Fujitsu Siemens Computers plans to launch in the middle of this year an enterprise desktop computer that consumes no energy when switched off.

Computers, like most electronics, consume a very small amount of energy even when switched off because of losses in the transformer or sensors that remain active for functions such as remote power-on. For a PC the consumption when powered off is typically between 1 watt and 4 watts, said Fujitsu Siemens. Right now, the best that energy-conscious users can do is keep electronics on a power strip that they must remember to turn off.

The Esprimo 7935 packs a system that achieves zero consumption without pulling the plug, said Lothar Lechtenberg, a spokesman for the company.

Businesses with a lot of computers stand to save a significant amount of money each year by ensuring their PCs aren't consuming any power overnight but there are disadvantages. Many companies administer software updates overnight and having the machines unplugged means that's not possible.

Fujitsu Siemens said it had solved this problem by allowing the machines to be awake and consuming a very small amount of power during a predefined time-slot during which updates can take place. Once the time slot passes the machine returns to zero-watt mode until it is switched on by its user.

Other green credentials of the new computer include a power supply that is 89 percent efficient, which means less electricity is wasted through heat, and motherboards with no halogen or lead. The PC conforms to the US. Environmental Protection Agency's (EPA) Energy Star 5.0 standard, which will come into use in the middle of this year, and the German Blue Angel mark.

The machine is likely to cost from around €600 or €700 (£530 or £620).

The company has also developed an energy-efficient entry-level server. The Primergy TX120 S2 is based on Intel Core2 Duo processors and achieves a 25 percent reduction in energy consumption over its predecessor. As a result it conforms to the Energy Star 4.0 specification, said the company.

The computer will be available in Fujitsu Siemens' EMEA sales area from the beginning of April at prices from €545 (£480).