Kill-A-Watt

[Reloadron]

I thought I would share some of this with those who may have an interest. I invested in a few of those Kill-A-Watt units we seem to hear so much about. The old curiosity thing prevails here. They arrived today and when I got home from work I had to see how they worked.

The first thing I did was set one of these units up and seek a good known load. I figured a few light bulbs would work. I chose a lamp with a 75 Watt bulb.

The sort of boring but important part:

I measured the resistance of the bulb for this test. It was 192 Ohms. A really good 192 Ohms too. The unit was plugged into a Variac so I could set the line voltage at 120.0 VAC. That was important if I wanted good results. Doing the math 120 Volts @ 192 Ohms should draw 0.625 Amps which yields 75 Watts.

Now this is based on a purely resistive load and not an inductive load in an AC circuit but the light bulb is as purely resistive as it gets. I plugged the lamp into the Kill-O-Watt and low and behold when pressing the Watt button I saw 75. Not bad at all. I added another 75 Watt bulb and made sure I kept the Voltage constant and I read 150 Watts. The resolution allows a person to read within a watt and it well did and quite accurately.

The next step was to plug a computer into the unit and see what we had. The "Beast" here is my workstation machine. The beast consist of the following:

• Intel dual Xeon processors running at 3.6 GHz with hyper threading.
• Intel SRCS16 SATA controller card with onboard memory.
• 4 GB of RDRAM Memory with ECC.
• Intel 7525 Series motherboard.
• Hot Swap 6 drive cage for the HDDs.
• 6 WD HDDs set up in RAID1 and RAID5 configurations.
• The GPU is a commercial graphics card with 684 MB of onboard RAM and is a 3D Labs Realizm 800 card. Placed in the PCI-E slot.
• Likely 6 fans including fan for the RAM, Fans for the Xeons, Fan for the HDD housing, and other assorted fans. (not that fans use much power).

At boot the machine drew about 400 Watts. This is a routine boot.

During boot the unit dropped to 300 Watts once the fans and things settled in.

Following boot with a stable desktop display the machine ran a stable 330 Watts.

I started folding to get the processors running. Bringing both processors to 100% got the power up to about 512 Watts.

The PSU n this system is a commercial PSU rated at 600 Watts. I built this system about two years ago. The case is actually an Intel case and I am clueless who actually built the PSU. Generally I like a 20% to 25% margin and obviously I am lacking that margin. The system runs stable and has for a few years so I sure as hell won't screw with it.

Interesting is how very accurate the Kill-A-Watt unit really is for the price. I paid about $25 US from NewEgg with free shipping. As time allows I will get more into this.

Ron

[gvblake22]

Awesome, glad to hear this product works well! I've been wanting to get my hands on one of these for a long time now, but everytime I go to buy one I either forget to add one to my Newegg purchase or they are out of stock.

I guess I'll keep on the hunt though, thanks for the review!!!

[screwballl]

heres some numbers from my systems, all under 100% load, all systems except my E6600 have been running for minimum 1 year almost 24/7:

E6600, GA-965P-DS3, 2GB DDR2-667, 1x 320GB hd, 3x 12cm case fans, HX520W Corsair PSU:
120V, 0.36A, 27W, 44 VA, 0.61-0.62 PF

XP3000+, A7N8X, 1GB PC3200, 1x 160GB hd, 5x 80cm case fans, 350W Antec Smart Blue psu:
119.5-120V, 1.73A, 137W, 206 VA, 0.66-0.67 PF

XP-M 2600+, Biostar M7VIGPro400, 1GB PC3200, 1x 40GB hd, 1 case fan, cheap mATX 125W PSU:
119.5V, 1.42-1.44A, 109-112W, 166-172VA, 0.65 PF

Dell 8200 P4 1.8GHz, 512MB RDRAM PC800, 1x 60GB hd, 1x 90cm case fan, 200W Dell psu:
120V, 1.26-1.29A, 119W, 153VA, 0.78 PF

[simple_inhibition]

those things are so handy (along with a multimeter) but i do what blake does....always forgets to add it to the cart... D'oH

[Reloadron]

Hopefully this weekend I will have more time to mess around with this little thing. I want to check out some of the other features. What I have managed to do this far is really next to nothing. I am real pleased, as I mentioned with the accuracy right out of the package.

Additionally, this was likely the fourth or fifth time and I finally remembered to toss a few into the cart.

Ron

[screwballl]

The one that surprised me of my systems was my C2D system at 27W! I think it skyrocketed on boot to 29W... that was just amazing.

[polobunny]

Originally Posted by screwballl

The one that surprised me of my systems was my C2D system at 27W! I think it skyrocketed on boot to 29W... that was just amazing.

This doesn't seem right at all. I'd say around 127W, not 27W. Hell, even at the lowest power consumption (0% of CPU used) it would be more than that.

[RangerXLT8]

Originally Posted by screwballl

The one that surprised me of my systems was my C2D system at 27W! I think it skyrocketed on boot to 29W... that was just amazing.

What are you reading with? I'd say it's reading mA setting and the decimal needs to be moved over one place so it would be 3.6A * 120V......

[gvblake22]

Originally Posted by screwballl

The one that surprised me of my systems was my C2D system at 27W! I think it skyrocketed on boot to 29W... that was just amazing.

Yeah, that cannot be right. I was gonna say you had a typo or something, but apparently that was the reading you got?! I say redo that one and see if you messed something up...

[RangerXLT8]

Originally Posted by gvblake22

Yeah, that cannot be right. I was gonna say you had a typo or something, but apparently that was the reading you got?! I say redo that one and see if you messed something up...

The device is probably reading in units larger then 1A So the decimal needs to be moved one place to the right.