So yesterday I wrote about Earth Hour and the effort to get unnecessary lights shut off at night — especially those glittering away in office towers. Today I’ll keep to the same vein, but turn my attention to another power suck draining the wallets of many companies: PCs left on all night.

According to 1E, a software and services company, U.S. companies waste $2.8 billion a year and emit 20 million tons of carbon dioxide powering unused PCs. These whopping sums are a result of 50 percent of U.S. workers who use PCs at their job neglecting to shut off their computers at the end of the day.

Why not hit the power switch at night? While some people share their computers or access their network remotely, many mistake the automatic sleep function to mean “off.” Other folks, though, actually operate under the orders of their company or IT department — something that seems counterintuitive considering that $2.8 billion a year.