What does it cost to leave a computer/server on 24/7? What does it cost if the computer/server is on standby? How much power does a 'standard' computer use?
By WolRon
After I had set up my own web server and couldn't successfully set it up to WOL (Wake up-On-LAN), I started to worry about how much money it was going to cost me to let the computer run non-stop 24 hours a day, 365 days a year. My server is a Compaq Deskpro with a Pentium III running at 1GHz. It has one CD-ROM drive, a floppy drive and one hard drive and not too many other bells and whistles since its sole purpose is to just run as a server.
Well, I decided to stop guessing at what it was going to cost me and I brought home my multimeter from work along with a very short extension cable I made up specifically to use to connect to the multimeter so I could measure current. I hooked up the multimeter in series with the 'hot' wire of the extension cord and plugged the computer into it. I probably could have just used a Kill-A-Watt meter (there's probably an add for one below) or similar device to read the power consumption but I don't own one.
I didn't bother to run the computer monitor through the multimeter because:
1. I wanted to see how much current the computer used as a stand alone device
2. I intended on leaving the monitor off 99% of the time anyways since the server doesn't
actually require a monitor to operate
Upon startup of the computer, I was surprised to see that it only drew around .6 to .9 amps, which is considerably less than the power supply should be able to put out (a 350 watt power supply at 120 volts could potentially consume nearly 3 amps). While starting it would occasionally peak at about .92 amps. After the startup phase, the computer began to draw less and less amperage (as the software finished off loading) and finally settled at about .57 amps. After a good deal of time (about 20 minutes), the amperage dropped slightly furthur (.55 amps) and the hard drive finally spun down to rest. Without the HDD, the total current draw for the PC was just .50 amps.
Even though I wasn't able to get the WOL feature working properly, I decided to test
just how little current the PC consumed while on standby, just in case I got that working
later on (and to see how much of a difference it would make). With the computer
sitting on standby, it only consumed .07 amps. However, I'm not sure my meter can
reliably read a current reading that small, and the actual current may have been even
less.
Well, Watts=Volts*Amps. If I use 120V as my voltage, then all of my current readings above relate to:
| Amps | Watts | Computer activity |
|---|---|---|
| .92A | 113W | peak power consumption (momentary time durations) |
| .71A | 85W | 'normal' consumption while performing routine tasks |
| .57A | 68.4W | mostly idle (no user interaction) |
| .55A | 66W | 'completely' idle (sitting idle for 20+ minutes) |
| .50A | 60W | completely idle with hard drive spun down |
| .07A | 8.4W | power consumption while in standby mode |
As you can see, the power consumption of a typical computer (or at least MY computer) doesn't usually consume much more power than that of a 100W light bulb, and it can reduce its power consumption down to about a 60W light bulb when sitting idle. So basically the cost of running a server 24/7 shouldn't be any more expensive than leaving a single light bulb on 24/7.
My electric company charges me 7.4 cents per kilowatt (your rate may vary greatly from mine). Knowing that, I can figure out just how much this PC is going to cost me depending on its usage:
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Altogether, it should never cost me more than $6 a month and most likely it will only
truly cost me probably in the range of $3.50 a month.
I can handle that!
And the best news of all is if I can ever get the WOL feature working, I'll possibly be
able to run my server for under a buck a month.
Not - too - shabby.
So there you go, blog away...