As much electricity as a refrigerator even when the box is turned off.
Since the set top box is always on even when the box says that it is off.
Unplug your set top and save a couple hundred dollars a year?
Six Stealthy Energy Hogs: Are They Lurking in Your Home?
Set-Top Boxes
These familiar electronic arrays sit on or near many televisions to connect cable to our entertainment systems. But it's not just their clocks that run when no one is watching. These devices function much like mini-computers that communicate with remote content sources or record favorite shows while you're out. That means they require a lot of energy.
"The issue with set-top boxes is that they never power down and they are almost always consuming their full power requirements even when you think you've turned it off," said Noah Horowitz, a senior scientist at Natural Resources Defense Council (NRDC). "If you have a DVR on your main TV, and a regular set-top box on a second TV, that could equal the energy use of a new refrigerator."
In 2010, an NRDC study found, the 160 million set-top boxes in the U.S. consumed the annual output of nine average coal-fired plants, some 27 billion kilowatt hours in all. That equals the total household electricity consumption of the entire state of Maryland. That kind of power costs money—more than $3 billion a year in electric bills—and most of that cash is spent on boxes running at full power while nobody is watching or recording their content. "We're spending about $2 billion a year in electricity bills to power set-top boxes when they are not even in use," Horowitz said.