Customer Review

1,569 of 1,603 people found the following review helpful
5.0 out of 5 stars Fascinating gadget, July 8, 2005
Verified Purchase(What's this?)
This review is from: P3 P4400 Kill A Watt Electricity Usage Monitor (Tools & Hardware)
I absolutely love this thing.

Having recently moved out on my own, and generally just enjoying statistics in general, I bought this to monitor my electric costs after two high electric bills in a row. The various results I found were quite surprising.

My air purifier, which I bought here on Amazon, uses 85 watts all the time... 85 * 24 hrs * 30 days / 1000 watts = 61.2kWhr * $0.20 = $12.24 a month.

Well, that's quite a costly monthly addition I never thought of. And that's just the begining.

My Vornado fan uses 45w... my air conditioner, on high 6 (out of 12) spikes up to 1200 watts. Jeez.

My computer, at idle with external drives, uses about 250w. When doing extremely intensive things, like encoding a video, 310w.

My light behind my computer desk, with five, 10-watt bulbs, doesn't actually use 50-watts total. No, it uses 50-watts for the bulbs, PLUS 30-watts apparently just for the light unit to function.

You too will find out all these things you never knew, and possibly save money by cutting out, or replacing energy guzzlers.

The product is also made in China. Just like everything else now.
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Comments

Tracked by 8 customers

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Showing 1-10 of 62 posts in this discussion
Initial post: Feb 14, 2007 4:39:38 PM PST
Rebecca King says:
Mr. Roncoroni, how warm is your light when it's not in use? Any device that uses 30 watts continuously but that doesn't have a cooling fan will be very warm or downright hot, unless it's something like a radio transmitter or X-ray machine that turns electricity into some form other than heat, which your lamp isn't when it's turned off. The reading of 30 watts makes me wonder whether the unit is correct, or whether it's possibly measuring volt-amps or perhaps screwing up on non-sinusoidal loads. See http://en.wikipedia.org/wiki/Power_factor for a hint of the mistake this device could be making. Even if it works correctly for ordinary inductive or capacitive loads it might screw up spiky loads.

In reply to an earlier post on Jul 18, 2007 8:10:37 AM PDT
Last edited by the author on Sep 29, 2007 8:14:29 PM PDT
D. Bohls says:
Rebecca, I got the impression he is reading 80 Watts when the light is on, and that he is just assuming 50 Watts are going to the lights and 30 Watts are being consumed by the device. I doubt this is the case though since lights are purely reactive loads. Perhaps the bulbs are really 15 watts and he just thinks they're 10.

This awesome little device can tell you Watts, Volt-Amps, and power factor. I'd imagine this device is optimally built for sinsusoidal loads.

Sincere question: Considering that the power company is providing a sinusoidal source, do we really have to worry about non-sinusoidal situations? I don't think we do.

In reply to an earlier post on Nov 2, 2007 1:26:09 AM PDT
Since when are lights reactive? Maybe you meant lights are purely resistive loads? (but even this isn't strictly true...)

In reply to an earlier post on Feb 8, 2008 12:44:48 PM PST
Last edited by the author on Feb 8, 2008 12:45:27 PM PST
My guess is that the table lamp unit uses five low-voltage (12V) high-intensity light bulbs, similar to that used in the head lamp of your car. Inside the lamp unit there must be a 120V AC to 12V DC converter. The efficiency of this converter is probably rather low at around 60%. Therefore to deliver 50W output power, it requires 80W input power.

In reply to an earlier post on Mar 22, 2008 9:59:46 AM PDT
[Customers don't think this post adds to the discussion. Show post anyway. Show all unhelpful posts.]

In reply to an earlier post on Sep 20, 2008 7:32:08 AM PDT
K. Thomas says:
[Customers don't think this post adds to the discussion. Show post anyway. Show all unhelpful posts.]

Posted on Feb 3, 2009 2:13:05 PM PST
Grant says:
Your first calculation says you are paying 20 cents per kwhr (kilowatt hour). That's about twice what the average American pays. Are you sure that is correct?

In reply to an earlier post on Feb 8, 2009 7:14:49 PM PST
tech-savvy says:
Who cares? He was just trying to point out how useful it is.

In reply to an earlier post on Feb 9, 2009 8:31:53 AM PST
Last edited by the author on Feb 9, 2009 8:40:37 AM PST
by says:
D. Bohls, I'm sure power company product is sinusoidal but I know that I can encounter performance issues whenever I have a UPS somewhere downstream on a 120 vac distribution circuit being shared by other items: ceiling paddle fan, compact fluorescent lights, etc. Also, since I am in Florida I have a portable generator (Yamaha high quality inverter) that cautions about deterioration of power quality (for motor loads) if a UPS load on an output circuit consumes in excess of 25-30% of the circuit's total capacity. Could we expect 'rough' power conditions (on this single distribution circuit) if we had a UPS of 900VA (and higher) rating connected to this same, typical home 120 vac convenience power / lighting circuit?

In reply to an earlier post on Mar 11, 2009 5:27:24 AM PDT
Hy Voltage says:
>"Sincere question: Considering that the power company is providing a sinusoidal source, do we really have to worry about non-sinusoidal situations? I don't think we do."

Actually, yes, we do. Why? Because some people (fer example, me) occasionally use inverters, which generally deliver a "modified" sine wave output. I've noticed that my microwave oven, for example, doesn't seem to heat food as quickly when on the inverter, compared with using regular AC power. Is this because the inverter puts out a lower voltage, or because the waveform is different, or some other reason? I dunno. I'd like to think this product ("Kill-A-Watt" meter) would answer those questions. But realistically, probably not. To really get an accurate answer for non-sinusoidal waveforms, you'd need to use a "true RMS" meter, and they're quite expensive. This "Kill-A-Watt" meter is, uh, currently [no pun intended!] listed at about $21, so there's no way it's a "true RMS" device. Still useful for sinusoidal situations, I'm sure (that's fun to say out loud! Try it!), but probably much less so when used with inverters that put out power with a so-called "modified" sine wave.
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