Idle Vista PCs 'to send themselves to sleep'

Vista PCs will be set to sleep after an hour of inactivity.

While businesses and consumers can change the setting, Microsoft said they would be smart to let their computers nod off.

The software behemoth estimates that allowing a PC to go to sleep during off hours, as compared with leaving it on all the time, saves anywhere from $55 to $70 per year, depending on the type of monitor.

Dean DeWhitt, a director in the Windows kernel team at Microsoft, said: "This is energy [consumed] when you are not even using the PC. It truly is a waste."

The company has done work in the upcoming Vista OS update to make sure the PC can rest more easily. With Windows XP, programs could veto a user's request for the PC to go to sleep. In some cases, that meant that laptop owners thought they had put a PC to sleep, only to discover a few hours later that the machine had remained on and their laptop's battery had been drained.

But Microsoft is hoping to make an even bigger impact with desktops. Today, many businesses leave their computers on at night. Some do it to make sure they can install security patches. By adding the new sleep option, businesses can wake machines to install security updates, while letting them remain in the power-saving mode the rest of the time.

Also in Vista, businesses will be able to enforce the power management settings through the group policy tool. That means companies will be able to require, say, that a screen goes blank after 15 minutes of inactivity. Although Windows XP did not have that capability built in, some third-party companies, such as Verdiem, have offered that feature as an add-on.

All that snoozing time could pay off environmentally as well. Microsoft said by putting six PCs to sleep, rather than leaving them on, businesses can save the same amount of carbon emissions that would otherwise require an acre of trees to absorb. That calculation depends on the means used to generate the power for the PCs, with the actual energy emissions varying greatly by region.

While Vista makes some notable steps forward, Bruce Twito, Veridiem's chief technical officer, said there is plenty that has yet to be fixed in the operating system. Although Microsoft is allowing companies to set policies, Twito said the group policy options are not flexible enough.

Veridiem plans to introduce its own Vista-compatible power management software within two months of the general availability of the new operating system - which is slated for release to large businesses in November and to the general public in January.

Vista is trying to make better use of power while the PC is on, too. In particular, the operating system now supports the same kind of power-throttling features on desktops that have been standard on laptops.

However, the fancy new Aero graphics in Vista are also fairly power-hungry. Testers of the operating system have reported significantly lower battery life with Vista than with XP running on the same machine. Microsoft has said it hopes to have nearly the same battery life with XP by the time Vista launches.

Microsoft had previously said it expected to be able to offer a significant savings in power use with Vista.

Windows chief Jim Allchin said in an interview last year: "We've done some calculations of power savings that we expect. When 100 million machines are running Vista, the power savings around the world [will be] unbelievable."

Ina Fried writes for CNET News.com