Putting up a small wind turbine on the roof of a suburban home may be a waste of time, according to a new report.

And in future grants for people who want to install small-scale wind turbines should only be given if it can be shown the turbine will actually save on CO2 emissions.

The claims are made in a joint study by the Carbon Trust and Met Office set up to establish whether household wind turbines - so-called microgeneration - will work and whether they can help cut CO2 emissions.

The report concludes that turbines in rural areas, where the wind is stronger and more consistent, can deliver four times as much electricity and carbon savings as in more sheltered sites cities and towns. They can also produce electricity at a competitive price.

To encourage a switch to more sustainable energy homeowners can apply for a Government grant of up to £2,500 under the Low Carbon Buildings Programme to help with the cost of installing microgeneration technology while not-for-profit and community wind farms and public sector organisations can apply for up to half the installation costs.

The report said small-scale wind energy could in theory generate some 41.3 terawatt hours of electricity - 12% of UK electricity consumption - and save 17.8m tonnes of carbon a year.

But with current electricity prices and the cost of small wind turbines, only a fraction of that is deliverable - with the study estimating that if 10% of households had turbines, they would produce just 0.4% of total UK energy consumption and save 600,000 tonnes of emissions a year.

As well as tougher grant criteria the report also calls for an increase in the height limit of stand-alone wind turbines to more than 11m to the blade tip in exposed rural areas - which can be built without planning permission under permitted development rights - to give the best chance of capturing the wind's power.

Dr Mark Williamson, Director of Carbon Trust Innovations, said: "Small-scale wind energy is attracting growing interest, and at the Carbon Trust we are receiving increasing enquiries from organisations considering installing small turbines. It's vital that people understand the wind resources available to them."

Cathy Durston, head of consulting at the Met Office, said: "Wind speeds vary considerably and since speed is the key determinant of power, the performance of small wind turbines is very sensitive to their location. This research has shed new light on the best locations for turbines to be installed."

Energy Minister Malcolm Wicks said: "Small-scale power generation like wind turbines can turn the concerned individual in to an active citizen in the fight against climate change.

"We are currently working to ease the planning rules for small wind turbines so more homeowners can install them with the minimum of fuss.

"The Carbon Trust's report provides useful advice on the potential of micro-wind. We will use these findings as we develop our policies to dramatically increase the amount of energy the UK generates from renewable sources."