Home (apparent) power monitor

Finished protoboard, ready for installation

Ignorance is a bliss: When you don't know how much power your air conditioner draws, it's easy to leave it running without feeling too guilty. And then the electricity bill comes...

The objective of this project is to get an approximate measurement of how much electric power is being used in my apartment. Additionally, for the sake of safety, the measurement system should not require me to modify the current electrical configuration of my apartment, i.e. the measurement should be non-invasive. This was achieved by using current transformers (CT). This system has been designed following the instructions provided by openeneregymonitor.org, which does a far better job at explaining how things work than I possibly could. At the moment, I am only measuring current, which limits me to computing my apartment's aparent power consumption, as opposed to its true power consumption.

Sensing current of a split phase configuration using CTs, provided by Maxim Integrated

The electrical system of my apartment is in a split-phase configuration. This required me to use two CT sensors, one per phase, as explained in this guide provided by Maxim Integrated.

The CTs output are processed by an ESP32, which I chose over an ESP8266 because of its multiple ADCs. This allows for the periodic broadcast of the measurements over MQTT. Additionally, the ESP32 serves webpages for real-time visualizatation of the power consumption. The web server used to serve those pages also provides the ability to update the firmware running on the ESP32 for OTA updates.

Here is a list of the parts used:

The source code for this project is available on GitHub