Wind power is proportional to the cube of the wind's speed, so relatively minor increases in speed result in large changes in potential output. Individual turbines vary in size and power output from a few hundred watts to two or three megawatts (as a guide, a typical domestic system would be 2.5 - 6 kilowatts, depending on the location and size of the home).

Uses range from very small turbines supplying energy for battery charging systems (e.g. on boats or in homes), to turbines grouped on wind farms supplying electricity to the grid.

Small scale wind and your home

Wind speed increases with height so it's best to have the turbine high on a mast or tower. Generally speaking the ideal siting is a smooth-top hill with a flat, clear exposure, free from excessive turbulence and obstructions such as large trees, houses or other buildings. Accordingly, you should expect turbines mounted on homes to provide a lower yield than those on a free-standing mast in open space.

Knowledge of the local wind is critical to designing a wind energy system and predicting output. For domestic installations a good source of information on local wind speeds is the NOABL database which can be accessed from the British Wind Energy Association.

You can also collect primary information by setting up your own monitoring mast to record wind speed. An ideal way of doing this is with an anemometer. You can buy one online for around £80.

Planning issues such as visual impact, noise and conservation issues also have to be considered. System installation normally requires permission from the local authority.

Stand-alone or grid-connected system?

Small-scale wind power is particularly suitable for remote off-grid locations where conventional methods of supply are expensive or impractical. Most small wind turbines generate direct current (DC) electricity. Off-grid systems require battery storage and an inverter to convert DC electricity to AC (alternating current - mains electricity).

You also need a controller to divert power to another useful source (e.g. space and/or water heaters) when the battery is fully charged.

It's common to combine this system with a diesel generator for use during periods of low wind speeds. A combined wind and diesel system gives greater efficiency and flexibility than a diesel only system. It allows the generator to be used at optimum load for short periods of time to charge batteries when there is little wind, rather than by constant use at varying loads.

Wind systems can also be installed where there is a grid connection. A special inverter and controller converts DC electricity to AC at a quality and standard acceptable to the grid. No battery storage is required. Any unused or excess electricity can be exported to the grid and sold to an electricity supply company. To maximise your gains and thus reduce the payback period, we recommend you switch suppliers to provide you with an export tariff, such as that provided by nPower or Good Energy.

Cost and maintenance

Systems up to 1kW will cost between £1500 and £3000, whereas larger systems in the region of 1.5kW to 6kW would cost between £4,000 - £18,000 installed. These costs are inclusive of the turbine, mast, inverters, battery storage (if required) and installation, however it's important to remember that costs always vary depending on location and the size and type of system.

Turbines can have a life of up to 20 years but require service checks every few years to ensure they work efficiently. For battery storage systems, typical battery life is around 6-10 years, depending on the type and usage, so expect to have to replace them at some point in the system's life.

Are there grants available?

Yes, householders and community groups in Scotland can access grants from the Scottish Executive. These grants are managed jointly by the Energy Saving Trust and the Highlands and Islands Community Energy Company. Householders can access capital funding of up to £4,000 (ex-VAT) and community organisations can access up to £10,000 for feasibility assistance and up to £100,000 for capital assistance.

For turbines larger than approximately 4kWp applicants may be able to receive more grant support from the national low carbon buildings programme.

For more information call the Energy Agency on 01292-521896 or the EST helpline on 0800 138 8858.

Energy Agency Case Study

To view a community wind project click on the following:

Gatehouse Development Initiative