Wind turbines have been on the United Kingdom's domestic market many years, but their popularity and public awareness is now increasing substantially. Claims about their efficiency and productivity are under some debate due to the disparity of manufacturer's forecasts with case study results. The prime problem is that they are routinely being installed in areas with wind speeds much too low to realise a useful level of energy return. Wind-powered electricity generation requires wind speeds above those found in the great majority of inhabited areas.