How long should I measure wind before installing a turbine?

Three months is the floor, not the target. The professional recommendation, set out in official guidance for small-scale wind, is a professional assessment of the local wind speed for a full year at the exact location where you plan to install the turbine³. The MCS small wind standard published in December 2024 offers a middle route: erect wind speed monitoring and data-logging equipment for at least six months, then use that data with the characteristics of the proposed turbine to predict annual energy generation⁴.

Why the measurement comes before the purchase

A wind turbine is one of the few home generation options whose output is decided almost entirely by something you cannot see until you measure it. The Centre for Alternative Technology advises that before spending thousands of pounds on a turbine, it could be worth spending a few hundred on wind monitoring equipment, such as a mast and data logger⁷. That asymmetry, a few hundred pounds against thousands, is the whole argument for anemometry.

The stakes are higher than the purchase price alone. Small wind turbines last over 20 years with regular upkeep⁵, and nidirect puts the life of a wind turbine at up to 22.5 years, with service checks every few years³. Maintenance typically costs between £100 and £200 a year depending on the size of the system⁵. A turbine sited in poor wind carries those costs for two decades while generating little.

Siting also matters more than most people expect. Studies show building-mounted turbines in built-up urban areas to be far less effective owing to lower wind speeds¹, and systems work best in exposed, windy locations, being less suitable for built-up or sheltered areas⁹. Measuring first tells you which kind of site you actually have, rather than the one you assume you have. For a fuller picture of how turbines behave once installed, see domestic wind turbines and wind speed and siting.

Three months: the stated minimum

The three-month figure comes from the Energy Saving Trust, which recommends you install an anemometer, or wind gauge, in the intended location for at least three months before considering a home wind turbine¹. Its field trial report on small-scale wind used the same threshold, with anemometry installed at sites for a minimum period of three months to measure the actual local wind speed before deciding².

Three months is enough to smooth out day-to-day weather and give a first indication of whether a site is remotely plausible. Electricity North West suggests a lighter version of the same check: fitting a wind gauge for a couple of months to check the wind speed near your property¹⁰.

The limit of a short measurement is seasonality. The UK electricity system saw a period of sixteen weeks with very little wind in one recent summer¹¹, and official weather statistics show wind speeds varying month to month across the year¹². A three-month record taken entirely inside a calm spell, or entirely inside a stormy one, will mislead. Treat three months as a screening exercise, not a prediction of annual output.

Six months to a full year: what the professionals do

The professional recommendation is a full year. Official guidance for small-scale wind is that a professional assessment of the local wind speed is carried out for a full year at the exact location where the turbine is to be installed before proceeding³. A year captures every season, including the summer lulls that a winter-only measurement would miss.

The MCS 033 standard, updated in December 2024, sets out two prediction methods for small wind installations. The first uses the proposed location to look up the mean wind speed using the Global Wind Atlas⁴. The second, for consumers happy to wait and pay for a more accurate assessment, is to erect wind speed monitoring and data-logging equipment for at least six months, with that data then used alongside the characteristics of the proposed turbine to predict the annual energy generation of the system⁴.

The parallel with other home energy monitoring is instructive. Smart heat-loss measurement runs for approximately three weeks during the heating season, because measuring outside the season the measurement is meant to represent would distort the result¹³. Wind is the same: the measurement period has to cover the conditions the equipment will actually face.

Where to put the anemometer, and what to record

Placement rules are consistent across the guidance. Higher placements catch stronger, steadier winds⁵, and turbines should ideally be located on a hilltop or raised structure, away from obstructions like trees or other buildings⁵. The anemometer should sit at the intended location of the turbine, at roughly the height it would operate at, so the data reflects the wind the machine would actually receive.

What to record is the average wind speed over the whole period, not the peaks. The number that decides viability is the annual average, and the consistent UK guidance is that you need around five metres per second: nidirect states a site should have a local annual average wind speed of five metres per second (m/s) or more³, the Energy Saving Trust recommends installing only in areas with at least 5 m/s of wind¹, and Electricity North West gives an optimum wind speed of around five metres per second¹⁰. A typical domestic system for a home would be 2.5 to six kilowatts, depending on the location and size of the house³.

A data logger matters because memory of windy days is not data. The point of the exercise is a defensible average, taken at the right height, over a long enough period to include calm spells.

What the data tells you before you commit

Once you have the average, the decision becomes concrete. If the annual average at your site is at or above about 5 m/s, a turbine is worth investigating further¹. If it is below that, the same data has saved you from a poor investment, and options such as micro wind vs solar for an off-grid home or other forms of microgeneration may serve the house better.

Be cautious with database shortcuts. The NOABL database behind online wind speed maps gives estimated speeds at heights of ten metres or more, modelled for flat terrain and averaged across a kilometre square⁷. That cannot reflect your particular hillside, hedge or valley. The Global Wind Atlas lookup in the MCS standard is one accepted method⁴, but on-site measurement remains the reliable one.

If the numbers support going ahead, the next steps carry their own timelines. In Scotland, a free-standing turbine under permitted development rules must be carried out within three years of the approvals being given¹⁴, and the prior approval process runs to 28 days from the application being received¹⁴. Local authorities may charge a fee for pre-application advice¹⁵. For the wider picture of what generation does for a household's independence from the grid, see microgeneration and energy independence.