Why can two properties inside one wind-map cell have different wind potential?

The short answer

A wind-map cell represents an area at a defined height and modelling resolution; it is not a measurement of every point inside that area. Two properties in the same cell can differ in tree cover, buildings, terrain and feasible tower height. The map is useful for screening, while the local layout determines how confidently it can be applied.

Read the map definition before the colour

Record the mapped variable, height, averaging period, grid resolution and whether values are modelled or measured. A strong colour on a map does not show the turbulence behind a local shed or whether the proposed rotor can reach the reference height.

Check whether the downloadable data identify the actual model point. A site coordinate entered into a website can select a surrounding grid cell without eliminating the distance between that cell's representative conditions and the tower.

Separate shared weather from local flow

Nearby properties may share broad weather systems while experiencing different local flow. Open upwind fetch, vegetation and terrain can change speed and direction at small-turbine heights. These differences are especially relevant where obstacles are large relative to the proposed installation.

Do not assign an invented correction percentage simply because one property looks more open. Use a qualified assessment, relevant measurements or a stated sensitivity range whose basis is documented. The purpose is to expose uncertainty rather than hide it behind a precise map value.

Use the map to decide what to investigate

Prepare a site plan showing candidate positions and the sectors in which local exposure differs from the map's broad assumptions. Ask which constraints could make a promising regional resource unusable at the proposed location.

The resulting screening decision might justify further measurement, reject a sheltered location or compare another technology. It should state that the map supports regional potential, not a guaranteed energy yield for a specific turbine. Equipment selection follows once site evidence and installation constraints are sufficiently resolved.