Computer Standby Power Consumption

Often I've wondered about my computer standby mode power consumption. How much electricity does my computer use when it is in sleep mode? Since my computer (a tower desktop with two LCD monitors) is several years old it takes a while to boot up so I like to leave it in standby mode when I can.

To test the standby mode power consumption of my computer I got a P3 International Kill-a-Watt meter for about $21 online to use as a PC power consumption monitor. The Kill-a-Watt power meter plugs into the wall and then the appliance plugs into the meter. It has a has an LCD screen to tell you how much electricity was consumed in that time period.

Here's what I found (cost per KWH in Maryland is 10.28 cents):

State Time Power Usage (KWH) KWH per hr KWH per day Cost per day
Off but plugged in 8hrs 0.08 0.01 0.24 2.5
Sleep mode 14hrs 23min 0.16 0.011 0.27 2.8
Regular usage 6hrs 40 min 1.15 0.173 4.15 42.7
Table of Sleep Mode Power Consumption

In Summary ...

The standby mode power consumption is just a bit more than leaving the computer plugged in but off. So I can use standby mode without any significant additional cost.

While I'm away for more than 8 hours it makes sense to turn the computer off at the power strip. At this point no electricity is being used by any of the devices on the power strip. I usually do this when I am done using the computer in the evening or plan to be away for a while.

Note - if you have power supplies (the black boxes you plug into a power strip or the wall) plugged directly into the wall they will be using electricity (feel them, they'll be warm). The power strip allows you to turn them off completely. This goes for stereo systems, power tools, etc.

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