Home energy guide
How windy does your site need to be for a wind turbine?
Wind speed is everything. A site that's only a little windier can make far more electricity, while turbulent gardens and towns usually disappoint. Here's how to check yours before spending a penny.
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Work out your own numbers with the wind turbine calculator →
A little more wind, a lot more power
Here's the magic (and the trap) of wind: the power goes up with the cube of the wind speed. Double the wind and you get eight times the power. Even 10% more wind gives about a third more power.
That's basic physics, and it's why location is everything. A few metres higher, or a few hundred metres away from trees, can make a big difference.
See the numbers
| Wind speed | Relative power |
|---|---|
| 4 m/s | 51% |
| 5 m/s | 100% |
| 6 m/s | 173% |
| 7 m/s | 274% |
1.1³ = 1.33, so 10% more speed gives about 33% more power.
Real turbines don't follow this curve exactly. They start at a "cut-in" speed, hit full power at a higher one and switch off in storms. Use the manufacturer's certified power curve.
The average isn't the whole story
Two sites with the same average wind can produce different amounts. Gusty, swirly wind around buildings and trees is much harder for a turbine to use than smooth wind over open fields or sea.
What a good site looks like
- Exposed: hilltops, coasts and open farmland. EST says turbines work best in exposed, windy spots and are less suited to built-up or sheltered areas.
- High: wind is usually stronger and smoother higher up, so a taller mast generally means more power.
- Clear upwind: especially towards the prevailing wind, which in the UK usually comes from the south-west (Met Office).
- Away from obstacles: buildings and trees stir up turbulence downwind.
How to check your site
- Look around. Trees bent over? On a hill or the coast with nothing upwind? Good signs.
- Check official data for a first look. The Met Office publishes wind climate information for UK regions.
- Measure. The most reliable way is an anemometer at the planned hub height for at least a year. Pricey for a home, but cheaper than a turbine that disappoints.
- Ask installers for an output estimate based on your own site's data, and how they worked it out.
From wind to units of electricity
A turbine's yearly output is its rated power × 8,760 hours × its "capacity factor", the share of its maximum it produces on average. On paper, a 6 kW turbine could make 5,000 to 10,000 kWh a year.
See the numbers
| Capacity factor (assumed) | Output a year | Value at 26.32p if all used at home |
|---|---|---|
| 10% | 5,256 kWh | £1,383 |
| 15% | 7,884 kWh | £2,075 |
| 20% | 10,512 kWh | £2,767 |
The capacity factors are illustrations, not measured data.
But a reality check: most homes can't use all that, and exported power earns much less (for example 12p on a flat SEG tariff). EST estimates a well-sited 6 kW turbine saves about £650 a year, far below these figures, which suggests lower output, less self-use, or both. Be very sceptical of quotes that promise high capacity factors without site data.
Guernsey and Jersey
The islands are exposed and often windy, which helps. But salt spray, storms and planning all matter. In Guernsey, exported power earns the 9.90p Buy Back Tariff. Check planning first in our planning guide.
Next steps
Put your site's average wind speed into the wind turbine calculator, read our payback guide, and compare costs in how much a turbine costs.
Frequently asked questions
What wind speed do you need for a home wind turbine?
There is no single cut-off, but output rises with the cube of wind speed, so exposed sites with strong, steady wind do far better. EST says turbines are less suitable for built-up or sheltered areas.
How do I find the wind speed at my house?
Use Met Office climate information for a first look, and ideally measure with an anemometer at hub height for a year.
Does height matter?
Yes. Wind is usually stronger and less turbulent higher up, so a taller mast generally produces more.
How much electricity does a 6 kW turbine produce?
Rated power × 8,760 hours × capacity factor. At an assumed 10% that is about 5,256 kWh a year, but real output depends on your site.
Related guides
- Small wind turbine payback (UK and Guernsey)
- How much does a home wind turbine cost?
- Planning permission for home wind turbines
- Are roof-mounted wind turbines worth it?
- Wind turbine or solar panels: which is better for your home?
- All home-energy calculators
Sources (checked 27 October 2026 unless stated)
- Energy Saving Trust: Wind turbines: exposed sites, built-up areas, £650 saving
- Met Office: Guernsey Airport long-term averages: UK wind climate and prevailing wind
- Ofgem: price cap 1 Oct–31 Dec 2026 (published 26 Aug 2026): 26.32p/kWh
- Octopus Energy: Outgoing Octopus: 12p export
- Guernsey Electricity: tariffs from 1 July 2026 and Guernsey Gazette tariff notice: 9.90p buy back
- Capacity factors in the table: our illustrative assumptions
- Cube law: standard physics