Did You Know Your PC Still Pulls Power When Hibernating or While Shut Down?

Do you know that your computer still pulls power even when it is in hibernate mode or even when it is shut down?


Many people say they use Hibernate instead of Sleep mode because Hibernate draws no power.  Unfortunately, when it comes to desktop PCs, they’re wrong.   Desktop PCs still use some power even while they’re shut down.

Laptops generally don’t use any power while shut down or hibernating, as that would cause unnecessary battery drain.  Desktop computers don’t have to worry about batteries, so they’re generally a bit more power-hungry.

When you use Hibernate mode, your computer saves the contents of its RAM to its hard drive and “powers off.”  When you boot it back up, it will read the previous contents of the RAM from the hard drive and restore them to RAM.  This may or may not be faster than a normal boot-up process, but it allows you to maintain your system state including all your open programs and documents, because the computer doesn't have to provide power to its RAM, Hibernate mode uses less power.

When you shut down your computer, it discards the current system state and powers off.  When you boot it back up again, it has to go through the typical boot-up process, initializing hardware drivers, loading start-up programs, and so on.

There are a few reasons why a computer will be drawing power in Hibernate mode or while shut down:

• Wake on Keyboard or Mouse: Many computers will wake up from hibernate when you press a button on your keyboard or move the mouse.  To do this, they have to keep their USB ports powered on, waiting for keyboard and mouse input events.

• Wake-on-LAN: The Wake-on-LAN feature allows a computer to be woken up — even if it’s shut down — by receiving  a special type of data packet over a wired network.  This isn’t something a typical home user will need, but it may be used on larger networks.  To enable this feature, the computer has to keep the Ethernet port powered on and listening for the packet, even while the rest of the computer is shut off.

• Trickle Power: If you look inside your PC’s case while it’s plugged in, you’ll likely see things using power even while it’s shut off.  You may see an LED on the motherboard that stays powered and an LED on the Ethernet port that flashes as the system listens for those wake-on-LAN packets.