Pay back time for Wind Turbines – show us the calculations

I have heard on the news and seen on irish websites claims of payback times for wind turbines of  8 – 12 years. These websites and company reps do not provide any data regarding the calculation or how these figures were derived.

Will these companies who state payback in 10 years, refund the cost of the turbine if after 2 – 3 years it is apparent that the turbine will not pay back in 10 years?
The spurious claims being made by some sales reps at energy shows and on web sites will come back to haunt us in 18 – 24 months, when radio chat shows will be clogged with angry people ranting about the fact that the payback is not being achieved. Do we want the 6 pm news doing a wood pellet type report on domestic wind turbines? The renewable energy sector needs to clean up its act and set standards for sales of renewable products.
How can some one state a payback to a client with out viewing the site?
I learned an important lesson about wind turbines, I measured my wind speeds for 1 year and at least I have factual data to help me make my decision.
Even though I live in a windy area my site is not great. There are better sites out there that are suitable for turbines, but how can the consumer make an informed decision?
We need to measure wind speed first, companies are under pressure to generate sales so if they are competing with cowboys who are telling porky pies about payback, what can they do, do they match their claims?
Any state assisted programme for wind turbines should mandate measurement of wind speed before the turbine is installed. I would recommend 6 months minimum measurement. Consumers should be made more aware about demanding calculations, results etc
Companies should produce factual energy output measurement and recorded data for energy production from at least 5 different sites. Sound levels should be measured from 20, 40 and 60 meters.
As part of a sales quotation companies should include a calculation from an application such as RETscreen which would indicate the kw hrs being produced, this would be backed up with the recorded wind speed analysis.
Some companies can provide data on the output generated by their turbines across different countries and different locations. My instinct is to trust these companies above a company that starts business on a Monday and imports a turbine from China on a Tuesday so as to sell it on a Wednesday. 
There are videos on youtube where enthuastic wind turbine installers have installed wind turbines and mentioned the figures being generated. I did my sums and the payback for that installer was 30 years plus. The problem was the site. That same wind turbine would have a payback time of 26 years on my site based on their cost.
The domestic wind turbine is fraught with issues that must be addressed in an open and transparent manner. We have the potential to benefit from this great resource but this can only be achieved using an ethical and honest approach. 
Student of the new Tipperary Institute degree in Computing in Smart Sustainable Energy will examine these modelling issues as well as the other factors that must be taken into account when modelling renewable energy sources.
If you are interested in learning some more on Wind Energy, you might consider reading this book.


  1. Derek says:

    I think these problems could kill the industry in its infancy. I have been talking to people who want to get into business in this area and the simply don’t want to know about the variabilities and uncertainties – never mind deal with them.
    What we need is
    1) a basic domestic 1kWh turbine that delivers – that is to say actually provides that output – in a 5m/s (typical Irish mean annual) wind. If we had that then you could list the conditions about LOCAL mean windpeeds, height above ground; clear of trees etc etc in an intelligble way.
    2) a price point that doesn’t require a mortgage. €10k with a payback of 14-18 years is manageable. €35k with a 20-30 year payback will have people buying oil.

  2. Liam Noonan says:

    Hi Derek,
    I agree with your sentiments about a standard.
    To generate 1 kw at 5 m/s would require a turbine with a 6.5 meter radius. At 5 m/s it would generate 1 kw, at 10 kw it would generate 8 kw.
    8 Kw turbines are very prohibitive in cost. The bottom line is to produce turbines and sell them in an ethical and honest manner so that the customer is matches with the appropriate turbine. The payback should be a max of 10 years.

  3. Andrew Flood says:

    What Liam said is spot on, most wind turbines are rated between 10 and 14 m/s. As with all things the buyer must inform themselves.
    When you double the wind speed you increase the power output by 8x. as it operates as a cubic function. This is all well but where aproblem arises is that the ESB will only allow you to export 6KW max to the grid. this then reduces the amount of power that you can produce at 5m/s.
    there are a lot more issues with wind turbines and I know as I have experience with several makes suffice to say that if you dont spend enough you will end up paying in the long run and possiblly have a turbine failure with no come back. If the blades snap in high winds the do a lot of destruction.
    I advise you dont deal with anybody who is relativly new to the buisness. Dont deal with anybody who dont perform 100 % of the installation. and definenitly dont go for east asian manufactured system.
    5-6 Kw machine should cost 24 K plus vat

  4. A friend of mine was considering installing a domestic wind turbine near Brighton, Uk. The sales rep visited his home, but immediately advised him not to as he would only be disappointed. I guess it just depends which company you ask. Personally, I would seek independent advice. Never ask a barber if you need a hair cut. 🙂

  5. liam noonan says:

    I would agree with your sentiments. There is a requirement for independent assessors.

  6. William says:

    there is requirements for optimum performance of the turbine based on info gathered from an nanometer at selected site. after much study of the site a reply to the customer is issued with a statement showing the annual payback derived from the an nanometer results. if the site does not match average wind speed or higher it will be made known to the customer. Now in relation to payback we have to not look at what the average is but look at what turbines are actually producing today. also it depends on how much your household is using. payback will be quicker as you are renewing energy that your buying form the grid at a set price. unlike when they pay you back for surplus energy you pump into the grid.

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