Home Energy Monitoring: Spying On Your Electrical Habits

Editor’s Note: EarthTechling is proud to repost this article courtesy of Do The Math. Author credit goes to Tom Murphy.

My wife calls it spying. I call it data. To-may-to, To-mah-to. It’s true that I know what she’s been up to (electrically) while I’m away. And it’s true that I can access this information anywhere in the world that has an internet connection. But domestic surveillance is not my aim (cameras and microphones would be far more informative in that regard). I just care about the energy angle.

In this post, I will present example results from monitoring and recording my home electricity use, demonstrating the marvelous secret world it reveals. My interest lies in putting numbers on my own behaviors, and in characterizing the appliances in my house. Some of this rubs off on my wife, and some of it rubs her the wrong way. But as I explained in an earlier post, I kept a note she once wrote that said: “Okay, TED’s pretty cool.”


image via Energy Inc.

Who is TED? TED is The Energy Detective. That same earlier post told the story of TED’s tortured journey to our home—a tale of excitement, rejection, and ultimate acceptance.

This post is not meant to convey anything deep and meaningful about the energy challenges we face, except for the fact that those challenges provided a background motivation for me to explore and monitor energy data in my home (it should be obvious by now that I’m a data-holic). Rather, I will simply showcase a number of data captures from TED so you can see for yourself the interesting hidden behaviors of appliances, and develop some intuition about how much of a toll various devices take.

TED Basics

I should spend a little time telling you a bit about TED. At the heart of TED are two current-measuring clamps that each encircle power lines delivering two phases of AC electricity into the home. Tying into a two-phase circuit breaker via wire, it also knows the voltages of the two phases. Power is current times voltage, so TED simply accumulates the instantaneous current times voltage for each of the two phases. Out pops Watts, measured once per second.

The data are communicated through the electrical wires themselves—via the same wires that connect TED to the breaker. A communication unit inside the house plugs into any outlet to receive the information and relay it via ethernet to the (separately furnished) home networking equipment. Configuration of the router can allow password-protected access to TED from outside the home. An optional display receives wireless communication from the plugged-in communication device—albeit over a pathetically short range in my unit—and presents (among other options) the instantaneous power usage of the house in Watts.

discussed before methods for using the utility meter on the side of the house to gauge power draw, but the methods are indirect and slow. Nothing beats a real-time reading in the house. Suddenly many curiosities may be satisfied. All the integrated devices (lighting, fans, air conditioning, electric ovens/stoves, hot tubs, etc.) that are not available for measurement via the Kill-A-Watt are now fair game. One useful exercise is to turn off breakers one by one during a quiet period in order to discover which circuits harborphantoms—making it considerably easier to track them down in the house.

Moreover, TED data are stored automatically so that periodic retrieval can result in an uninterrupted record of electrical activity in the house. My favorite!

1 Comment

  • Reply July 18, 2012


    Very informative and thorough article describing TED.  I have been toying with purchasing TED for my own home and I believe this article gives the justification to take the plunge.

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