Computer's standby power consumption

Posted by Martin Vilcans on 18 January 2011

I guess you know that many electronic devices aren't really switched off when you switch them off. Sometimes this is convenient. It is easier to switch on the TV with the remote than pressing a button on the set. This requires the device to be in standby mode to be able to receive the signal. The problem is that standby mode consumes power. Even many devices that you switch on with a physical button are in standby mode. The button is more like a key that the electronics in the device is constantly waiting for you to press. Few devices today, except for lamps, have a real button that physically disconnects the power. (I have a network switch that is marketed as "green" because it has this environmentally friendly feature, an actual on/off button.)

In total, there is a lot of power consumed by all those devices that are in standby. I bought a cheap power consumption meter to see how much power my electronics use when I'm not using them.

I tested it on my desktop computer. I don't use the computer daily, and only in the evenings, so it is switched off most of the time.

Or is it really switched off? I measured the amount of power used after I shut down the computer.

When the computer is in standby, the whole system still consumes 13.5 watts. By switching devices off, I found out the power consumption for each of them:

  • Computer: 2 watts
  • Two monitors: 3 watts (1 watt in standby mode initiated with button)
  • Powered USB hub: .5 watts
  • Eight port gigabit switch: 8 watts

As you can see, most of the power is used by the switch. This makes sense, since it doesn't have a standby mode, and it's still on. This is not the "green" switch I was talking about before, so to turn this one off, I'd have to pull the plug.

The monitors enter some kind of power saving state when I switch off the computer. An interesting discovery was that when I press the standby button on the monitors, they enter a "deeper" standby state that uses less power. The monitor still uses power while keeping itself busy waiting for me to press the button again.

OK, 13.5 watts is not a huge number, but it is unnecessary since I don't use this computer that much. In the future, I'll be more careful switching off the whole system with the button on the power strip.

Some more "fascinating facts":

  • The "micro monitor" speakers use 10 watts when not in use, but they have a real power button and I remember to switch them off most of the time.

  • The whole system uses 230 watts when the computer is on and idle, 134 watts when it's idle with screen saver (the kind that puts the monitor in the "light" standby state).

  • When the computer is in sleep mode, the system uses 1.5 watts more than when the computer is switched "off."

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