Needless to say, there’s nothing better than finding a way to save a little bit of money on your electric bill. And the first step in doing that is knowing where your electricity goes each month. Once you know all of the places, large and small, where electricity is being used, and possibly wasted, you can take some steps to change things.

That’s where the Kill A Watt EZ comes in. This clever little device lets you read and understand the electrical usage of a variety of 120-volt electrical appliances and other devices around your home in real time, so you know specifically how much power they’re using, and how much money — in real dollars and cents — they’re costing you to operate.

Now you can accurately assess if those "phantom" electronics like phone chargers and unused TVs are costing you money, or if replacing that old clunker of a refrigerator will show a return on your investment.

Kill A Watts are available for around $25 through many home centers and other retailers, as well as online through places like Some utility companies also have them available for a free loan to their customers.

Just plug it in and set your rate

The Kill A Watt is really simple to operate, and requires little more than plugging it in. Here’s how it works:

First, select an appliance or other device that you’d like to monitor, let’s say your refrigerator. Plug the Kill A Watt into a wall outlet, then plug your refrigerator into the grounded receptacle on the front of the Kill A Watt unit. (You’ll want to be able to read the screen on the Kill A Watt, so in the case of a refrigerator, where the outlet is behind the appliance, you may need to use a short grounded extension cord to make things more convenient.)

Press and hold the Reset key to clear the old settings, then press and hold the Set key until "Rate" appears in the screen. This is a feature I really like, since it allows you to set your actual electrical rate, so you know the readings you’re seeing are accurate. You can get the rate you’re paying for electricity off your utility bill, or by calling your utility company. Simply press the up and down arrows to enter the rate per kilowatt hour. For example, if your utility is charging 10.5 cents per kilowatt-hour (kwh), press the buttons until the display reads $0.105, then press Set again. The rate is now saved. That’s it!

Measurement options

Now you have lots of options for understanding how much electricity the refrigerator is using. For example, the Kill A Watt will begin an elapsed time clock, and will begin tracking actual cost. So at any given time, you can look at the clock, then press Menu, scroll through to Cost, and see the actual cost of electricity that the refrigerator has consumed during that period of time.

Also under Cost is a simple projection, which I found very handy. By pressing the Up and Down keys, you can cycle through Hour, Day, Week, Month and Year, and Kill A Watt will give you an accurate projection of how much electricity — in actual dollars and cents — your refrigerator is going to use over that selected time period.

The display will also show you the actual kilowatt-hours being consumed by the appliance. That’s another way of determining cost, by looking at the actual electrical usage over a given period of time, then multiplying it by the cost you’re paying per kilowatt-hour. Other display options include the exact voltage and wattage being used, as well as the frequency.

How does this information help?

So now that you have the information, what do you do with it? For one thing, you can decide which appliances might need replacement. Replacing an old refrigerator with a new Energy Star model, for example, can save $100, $200 or even more each year in electrical costs, so the payback might be shorter than you think.

Another place this is helpful is with what are known as "phantom" electronics — things that are using power, even when you think they aren’t. Some examples include phone chargers, DVD players, microwaves, answering machines, TVs, and many other electronics. By testing them with Kill A Watt, you can see what’s using power even when you think it isn’t, and then consider shutting it off by plugging it into a convenient power strip that shuts several devices off at once.

Another simple formula

Without the Kill A Watt, there’s another way that you can calculate the cost of the power used by an electrical appliance or other device, using the following formula:

Watts x hours of use ÷ 1,000 x cost per kwh = cost of operation

For example, let’s say you want to know how much it costs to operate four light fixtures that each have two 60-watt light bulbs in them. The fixtures are on eight hours a day, and electricity in your area costs 10.5 cents per kwh.

4 lights x 2 bulbs each x 60 watts each = 480 total watts

480 watts x 8 hours = 3,840 watt-hours ÷ 1,000 (to convert to kwh) = 3.84 kwh x 0.105 = approximately 40 cents to operate those four fixtures for eight hours.

How about your furnace? Let’s say you have a 15 kW (15,000 watt) electric furnace that cycles on and off during the day. You estimate that it’s on for a total of six hours out of any 24-hour period during the winter.

15,000 watts x 6 hours ÷ 1,000 x 0.105 = $9.45 to run the furnace for those six hours.

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