While browsing the Ottawa Public Library site I noticed that they had watt meters available for borrowing. These are the kind of meters you can plug into the outlet and then into which you can plug various electric devices. I put one on hold and it arrived less than a week later.

I've been curious for a while about the actual draw of the many electronic devices we have, especially when in 'standby mode'.

How much electricity does it take to run the VCR's clock?

What is the difference between a computer in 'sleep' mode versus a computer in 'hibernate'?

How accurate are the watts/amps on the device's labels?

What uses more power a flat screen monitor or a CRT monitor?

Now I can find out!

 My first project was to check out my computers.

Computer Electricity Usage

When measuring the computer electricity usage I noticed that the numbers varied quite a bit depending on what the computer was doing. Booting up took more power than idling. Anytime the hard drive was accessed the numbers jumped up. The numbers below are averages of a few seconds of observation. Where there was a large spread I have given the spread as best I could observe. I assume that there are probably other factors I didn't consider that may affect usage.


  Watts VA Amp
Laptop Sleep Mode .03 14 .13
Laptop On 53 93 .70
Laptop Hibernate .03 14 .14



  Watts VA Amp
Desktop On  60-80  93-117  .77-1.00
Desktop with Flat Screen  80-90  158  1.11
Desktop with Two Flat Screens  110-120  164-185  1.36
Desktop with Monitors and External Hard Drive (running) 120-130 119 1.5
Desktop with Two Flat Screens and iPhone plugged into USB port 115 177 1.47


It turns out that usage varies quite a bit and seems to depend on what the computer is doing. If I were testing multiple computers for comparison I would have to be pretty rigorous in my approach to ensure that each computer was working the same. It does make me wonder if different operating systems would have different electricity usage. Plugging and unplugging my iPhone had a small but measurable effect on usage.