Unlike other forms of renewable energy, wind power requires very little explanation. Most of us will understand that the wind rotates a wind turbine generating electricity.

The question addressed here is how effective are they and are they worth the investment. To work out how much energy you may generate you need to know how windy it is in your area, and there are several resource on the internet to do this, just do a Google search, The UK Government has various resources but they insist on arching them or moving them around in line with political change, rather dumb. In a very urban area wind may be totally impractical for so many reasons, not least of all how much wind there is with buildings disturbing the wind flow, so do you your homework for your specific location.

The wind databases give you wind speeds at 45m, 25m and 10m above ground level, to give you and idea of placement. Wind speed also vary with time, from nothing on calm days to occasional violent gusts. If the wind speed at a site is recorded over a year, it will be seen to vary about a mean wind speed value. This is the annual mean wind speed (AMWS) and is an indication of how much wind energy is available. In the UK, AMWS could be as low as 4 m/s (9.0 mph) for an inland site to around 8 m/s (13 mph) or higher on the most exposed sites.

The general consensus is that you will need at least 5m/s to make it worthwhile and this seems to be the number most suppliers use when they quote the generating capacity of their systems. It is also apparently the average wind speed in the UK. The table below shows a few systems with a range of typical manufacturer quoted generating capacity and estimates of payback periods. The total cost for the installation of a larger domestic installation is around the £15,000 mark +/- £5000. Accuracy is very tricky here because it depends on the foundations required, the battery storage system used (or grid connection) and the windmill chosen, so the table includes a range of data so you can see what install cost you should aim for. The smallest installation we have found is a 1.75 turbine it costs between £2500 and £5000 installed and ready to use, and "with a fair wind" could produce about 1000kWh each year.

System 4 is at the high end of what is possible with a 5m/s wind speed and the numbers in the table for this system probably reflects what would happen with an average annual wind speed closer to 7m/s, So to get a payback period for your investment below twenty years you probably need to be in a very windy area and have paid as little as possible for your system.