The second most popular renewable energy choice – a distant second after solar (PV) panels – is wind turbines. As you might expect, the primary consideration for anyone considering a turbine to generate electricity is wind – how much there is, what kind it is and how often it's present.

As a general rule, with other things being equal, wind speed increases with distance above ground level. This means that while the wind speed at the bottom of your turbine tower may not be enough to generate much electricity, the speed at the top could quite well be sufficient. Most experts agree that an average wind speed of at least 7-9 mph (about 4 meters per second) is the minimum for a residential turbine.

One of the most useful sites for anyone looking at wind power is the government's own "Wind Powering America" ( www.windpoweringamerica.gov) which boasts land-based and offshore wind maps, summaries of how much wind power is generated across the country and up-to-date lists of activities by state (which include all the resources for each state, not just news, so start there).

For a quick view of average wind speeds for major cities, there's a table at the National Climatic Data Center's (NCDC) site: www.ncdc.noaa.gov/oa/climate/online/ccd/avgwind.html

The National Renewable Energy Laboratory (NREL) has a variety of wind maps available, including a very useful one for average wind speeds at 30m (the height of a smaller turbine): www.nrel.gov/gis/wind.html

Of course, it's impossible to know the exact statistics for your particular site without performing a survey, for which you are likely to need professional help. Everything from the topography to local vegetation and buildings can affect wind flow, so it's worth talking to an expert.