Unfortunately, this is a myth. When you turn off an appliance, it may continue to consume electricity when switched off. Sometimes they use as much power off as when they're on! Energy experts call these devices "Energy Vampires!"
A large number of electrical products - from air conditioners to VCRs - cannot be switched completely off without unplugging the device or turning it off at a power strip. These products draw power 24 hours a day, often without the knowledge of the consumer. We call this power consumption "stand-by power," but we call these products "energy vampires."
According to Lawrence Berkeley National Laboratory, in particularly inefficient designs, the stand-by power use can be as high as 15 or 30 watts. For a single appliance, this may not seem like much, but when we add up the power use of the billions of appliances in the United States, the power consumption of appliances that are not being used is substantial.
A chart showing stand-by power consumption by type of appliances can be found at: http://standby.lbl.gov/summary-chart.html
|Appliance Category||Appliance||Power Consumption
|Garage Door Opener||1.4||3.0||4.0|
|Set-top Boxes||Cable Box||4.6||10.8||24.7|