Co2 saved. so the displacement is higher than the value in your study.

  6. Hi Steve, thanks for your comments. As you say, emissions savings are a system-dependent, collective property of the grid. Savings per MWh wind generation also change from year to year, depending on fuel mix.

    The two parameter model is the simplest empirical approach that can capture what is going on. The linear assumption works very well for Ireland, but it might not work for every grid. It would be interesting to do the calculation for the UK. Data access may be an issue though.

  7. Hi Joe,

    Great paper. Has it been published anywhere?

    I have 2 questions.

    1. This sentence struck me “If there was no wind in 2011, emissions would have been 12.9MtCO2 versus 11.8MtCO2 observed i.e. a savings of ≈ 9%.” Am I reading that correctly? If so, it is damning for wind.

    2. There has to be a break even point, where additional wind plant would provide no further CO2 savings. Would it be possible to model this, using the 2011 load demand as typical.


  8. Yes, it was published in Energy Policy http://www.sciencedirect.com/science/article/pii/S0301421513007829.

    Re. 2. The original aim of the study was to find empirical evidence for the expected non-linearity between co2 emissions and wind generation. Unfortunately the grid operator instructs wind farms to shut down when wind generation is too high (curtailment). This seems to have masked the non-linear effect, at least in 2011. However if wind capacity is really increased to 40% as proposed, the break even point will be all too obvious.

  9. Hi Joe,

    Thanks for your answer.

    I have a few more questions. Has anyone from Eirgrid or the Dept. Of energy contacted you in relation to this study?

    It appears to me that this issue has very little coverage in the media. I don’t understand the push for renewables just for the sake of it, especially if it’s resulting in increased CO2 emissions and the inefficient operation of our thermal plant. More importantly, consumers will have to pay the price for a lot of wind turbines which will be idle half the time because of curtailment.

    I think this issue needs to be highlighted by people who are impartial to raise awareness among consumers of what is happening in the electricity market. Further increases in retail prices of electricity could also have a detrimental effect on our economy. Would you mind if I referenced your paper if I try to raise awareness?

  10. Tim,

    I think DoCENR, Eirgrid are aware of it. However their focus seems to be on implementation of ambitious wind energy targets (NREAP), not policy analysis or review.

    Note that, at current capacity level, wind does reduce emissions, just a lot less than had been claimed. The article is in the public domain so of course you can refer to it any way you like. regards.

  11. Actually, the savings occur in a much larger system. Eirgrid have connected much more thermal plant than forecast, due presumably, to the increased wind penetration.

    The question is how much of this back-up plant is running and at what capacity behind the wind. I’ve tried to get the info from semo website but very hard to navigate.

    But all these plants get capacity payments, so presumably they are all running for long periods during the day. Forced outages are more common now, another factor to take into account. Again, presumably due to wind.

  12. There seems to be no discussion here of something pretty obvious.

    If you commission Z GW capacity of wind, then you had better have at least 0.9 Z GW capacity of fast-response CCGT in your grid to cover the variability of wind. Installation of this 0.9 Z GW of CCGT should displace 0.9Z GW of coal (or peat in Ireland or lignite in Germany).

    So you have immediately taken 55% of the CO2 abatement by replacing coal with backup for wind. It does not look like existing coal plant takes kindly to having its output modulated, and it is unlikely anyone is going to install new coal plant after the Paris agreement. See http://www.iea-coal.org.uk/documents/83500/9158/Increasing-the-flexibility-of-coal-fired-power-plants,-CCC/242

    Now when the wind is blowing you will find it hard to displace further coal produced CO2 because it is operationally costly to modulate the coal generation. Therefore wind dynamically displaces CCGT generation, which has around half the CO2 emissions (~ 500 vs 800-1000 g CO2 equivalent / kWh). http://www.parliament.uk/documents/post/postpn_383-carbon-footprint-electricity-generation.pdf

    So it is a bit pointless to quote the dynamic displacement of fossil-fuel
    generated CO2 by wind. The problem is of wind’s making – just that the coal-fired generation is intrinsically inflexible compared with CCGT.

    Nevertheless, wind is a valid and cost-effective means of eliminating CO2 emissions completely from a given fraction of generation, and has a significant contribution to make in getting down to zero CO2 emissions from electricity generation in the 2030-50 time frame.


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