From an article by Tom Content in the Milwaukee Journal Sentinel:

TVs, computers, others leach energy and money

In one of the first studies of its kind, energy researchers in Madison have uncovered a simple way that most consumers can save on their electric bills: pull the plug.

The researchers set up more than 700 in-home metering devices in about 50 homes to monitor the proliferation of electronic devices in our homes, and how they affect our energy use.

Thirty years ago, federal data shows, a typical home had about three plugged-in devices. The new study shows our wall sockets are jammed, with each home hosting 30 or more devices. All told, computers, printers, televisions and other devices account for 15% to 30% of a home’s total electricity use – about 20% on average, the study found.

The Energy Center of Wisconsin study was able to quantify the impact of having so many devices plugged in and ready to go – sometimes on, sometimes off, and sometimes in standby mode.

Case in point: Home computers that are left on around the clock in some cases suck power even when they’re sitting idle.

“Most computers are set up to turn the monitor off after about 20 minutes,” said researcher Scott Pigg. “So we turn it on and use it and walk away and come back into the room and see the monitor’s off. We think: ‘Well, my computer is managing its power and it’s shut down.’

“What they don’t realize is that two-thirds of the electricity draw is the thing that’s sitting on the floor – not the thing that’s sitting on the desk,” he added. “And the only visual indication that you have that computer’s on is a little fan noise and a little green light somewhere.”

A step as simple as changing the power management settings on a home PC will take less time than running to the store and buying another energy-saving light bulb, Pigg said.