Wind farm operators were paid £34million last year to switch the turbines off in gales.
Two days last week saw householders effectively hand £400,000 to energy firms for doing nothing.
The arrangement compensates wind farms for the National Grid’s inability to cope with the extra energy produced during high winds.
The exact structure of the payments is mired in secrecy – even though families have to carry the cost in the form of higher power bills.
Hidden payments discovered by the Mail show that wind farms are given much more money than previously thought.
It was always known the National Grid made ‘constraint payments’ – cash given to operators to temporarily shut down their turbines when electricity supply outstripped demand.
But what was not made public were details of so-called ‘forward trades’, in which the National Grid agrees a pay-out when the weather is expected to be stormy.
The money is paid out even before a turbine shuts down.
Limited information about the forward trade deals is published in an obscure section of the National Grid website – and in a format that even energy experts have struggled to interpret.
The National Grid has admitted £15.5million was paid out to energy operators in the form of conventional constraint payments in 2011-12 in England and Scotland.
But for the first time it has emerged that an even greater sum – £18.6million – was paid out in forward trades. It means the total payments for that year were £34.1 million, far higher than previously reported.
Lee Moroney, of the Renewable Energy Foundation, said: ‘The UK electricity market needs to become very much more transparent.
‘Wind farms are already heavily subsidised and it is only right that all payments made to wind farms to reduce output are in the public domain, so that consumers, who ultimately bear these costs, are able to judge whether the charges are reasonable.’
Murdo Fraser, a member of the parliament in Scotland, where many wind farms are sited, said: ‘Why have the authorities been so anxious not to release this information? Is it because they feared this would undermine any remaining public confidence in renewable energy policy?
‘People will wonder if they were trying to cover up the truth.
‘The revelation that vast sums are being paid to wind power developers will just lead to more and more people questioning government policy.’
Details of which energy firms scooped the money is kept secret because of ‘commercial confidentiality’.
Although the figures cover all forms of power generation, including coal and gas, energy experts say the overwhelming majority relates to wind energy.
On Monday and Tuesday last week, when it was exceptionally windy, the National Grid said it paid £16,118 in compensation.
But only when prompted by the Mail did it admit the true figure – including forward trades – was £387,000.
Yesterday National Grid spokesman Chris Mostyn said: ‘We have a number of tools available to help us balance the network minute by minute and keep the lights on, and constraint payments are just one of those tools.
‘Our incentives are set by the regulator to operate the network as cost-effectively as possible, and it currently makes up less than 1 per cent of the average domestic bill.
‘We are always working with the industry to improve and develop the way we operate the Grid, as well as investing millions of pounds in the coming years to help move the power to where it’s needed.’
Up to 32,000 wind turbines could be built in England and Wales over the next 40 years to meet government targets. Many of the existing sites are owned by foreign firms which have made record profits in recent years.