I live in the US and have two-phase, 240 VAC, 60 Hz electric service to my home. I’ve wanted to better understand the electricity consumption patterns at my home, to see if I could reduce that consumption. I had a WattNode from a previous project in my inventory, so it was time to finally put it to good use.

The WattNode model I have is capable of monitoring up to three phases, so I’ll only use two-thirds of its capacity. Communication with the WattNode is via an RS-485 bus, so I’ll need a way to connect it via USB to my dedicated monitoring server. For that I plan to use an opto-isolated USB-to-RS485 device from B&B Electronics.

I’ll write the monitoring software myself, using Python and the MinimalModbus module. I have not yet found a good off-site place to publish and store my consumption data, so I’ll store it locally in an RDBMS. I have a basic class written in Python, which I’ll use to collect the frequency, voltage and current measurements from the device.

The next step is to install the WattNode in my primary electrical panel and then pull some low-voltage wire from it to my server.