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Kill-a-watt, does it really work?

manny1222

Gawd
Joined
Mar 11, 2012
Messages
732
Sup guys,
I went out to menards today and picked up a kill-a-watt sensor to see my actual wattage on my gaming rig. You could say I did it because I was feeling buyers remorse for picking up a corsair hx 1050w off ebay to replace the hx 750w in my rig right now. I'm upgrading to see if my sli gtx 680 ftw+ 4gb cards don't overclock well because they are maxing out the power from the psu.
I didn't really have time to do a bunch of tests on it, but on single passes of iracing and dirt3, the max reading on the kill-a-watt was 425 watts. That's with a 2500K overclocked to 4.5GHz on 1.25v and stock clocks on the sli cards. The rest of my rig is in my sig, plus 4 gentle typhoon AP-00 fans (2150rpm) on the H100, 1 corsair 200mm fan, and 4 xigmatek xaf-f1255 fans (soon to be 6 of them). all of these on the hx 750w..
So now I'm asking myself do I really need a 1kW psu?
(BTW I quickly ran Intelburntest with standard settings and it maxed out at about 280w. The thing that worried me though is that the runs took longer 11-12secs instead of 8-9secs, and the gflops were lower about 78 instead of the 100s. CoreTemp stated that my 2500K was still at 4.5GHz. Not sure why)
 
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It works. You bought a bigger power supply then you needed. Its not exactly the end of the world though. You have some extra capacity if you switch to hotter components and a ton of wiggle room for capcitor degredation over time. (Though Its only a few percent per year)..
 
Yes they work.

powerkaw.jpg


That was from when I was running a Q9650 @ 4.4Ghz with 2 4870x2s (4 GPUs) in Quad Crossfire. I felt completely justified having purchased a 1000w PSU in that situation...

Since then I'm now running a 2500k @ 5Ghz with 2x GTX680 in SLI and I wouldn't be surprised if my computer consumes half the amount of power it did previously. The 1000w PSU is still chugging along though, and I don't regret buying it.
 
They are not really accurate. They have a 3-7% error rate from what I've seen.
example:
actual wattage used = 500watts
kill-a-watt reads = 515watts

I think Kyle did a few tests here on [H] not too long ago.
 
i have this

http://www.amazon.com/WANF-Electric...t&ie=UTF8&qid=1364527004&sr=1-1&keywords=wanf

I like it and it is back lit which makes reading it pretty easy ... i probably wouldn't calibrate a nuclear reactor with it..but it seems close enough to be useful.. (tested it with a few lamps with 40watt , 75watt and 100watt bulbs and got pretty accurate readings.

probably not totally spot on but close enough for my requirements
 
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While you did indeed overspent on the PSU, the KAW isn't exactly accurate. If you're unlucky, you may have gotten a really inaccurate KAW:
Here's Paul Johnson's post, PSU reviewer of HardOCP.com, about the inaccuracy of the Kill-A-Watt:
http://hardforum.com/showpost.php?p=1032190998&postcount=7

Another Paul Johnson's post:
http://www.jonnyguru.com/forums/showpost.php?p=27745&postcount=26

In addition, three other PSU experts backs up Paul Johnson's statement:
Oklahoma Wolf of JonnyGuru.com:
http://hardforum.com/showpost.php?p=1034843536&postcount=21
http://hardforum.com/showpost.php?p=1034555880&postcount=17

JonnyGuru of JonnyGuru.com and the former product manager for BFG acknowledge the inaccuracies of a KAW (Post #7 in regards to Post #2):
http://www.jonnyguru.com/forums/showthread.php?t=5977
http://www.jonnyguru.com/forums/showpost.php?p=29907&postcount=2

Redbeard of Corsair also acknowledges the inaccuracies:
http://hardforum.com/showpost.php?p=1032811067&postcount=22

Related discussions:
http://hardforum.com/showthread.php?t=1447774
http://hardforum.com/showthread.php?t=1509210
http://www.jonnyguru.com/forums/showthread.php?t=3102
http://www.jonnyguru.com/forums/showthread.php?t=2695
http://www.jonnyguru.com/forums/showthread.php?t=2284

So just take the KAW readings with a grain of salt.

But again, disregarding the KAW readings, you really didn't need to buy a new PSU. You can see here that a 2600K OC'd to 4.8Ghz, a single HDD, and two GTX 680 cards that are OC'd draws around 556W at post under BF3.
 
Ahhhh, I knew it was someone from [H] that showed accuracy of the KAW meter.

Thanks for that post Danny!
 
As a ballpark it will give you a decent idea, if you're looking for super accuracy on a $14 item you might be disappointed. However, if you take it for what it is it can be a helpful tool since it is cheap and easy to use.

OP, you rig is definitely not in need of a 1000W PSU, but now you can add more stuff in the future and not worry.
 
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