Simple measures such as turning electrical appliances off at the mains and installing energy-efficient lightbulbs could slash the UK's carbon dioxide emissions by about 40 megatonnes a year, or up to one third, according to new research which says that cutting electricity consumption is up to 60 per cent more effective than previously thought. Such basic lifestyle changes would be the equivalent of removing about 10 large gas-fired power stations from operation.

The calculations, which come from the highly regarded Grantham Institute for Climate Change at Imperial College London, suggest that the Government has vastly underestimated the potential savings from encouraging people to use less electricity.

Adam Hawkes, a visiting fellow at the Grantham Institute, told The Independent on Sunday yesterday that the Government misjudged potential greenhouse gas savings because it failed to allow for the fact that different types of power stations emitted different amounts of CO2. "The Government uses average emissions rates, but when you do have a small change in demand, it's the power stations that have a higher carbon intensity such as coal and gas that respond. So it's the emissions rates of those power stations that you should use to calculate how much you'd save [if you used less electricity], rather than an average that includes nuclear and wind power stations."

Dr Hawkes's findings could be crucial in helping to kickstart many households' faltering efforts to conserve energy, experts believe. They come just weeks after the Government admitted Britain will fail to meet its 2010 target for cutting CO2 emissions: a pledged 20 per cent reduction on 1990 CO2 levels is likely to be missed by a wide margin. By the end of 2008, emissions had come down by 10 per cent.

Ben Castle, strategy manager at the Energy Saving Trust, a lobby group that campaigns to cut greenhouse gases, said: "It's a very interesting piece of research. Small, no-cost behaviours in the home really add up." Martyn Williams, a climate change campaigner at Friends of the Earth, said: "In light of this, the Government should be redoubling its efforts to curb carbon emissions. Smart meters will help, as well as smart billings to tell people what areas they need to cut back on."

Caroline Lucas MP, the leader of the Green Party, said: "The Green Party welcomes this research, which helps shed further light on the potential to cut CO2 emissions from energy use in the home. We need to step up public information about climate change and about the need to take simple measures like switching off unwanted lights. Pump out more information and we'll pump out fewer emissions.

"But it's clearly not enough to just encourage people to cut their energy use. The Government should take every step it can, for instance by banning the fitting of stand-by switches to televisions and by enforcing tighter regulations on the energy-efficiency of electrical goods and by setting higher energy standards for homes. Those are actions that would cost nothing and hurt no one, but would have a significant impact on overall energy use."

Dr Hawkes said his new estimates showed that turning off all appliances at the mains when going to bed or on holiday would save around 100kg of CO2 per year; installing 10 energy-efficient lightbulbs would save up to 350kg of CO2 per year; and hanging out wet washing to dry rather than using tumble dryers would save 260kg of CO2 per year. "If every house [took these steps], we'd save about 40 megatonnes of CO2 a year, which is the equivalent to the annual CO2 production of about seven million houses [a third of all households] in the UK – that's a lot!" he said.

The scientist, who works for the energy and climate change consultancy AEA Technology, based his study on the output of all UK power stations between 2002 and 2009. He said his findings showed the figure used by scientists advising the Government on the best ways to reduce electricity was 60 per cent lower than the actual rates observed, which meant that "policy studies are underestimating the impact of people reducing their energy use".

A spokesman for the Department for Energy and Climate Change defended its figures: "The Government believes that its estimates of marginal electricity emissions factors are soundly based. Our figures are lower than those of the Imperial study, because Imperial uses historical data, and because new power plants are more efficient and less carbon-intensive than older power stations."

However, the study is likely to influence political thinking on the issue, particularly as Chris Huhne, the Energy and Climate Change Secretary, said this weekend that Britons need to wean themselves off their "addiction to fossil fuels". He warned: "Inaction is not a option... The cheapest way of closing the gap between energy demand and supply is through energy-saving measures [such as] smart meters and smart grids that give consumers control over their appliances, curb energy waste and save money."

Additional reporting by Jonathan Owen and Sanna Chu

Case study: Saving money the easy way

John and Eriko Elford and their daughter Amalia, of Totnes, Devon.

"We've had low-energy lightbulbs ever since they came out, seven or eight years ago. I think they've definitely saved us money; our electricity bill is about £200-£220 a year. They're dearer, but the money you save in the end is worth it. We turn off lights when not using them. My daughter needs encouraging, but she does turn some things off. I always turn the TV off at the wall. There's not much we leave on stand- by except the computer router and my wife's electric toothbrush."