Likely to be money very poorly spent! Consider: size of turbine required versus practical size; significant effect of surrounding structures; load of turbine on building structure; even in ideal circumstances are the manufacturers power output claims verifiable. My advice - unless you have a large turbine, mounted at least 10 metres above any surrounding obstructions, don't bother. Opt for energy saving measures instead.

That sounds almost incredible Jane, but it does not surprise me and I would readily accept your figures.

B & Qs water tank at £798 could probably be bought elsewhere for £200. I suspect the solar panels and turbines are similarly inflated. So shop around and look for a local guy with the proper expertise is my advice!