Sleep saved Starwood Hotels and Resorts $350,000 in 2009.

The company initiated a program in 2007 to put employee PCs into sleep mode after an hour of inactivity, according to Mark McBeth, Vice President IT, North America for Starwood. IT managers often come up with these sorts of programs, but the goals can get sidetracked when employees reset their computers.  (The system also does an early sleep on desktop monitors.)

For its 13,000 desktops, the company installed ScriptLogic's Desktop Authority, which lets IT managers figure out different sleep regimens for various groups in the company.

The company expects to save $400,000 this year and $1 million over a three-year period. Starwood started using the technology at 20 properties but now has expanded to 150 locations. Verdiem, a start-up that has partnered with Cisco Systems for desktop energy management, has signed similar large contracts.

Computers and IT equipment are not the biggest energy hogs out there. Computers only consume 4 percent of the energy in U.S. commercial buildings, or about the same as refrigeration, according to the Department of Energy. Other electronics like printers and phones account for 7 percent. Still, green IT will likely become a growth market because 1) solutions exist to curb power and 2) IT giants like Intel, IBM, Cisco, Oracle, Dell and others see energy efficiency as a way to drive demand and differentiate their products. Antivirus companies will likely make a more concerted push into PC energy management -- Symantec has already started.Thin client manufacturers like N Computing and Wyse say that their products are gaining traction because of reduced energy consumption.

Companies and organizations in the U.S. waste $2.8 billion a year in energy costs by leaving computers on overnight, according to a 2009 study by software company 1E and the Alliance to Save Energy.

"Though there is a small energy surge when a computer starts up, this small amount is still less than the energy used when a computer runs for long periods. For energy savings and convenience, consider turning off the monitor if you aren't going to use your PC for more than 20 minutes, and both the CPU and monitor if you're not going to use your PC for more than two hours," the Department of Energy advises.

Because hotels operate on a 24-hour basis, Starwood chose to go with putting computers in sleep mode rather than switching them off entirely.