View Full Version : how much power is this computer using?

18-08-2004, 02:23 AM
The system is my web server / router.

a k6II 300MHz cpu
ga586tx3 motherboard (old)
64Mb ram PC100
a 4Mb 2D pci video card that is very old.
a compack flash card type I for a hard drive.
a external modem.
a network card.

nothing else.
no cdrom, no moniter, no keyboard, no fans, no speaker , no blinkin lights.

would this setup use more than 50W ???
is there an easy way to mesure what is being used??

18-08-2004, 02:27 AM
assuming 50W is being used then is my cost of running right??

50W * 24 hours per day * 31 day = 37200W

which is 37.2 units per month at a cost of about 16 cents = $5.58

18-08-2004, 07:26 AM
Your maths are very close. It is $5.95 for the month or 0.8 cents/hour

18-08-2004, 09:36 AM
I have a very similar rig to robsonde that I leave on 24 / 7, except mine has 128MB Ram.

That's good to know how much it does cost each month to leave on.

18-08-2004, 05:10 PM
I thought the $$ math would be about right

the real question is how many watts is the system using??

i have use 50W in my math but i have no idea if that is right or even close.

18-08-2004, 09:38 PM
The only easy way is to use a multimeter, if you have one, that will measure AC current. Bear in mind that small meters don't like large current flow. If your PC was in fact a 50w device the current flow at 230V would be 220mA. Dick Smith have a small $30 digital multimeter in stock that will measure AC current in the range 400uA to 400mA. A 400mA upper limit would restrict it to a 90 watt load at mains supply voltage.
I can't be much more help than that.

18-08-2004, 09:53 PM
Sorry. That DSE meter I mentioned is Cat. No Q1569 and it is actually $39.00

18-08-2004, 10:30 PM
The meter has to be in series with the phase connection, which means it has to be connected before power-up. Just getting the 230v input to that position is not easy and involves modifying the 230v wiring to the PSU.

Its most probable that the inrush current of the power supply would pop the 400 mA fuse of the meter. Switchmode supplies have quite a high inrush (it would be quite a few amps, not mA) for a few cycles.

And its not a very "safe" activity unless you really know what you are doing.

Graham L
19-08-2004, 02:11 PM
Interrupted phase tapons are useful things. :D So are AVOs. ;-)

You can (at a considerable price) buy clipon ammeters, which you can use with a short extension cord made with trurip with the phase wire separated.

Silicon Chip are running a series on building a power monitor which would be ideal. Of course, this (a) is a kit requiring some skill, and (b) will cost a hundred or so.

19-08-2004, 02:33 PM
[ fears showing great lack of understanding] is there such a thing as a device that sits between the mains plug and the computer's power lead [ like and extension box] that shows how much current is being drawn? This would also take into account the power used by the power supply fan[s] ?:|

Graham L
19-08-2004, 02:40 PM
Yes. The Silicon Chip project is one. In the July Silicon Chip there is an advertisement for a commercial box. This costs something like $AUS350I think.

Try "power monitor" to Google. Then add "site:nz" for any local sources.

But you may find that ignorance, even if it isn't bliss, is at least cheap.:D

19-08-2004, 09:31 PM
Turn off every electrical device in the house except for the computer. Set up some automatic tasks for the computer to do.

Check the reading of the power company's meter in the meter box outside the house.

Go away for a day, or week, or however long it needs to record a meaningful figure for such a small usage of 50 watts or so.)

Upon returning, recheck the meter reading and do the appropriate calculations.

And finally:

Clean and restock the freezer 'cos everything's probably thawed out during your absence. :D :D