It is good to know the low end resolution of the kill a watt devices is not that good. For people building ultra low power machines, such as those with Atom or Via processors, that meter may not work well for them.

Oh, I do so wish.

My Atom server is sixteen watts. Sure, a 1 watt resolution may mean that it is off by six percent, but until I can find a "Z" family Atom (and get under 8 watts) I can live with six percent.

The more advanced kill a watt unit, the P4460, states it is between .5-2% accurate in it's manual. The P4400 doesn't seem to list this information in it's 1 page manual.

I am a bit curious about the current meter function. Does it display the current in mA or just amps to a few decimal places?

You are refering to instant wattage numbers. The feature that makes Kill A Watt P4400 unique is its ability to measure power draw in Kwh. Plug your computer in and measure for 24 hours to see how much power it consumes. The Kwh values are recorded in 100 th's as well.

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Overclock with the MSI G31M3-L and Intel E8600 3.33Ghz
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Im gonna leave a comment for ya. Get a battery backup for your computer and it will tell you real time power consumption.

Just an example to throw out there from my main system im sure people wonder on this one since its not a popular setup yet.

Dual E5520's 4x seagate hdd... 2 sticks ecc ram. 9800GTX+

Fully loaded all 16 cores and gpu i hit right around 420watts.

Note this is also with a normal powersupply. Not one of the 80 or 85Plus rated ones. Figure with a 85plus psu around 395watt.

Im gonna leave a comment for ya. Get a battery backup for your computer and it will tell you real time power consumption.

Just an example to throw out there from my main system im sure people wonder on this one since its not a popular setup yet.

Dual E5520's 4x seagate hdd... 2 sticks ecc ram. 9800GTX+

Fully loaded all 16 cores and gpu i hit right around 420watts.

Note this is also with a normal powersupply. Not one of the 80 or 85Plus rated ones. Figure with a 85plus psu around 395watt.

Power supply efficiency is a very good point.
I shopped around when building my last system to try and find the most efficient power supply that would work for me. Also that I was willing to pay for. I ended up with an Enermax PRO82+ (525W) unit that is 80Plus Bronze certified. Based on my power measurements I'm pulling 20-30% of that power from the wall. So I'm on the lower edge of the efficiency rating scale.

I was just measuring some other things and found my computer speakers use 35w when powered on and nothing is coming out of them. :/

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I have an APC battery back-up on a couple computers. Has anyone ever measured what they draw when loaded during normal operations, over and above the power passed on to the computer?

I have an APC battery back-up on a couple computers. Has anyone ever measured what they draw when loaded during normal operations, over and above the power passed on to the computer?

Usually not very much, even when the battery is fully discharged.

Most UPSes charge the batteries too fast, killing them.

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I have an APC battery back-up on a couple computers. Has anyone ever measured what they draw when loaded during normal operations, over and above the power passed on to the computer?

99% of the worlds UPSs are switching UPSs. Meaning that most of the time they are providing the wall power to your equipment thought just some filters then switch over to the batteries in a matter of micro or nano seconds when needed.

I did measure the battery charging load of a 1500va rack mount UPS at work when we were having to sort out some power wiring issues. It measured around 100va for the SUM1500RMXL2U.

A lot of the UPS units run a weekly maintenance cycle. Where they will run the load off the batteries for a few minutes then switch back. So if you wanted to figure the extra electric cost form using a UPS you would need to take that into account as well.

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Thanks. There is a lot of focus on sustainability, "net-zero" homes, etc. in my neck of the woods and even when plugged in but unused, little cell phone charger loads are deemed worthy of switching off. Obviously, the commercial example below of 100 VA would be a problem in a home setting; apples and oranges, however.

Thanks. There is a lot of focus on sustainability, "net-zero" homes, etc. in my neck of the woods and even when plugged in but unused, little cell phone charger loads are deemed worthy of switching off. Obviously, the commercial example below of 100 VA would be a problem in a home setting; apples and oranges, however.

100va is somewhere around the typical incandescent light bulb (if the power factor is exactly 1, 100va is 100w), so should not be an issue in a residential environment.

According to the electrical code, a UPS must not draw more than 80% of the rating for the plug -- if the cord has a 15 amp "plug" (the most common in the U.S.) it can't draw more than 12a total, or 1440va.

That includes the load and the power to charge the battery.

The typical cell-phone charger draws less than a watt when it isn't actually charging, but plugged in. For most of us, this is going to be one of the very smallest "wasteful" loads. Look at your home entertainment system, you can probably find something there draws far more. Got an extra 'fridge? That's a biggie.

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Thanks. There is a lot of focus on sustainability, "net-zero" homes, etc. in my neck of the woods and even when plugged in but unused, little cell phone charger loads are deemed worthy of switching off. Obviously, the commercial example below of 100 VA would be a problem in a home setting; apples and oranges, however.

100va is somewhere around the typical incandescent light bulb (if the power factor is exactly 1, 100va is 100w), so should not be an issue in a residential environment.

According to the electrical code, a UPS must not draw more than 80% of the rating for the plug -- if the cord has a 15 amp "plug" (the most common in the U.S.) it can't draw more than 12a total, or 1440va.

That includes the load and the power to charge the battery.

The typical cell-phone charger draws less than a watt when it isn't actually charging, but plugged in. For most of us, this is going to be one of the very smallest "wasteful" loads. Look at your home entertainment system, you can probably find something there draws far more. Got an extra 'fridge? That's a biggie.

Is that coding just for standard wiring or does that include dedicated outlets as well? APCs 2200va and 3000va 120v UPS are over spec it would seem if it doesn't. Running 91.6% and 83.3% of their supply circuits. I'm sure any books that covered coding such as that are WAY out of date by now lol.

I know I ahve severa lthings on wasing power now. For one the cable TV box that gets updated randomly and sucks up 25w when turned off. Which doing the math right now costs me about $36/yr if it was just left turned off all the time. :(

I do use the lower pwoer CFLs and led lights for my home. So I would guess I've made up the diff in power cost there. I would really have to put a sensor on every light and device in my home to see if it all really works out tho. Any one want to come wire that up for me? :D

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According to the electrical code, a UPS must not draw more than 80% of the rating for the plug -- if the cord has a 15 amp "plug" (the most common in the U.S.) it can't draw more than 12a total, or 1440va.

That includes the load and the power to charge the battery.

Is that coding just for standard wiring or does that include dedicated outlets as well? APCs 2200va and 3000va 120v UPS are over spec it would seem if it doesn't. Running 91.6% and 83.3% of their supply circuits. I'm sure any books that covered coding such as that are WAY out of date by now lol.

The electrical code is a safety code, so it makes a number of assumptions.

It assumes that, sooner or later, a UPS is going to be plugged in to a non-dedicated line.

It assumes that a 15a branch circuit is wired with 14 gauge copper, and that it will start warming up if you draw more than 80% sustained.

Even on a dedicated circuit, the 1500va unit mentioned in the original post is right at the edge, and if you need a bigger UPS you should have a bigger circuit for it.

A 20 amp circuit is 2400va, a little small for a 2200va UPS.

The 3000va units need a 30 amp circuit.

You can get away with it if you "derate" -- I have two 2200va UPSes carrying a 650va load, with 15a plugs.

Fortunately, peak loads and average loads vary.

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The electrical code is a safety code, so it makes a number of assumptions.

It assumes that, sooner or later, a UPS is going to be plugged in to a non-dedicated line.

It assumes that a 15a branch circuit is wired with 14 gauge copper, and that it will start warming up if you draw more than 80% sustained.

Even on a dedicated circuit, the 1500va unit mentioned in the original post is right at the edge, and if you need a bigger UPS you should have a bigger circuit for it.

A 20 amp circuit is 2400va, a little small for a 2200va UPS.

The 3000va units need a 30 amp circuit.

You can get away with it if you "derate" -- I have two 2200va UPSes carrying a 650va load, with 15a plugs.

Fortunately, peak loads and average loads vary.

I blew the dust off of my NFPA 70 1998 edition. Sooooo much stuff I haven't bothered to rmember. Like the 80% is only for 3 minutes.

I tend to get UPSs that are way overratted for what they will be used for as well. It's cheaper to just get a larger capacity UPS then getting the extended run time ones generally. The 1500va unit I'm using right now runs at 9-11% load to hopefully keep up for any minor outages we have.

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I blew the dust off of my NFPA 70 1998 edition. Sooooo much stuff I haven't bothered to rmember. Like the 80% is only for 3 minutes.

I tend to get UPSs that are way overratted for what they will be used for as well. It's cheaper to just get a larger capacity UPS then getting the extended run time ones generally. The 1500va unit I'm using right now runs at 9-11% load to hopefully keep up for any minor outages we have.

The saving grace on all of this "code" stuff is that it generally works off of peak loads, and the averages are all much lower.

Current draw comes down to battery charging time. You don't want to charge batteries too fast, or they fry. Slow charging means low current, so UPSes just plain don't draw alot over the load when they're standing or recharging after an outage.

I buy UPSes on the used market (eBay is your friend) and then replace the batteries with much larger replacements. For best battery life, you want a 20 hour run-time.

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Thanks. There is a lot of focus on sustainability, "net-zero" homes, etc. in my neck of the woods and even when plugged in but unused, little cell phone charger loads are deemed worthy of switching off. Obviously, the commercial example below of 100 VA would be a problem in a home setting; apples and oranges, however.

100va is somewhere around the typical incandescent light bulb (if the power factor is exactly 1, 100va is 100w), so should not be an issue in a residential environment.

According to the electrical code, a UPS must not draw more than 80% of the rating for the plug -- if the cord has a 15 amp "plug" (the most common in the U.S.) it can't draw more than 12a total, or 1440va.

That includes the load and the power to charge the battery.

The typical cell-phone charger draws less than a watt when it isn't actually charging, but plugged in. For most of us, this is going to be one of the very smallest "wasteful" loads. Look at your home entertainment system, you can probably find something there draws far more. Got an extra 'fridge? That's a biggie.

Yes, 100 W was not a real problem and 1 W was trivial when "sustainability" wasn't an issue. It is becoming a larger concern with environmentalists and government panderers, although the average joe couldn't care yet. But, all else being equal, we probably should shut off the silly things that do no useful work. (That is why I hope our processed seti data gets analyzed so I can claim 'useful work' was done with all the watt-hours we've donated.)

Is that coding just for standard wiring or does that include dedicated outlets as well? APCs 2200va and 3000va 120v UPS are over spec it would seem if it doesn't. Running 91.6% and 83.3% of their supply circuits. I'm sure any books that covered coding such as that are WAY out of date by now lol.

I know I ahve severa lthings on wasing power now. For one the cable TV box that gets updated randomly and sucks up 25w when turned off. Which doing the math right now costs me about $36/yr if it was just left turned off all the time. :(

I do use the lower pwoer CFLs and led lights for my home. So I would guess I've made up the diff in power cost there. I would really have to put a sensor on every light and device in my home to see if it all really works out tho. Any one want to come wire that up for me? :D

There are units that mount to your power meter and provide readings on your local wireless network, for display on your computer (or internet). That might be a way to go, replete with an interesting display on your CRT! (just kidding about the crt)

The typical cell-phone charger draws less than a watt when it isn't actually charging, but plugged in. For most of us, this is going to be one of the very smallest "wasteful" loads. Look at your home entertainment system, you can probably find something there draws far more. Got an extra 'fridge? That's a biggie.

Yes, 100 W was not a real problem and 1 W was trivial when "sustainability" wasn't an issue. It is becoming a larger concern with environmentalists and government panderers, although the average joe couldn't care yet. But, all else being equal, we probably should shut off the silly things that do no useful work. (That is why I hope our processed seti data gets analyzed so I can claim 'useful work' was done with all the watt-hours we've donated.)

How many kilowatt hours do you draw per month?

Around here, it's somewhere around 720kwh.

Ten 1 watt wall warts would be about 7 kWh per month.

There are easier ways to save 7 kWh per month.

Do I pay attention to wall warts? Yes. I also have a power strip on my TV that turns off all the ancillary equipment, and a device on my workstation that turns off the speakers and LCD and etc. when the computer is off.

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Last month this house drew 1600 KWhr but on average about 1100 KWHr. But this data is probably irrelevant to the general idea.

It hardly pays to buy the switches, etc. to turn the "vampires" off if it only saves about $1/mo.

Looks like I do have to buy a kill-a-watt to do this right.

Last month this house drew 1600 KWhr but on average about 1100 KWHr. But this data is probably irrelevant to the general idea.

It hardly pays to buy the switches, etc. to turn the "vampires" off if it only saves about $1/mo.

Looks like I do have to buy a kill-a-watt to do this right.

They're cheap, and they'll give you a fair idea of what counts big, and what is less important.

One other thing you might learn from a kill-a-watt: that nice refrigerator you have that's maybe 6 or 7 years old? The energy savings from a new one may pay for the new 'fridge in less than a year -- and that's way better than wall-warts.

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Is that coding just for standard wiring or does that include dedicated outlets as well? APCs 2200va and 3000va 120v UPS are over spec it would seem if it doesn't. Running 91.6% and 83.3% of their supply circuits. I'm sure any books that covered coding such as that are WAY out of date by now lol.

I know I ahve severa lthings on wasing power now. For one the cable TV box that gets updated randomly and sucks up 25w when turned off. Which doing the math right now costs me about $36/yr if it was just left turned off all the time. :(

I do use the lower pwoer CFLs and led lights for my home. So I would guess I've made up the diff in power cost there. I would really have to put a sensor on every light and device in my home to see if it all really works out tho. Any one want to come wire that up for me? :D

There are units that mount to your power meter and provide readings on your local wireless network, for display on your computer (or internet). That might be a way to go, replete with an interesting display on your CRT! (just kidding about the crt)

There are also people tat put measuring devices on each breaker and chart the data coming off of that. So they know how much of a load something is on each circuit. In my case I have breakers feeding various things all over my condo. I'm still not 100% if I have everything mapped out right. I have things like all the wiring for my sun room is on the same breaker at the vent hood for my stove. and my bathroom is the same breaker as my porch light. Mind you in both of those cases those things are on the other side of the condo from each other.

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One other thing you might learn from a kill-a-watt: that nice refrigerator you have that's maybe 6 or 7 years old? The energy savings from a new one may pay for the new 'fridge in less than a year -- and that's way better than wall-warts.

Interestingly, one of the key improvements in modern fridges was the inclusion of a solid state power factor corrector. They make the beasts considerably more efficient and much longer lived. (Relatively little energy efficiency has been gained since with insulation and other tweaks.)

I found an external power factor correction unit at Walmart in FL about 15 years ago and installed it on my old Whirlpool on a whim. I can't tell you about its power use, but the Whirlpool has lived now for about 25 years with only one freezer fan repair despite a large family of door swingers. But, yes, it makes sense to measure.

The typical cell-phone charger draws less than a watt when it isn't actually charging, but plugged in. For most of us, this is going to be one of the very smallest "wasteful" loads. Look at your home entertainment system, you can probably find something there draws far more. Got an extra 'fridge? That's a biggie.

Yes, 100 W was not a real problem and 1 W was trivial when "sustainability" wasn't an issue. It is becoming a larger concern with environmentalists and government panderers, although the average joe couldn't care yet. But, all else being equal, we probably should shut off the silly things that do no useful work. (That is why I hope our processed seti data gets analyzed so I can claim 'useful work' was done with all the watt-hours we've donated.)

How many kilowatt hours do you draw per month?

Around here, it's somewhere around 720kwh.

Ten 1 watt wall warts would be about 7 kWh per month.

There are easier ways to save 7 kWh per month.

Do I pay attention to wall warts? Yes. I also have a power strip on my TV that turns off all the ancillary equipment, and a device on my workstation that turns off the speakers and LCD and etc. when the computer is off.

Here are the last 12 months for me:

Bill Date KWH Charges Therms Cost Total
7/16/2009 2,143 $274.69 18.1 $21.09 $295.78 
6/15/2009 2,107 $270.43 22.2 $23.57 $294.00 
5/14/2009 1,693 $218.55 25.3 $25.75 $244.30 
4/15/2009 1,774 $212.28 50.5 $51.41 $263.69 
3/16/2009 1,788 $213.92 88.4 $95.43 $309.35 
2/13/2009 1,712 $209.55 107.6 $123.20 $332.75 
1/15/2009 1,928 $232.81 106.7 $124.40 $357.21 
12/15/2008 1,982 $236.87 69.3 $79.72 $316.59 
11/13/2008 1,428 $173.18 23.1 $30.60 $203.78 
10/15/2008 1,285 $165.70 17.1 $27.87 $193.57 
9/15/2008 1,327 $171.32 14.1 $27.48 $198.80 
8/14/2008 1,383 $177.44 15.1 $31.95 $209.39 
7/15/2008 2,063 $256.99 21.1 $43.31 $300.30 

Gotta cut back on the GPUs...but the credits at MW are nice...

However, when the AC is on, I generally cut back to 1 or 2 PCs on at home, to offset the power used by the AC...

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