The Tory leader announced he was setting up talks with industry chiefs to ensure all electrical products sold in the UK were energy-efficient. It could also lead to printers being set up to use both sides of paper automatically.
Mr Cameron wants to persuade manufacturers and importers to make electrical goods "greener" but aides said he was not ruling out legislation.
He told a conference in London: "This country emits an astonishing 800,000 tonnes of carbon a year through leaving electrical appliances ticking over, or on standby, when they are not being used. That is completely unsustainable, as well as a colossal waste of money... it is time industry manufactured products that automatically economize on their energy use."
Consumers had to be given "carrots not sticks" to persuade them to live greener lifestyles. Mr Cameron praised schemes by Conservative councils to pay people to recycle by giving them vouchers to spend in local shops, which he said had boosted recycling rates by 30 per cent.
He also said he wanted to introduce U.S.-style schemes enabling householders to see how much gas and electricity their neighbours were using, which he said would drive down energy consumption. A Tory government would also seek to force energy companies to inform consumers on their bills how much money they might have saved by using the cheapest tariff available.
Labour sources claimed that Tory hostility to co-operation at EU level would undermine their attempts to persuade manufacturers to make products more energy efficient.