The UK is the windiest country in Europe. Wind farms are therefore a great way for us to meet our energy needs without carbon emissions. Small-scale wind power can also be effective. However, a small turbine must be very carefully sited to be a cost effective and low-carbon option. For most of us, supporting and investing in large scale wind power is the more effective option.

CAT has been using wind power since we started in the 1970s, trying out different types of turbine. You can learn more on one of our courses.

Can I put a wind turbine on my roof?

We strongly advise against mounting turbines on rooftops or buildings, as they will receive only weak and turbulent winds. Several field trials have found that building-mounted turbines perform poorly, producing only a small fraction of the energy they would produce if properly sited.

Clearly a turbine that does not spin will not save you money or reduce carbon emissions. In addition, turbines can resonate in the wind and produce vibrations, which can damage the structure of the building.

Where should I put a wind turbine?

An ideal site is a smooth hilltop with a clear open stretch – at least in the prevailing wind direction. Towns & villages don’t usually have open stretches like this, which is why they’re usually bad sites.

Before spending thousands of pounds on the sort of wind turbine that gives a few kilowatts of power, it could be worth spending a few hundred on some wind monitoring equipment – such as a mast and data logger. Be wary of relying only on an online database that gives wind speeds for a given postcode or map reference. Those figures don’t really account for the local conditions that a small turbine will be affected by.

How big does a wind turbine need to be?

When you double the diameter of a rotor it makes the swept area four times as big. This is because the area of a circle comes from the square of the radius (A = π r²). A rotor with a 10 metre diameter will therefore capture one hundred times as much wind as one with a one metre diameter. This means that very small turbines can’t capture much wind.

The smallest turbines, costing a few hundred pounds, are fine for charging up a 12volt battery in a boat or caravan. However, to produce an output similar to that from a domestic solar PV roof, a much larger turbine would be needed. Turbines that give an output of a few kilowatts will have a rotor diameter of a few metres, and will need to be mounted on a high tower.

How much electricity will a wind turbine make?

This is very hard to predict, because wind speeds vary a lot from site to site. The output of a solar PV roof is fairly straightforward to estimate, but it’s much harder to do the same for a small wind turbine. There are two factors that make a big impact on energy output – the size of the rotor and the speed of the wind.

Suppliers of wind turbines should have information about the power a wind turbine will make at different wind speeds. They should also have an estimate of likely annual energy output for a location with a given average wind speed. If you have an estimate of wind speeds for your site, you can then work out how much electricity you may be able to generate.

If a site has good average wind speeds, then a turbine with a rotor diameter of about 1 metre could give you a few hundred kilowatt-hours (kWh) of electricity per year. This is about the same as one solar panel. To get as much energy per year as a whole solar roof array, you’d need a rotor about 4 metres across. For most houses this sort of turbine would not be feasible, but if you have enough land around your home it may be possible.

How important is wind speed?

Doubling the wind speed will yield eight times as much power. This means that if you get half as much wind as expected, you’ll only have one-eighth as much power available to you. Therefore it’s vital that a wind turbine is put up in the windiest possible position.

Many sites are not windy enough – especially at a small scale. Wind speeds increase significantly with height, so even small turbines need to be mounted on a high tower, away from buildings and trees. Those obstacles will create turbulence that reduces power output and increases wear and tear.

How much do small wind turbines cost?

A turbine plus tower and installation might cost between £2,500 and £6,000 per rated kilowatt (kW). Very small wind turbines may cost a few hundred pounds, and their power output will be a fraction of a kilowatt.

When calculating likely installation costs it’s important to include the tower, cables, inverter, charge controller, and any other components.

Turbines are built to operate without much maintenance, but some moving parts of the turbine may have to be replaced during its lifetime of around 20 years. If an inverter is needed, then this is likely to need replacing within the life of the turbine.

How much will it pay back?

A small off grid turbine can save running a diesel generator on a boat or in a remote cottage. As that can be very expensive, a wind turbine could be a good investment in a suitable spot.

For a larger grid-connected turbine, the savings will depend on how much you use onsite, and what price you can get for exporting any excess. For what you use onsite, comparison import prices have been dropping, with the July 2024 price cap about 22.36p per unit (kilowatt-hour, kWh). That cap could continue to drop, but long term prices are hard to predict. In addition, special tariffs are increasingly offering better deals for different patterns of use (such as charging an electric car at night).

For exporting the excess, you can get payments back under the Smart Export Guarantee (SEG) scheme. To claim SEG payments you need a type of smart meter that will measure exported electricity (many first generation smart meters can’t do this). You can shop around and compare the prices offered for your exported electricity. Some companies may offer more than 15 pence per kWh, but some might pay 1p per kWh or less.

Community Power

Large-scale wind turbines can harness the much stronger winds on hilltops, away from towns. Investing in a big community owned wind turbine is therefore usually the best way for most of us to benefit from wind power.

Find out more

For some additional details see our questions and answers section below.

You could also attend one of our short courses on renewable energy. Our courses on DIY wind turbines are based on the robust designs of Hugh Piggott (Scoraig Wind).

To find suppliers of wind turbines rated at a few kilowatts, such as those for connection to the grid, you could use the Microgeneration Certification Scheme (MCS) listings of accredited installers and products.