Kill-A-Watt: Analysis of Electrical Goods @ Home

Well, looks like the Hamilton Public Library has tons of Kill-A-Watts available for borrowing. Take a look @ their website to see if they have any on hand, although I wouldn't put too much faith in it. Their site said that there were 3 on-hand @ my local library, but I took the one and only that was there.

Bit of background on the Kill-A-Watt

Basically, the device just measures the amount of energy that flows into whatever is plugged into it. From that, you can figure out how much you would save if you were to not run that device, or not run it as often. Now with two-tier electric billing coming on-board, it may be possible to run many devices on a timer, if they only need to run for a certain time each day. For example, a pool-pump could be run only at night, instead of in the middle of the day when electricity is expensive, or a chest freezer could be set to only chill things at night, with the hope that things would be able to survive throughout the day.

First Looks on the Kill-A-Watt

My first concern was, since I was borrowing this from the library, that the batteries in the thing would be dead. Of course, I quickly found that it doesn't use batteries at all, it is only on when it is plugged in. If you un-plug it, any stats that you once had would be lost.

The device is pretty simple, and you can't really mess it up. The only way to reset it is to unplug it and plug it back in, so feel free to press any button you like without fear. Pressing any of the buttons just gives you a number of whatever is being measured.

To measure things like fridges that aren't quite on all of the time, you can just leave it plugged into the Kill-A-Watt for a couple days. The Kill-A-Watt will keep track of Kilo-Watt-Hours used and the amount of time the device has been plugged in.

Just keep in mind: "Watts" is the amount of energy that is being charged to you on the meter. "Volt-Amps" or"VA" is the amount of energy that is used by the device throughout the entire grid infrastructure. Essentially, if the VA is much greater than the Watts that a device uses, you're getting some free energy (which is why they charge you an additional 4.2% or so on your bill for). But keep in mind, this energy difference is actually lost as heat throughout the wires and substations on its way to you, so you're not getting it yourself. Generally, resistive appliances, like heaters and computers, should have a similar measure of Watts and Volt-Amps. However, devices like motors (such as those in refrigerators) have a much higher Volt-Amp usage than Watt usage. "Power Factor" times "Volt Amps" will equal "Watts".

Kill-A-Watt Findings So Far:

Electricity Usage
Asus M6N laptop (not charging, screen on)
31 Watts
Asus M6N laptop (not charging, screen off)
28 Watts
Asus M6N laptop (charging, screen on)
68 Watts
27" TV + VCR + Set Top Box (while on)
128 Watts
~25 year old huge chest freezer
100 Watts (continuously)
Cordless Phone Recharger station (not charging)
0 Watts

I felt that there was really no need to build a contraption to measure lights, if they state that they are 60W, they'll use that. If a CFL is 13W, that is what it will use.

Surprising Results

What really surprised me was the chest freezer. It seems to be operating continuously, while I expected a refrigeration device to operate on an on/off cycle. Perhaps the thermostat on it (wherever it is) is set to a point where it can't get to, or it is just all-out broken. It is not a huge consumer of electricity, but I really wanted to run it on a timer where it would perhaps run only at night and a little bit during the day when two-tier electricity billing comes on in Hamilton (they've installed the meters, but haven't started for some reason).


Hi, there is the question

Good article in general. I

Good article in general. I have a Kill-A-Watt, and it's fascinating to plug various devices into it and see how they operate. Just one quibble from this cranky old electrical engineer: Watts and volt-amps are measures of power, not energy. Electric untilities bill for the amount of energy used, measured in kilowatt-hours. A kilowatt-hour is the amount of energy used to provide one kilowatt of power for one hour.

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