Question

Is there a definition of a small wind turbine?

There is no hard and fast rule as to when turbines are small or large. As a general rule of thumb each proposal, regardless of size or number should be determined in accordance with the development plan unless there are further material considerations. Policy should avoid being overly prescriptive and should provide guidance on the type of development that may be appropriate in a given scenario. Neither PAN45 nor SPP make reference to the different approaches required for assessing small or large turbines.

However, as guidance, the following definitions are provided to give an indicative scale of development:

In terms of Schedule 2 section 3(i) of the EIA (Scotland) Regulations 1999 installations for the harnessing of wind power for energy production (wind farms) may have significant effects on the environment and require an EIA  where:

(1) the number of turbines in any development  exceeds two, or

(2) the hub height of any turbine or height of any other structure exceeds 15 metres.

Given that it is accepted that a turbine consists of a foundation, tower, nacelle and two or more blades it should be assumed that the term 'other structure' does not include the blades (i.e. additional height from the blades should be disregarded).

The British Wind Energy Association provide a definition of small wind systems as those with a rating under 50kW, and can be either building mounted or free standing. This is also defined within the Energy Act 2004 as being the upper limit of 'microgeneration' .

Whilst PAN45 and SPP6 do not make reference to size constraints, planning guidance for England and Wales, in PPS22: Renewable Energy A Companion Guide, also suggests that a turbine which generates less than 50kW should be considered small.