Wind Turbine

At the time of writing, the methodology for EPC assessments of existing dwellings is RDSAP 9.94. This updates to RDSAP 10 on 15th June 2025 and a significant methodology overhaul from RDSAP to the Home Energy Model (HEM) is proposed for 2026. In addition, government consulations indicate future changes to the format of EPCs and minimum rating levels required for priate rental properties. Methods for improving EPC ratings may therefore change in the future.

Wind turbines convert the kinetic energy of wind into electricity which can then be consumed within a property.

This then reduces the amount of electricity the property needs to draw from the National Grid, and if the quantity of power generated is sufficient, it can even be exported back, or used to charge a home battery.

In turn, the presence of a wind turbine can increase your EPC rating when recorded in an assessment.

Unfortunately wind turbines are often seen as a comical option by the general public when observed as an improvement measure on an EPC, but as a form of energy generation, wind power has it's advantages.

Wind energy has the advantage of being available night and day, wheras solar is only available during the day.

Wind energy is also available significantly during the winter, at a time when solar is much reduced.

Use of both Wind and Solar technologies together could therefore help balance the level of energy generation available.

In fact over the last few years wind energy has quickly become a significant contributor to GB national energy generation. Take a look at the GB Energy Dashboard to see the significant proportion of Great Britain's electricity consumption which is now generated by wind power (Choose the 'Historical' view for the best display of this):

https://www.energydashboard.co.uk/historical

In general, the power generated by a wind turbine is related to:

• The square of the diameter of the rotor
• The height above ground
• The wind speed (which is related to geographical location) 

Therefore generation is better suited to larger diameter rotors, located as high up in the air as possibe.

In order to appear as a recommendation on an EPC certificate:

• The the property needs to be a house or a bungalow
• The 'Terrain Type' of the property needs to be 'Rural'
• No wind turbine should be present currently

So for most propertes, the main thing that triggers a Wind Turbine recommendation is where the energy assessor decides the property is located in a 'Rural' area, and sets the Terrain type in the assessment to 'Rural'.

If the 'Terrain Type' is described instead as Urban or Suburban, or the property type is a flat, maisonette or a Park Home, or a wind turbine is already present then a wind turbine will not be be listed as a recommendation on a new EPC.

If it is presented as a recommendation, the suggested EPC rating will be based on one wind turbine on a mast with a blade diameter of 4.0m and hub height 10m above the ridge of the property.

If a wind turbine is present at a property, it can be recorded in an EPC assessment by an energy assessor.

If exact details of the wind turbine are known, they can be entered manually in the assessment. The rotor diameter and hub height above ridge are required, and sight of documenatry evidence will be required to support the entry in case the EPC is audited.

If the wind turbine details are not known, default properties can be assumed, which I think are a 2m rotor diameter and a hub height above the ridge line of 2m. These are at least the details which are pre-filled in the assessment software when the the 'details known' option is first enabled.

The other key factor is the Terrain Type, which we shall see in the next section. This can be set to Urban, Suburban or Rural.

Normally, you would expect wind turbines to be present in Rural locations. In other terrain types, planning issues and community relationship issues are much more likely to occur. 

It's likely (but I have not researched this) that geographical location may also play a part in the calculations, with local weather statistics used to determine the level of generation. 

In this section, I add a wind turbine to my house in the EPC assessment software and record the resulting EPC ratings.

My house is a 3-bed mid-terrace 1950s house for which further details can be seen on our Case Study 2 page.

These indicated results of course are only valid for my property. If you are interested in potential improvements for your property, please contact a local energy assessor who will be able to advise you about your potential ratings.

Anyhow, here we are, adding either a 'default' wind turbine, or a 4m wind turbine, and also noticing differences with Terrain Type set to either 'Suburban' or 'Rural': 

So, the 4m rotor and 10 height from ridge would give me a 7 SAP point increase in my EPC rating. This is with Terrain type set to suburban, which is correct for my location.

In contrast, if the turbine details are not known then I only have a 1 SAP point improvement in EPC rating.

The ratings are noticably better though if the Terrain Type is set to 'Rural', likely due to an expected higher wind speed resulting from fewer surrounding obstructions. This is something that would have been researched by the Building Research Establishment (BRE) when developing the SAP methodology.

In a real assessment, the terrain type needs to be set correctly, but a 4m rotor at 10m above ridge line in a Rural loacation would have added 21 SAP points to my EPC rating. 

Any rating improvement for your property is likely to be different to this. As always, contact a local energy assessor to confirm the potential rating for your property before making any decisions.

For increasing your EPC rating, wind turbines are suited more for properties that are located in a rural setting. The turbine itself needs to be reasonably large in diameter and a good distance above the ridge height of the property to contribute significiantly to an EPC rating improvement.

As we can see from the results in the table above though, for the right properties this mght be a viable option.

If you have a wind turbine already, it would definitiely be beneficial to show any visiting energy assessor a copy of your installation documentation so he can enter the details of your specific turbine, rather than relying on the default properties in the assessment software.

If you're thinking of getting a wind turbine, are you confident that an energy assessor would consider your Terrain Type as Rural?

Click here to return to our 'Improve Your EPC' main page, and see if there is another way you could improve your EPC rating.