Dell has met the US government's new energy efficiency rating seven months early.

The PC giant has announced that a selection of its laptops and desktops already match 2009's new Energy Star 5.0 standards, which require a minimum internal power supply efficiency of 85% - up from the previous 80% for Energy Star 4.0.

So far, the only compliant Dell PCs are business models. Certain configurations of the OptiPlex 760 and 960 desktops and the Latitude E6400 (pictured) and E4300 laptops match the stringent new standards.

Dell says the Optiplex 960 uses 43% less energy than the previous generation Optiplex.

"By meeting Energy Star 5.0 seven months ahead of schedule, Dell is demonstrating what it means to be a leader in energy-efficient technology", said Kateri Callahan, president of the Alliance to Save Energy.

Dell also claimed that since 2005 its green computing measures have saved Optiplex owners around $3 billion in energy and 29 million tonnes of carbon.