Hitachi has launched what it says is the world's most energy-efficient desktop hard-disk drive.

The company said the DeskstarP7K500, available in capacities ranging from 250GB to 500GB, includes a number of power-saving technologies aimed at reducing active and idle power consumption by up to 40 percent over the previous generation of products.

When idle, the 250GB model uses 3.6W, while versions with 320GB or higher capacities use 4.8W. Hitachi said typical hard drives use around 7W when idle.

Furthermore, the P7K500 has active power requirements to 6.4W and 8.2W for its one- and two-disk models, respectively.

Hitachi said the models also use Hitachi's second-generation PMR (perpendicular magnetic recording) heads and disks, enabling 250GB-per-platter areal density.