https://green-energy-efficient-homes.com/waste-electricity.html Even with the PC itself turned off, the combined power draw of a cable or DSL modem, a wireless router, and a computer printer sitting idle and waiting for work to do, can exceed 50 watts (about the same draw as one moderately bright incandescent bulb or 4 compact fluorescent bulbs). That might not sound like much but that 50 watts when running continuously through the year works out to 50 x 24 x 365 watt hours, or 438,000 watt hours (438 kilowatt hours). That costs roughly $44 a year ? to keep your computer equipment running 168 hours a week, when you probably only need it running for 10 or 20 hours a week at most.