Businesses that want to save money could start by asking employees to shut off their computers.

USA Today reported that "U.S. organizations squander $2.8 billion a year to power unused machines, emitting about 20 million tons of carbon dioxide -- roughly the equivalent of 4 million cars."

The information comes from the 2009 PC Energy Report, which says that "if all the world's 1 billion PCs were powered down for just one night [PDF], it would save enough energy to light up New York City's Empire State Building -- inside and out -- for more than 30 years."

Interestingly, the study says we do tend to power down our computers at home.

(E1, which produced the report with the nonprofit Alliance to Save Energy, is an energy-management software company, so just be aware that it has a financial interest in you paying attention to the results.)