This project was an attempt to create an inexpensive home automation and monitoring system. While off-the-shelf solutions like Nest often use high end processors with displays for each device I chose to keep the hardware simple and push the application logic to the cloud.
It consists of a non-invasive power monitor for the home electrical panel, wireless thermostat, wireless Smart Meter reader and a relay to control individual appliances. At the core of each device is an 8-bit microcontroller with an RF transceiver operating in the ISM band. The BOM is around $15 for single quantities.
The result was a realtime display of power usage for major subsections of the house (See image above). With this information you could determine the efficiency of major appliances, when your laundry finished or whether you left the iron on upstairs. For more accurate measurement of the utility bill the Smart Meter reader periodically reported the power usage for the entire home. The wireless thermostat and appliance switch can be controlled via a web interface.
nabil 