Is your printer robbing you blind? Calculate your Electricity Usage with a Kill A Watt


in Efficiency,Frugality,How To...,Savings

Kill-A-WattIs it worth your time to reduce electricity usage?  Common sense would say yes, but what does that really equate to in real dollars?  Where’s the best bang for the buck?  More importantly how would I really know how much I’m saving?  On the recommendation of a friend I recently purchased a P3 International P4400 Kill A Watt Electricity Usage Monitor from  The device is very simple you plug it into an outlet and then you plug anything that you want to monitor into the Kill A Watt and you can see Voltage, Amperage, Watts, and Kilowatt Hours over time. It’s remarkably easy to use, and in mere seconds you can see the wattage use of anything you can plug into the Kill A Watt as long as it draws less than 15 amps which should be most everything except say your dryer, hopefully you also realize that super huge plug won’t fit in the Kill A Watt.

How to Use the Kill A Watt

It does not take a hacker with elite skillz to operate the Kill A Watt, if you can plug in an electrical cord and push a button you can get usable data.  There are really two ways to get the energy usage of your devices: output the wattage use of the device and calculate Kilowatt Hours or you can leave the Kill A Watt plugged in and let it monitor the electricity usage for the duration of the items operation.  The latter is useful for something that may cycle through different levels of electricity use like say your refrigerator.

How to Use the KWH/Hour Function

This is the simplest method for determining electricity usage if you’ve got the time. “I was told there would be no math.”  Plug in the Kill A Watt then plug in your device.  Push the KWH/Hour button and it will start to display the KWH/Hour usage starting from the time the Kill A Watt was plugged in.  Simply let your device run through a cycle for such things as a washing machine or for a time period.  When that period is done record the KWH/Hour usage.

How to Calculate KWH/Hour usage when you Know Wattage and Time

Electricity usage is measured in Kilowatt-hours (KWh) so we need to get from Watts to KWh which means we also need to know time.  Let’s start with watts, 1 watt-hour is the same as 1 watt used for 1 hour so that means that 1 kilowatt-hour is equal to 1000 watts used for one hour.  So if we know that we use 75 watts for our desktop computer and we run it for 30 minutes we can:

Calculate Kilowatts:  75 watts / 1000  = .075 Kilowatts
Calculate Time in Hours: 30 minutes/60 minutes = .5 Hour (duh)
Calculate KWh: .075 x .5 = .0375 KWh

wa_kwhArggh this is horrible there’s got to be an easier way!  Sure, head over to  Let’s assume we have a device that uses 30 watts of electricity and that we want to know the KWh after it’s been running 10 minutes.  Enter: 30watts*10minutes to KWh in the WolframAlpha search box and you’ll get your answer.  Easy enough.

So How Much does My Device Cost?

You may be surprised at the answers here.  In most cases the devices and appliances my family uses are much more energy efficient and cost pennies to operate.  Calculating your own costs is simple enough, multiply your KWh times your KWh rate.  Check your power company bill and there should be a listing of your KWh cost.  With Puget Sound Energy my provider I get two prices depending on use.  The first 600 Kilowatt Hours are billed at $0.084772 and after that they are billed at $0.102851 per KWh.  It’s in my best interest to try and keep my usage under the 600 Kilowatt Hours which might be trick since my standard usage is about 1000 KWh a month.

Breakdown of some Common Items



Cycle Time

Cost Per Month



3 minutes


Finny’s Fish Tank


1 Month


Lexmark Printer on Standby


1 Month


60Watt Bulb


1 Month


Compact Fluorescent


1 Month




48 times a month


Desktop Computer, Monitor, External Drives


1 Month


Gibson Freezer


1 Month


Opportunities for Savings

I understand volumes of data has been published on energy consumption, conservation and the like.  All you need to do is read the back of your electricity bill for some more information but for me actually monitoring my devices was an eye opener.  The device is relatively inexpensive at about $20 and with some simple changes you can bring down your electric bill drastically.  Some eye opening information was taking a look at the power saver modes of various devices versus their “full” modes for instance with our wireless printer and the difference was 1 watt.  Don’t be fooled, arm yourself with all the information you can and get saving.  I for one will be defrosting and emptying our “free” Gibson Freezer we got a couple of months ago.  Wasn’t the brand of supercomputer in Hackers a Gibson?

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