How do I find the wind speed at my postcode?

The number that matters most is five metres per second (m/s). Energy Saving Trust guidance says a small wind turbine should only be considered where the local annual average wind speed is 5 m/s or more, and where there are no major obstacles nearby such as buildings, trees or hills that would reduce the wind speed or increase turbulence³. Below that, output collapses, because doubling the wind speed yields eight times as much power⁴.

What a postcode wind speed predictor gives you

A postcode predictor returns a modelled average wind speed for the area your postcode covers, not a measurement taken in your garden. The free maps householders most often meet are built on the NOABL database of estimated wind speeds at heights of 10 metres or more, modelled for flat terrain and averaged across a kilometre square⁵. That is a coarse grid: everything within that square, from an exposed hilltop to a sheltered cul-de-sac, gets the same number.

The predictor's job is screening, not answering. If your postcode comes back well below 5 m/s, a wind turbine is very unlikely to pay off anywhere on your property, and you can stop there. If it comes back at or above the threshold, the figure says the general area has usable wind, but says nothing about whether your particular spot can catch it. MCS's own updated standards for small wind turbines set out a first prediction method that looks up the mean wind speed for a proposed location using the Global Wind Atlas², which is the same idea at a similar scale: a starting estimate that an installer then has to test against the real site.

Entering your postcode and reading the results

The mechanics are simple: enter your postcode into the tool and read off the average wind speed it returns¹. Two things decide what the figure is worth. First, the height: NOABL speeds are estimated at 10 metres or more⁵, which is above the roofline of most houses, so a roof-mounted turbine will see less wind than the number suggests. Second, the terrain assumption: the database was modelled for flat ground⁵, so a sloping or valley site departs from it in ways the tool cannot show.

When you read the result, compare it against the 5 m/s threshold³ and then walk your own ground. Energy Saving Trust's conditions for considering a turbine are that the annual average is 5 m/s or more and that no major obstacles such as buildings, trees or hills are close enough to slow the wind or add turbulence³. Both conditions have to hold: a good postcode figure with a hedge-lined garden fails the second test just as surely as a poor figure fails the first.

Understanding wind speed data for domestic turbines

Wind power scales steeply with speed: doubling the wind speed yields eight times as much power⁴. This is why a small shortfall against the 5 m/s annual average is not a small shortfall in output, and why a postcode figure that is "nearly there" is, in output terms, nowhere near.

In Scotland, domestic wind turbines generally range between 4 and 15 kW⁶. At the small end, a turbine with a rotor diameter of about 1 metre on a site with good average wind speeds could give a few hundred kilowatt-hours (kWh) of electricity per year⁴, a fraction of a household's consumption. Where the postcode figure is marginal, studies show building-mounted turbines in built-up urban areas to be far less effective owing to lower wind speeds⁷, so the mounting height and the site matter as much as the area average.

For more on matching a machine to a site, see wind turbine output and sizing and wind speed and siting for a home wind turbine.

Why one postcode can contain very different winds

A postcode is an administrative boundary, not a wind climate. Within a single postcode you can have an open field, a wooded lane and a housing estate, and the wind at each differs far more than the postcode average admits. The database smooths all of that into one figure for a kilometre square of flat terrain⁵.

The physical reasons are familiar to anyone who has walked a boundary between open ground and shelter. Wind speeds up over exposed ridges and open water and slows in the lee of buildings, trees and hills; the same obstacles also add turbulence, which is separately harmful to a turbine. Energy Saving Trust is blunt about the pattern: systems work best in exposed, windy locations and are less suitable for built-up or sheltered areas⁸, and domestic wind power suits an exposed or isolated spot⁹.

The limits of postcode-level wind estimates

The honest summary of a postcode figure is this: it is a modelled average for a kilometre square of flat terrain at 10 metres or more⁵, and every one of those qualifiers is a way it can mislead you. It is not measured at your site, not at your turbine's height, and not adjusted for your obstacles.

Accuracy has a formal side too. Where wind speed is actually measured as part of certified product testing, MCS 012 requires it to be measured to a maximum inaccuracy of 0.5 m/s¹⁰, a standard of precision a postcode lookup cannot approach. And the practical evidence is sobering: building-mounted turbines in built-up urban areas have been shown to be far less effective than their ratings suggest, owing to lower wind speeds⁷. A postcode number that clears 5 m/s does not clear it for a rooftop in a town.

Location, exposure and planning rules for your site

Exposure is not only a performance question but a legal one. Under the permitted development rules for wind turbines on domestic premises in England, development is not permitted if any part of the turbine, including the blades, would be positioned within 5 metres of any boundary of the curtilage¹¹. That rule pushes turbines away from boundaries and, in practice, towards the middle of larger plots, which is often where the exposure is anyway. In Scotland, the permitted development consultation has considered domestic micro-scale wind turbines of under 50 kW capacity sited over 100 m from the nearest property boundary¹².

On the building side, if the wind turbine is not attached to your house, only the electrical installation and connection are captured by the requirements of the building regulations¹³. The upshot is that the rules reward exactly what the physics rewards: a tall machine, well clear of boundaries and obstacles, on an exposed plot. For the detail, see wind turbine planning permission in England and wind turbine planning permission in Scotland.

What the wind speed figure means for your independence

A genuine 5 m/s-plus site is one of the few places where a household can generate a meaningful share of its own electricity in winter, when solar output is at its lowest. A well-sited pole-mounted turbine of a few kilowatts can cut imports and keep some power flowing in grid failures, which is the core of energy independence. The dependence that remains is real: the machine, its inverter and its maintenance come from a manufacturer and installer, and unless you add batteries you still draw from the grid in calm spells, because wind, unlike the postcode figure, is anything but average day to day.

The postcode check is therefore the first gate, not the verdict. Pass it, then test the site itself: the exposure, the obstacles, the height and the rules. Only then does the postcode number become a decision.