The number of onshore wind turbines in Britain has reached 30,000 after increasing by 13 per cent last year, according to research.
The disclosure has prompted suggestions that the wind industry is encroaching upon the countryside by stealth. The figure dwarfs the total that is commonly quoted by the industry, which currently stands at 4,399.
The discrepancy is because the lower figure does not include the vast numbers of small and mid-sized turbines that have the capacity to produce less than 100kW of electricity each.
The smaller turbines range from “micro” roof-top turbines to those that can reach over 100 feet tall and have been installed by thousands of farmers and landowners across the UK.
By comparison, the biggest onshore turbines can reach 475 feet tall.
The issue of wind power is likely to be a key election battleground after David Cameron pledged that there would be no more subsidies for onshore wind under a Conservative government.
Wind farms have often met with strong local opposition, and are estimated to add £765 million a year to consumers’ bills through subsidies, according to the Renewable Energy Foundation.
Many Tories fear that the issue could cost them crucial votes in rural areas.
Analysis by RenewableUK, the wind industry body, shows that the total number of turbines increased by 13 per cent, to 29,353 at the end of last year, and is now expected to have surpassed 30,000.
Developers have told The Telegraph that they have seen a surge in interest in smaller wind turbines around the country.
Data compiled by Earthmill, a specialist in farm turbines, showed a 60 per cent rise in the number of “live” planning applications for small and mid-sized turbines since October, with 810 applications in the system at the end of last month.
Chris Heaton-Harris MP, who has led the campaign against onshore wind turbines, said: “The true scale of onshore wind and its cost is only just beginning to come to light.
“Small-scale turbines can be as controversial as big wind farms, depending on where they are sited. I am very pleased my party has said we will let local communities decide where to site these things.
“But my opinion is we have too many already because the subsidy is too high, and we are backing a losing horse in the race for sustainable energy.”
He said the smaller turbines “can go much closer to people’s homes”.
He added: “It is proximity to other dwellings that causes the upset.”
In 2013, 605 medium and large-scale turbines of more than 100kW were installed. In the same year, RenewableUK estimates that 3,536 smaller turbines were also installed.
However, the data for so far in 2014 shows that the installation rate for the larger turbines is slowing, amid a tougher planning regime as communities secretary Eric Pickles calls in more applications for review. Only 141 turbines of 100kW or greater capacity have been installed so far this year.
Steve Milner, director of Earthmill, said that small and mid-sized turbines were popular with farmers as they reduced their energy costs.
He said that a 225kW turbine – which could reach 147 feet tall – could cost up to £500,000 to install.
A farmer could however expect to recoup that cost within 10 years through a combination of subsidies, which are funded through levies on consumer energy bills, the avoided costs of buying power, and additional income from selling surplus power. The subsidies would continue for a further 10 years, meaning they could expect to make a further £500,000, he said.
But Mr Milner said that gaining planning permission was getting “significantly harder”. “There are more objections and more hoops to jump through,” he said.
Jennifer Webber, director of external affairs at RenewableUK, said: “Small and medium wind turbines are a lifeline for Britain’s rural economy – research shows that 40 per cent of farmers are generating much-needed income from renewables, and a further 61 per cent are intending to do so over the next five years, so we could soon see three out of every four farmers using renewable energy.
“The vast majority of the onshore wind turbines installed in the UK are micro, small and medium-sized turbines installed by people living in rural areas generating their own power, and protecting themselves from the cost of having to import energy”.