The Kill A Watt Energy Meter: A green gadget lover’s dream

Kill A Watt power usage meter by P3 International

Kill A Watt power usage meter by P3 InternationalThe Kill A Watt Energy Meter is a simple and remarkably useful device for revealing how much appliances are costing you to operate.

A few experiments with one of these meters have saved me hundreds of dollars in energy waste and hundreds more in unnecessary appliance upgrades that I probably otherwise would have made.

A while back, I was ready to replace our ten year old upright freezer with a new energy efficient freezer. I assumed that, given the age of the appliance, replacement would be the most economically sensible thing for me to do. After all, newer appliances, built to Energy Star standards, are much more efficient, right?

I wasn’t completely certain of the wisdom of the investment. I needed real numbers to make this decision.

Fortunately, I had a Kill A Watt meter in my office (actually, we have several of these great little gadgets).

Kill A Watt meters allow anyone to enter their local electrical rate per killowat hour, then plug a 110v (up to a 15 amp load) appliance into the unit to collect real-time data on what the device is costing to operate.

There are several similar meters on the market, but I prefer the Kill a Watt by P3 International for the price and the number of features the unit offers.

Programming is truly simple and the included instructions are complete, though operation is so simple that you are unlikely to need to refer to the manual for basic electrical load monitoring.

For larger appliances such as freezers or refrigerators, I use a three foot appliance extension cord so the meter can be left in place with the appliance in its normal resting spot, all while placing the meter where it can be read. Be certain that you use an extension cord that is at least as heavy as the cord on whatever appliance you are testing.

Using the Kill A Watt Meter
When collecting data on a household appliance such as a freezer, it is important to get a fair sampling of usage. If you plug in a freezer for just a moment, the meter will give you a reading, but that reading may look either extremely low if the compressor is off the whole time you test, or crazy high if the compressor is on for the few moments that you collect data. If you happen to catch your appliance while the automatic defrost is operating, the numbers will really scare you.

To get accurate electricity consumption data, let the appliance run through the meter for a few days to capture a true representation of usage patterns.

In the case of a freezer or refrigerator, energy consumption will vary according to how often the appliance door is opened, how long the door is open at a time, the temperature of anything that is added, how full the unit is, how often the auto defrost (if equipped) operates, and the temperature of the room.

Averaging the use over a longer period will equalize the spikes or lulls in usage and give you a much more accurate reading overall.

I’ve found that exploring home energy usage is a little addictive. I’ve tested televisions, lamps, computers, cellphone chargers, our HRV, space heaters, and just about every other 110 volt load I’ve been able to come up with.

Findings With Our Kill A Watt
Not surprisingly, I’ve found the value of lighting with LEDs and using a power strip to completely turn off such vampire loads as instant-on TVs and unused chargers. My Kill A Watt made me swear to never buy another non-LED Christmas light string again.

I also discovered that our old freezer was actually doing quite well. Replacing it was not at all worthwhile. This finding alone was worth hundreds.

Kill A Watt Limitations
The most glaring limitation of the Kill A Watt meter is the inability to meter 220 volt loads such as well pumps, ranges, electric furnaces, and air conditioners. For those larger appliance loads, look to a whole house meter such as the home electrical load center mounted Home Energy Monitor by Battic Door.

About the Author:
David Arthur, LEED-AP, Energy Auditor and green building consultant is an admitted green building nerd. He gets quite animated about such subjects as the embodied energy in concrete and window emissivity. He operates the website

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