New specifications for PCs carrying the popular Energy Star energy efficiency label were officially launched this week, increasing pressure on manufacturers to deliver highly efficient desktops, laptops and monitors.

The Energy Star 5.0 specifications will require IT manufacturers to deliver significant energy efficiency improvements and meet tough new standards governing the energy use of devices when in standby, active and sleep modes.

Katharine Kaplan, a spokeswoman for the Energy Star programme at the EPA, told news agency Reuters that she expected that "products that meet the Energy Star 5.0 requirements will use 30 per cent to 60 per cent less energy than the standard [devices] on the market, which are largely 4.0 models".

According to figures from the US Environmental Protection Agency (EPA), the new standard could deliver annual energy cost savings of $2bn (£1.2bn) a year if all computers sold comply with the specifications.

A number of manufacturers, including Apple, Dell, Lenovo and HP, are already offering Energy Star 5.0. More are expected to comply with the specifications as government departments will not procure machines that do not carry the label.

Growing numbers of PCs sold in Europe are also expected to carry the new label where the European Commission has endorsed the labelling programme and a number of governments also require IT suppliers to meet Energy Star specifications.

Under the new specifications, desktop computers can set use between 148KwH and 234KwH depending on whether they are in standby, active or sleep mode. Laptops can only use up to 88.5KwH, while monitors, small-scale servers, and thin clients also have to meet new more stringent standards.

The new label comes just two years after the introduction of the Energy Star 4.0 specifications, and marks a major shift in policy following a seven-year period between 2000 and 2007 when no new PC energy specifications were introduced.

The move is also part of a major push from the EPA to curb IT energy use and follows on from the first Energy Star specifications for computer servers, which were introduced in May.

Kaplan hinted that the Energy Star scheme would be extended further with new specifications for routers and modems already in the pipeline, and proposed specifications for uninterruptible power supplies and storage technologies being investigated.