The annual average windspeeds are only indicative and there are inevitable differences within the 1km square due to topography and obstructions. However it will give a good first estimate of whether a wind turbine is going to be viable and worth investigating further, usually requiring a windspeed of 6 m/sec or more.

This is old software and is not very user-friendly, the most difficult item being the finding of the OS Northings and Eastings required. This is not the same as the map reference on an OS map.

It is worthwhile getting this right and a useful check is to input a site reference that you know will have an effect on windspeed, usually a remote hilltop. Just North of Wind and Sun HQ is Clee Hill, a not very high (533m) but steep ridge rising within a km.

Clee Hill would have a map reference of 596 779 usually. However the full reference is 359600E 277900N (roughly!)The point we need is the bottom left corner of the km square of interest, so the coarser resolution reduces the OS reference to 359E 277N. The number inserted before the usual twin three figure map references (shown in yellow above) is printed as a small subscript in the corner of the map.

The km grid output centred on Clee Hill outputs as:

Annual mean windspeed (m/sec) for km squares around 359 277

Picking a similar feature in your location shows the level of speed-up that hills can produce and also gives confidence that the Easting/Northing numbers are being properly input.