Design and Implementation of a Low-Cost IoT-Based Remote Power Monitoring System Using ESP32, Modbus RTU and MQTT

This report presents a low-cost, open-architecture system for remote monitoring of electrical power parameters using commodity hardware and open-source software. A three-phase power analyzer (Grup Arge ANL21) is polled over RS-485 using the Modbus RTU protocol by an ESP32 microcontroller acting as a gateway. The gateway publishes measurements over Wi-Fi to an MQTT broker over TLS. A Python FastAPI service subscribes to the broker, stores the data in a TimescaleDB time-series database, and exposes historical data through a REST endpoint and live data through a WebSocket. A React web dashboard visualises the measurements in real time. The system is deployed on a single cloud virtual server using Docker containers and an Nginx reverse proxy with HTTPS. The implementation demonstrates that an end-to-end pipeline from field device to browser can be built from off-the-shelf components for about USD 15 of gateway hardware and USD 6 per month for the server. Over a seven-day evaluation the system delivered 92.75 % of the expected 2 s readings, and data were present in 98.26 % of all minutes. The remaining losses were concentrated in the facility's working hours and are attributed to RF interference on the Wi-Fi link.