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Wind Power

Introduction to wind power

The pros and cons of wind power regularly fill the pages of newspapers, yet it’s still quite difficult to pin down the facts about it. Two things there’s no dispute about are that:

  • the UK is the windiest country in Europe, and
  • the wind blows most in winter, which is when we use most electricity.

There’s considerable agreement that wind has huge potential for affordable, large-scale generation through onshore and off shore wind farms.

At a domestic level, things are less clear. Whether wind is right for you will depend on your location and circumstances. If you have a clear site for the turbine, away from obstructions, with high average wind speeds, it’s worth investigating.

How do wind turbines work?

Wind turbines are mounted either on a building or, preferably, on a mast.

  • The wind rotates the blades of the turbine
  • which turns a rotor shaft
  • which generates low voltage DC (direct current) electricity.
  • An inverter converts it to AC (alternating current or mains type) electricity.

What happens next depends on whether or not the system is connected to the grid.

In off-grid systems the power generated charges a bank of batteries. To get the most from the system, you can programme it to divert electricity to other uses such as water or space heating if the batteries are full.

If you are connected to the mains grid, then when you generate more electricity than you use, you can sell the excess to your supplier. When you are not generating enough to cover your needs, you can buy electricity from your supplier.

Micro turbines, mounted on the roof of your house, are designed to supplement the mains electricity supply, reducing the amount you need to buy. They can plug into a standard 13amp socket.

Turbine life is up to 22 years. They need servicing every few years to ensure they are efficient. Battery life is shorter – about six to 10 years.

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Is wind power suitable for my home?

The success of wind power depends totally on the suitability of your site.

The key factors are:

  • An average wind speed of at least 5 or 6 m/s (metres per second).
  • No obstacles nearby which might reduce the wind speed or create turbulence. These include buildings, trees or hills. An ideal site is a smooth hill top with a clear, open stretch to the prevailing wind. 
  • You are able to connect the turbine to your property and to the national grid.

Noise: data on noise is generally available from the manufacturer. It is measured in decibels per wind speed. For example, the Proven 6kW wind turbine creates a noise of 45dB at a windspeed of 5m/s and 65 dB at 20m/s. This compares with whispering, or leaves rustling (30dB) or the noise of city centre traffic 95dB. Click the link for more on wind turbine noise.

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Wind speed lookup

 Please note this is based on an average wind speed in your postcode area, and is only an indication. If you have trees, buildings etc between you and the prevailing wind the speed may well be lower than shown.

What size / cost for wind turbines?

Micro turbines, which are generally in the range of 500 watts to 2.5 kW, will cost around £2,000 upwards installed according to the Energy Saving Trust.

Small turbines, ranging in size from 2.5kW to 8kW, are a much heftier investment. Prices are likely to be anything from £11,000 upwards.

The size you choose will depend on your site, the amount of power you want to generate and how much you want to spend. Connecting to the grid is expensive, and probably won’t be worth it for less than a 2kW turbine. A 5kW system is likely to generate around 15,000kWh of electricity in a year – which means it would cover its cost in 10 years.

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Wind turbines are eligible for Feed-in-Tariff payments, meaning you will be paid for the electricity generated by your system as well as another payment for the electricity you export.

Do I need planning permission for wind turbines?

There are permitted development rights for (a very small number of) small wind turbines. However, none of the turbines currently accredited by MCS meets the criteria for permitted development, so if you want to get the feed-in tariff you will need to apply for planning permission.

Your local authority will be looking at the visual impact, noise, vibration, electrical interference (with TV aerials) and safety, in making a decision. More information can be found on the planning portal.

If you want to install a building mounted turbine building regulations will normally apply around size, weight and force exerted on the mounting points. They also apply to the electrical installation work.

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What’s the best mounting for wind turbines?

Mast-mounted wind turbine

Mast-mounted wind turbine

Turbines can either be mounted on a free standing tower (mast) or micro turbines can be fixed to the roof of a building.

Wind speeds increase with height, so it is generally considered best to put your turbine on a mast. A small increase in the wind speed will lead to a proportionally much larger increase in the amount of electricity generated (the change is cubed – so twice the wind speed will lead to eight times as much power; half the wind speed will generate an eighth as much). A tower also helps avoid turbulence caused by trees or buildings.

Energy Saving Trust field trials both found that no building-mounted turbine performed as well as expected, and where micro turbines are viable, people would be better off going for larger systems. Wind turbines are generally not suitable in urban or suburban settings.

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Calculate wind power potential

How do I choose a wind turbine?

There are two measures of performance for wind turbines: a power rating and the energy output for the turbine. The latter, which is measured in kWh (kilowatt hours, the unit that electricity is measured in), is the most significant. It’s no good having a high power rating if the turbine needs hurricane strength winds to turn it and it stands idle a good deal of the time.

While these figures can indicate comparative performance of turbines, the actual performance depends entirely on the conditions at your site. The Warwick Wind Trials found that variation in the performance of the same wind turbine can be as much as 28 times when comparing two sites less than a mile apart.

If you wish to claim the feed-in tariff you must use a MCS accredited installer and product.

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