PC power consumption, Kill-A-Watt Test results

Many of us have been curious on the power consumption of our systems. I purchased a Kil-A-Watt meter and hooked it up last night.

On this circuit test I have the following

6 PCs (Power Supply info below)
4 PSU 500w
1 PSU 300w
1 PSU 650w

4 LCD 17” monitors
2 LCD 22” Wide screen monitors

Misc:
Router
Hub
Wireless devices (Mouse charging units)


Here are my results.

Turning everything at once it spiked at 1280W

Consistent run time it was steady at around 950W – 1000W

I let the meter run for 4 hours. It came out to .38KWH an hour. I’m totally surprised the number is this low! I figured twice that.

therefore...

24 hours * 0.38 KWH ==> 9.12 KWH/day
9.12 KWH/day * 30 days in a month ==> 273.6 KWH/month

assuming $0.08/KWH
$0.08/KWH * 273.6 KWH/month ==> $21.89 / month

and that is if you are running it full out every day of the month. your mileage may vary

Also be sure to test idle vs at load. Some of the higher end video cards can take up an extra 50+ watts each under load and the same goes for CPUs too. Multiply 100 x 5 and thats 500 extra watts.

CRTs take up A LOT MORE power than LCDs, although the 30" ones take up 120+ watts each.

A normal 15A residential circuit is good for about 1440 watts continual use.

15A X 120V * .80 (80% load) = 1440 Watts.

If you run above that for a period of time, you will [Edit: HOPEFULLY] eventually trip the breaker as the wires overheat.

Just goes to show how smaller, more efficient CPUs can beat out other ones. My main rig is a quad core that runs 400 watts for the CPU - IDLE. The monitors push another 720 or so watts. That alone is nearly 1440 watts under load and does not count any other computers, cooling, etc.

1000 Watts costs @ .10 per KW/H about ten cents an hour to run. Or 744 hours @ .10 for $74.4 dollars per month to run 1000 watts 24/7 for a month.

.38 KW/H would be 380 watts running for 1 hour. So something about your math or total power use is wrong.

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Originally Posted by Fursphere

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If you run above that for a period of time, you will eventually trip the breaker as the wires overheat.

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Actually, its worse than that. If you run it at 90% - 95% load for extended period of times, it'll cause the breaker to heat up, but it won't trip it.

Trips are caused by spikes in the load. If you ease into it, you can exceed load and burn up your breaker / panel at the time. It takes time, but it'll happen.

Best case - your break will burn up and cease to function, but won't start a fire.

Worst case - fire.

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I am going to reiterate this warning. Don't push the limits of your breaker. It should ONLY kick in because of a short or if you are overdoing it. You need to be very careful and should NEVER EVER overload a breaker. They are there as a final failsafe - NOT as a "to let you know when you have over done things". And yes, it is possible to reach the limit where you are toeing the line between it not breaking and breaking but you are going to be playing, perhaps literally, with fire. Don't ever do that. Install another dedicated line.

I installed 3 new 20 amp lines and spread everything out to those dedicated circuits. For some unknown reason, TWO ENTIRE ROOMS are on the same 15a circuit - so that is unfortunately standard practice it seems. And combined that is something like 700 sq ft - at least. The bathroom is on a separate one but.... why is this the case, I have no idea. Laziness I guess. It meets code but the overhead fans use quite a bit of power and the incandescents in there when I moved in (since replaced with energy efficient bulbs) also took up quite a bit. Plus whatever else that is on that circuit that I don't even know about. Hall lights are on the same circuit.... etc etc. Glad I rewired it. It was unsafe to use that much on a single circuit (and after I upgraded it was literally impossible short of over riding the breaker and being at a severe risk for fire, something I was obviously unwilling to accept).

In norway we have 230V power, and a 10Amp circut can then provide up to 2300W. So I guess power isn't as much issue here. However power costs about $0.12+ /KWH, so I guess its a bit more expensive :P

Also, keep in mind that normal US code wall plates (dual outlet) are typically rated at 15A even though some houses (like mine) carry breaker/line ratings of 20A.

I noticed that in mine too although I question the code satisfaction there but 20A in theory cost more than 15A breakers so..... what gives I don't know. There is a safety margin built in but they are built in FOR A REASON. If you need to lift 100 lbs safely, the breaking point should be 10x or 20x that so WHEN (not if) the rope becomes frayed/broken down/whatever then you STILL are safe(r).

Electricity is not the same (the margins are less) and needs to be respected even more so. You can't always know the condition of the wires (that are typically in your wall). You might not even know if they are copper or aluminum (the latter can be hazardous in some cases due to thermal expansion and contraction and dissimilar metal on metal contact). I am NOT a licensed electrician (although I feel comfortable enough adding new lines, upgrading breakers and even installing 220V lines) but I STRONGLY suggest you consult with one if you have any questions about anything you are uncomfortable about. You are talking about adding A LOT of power to a single outlet (in effect) and that is problematic if not properly spread out.