Although it’s been around for a few years now, the Kill-a-Watt and other “outlet” power monitors have gotten a lot of press for their ability to highlight the power use of many household devices that are otherwise black boxes. However, measuring your power usage 1 appliance at a time is difficult and time consuming. Even if your energy provider isn’t thinking about smart metering yet, why not analyze the energy consumed by your whole house over time?
This project makes ingenious use of a common feature on many household electric meters – most emit an infrared pulse every time a watt-hour is consumed. Paul Fox, the author and architect, uses an AVR and an inexpesive infrared sensor to capture the pulses and send them over USB to a waiting computer. Once the data is collected, Paul graphs it using gnuplot, a graphing utility for Linux, and can then display the data or peruse it at his leisure.
His project blog is a great write-up and shows some of the insights you can gain even from such a broad monitoring solution. He also wrote a followup post with a large collection of related projects, so if you’re looking to roll your own home power monitor, it’s a fantastic place to start your research.