SAN FRANCISCO  Even during an economic meltdown, when companies are scrambling to cut costs, businesses are wasting billions of dollars by leaving their PCs on at night. 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 — according to a report to be released Wednesday. About half of 108 million office PCs in the USA are not properly shut down at night, says the 2009 PC Energy Report, produced by 1E, an energy-management software company, and the non-profit Alliance to Save Energy. The report analyzed workplace PC power consumption in the USA, United Kingdom and Germany. Wastefulness does not just affect a company's bottom line, it creates environmental concerns, the report says. If the world's 1 billion PCs were powered down just one night, it would save enough energy to light the Empire State Building — inside and out — for over 30 years, it says. "Workers do not feel responsible for electricity bills at work, and some companies insist PCs remain on at night so they can be patched with software updates," says 1E CEO Sumir Karayi. He says 63% of employees surveyed said their companies should take more steps to save PC power. "It is scary how much energy is wasted," says Michael Murphy, senior manager of global environmental affairs at Dell, a business partner and customer of 1E. It has used 1E software to efficiently manage its 50,000 PCs globally, saving about $1.8 million a year. Simply shutting down PCs at night can save a company with 10,000 PCs over $260,000 a year and 1,871 tons of carbon dioxide emissions, the report says. "PCs can be a tremendous drain on electricity," says Doug Washburn, an analyst at Forrester Research. "During a nine-hour workday, it isn't always in use because of lunch, meetings and other things." Guidelines: You share in the USA TODAY community, so please keep your comments smart and civil. Don't attack other readers personally, and keep your language decent. Use the "Report Abuse" button to make a difference. You share in the USA TODAY community, so please keep your comments smart and civil. Don't attack other readers personally, and keep your language decent. Use the "Report Abuse" button to make a difference. Read more