In a report released on Monday, the PC maker claimed that about $217 million (123 million pounds) is wasted every year in the U.K. alone powering PCs that could have been shut down or left in hibernation mode. The report also pointed out the environmental impact of all the wasted energy.
Fujitsu Siemens surveyed 1,000 employees and found that some 370 never turned off their computers before leaving the office for the day.
"U.K. businesses need to consider both the financial and environmental implications of leaving a computer running and make turning off their PCs each night a policy," said Garry Owen, head of product marketing at Fujitsu Siemens Computers, who added that simply putting a computer into standby means it still is consuming power.
Fujitsu Siemens released its report to coincide with the start on Monday of Energy Saving Week, a nationwide initiative aimed at raising the awareness of the damaging effects of climate change and ways to prevent it.
With energy prices having soared in recent months, plus growing concerns over climate change, the amount of power used by PCs is a hot topic. The European Union recently agreed legislation to cut down on energy wasted by idle computers, including those left in standby.
"Hundreds of thousands of tons of carbon dioxide are needlessly produced every year by computers, digital set top boxes, chargers and many other products left on standby mode," said Environment Minister Elliot Morley in June. "We know that products can be designed to be much more efficient and do less harm to the environment. Wasted energy is a hidden cost for consumers and in this day and age that is unacceptable."
There has been confusion in the past about whether it is better to turn PCs off when not in use, or to leave them switched on. Some people have claimed that regularly turning computers off can, over time, weaken links between components and damage hardware such as the hard drive.
According to some estimates, just turning off a monitor can save 75 percent of the overall energy consumption of a PC.
Graeme Wearden of ZDNet UK reported from London.