Windsave, again

Anent my previous rant about Windsave claiming impossible efficiencies, they’ve made some changes to their website. The machines now have larger diameters (1250 and 1750 mm — up from 1000 and 1400mm), and much lower rated power (500W and 1000W at 27mph — down from 750 and 1200).

Plugging in those numbers to Cp = P / ( 0.48106 d2 v3 ), we get more realistic efficiencies of 0.378 and 0.386 (for the small and large machines, respectively).

The Lakota turbine we installed last week has a nominal rated power of 900W at 28.8 mph for a 2.09m diameter rotor. It has a very conservative Cp = 0.20, although David Cooke says that typically they see 1,000 Watts at around 25mph (a Cp of around 0.34).

At the other end of the scale, the Lagerwey LW52 is a 51.5m diameter machine rated at 750kW at 12ms-1. This advanced utility scale, variable pitch machine has a Cp = 0.34.

Windsave’s revised figures are much more credible, but until we have real figures backed by a few years of installations, there’s little more we can say about them. I’m a little concerned that, although there are claims that 1000s of these machines have been sold, there’s not a single real photo of one on the web.

I’m going to enjoy putting up an anemometer and logging system alongside the urbine downtown. We’ll see how it runs.


  1. we are a supplier to Windsave
    Windsave has never intended to mislead, unfortunately like a lot of start up companies it is not the technical people that write the marketing literature. When a genuine mistake is discovered it is corrected. The product is truly innovative due to its gridlink application time will tell whether this wins out

  2. There has been a lot of interest in the UK recently about roof mounted turbines. Both Windsave and Swift say they will be in mass production before the end of 2005 and the sales pitch is that these turbines will bring a revolution in domestic microgeneration – that soon they will be as common a site on UK rooftops as satellite dishes. The makers of the Swift claim that their turbine will produce as much as 4500KwH per annum!

    I know sweet FA about wind power and I would love to know if these rooftop systems are really workable? I came across this blog in my efforts to find out more and I would really appreciate some advice from the writer. I am not a techie so would need any response spelt out real slow. Hope you can help. Thanks. Joe

  3. Hi there,

    Like Josef I came across this after picking up a flyer for the Windsave system at one of those home type shows. I was very impressed by the blurb and would truly like to know if these things work as advertised.

    Also – I checked out some info on the Swift system mentioned also and wondered what exactly makes one system “better” than another, I’ve no technical experience but obviousely would like to go for a system that was as cheap, reliable and efficient as possible – this is a big move.

    Anyone know *roughly* how much these systems cost also – that will go a long way to determining whether I’ll go for it or not, i.e. how man years (decades!) will it take to pay for itself?



  4. Chris – I think you might get any two out of your three ‘cheap, reliable, efficient’. You should be able to get the cost of each system from the manufacturer.

    We’ll only know if they work as advertised after they’ve been in use for a few years. No matter how cheap (or reliable, or …) they are, they will be several times more expensive than joining a renewable energy co-op, and sharing the cost of a large, efficient utility-grade turbine in a windy location with a few hundred like-minded folks.

    The big unknown for most homeowners is just how windy their rooftop is. Short of investing in anemometry (which would be about the same price as a turbine, with no return in power for the homeowner), they only way to find out is to buy a turbine, and see how well (or otherwise) it works.

  5. Good point, Scruss! The crux is, how windy is your rooftop, because looking at the original sums you can see a CUBE dependence on windspeed. That means if my roof has a mean windspeed of 6 m/sec and not the 12 m/sec mentioned in the rating, my power will be down from that promised by a factor of 8, not 2.

    There’s a freely available national database called NOABL,
    where you can look it up, you can see from this map that the only places where you get more than 10m/sec averages are way up high, Lake District fells and Scottish mountains. Beautiful places, but not what you might call prime sites for housing.

    The bit about energy ministers sitting on the board is truly worthy of Private Eye-type exposure, ‘I Think We Should Be Told’ and all that.

  6. I would like to know how much wind these things can stand Orkney is very windy to say at the leased gale force 3 days a week in the winter, seldom under 20 mph

  7. Subject to survey, I have just ordered a unit from Windsave. It looks as if they are handing out sweeties according to their order specification, “first come-first served” to quote from their conditions. I must say that I don’t like their marketing technique. The other energy saving companies that I am flirting with also have excrable marketing techiques, it must be catching. I am completely non technical, but I do have industrial purchasing/vending experience. I noticed that Windsave supplied the turbine on the current TV family energy conservation series
    We shall see if I deserve the goodies

  8. I notice that unlike other microgeneration, Windsave (distributed my the electricity generator British Gas) makes no mention of two-way metering, ie credit to the householder for their “green-electricity”. The only mention of what happens to excess power is where it describes ‘spillage’ which sounds like they’re doing you a favour for cleaning up your mess rather than getting free electricity from you!

  9. Re. the earlier comparison of Swift vs WindSave – WindSave life expectancy seems to be 5 years vs 20 years for Swift. Swift’s 5-blade system says it is the quietest around, but WindSave says “Our system is 3-bladed and, as with all similar generators, there is a degree of noise caused by wind-rush on the structure and by the blade tips cutting through the air”. Swift is larger but it looks less industrial and more agricultural in design. Swift generates more power (though I don’t know which generates the most in any given wind condition). WindSave website looks professional, but has at least one importnat dead link and the FAQ page doesn’t render properly on my browser (it doesn’t scroll so you can only see the top), but the Swift web page is very very sparse (except for a nice pdf) and doesn’t give a price.

  10. For info, I read that B & Q will be selling Windsave’s for £1498 inc vat and installation from October and there is a potential 30% grant available.

  11. On he spillage point, I was told by Windsave that they viewed ‘spillage’ as negligable and not worth selling back to the utility. That is Bollocks. If the generated amount is negligable why would I want a wind generator in the first place. Interestingly beforw Windsave were selling through British Gas, they made great play of Windsave customers selling back electricity. Smell a rat??? I do.

  12. HI,

    We are uk destributors to clear skies registered installers of the Zephyr Air Dolphin which is made in Japan after meany years of development funded by the Japanese Government.

    We are interested to hear what the opinion if it is? Good or bad comments are appreciated.

    If you live near Aberdeen call in at Kingswells where we have one installed at a test location which is our MD, Dave McGraths house. Have been testing for about 6 months now with one planned for shetland or orkney.

    Engineering Manager,
    siGEN Ltd.
    sjg {at}

    ps. i hope this isnt picked up as advertising as its not ment to be, im an engineer not a sales person and would appreciate learned comments.

  13. In reply to Jim on Sep 16th;
    If you think about the baseline energy usage of your house.
    Fridge and Freezer 300-600W,
    TV 50-100W
    Plasma 400-500W
    PC 80-500W
    on average the Windsave seems to be generating around 500W (probably less if you look at the average UK windspeed). Therefore the spillage is small, maybe ~5 units per day. The sell back price for a unit is ~2p the cost of the meter (£?) and the current price of setting up a payback contract (~£150) will make this uneconomical.

  14. Like so many people I am trying to find ways of reducing my energy costs and have considered wind turbine. However although wind turbines have been around a long time they have been often sited well away from towns and citys. This is because they need to be sited on high ground or near our coast lines to generate more efficiently. If we start to erect turbines onto the side of our houses we will then have to consider the following.
    1. A increase in noise generated by X amount of turbines in your street.
    2. The potential danger of one or more turbine blades braking free of the main structure and slicing into your roof, or even worse scenario of slicing through a person. Just try and lag your roof, its a lot cheaper and safer.

  15. I have just seen a Windsave in B&Q. The sales person admitted he had not visited web sites that discussed wind turbines and I think he was just a sales person that had been quickly trained the give the Windsave line. In the sales blurb the wind turbine is pictured on a mast which is lower than the ridge of the roof. This is the same as siting solar themal panels under a tree; B&Q was also selling these using the same sales person. I’ll let you guess why the mast is so low.

    As pointed out in other postings, Windsave is a use-it-or-lose-it system, if you are not drawing power when the turbine is generating power, the electricity is given away free to the grid.

    This turbine is the Sinclair C5 story all over again, watch out for the grand dumping of Windsave turbines at a cheap price in the near future.

  16. If the generator happens to generate more than is used in the house, will the meter not run backwards (net metering) Maybe not.

    With a bit of control the power could be used in an immersion heater or something rather than just giving it away.

    The Zephyr seems good but at over 2500 it’s a lot more expensive. If it’s as quiet as the videos show, that’s good. I have an Air303 and it sings in the strong wind!

    B&Q are now selling the Windsave in Ireland for 2400 euro, but I think it’s illegal to connect a generation system to the grid here. But I suppose I must be wrong on that too!

    I wonder if David (May06) has got connected yet?

  17. Windsave is not interested in net metering and says so in their advertising literature. Also it is illegal to wind you meter back in the UK, you must have two meters, one in and one out. Polititians here have not got around to discussing winding meters back yet. Seeing as one of the top blokes at Windsave is an ex energy minister of this Labour government, one wonders what he was doing for micro generation while he was in office.

    Also I heard on the BBC on Friday, that the subsidy for micro generation for this year will run out in a couple of weeks – so you can forget about that £400 rebate when you buy a Windsave turbine.

  18. In reply to Steve (Oct5th)
    The baseline consumption you state does not allow for the fact that for a large number of hours per day typical households are not occupied therefore electricity consumption will not include items such as t.v.s.
    Also fridges and freezers cycle on and off as they reach the set temperature and if undistubed i.e. doors not opened, will draw no power for hours on end. (check the instruction manual for any freezer and it will tell you in the event of a power cut the freezer can stay frozen for up to 15hrs if not opened)The same obviously applies at night.As long as other devices are not left on standby, all of the power generated by the wind turbine could then be sold to the grid.

  19. For those of you wanting to get a realistic idea of wind speeds etc in a reasonably-typical domestic location, take a look at-

    That site started up in February 2006, so covers in part the windier months of the year.

    The anemometer is mounted on an extension of the TV aerial installation, so is distinctly above the roof level.

    The Web camera gives a good idea of the exposure to the North-West; but the ground and town continue rising behind the camera to the South-East for about 1/2 mile.

    Prevailing winds are from the South-West as for most of Britain. See elsewhere on that Web site.

    I also have an anemometer and weather station about 2 miles to the west, mounted in a less favourable position relative to my house; but generally the two show good consistency in their readings; and that also applies to the other parameters such as temperature, rainfall etc. (Different manufacturers)

    Generally, because of their lower and more congested locations, I would expect domestic anemometers to record lower wind speeds than Met Office ones, which are located for the most part in exposed situations such as airfields so not representative of the typical locations for domestic wind-powere turbines.

    Alex Dow

  20. Is there anyone out there, that is actually using a cheap wind turbine? It seems to me that most people are sitting on the fence with a real negative atttitude, instead of putting their hands in their pockets and trying one out. Who knows, they may just work??????

  21. Off you go, Knobby, let us know how you get on. But I think I’ll take notice of the maths of roof top turbines and let the suckers blaze a trail.

  22. Just when you thought Sat dishes, were ugly, that pox the facades of Council/housing association/and other subsidized housing blocks, with cable trailing brackets rusting. (Planning Law England Wales one satelite dish per building, all others require planninng permission ) Local Authorties rarely enforce this, but have a duty to do so.

    Goverment planning changes mean that very shortly no planning will required for installation of turbines, – open to debate if property prices will effected, I guess likely to be negative., noise vibration etc.

    These turbines will be sprouting soon on lo-cost housing in town near you. All about saving “the community” fuel bills etc , use will have no bearing on the capital cost of installation and servicing, and carbon emited in manufacture and installation and servicing. Taxpayers get a very poor return, very likely a loss!

    Polititians will love them, as visual vindication of being “green,” the whole stinks of green spin,

    Efforts should be going in to tried a tested insulation, less sexy , but easy to install no maintence .

    Thank you for this site, PS I would be pusuaded to install tubine if the economics added up…………….. and this does not.

  23. Does anyone have a Windsave turbine fitted?If so ,could we have some experienced feedback please?.Thanks,Ritchie.

  24. Hi Folks,
    I went along to B&Q today to see the Windsave WS1000 turbine and decided that I would not like it strapped to the side of my house for visual impact, noise, and vibration reasons. Nobody could or would tell me about the noise or vibration levels.
    On coming home I did a rough cost/saving estimate and at my current electricity consumption it would take me at least ten years to recover the cost of the turbine, the projected lifespan, and that is based on the turbine operating at max. output i.e. a third of my electricity consumption.
    Saving the environment and reducing energy consumption are all very well
    and I support Marco’s views and anyway if everybody reduced their energy consumption energy producers would react by increasing prices and cutting costs, i.e jobs, maintenance, etc., as they must maintain and increase profits for their shareholders and investors. And the usual suspects who are unable or cannot afford to conserve energy will suffer physically and financially.
    It looks like the more you save the more you pay.
    I like the idea of Micro Renewables but it’s going to take a lot of convincing.

  25. Hi

    I went to B&Q in Oxford to see what they could tell me. Now Oxford is a reasonably large city with a sizable environmentally aware community. Th best response
    B&Q gave me was “Dunno mate heres a brochure.” MMMMM! Micro wind wont work in the Urban environment without getting turbines 10m above the highest roofs…

    This Windsave and Swift stuff is a rip off


  26. I would still like to hear from people with REAL experience of Windsave or similar generators,not what the salesman in B and Q was like!I think we all know that!
    I drive an Aixam Mega electric van{very good!but slow!}and would love to produce electricity.I have just had Solar thermal water heating installed,seems good so far with the Thermomax tubes.Today I fitted a BIG ,used Jotul woodstove at work,hey,no more gas!I have a woodstove in the house and one in my home workshop.They are all very good.It seems hard to sort some of these things out and get the info and the grants,but,it all helps,never give up and dont be too cynical!
    Positive Ritchie

  27. I have read with interest all the comments, I’ve looked at numerous web sites, and all have one thing in common, the best and most efficient wind turbines are big, and only work well in clear air. I’m not going to spend £1500 trying to generate electricity, that’s very silly. I’m going to make a turbine and use it to keep my hot water hot. That way the energy store is a useful product, I don’t have to hope that the wind is blowing when I need electricity, I just know that the water will be kept hot, handy as it’s often windier in winter.
    just my 2p.

    for those of you who are wondering, a well lagged cylinder will probably only need about 100w to keep it hot, that’s easy and not time critical.

  28. Congratulations on having the 2nd Google spot for a search on “Windsave”!

    I had the usual B&Q experience in my local store (East Kilbride). The turbine is big enough to be a nasty eyesore and vibration generator, but small and potentially fast spinning enough to be seriously noisy. The salesman was a Spotty Herbert who knew less about it than I did, and fobbed off all questions about noise and vibration by saying that would be covered in the pre-installation survey, which he also had no information on, about how soon or how thorough it would be. I think he considered calling security when I asked how it minimised trailing edge turbulence. Poor Spotty Herbert.

    Worryingly, he knew nothing about the warranty term, and that’s vital information. It needs to be at least ten years, which is the break-even time, assuming about 250-300W practical average usable generation, rising energy prices and (vitally) no ongoing maintenance issues.

    Even if it is ten years or more, I’m seriously doubtful that Windsave will be around that long. They have no margin for paying out on warranty or third party liability claims, for one thing.

    A couple of other things that you should be aware of:

    First, to qualify for a grant (if you can get one before the money runs out), you first have to have: cavity wall insulation; CF lightbulbs fitted wherever possible; 270mm of loft insulation. As my loft is floored, I actually can’t meet that last criteria, unless I lag above the flooring.

    My home insurers are “going to get back to me” about the implications of slapping one of these on my brickwork. The phone drone knew nothing about it, but advised not fitting one until they’d checked, as there could be serious implications on both the house structure, and on third party liability (I assume if if came off and flew through my neighbour’s roof – or person).

    So while I’d like to save the dolphins and all that, I’m not going to splash out £1500 on something that might actually end up costing more in insurance and brickwork damage than it saves in electricity, quite apart from the sleepless nights and neighbour-annoyance (and slaying) potential. I remain ready to be convinced, but it’ll take more than a high-gloss, low-information sales brochure to do it.

  29. Interesting looking at the windspeed data on the Fife House website. Year to date I make that 2.27m/s (ie just over 5mph). The DTI windspeed database for Lochgelly gives for that location and the immediate km squares at a height of 10m

    5.2 5.4 5.2
    5.8 6.0 5.9
    6.4 6.5 6.4

    ie significantly higher. So if the measurements from the house roof are accurate/typical – real yields will be way down on any manufacturers claims.


  30. David,
    I have a small (10w) turbine connected, and like you find that the actual wind speed is far less than the DTI web indicates. Often the turbine doesn’t spin as the wind is too turbulent, and even on a windy day I often get less than 2w from it.


  31. I wonder how many people realise that when the wind gets above 14m/s the Windsave turbine switches off. If you google “windsave chocolate” you should arrive at a discussion on the website. I have been trying to get verification there from somebody who works for Windsave if the Winsave turbine furls, I don’t think it does.

    If the turbine doesn’t furl, then the inverter cuts it out (stated in the B&Q flyer) at 14m/s – a fraction over its rated speed. It would take 15 hours of 5m/s wind, its cut in speed, to make up for each hour of 14m/s plus windspeed lost through the lack of a furling mechanism.

  32. Firstly.
    I take it that these people want the money up front ie. before the survey is carried out,so are you going to get some little herbert who was ripping your granny off over double glazing the week before.
    If you really want to piss your neighbours off buy some guinea fowl much more entertaining and you can eat them when they’ve had the desired effect.

  33. Colin, if rooftop wind speeds are as low as we expect them to be, overspeed cutout will seldom, if ever, be a problem.

  34. It appears that in order for any of us to get into energy saving it won’t be for saving money which is what I was looking for but it still remains a matter of conscience about going green that will motivate us to spend more to save our envoirnment. Personally I will begin saving in order to make a contribution to a cleaner earth but I won’t expect to save money on wind energy at this moment in time. We all would be better off trying to conserve energy at home in other ways like Cfl bulbs, insulation,and recycling which are the steps I am currently going to put into practice.

  35. Scruss,

    Here in rural Norfolk(UK) last week, for several days we had winds that, at times, I am sure were higher than 14m/s. This would have meant that because the turbine would have shut down I would have lost the opportunity to donate kilowatts free energy to the grid – during the times I was not drawing electricity. Should Plug n Save, trademarked by Windsave, be Plug n Give ?

  36. If roof top wind-turbines are looking like they won’t provide the required energy – what the chances of a “community” wind turbine making some form of payback.

    I note that Proven are now trying to promote “Wind-crofting”. (Like the name, but can it work either for him or other people).

  37. I’m sure that a little research on line will reveal lower cost turbines, that way the pay back period will be shorter. The alternative is to go for a lower tech (lower cost) solution and just be prepared for the turbine to do something very basic, eg maintain hot water temperature. How about a plug in element for a normal domestic radiator, if it were fitted to a downstairs unit, then the system would auto syphon spreading the heat through out the house? Ok you’ll need more than 300w for that to work,…..just a thought.

    I’m going to make mine at home for a cost of £300, at 20p per daytime unit I think the payback period will be that much shorter.

  38. Thankyou all for your wonderful and amusing views on this subject. I also found this site while looking for more info on the infamous B&Q turbine and am glad I did! Like most people I am not technically minded and was interested in saving money but after reading through your thoughts on the subject I think i’ll go with the general consensus and not bother. I would also like to thank Mark Gadd, who sounds like my kind of person. A few chickens and a rooster will do the trick too.

  39. Re David on Nov 7: it has a fair to excellent chance of making a good return. Depends on the siting.

  40. Re all of the theory above. I live in a place where the wind never ceases, and, whilst accepting that the 14m/sec criterion will have a Windsave alternator furled for some of the time here, I was nevertheless interested enough to look into the sysem – some time before B&Q began to retail it.

    Having preached for 30-odd years that “green” does not mean having the latest low emission vehicle; it means keeping the same car on the road for years (in my case, 21 years for one particular car, thereby avoiding the life-cycle cost of your 5 cars to my one), I consider that I have built up sufficient “carbon credit” to buy the Windsave system just for the fun of it. At my time of life, I can also afford to write off £1,498 without weeping too much either!

    It has taken me some time (and £130) to push my application through Planning, and – as a tenant – I am in no position to claim a grant. However, I have a siege mentality (2.5KVa petrol alternator in the shed, and 2 tons of anthracite in the bunker), so “free” electricity has a certain appeal anyway. Thus, with Scottish Natural Heritage’s blessing (though they caution that I am on Whooper Swans’ migratory flightpath), I am pushing ahead with my Windsaver installation, and I signed up yesterday.

    What prompted my thinking in the first place was the fact that I was contemplating installing gas (tanked) central heating in a house which currently is all electric. That was going to cost £5,000 plus, as well as the upheaval and inconvenience. It seemed to me, then, that, so long as Windsave brought down by a little the overall price I was paying for electricity to run my home, its installation was a worthwhile experiment.

    So, watch this space. My total power consumption (all-electric house) averaged over the past two years is 12,283 units pa, and I should like to see the Windsave system make a moderate hole in that. The next hurdle I have to surmount is for Windsave’s agents to survey the site and to tell me whether they think that it is suitable.

    I shall keep you posted.

  41. Just another idea: if the overall assumption is that a Windsave turbine can reduce an average household’s yearly energy consumption by a third, doesn’t it make sense to mount three turbines on your rooftop? Anyone experience with multiple installations on a single roof?

  42. I was rung today, on behalf of B&Q, by a lady at the “Installations Centre”; the call came to my house phone. The lady said that the mobile phone number I had given was incorrect; I told her that it wasn’t – but that the assistant in B&Q (Carlisle) must have written it down wrongly.

    She started to argue, but I cut her short by reiterating the correct number, and asking her why she had called. She told me that she had to make sure the numbers were correct, so that Windsave’s agents could phone to arrange a suitable time for survey.

    I said “That’ll be a call within three working days of 2nd Dec, then.” (The date I signed the contract.)

    “Oh no.” She said. “It’s 7 working days.”

    I fished out the contract. It says “3 working days”, I told her; however, not wanting to start an argument, I said that I’d look forward to Windsave’s agent contacting me whenever and however.

    Out of interest, I still have the contract in front of me, and it still says “3 working days”.

    Is this a hint of worse to come?

    Keep watching.

  43. Kevin,

    I think you have the wrong idea about furling. On modern furling wind turbines the idea is to continue to generate electricity while in a state of furl, unless the wind strength is so high the tail ends up at 90 degrees to the blades. Windsave from B&Q does not furl it cuts out at 14m/s, If the wind strength is as great as you say where you are you are going to lose a lot of electricity with this turbine. I still do not know what the Windsave system does about the free spinning of the blades once the braking effect of generating electricity is stopped; perhaps they explained that to you at B&Q, but I very much doubt that.

    It seem B&Q’s service on this product is about as good as the product itself.

  44. I was more struck by the vibration caused by the blade ring – that’s not going to be good for the bearings, or the mount.

  45. Hi All,
    It is very easy to slate the companies involved in providing these turbines for domestic consumption isnt it!! We have go to remember here this is NOT just to save money (although 1/3 rd of a 3.5kw home is very achievable for a domestic property) Has everyone forgotten about he energy savings and reduction of carbon emmissions here? If only 1% of the country had one of these we would reduce 1000’s of tonnes of carbon emmissions each year going into our atmosphere. Also the Windsave system is only and has only ever been advertised as a ‘contributory’ system which will supply an accumulative supply of energy to your household when the wind blows between 4m/s and 15 m/s. Not to be bought if you want to give back to the national grid because your household will consume more than what the turbine will make in normal running conditions. This WILL save you money but more importantly this is the ONLY totally green turbine on the market at the moment because storage batteries are not used in the inverter plug n save unit, this powers directly into your ring main. When batteries are used we are also then making more carbon deposits in the production of those batteries which kind of defeats the whole object of having a turbine. In my eyes the Windsave system pound for pound out beats any other system on the market with cost outweighed by the return time. GET ONE !!!

    (Well, Sean really seems to have drunk the KoolAid here. I can’t determine if he’s posting from WindSave’s office. I still think that a well-sited utility-scale wind turbine bought by 1000 potential domestic turbine users would have a better energy yield. – scruss)

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