CAT Logo
Wind power

Wind power

The UK is the windiest country in Europe. Wind farms are therefore a great way for us to meet our energy needs without carbon emissions. Small-scale wind power can also be effective. However, a small turbine must be very carefully sited to be a cost effective and low-carbon option. For most of us, supporting and investing in large scale wind power is the more effective option.

CAT has been using wind power since we started in the 1970s, trying out different types of turbine. You can learn more on one of our courses.

Can I put a wind turbine on my roof?

We strongly advise against mounting turbines on rooftops or buildings, as they will receive only weak and turbulent winds. Several field trials have found that building-mounted turbines perform poorly, producing only a small fraction of the energy they would produce if properly sited.

Clearly a turbine that does not spin will not save you money or reduce carbon emissions. In addition, turbines can resonate in the wind and produce vibrations, which can damage the structure of the building.

Where should I put a wind turbine?

An ideal site is a smooth hilltop with a clear open stretch – at least in the prevailing wind direction. Towns & villages don’t usually have open stretches like this, which is why they’re usually bad sites.

Before spending thousands of pounds on the sort of wind turbine that gives a few kilowatts of power, it could be worth spending a few hundred on some wind monitoring equipment – such as a mast and data logger. Be wary of relying only on an online database that gives wind speeds for a given postcode or map reference. Those figures don’t really account for the local conditions that a small turbine will be affected by.

How big does a wind turbine need to be?

When you double the diameter of a rotor it makes the swept area four times as big. This is because the area of a circle comes from the square of the radius (A = π r²). A rotor with a 10 metre diameter will therefore capture one hundred times as much wind as one with a one metre diameter. This means that very small turbines can’t capture much wind.

The smallest turbines, costing a few hundred pounds, are fine for charging up a 12volt battery in a boat or caravan. However, to produce an output similar to that from a domestic solar PV roof, a much larger turbine would be needed. Turbines that give an output of a few kilowatts will have a rotor diameter of a few metres, and will need to be mounted on a high tower.

How much electricity will a wind turbine make?

This is very hard to predict, because wind speeds vary a lot from site to site. The output of a solar PV roof is fairly straightforward to estimate, but it’s much harder to do the same for a small wind turbine. There are two factors that make a big impact on energy output – the size of the rotor and the speed of the wind.

Suppliers of wind turbines should have information about the power a wind turbine will make at different wind speeds. They should also have an estimate of likely annual energy output for a location with a given average wind speed. If you have an estimate of wind speeds for your site, you can then work out how much electricity you may be able to generate.

If a site has good average wind speeds, then a turbine with a rotor diameter of about 1 metre could give you a few hundred kilowatt-hours (kWh) of electricity per year. This is about the same as one solar panel. To get as much energy per year as a whole solar roof array, you’d need a rotor about 4 metres across. For most houses this sort of turbine would not be feasible, but if you have enough land around your home it may be possible.

How important is wind speed?

Doubling the wind speed will yield eight times as much power. This means that if you get half as much wind as expected, you’ll only have one-eighth as much power available to you. Therefore it’s vital that a wind turbine is put up in the windiest possible position.

Many sites are not windy enough – especially at a small scale. Wind speeds increase significantly with height, so even small turbines need to be mounted on a high tower, away from buildings and trees. Those obstacles will create turbulence that reduces power output and increases wear and tear.

How much do small wind turbines cost?

A turbine plus tower and installation might cost between £2,500 and £6,000 per rated kilowatt (kW). Very small wind turbines may cost a few hundred pounds, and their power output will be a fraction of a kilowatt.

When calculating likely installation costs it’s important to include the tower, cables, inverter, charge controller, and any other components.

Turbines are built to operate without much maintenance, but some moving parts of the turbine may have to be replaced during its lifetime of around 20 years. If an inverter is needed, then this is likely to need replacing within the life of the turbine.

How much will it pay back?

A small off grid turbine can save running a diesel generator on a boat or in a remote cottage. As that can be very expensive, a wind turbine could be a good investment in a suitable spot.

For a larger grid-connected turbine, the savings will depend on how much you use onsite, and what price you can get for exporting any excess. For what you use onsite, comparison import prices have been dropping, with the April 2024 price cap about 24.5p per unit (kilowatt-hour, kWh). That should drop again this summer, but the longer term price is harder to predict. In addition, special tariffs are increasingly offering better deals for different patterns of use (such as charging an electric car at night).

For exporting the excess, you can get payments back under the Smart Export Guarantee (SEG) scheme. To claim SEG payments you need a type of smart meter that will measure exported electricity (many first generation smart meters can’t do this). You can shop around and compare the prices offered for your exported electricity. Some companies may offer more than 15 pence per kWh, but some might pay 1p per kWh or less.

Community Power

Large-scale wind turbines can harness the much stronger winds on hilltops, away from towns. Investing in a big community owned wind turbine is therefore usually the best way for most of us to benefit from wind power.

Find out more

See our questions and answers section below and the books we sell, such as Wind & Solar Electricity.

You could also attend one of our short courses on renewable energy. Our courses on DIY wind turbines are based on the robust designs of Hugh Piggott (Scoraig Wind).

To find suppliers of wind turbines rated at a few kilowatts, such as those for connection to the grid, you could use the Microgeneration Certification Scheme (MCS) listings of accredited installers and products.

Related Questions

How much power will a wind turbine produce?

The ‘rated power’ of a wind turbine, given in kilowatts (kW), is the power produced at a chosen wind speed. This speed is quite high – often 10 or 12 metres per second. Different turbines have different rated wind speeds, so don’t just go by the rated power when comparing them.

The power output at lower wind speeds will be substantially less. For an overview of the performance of a turbine, look for a ‘power curve’ – a graph of power output against wind speed.

wind turbine power curve

Domestic wind turbines are typically rated between 1kW and 10kW. A very small turbine for use on a boat might be rated at only 100 to 200 watts.

Many factors affect how much energy you’ll get, but a conservative rule of thumb is that a 1kW turbine on a reasonably good site could generate 1000kWh over a year. On a better site, an annual output of 1500kWh per rated kW could be possible.



What is a windpump?

A windpump is used for raising water from a borehole to provide a water supply or irrigation. The design uses a fairly large multi-bladed rotor, mounted on a high tower.

Over the last 150 years or so, windpumps have been popular in America and Australia to provide water for agriculture. More recently, windpumps have been used in developing countries.

We’ve had a windpump at CAT for many years. We have no need to pump water from the ground, so ours moves a seat up and down to demonstrate the power available.

Windpump at CAT

They are quite site-specific, requiring a steady moderate wind to start up and keep turning. You’ll need to monitor and evaluate your site to properly size one. A 3.5 metre diameter rotor operating in a windspeed of 3 metres per second could pump 45,000 litres a day from a depth of 5 metres.

Windpumps have a relatively low capital cost and long lifetime (about 25 years). They’re good for off-grid sites, as they’re entirely mechanical – no need for electricity to run a controller, for example. However, they do require a 6-monthly service, and the pumping efficiency drops off in high wind speeds. A windpump may cost several thousand pounds, but could be a cost-effective solution for a large scale application.

For more information on a DIY option, CAT’s online store sells the book How to Build a Wind Pump. For commercial opions, the Poldaw Windpump is manufactured around the world but unfortunately the UK supplier (GB windpumps) recently ceased trading. The Bosman windpump is a design used in the Netherlands.

How can I pump water using wind or solar power?

A renewable energy technology could be ideal for pumping water where there is no mains electricity available, as a grid connection may be expensive and a diesel generator noisy and polluting.

Sizing a pump

The two main factors to consider when seeking a suitable pump are the flow rate – the amount of water that the pump will deliver, and the head – the height through which it will raise the water. These are related, as increasing the head will decrease the delivered flow. It’s important to minimise bends and other friction losses in pipework, as navigating these will require greater pressure, and as pressure and head are directly related, this effectively means a greater head.

Manufacturers’ technical data sheets will give the performance range of each pump, with graphs showing optimum combinations of flow and head. A pump sized properly to your needs will operate most efficiently. Suction pumps are limited to a depth of a few metres, so to draw water from a well or borehole, you’ll almost certainly need to lower in a submersible pump. Pumping wastewater or sewage necessitates one designed to handle drainage or effluent.

Small electric pumps for circulating water could cost tens of pounds, whilst those for drawing water from a well or borehole supply are likely to be a few hundred pounds. The main cost will be providing power to the pump, particularly when off-grid. Therefore, do first take all appropriate water-saving measures (such as spray-head fittings, mulches on plants to minimise water loss, etc) as these easily pay for themselves in the energy saved by reduced demand.

Off-grid electric pumps

Meeting a year-round water demand with a renewably-powered pump may require a combination of PV panels and a wind turbine, as this will balance energy production over the year. Sunshine and wind are naturally intermittent, so you may need some form of storage. Pumping water up to a tank (with demand then fed by gravity) during sunny or windy periods is more efficient than transferring the energy to batteries. If storing lots of water, you’ll need to balance the costs of a large tank (and supporting structure) against the costs of batteries (and their environmental impact and toxicity). An inexpensive control system can pump when needed, and otherwise divert power to batteries, giving extra backup facility.

The price of a small-scale renewable energy system will depend on the power and the maximum capacity needed. A very rough estimate is around £5 to £10 per installed watt. Siting generating equipment close to the pump minimises the cost and power loss incurred by cabling. As small turbines and PV panels usually produce power at 12 or 24 volts, a low-voltage pump would enable you to do without a costly inverter (for stepping up to 240 volts).

Mechanical pumps

For larger-scale pumping applications, you can avoid the losses in electrical systems by using mechanical power directly. See for example the question on our wind power page about wind pumps, or the question on our hydro power page about hydraulic ram pumps.

Should I sign up for a green tariff?

Signing up for a ‘green tariff’ from a company focused only on renewable energy is a great way to support the renewable energy industry. Changing your supplier is now very easy, and in most cases won’t make any difference to your supply.

One issue is that the small companies that specialise in renewable energy may not be part of the ‘Warm Home Discount’ scheme (although if they get enough customers they will be brought into it). This scheme gives a rebate to people at risk of fuel poverty, such as those receiving Pension Credit Guarantee Credit and some others. If this applies to you then you’ll need to stay with a larger provider to get this rebate.

Which green tariff?

We recommend choosing a company that only supports renewable energy. This means your money will not indirectly go to operate or build fossil-fuel power stations.

All electricity providers are required by the government to include some electricity from renewable sources. If they just offer a green tariff as one of a range of tariffs, then they may be simply charging a premium for electricity they’re legally required to produce! This is why we recommend companies that invest your electricity bill payments only in more renewable electricity.

If enough people sign up for renewable energy tariffs with these suppliers, then demand for renewable electricity will rise above the minimum government requirement. Therefore, as well as signing up yourself, encourage others to do the same.

The Ethical Consumer website gives a ranking based on the ethical and environmental record of electricity & gas suppliers. You have to be an Ethical Consumer subscriber to see the whole report, which gives more details.

I’m on a green tariff – so can I use as much electricity as I like?

It’s important to bear in mind that signing up to such a tariff does not mean you can leave all your lights on because it’s all zero carbon!  If you use more electricity through your green tariff it means that less renewable electricity is left for those that are not on green tariffs. This means that more fossil fuel will be burned to meet their share of energy use.

Also, every means of generating electricity has some environmental impact, including the energy and materials that go into manufacture and installation. Energy saving measures are vital, because it’s them much easier to meet our electricity needs with energy sources such as wind farms, and wave & tidal power. Our Zero Carbon Britain project has a lot more details about how we can meet all our energy needs using only renewable energy.

More news

Related Books

Related Short Courses: Energy

Join a CAT student teaching week and explore the energy requirements and carbon emissions of different international contexts and their potential to meet their energy needs more sustainably. Through a…

Read More
glass dome greenhouse

Did you know we are a Charity?

If you have found our Free Information Service useful, why not read more about ways you can support CAT, or make a donation.

Email Sign Up

Keep up to date with all the latest activities, events and online resources by signing up to our emails and following us on social media. And if you'd like to get involved and support our work, we'd love to welcome you as a CAT member.