Kill A Watt: Now with Less Math!

If you're interested in how much energy your electronics use, it's hard to find a device better than a Kill A Watt—except maybe the Kill A Watt EZ! P3 International now offers model P4600, which provides the same features as its predecessor, but it also automatically calculates device cost per day, week, month or year.

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P3's new version does automatic calculation, and it also has a battery-powered memory to retain measurements even when unplugged. We still recommend using a short extension cord, because it's often difficult to read the Kill-A-Watt when it's plugged in to the wall. We recommend checking devices you suspect of high usage, and also those you don't. A laser printer, for example, uses very little power when idle, but things like an electronic pet-containment fence or even a doorbell can use much more than you'd suspect. Visit for more information.


Shawn is Associate Editor here at Linux Journal, and has been around Linux since the beginning. He has a passion for open source, and he loves to teach. He also drinks too much coffee, which often shows in his writing.


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The best device to measure

mirellaya's picture

The best device to measure voltage and current. I have this one Camiseta Personalizadas


Marcos gail's picture

Much better than multimeters and clamp ammeter, but of course only within the measuring current and voltage. We must not confuse imobiliaria em extrema

EZ model is an improvement

PureDCA's picture

The EZ version is much better than the old version. With the old version you would lose all your data if you unplugged it, I found this out the hard way.

There are still some complaints that is not very accurate when you do the math using amps and volts but its the only device I could find that will give me a good idea how much power something is using

If you make a look around,

cristt's picture

If you make a look around, then you can get number of other devices too. having Smartphones, you can get some of the best mobile apps


samantha008's picture

Hello, I have just visited a good part of the site. I find it interesting, comprehensive, well done, nice to see. there are many different views, that's rich! Congratulations


Good tools

starmall's picture

It is a useful tools for us to save energy. But I think it also can check the detail info for every machine using.

Devices you don't suspect ...

Anonymous's picture

Your recommendation of "checking devices you suspect of high usage, and also those you don't" is spot on - it is even worth spreadsheeting and piecharting your energy use because mental images of energy use are very distorted. Lights (which are on for such a long time) are a major element, along with many, especially older, devices in "off", "standby" or "on but idle" modes. There are also some invisibles, like central heating pumps (up to 500 watts, intermittent) and many continuous drains like refrigerators or air-conditioning.

A spreadsheet of measured use through sockets versus your paid bill is essential to spot the serious drains, and to assess the benefit of replacement now or at end-of-life.

There is a lot of cant talked about mobile chargers, game consoles and their like which look impressive when multiplied by hundreds of millions of devices. In reality they will barely show against using an electric kettle, roasting a dinner or leaving a stair light on in daylight - or against the energy embodied in even the smallest manufactured product. Pressure cookers, microwave ovens, timeswitches, ambient light sensors, occupancy sensors etc will save many times their own cost over a lifetime. Using products to end-of-life is an even bigger saver.

And drink from the tap in preference to bottles, while thanking your chosen higher power that you have continuous access to clean, safe water.