OpenDTU — Open-Source Solar Inverter Monitoring
Replaces Hoymiles, TSUN, and Solenso cloud gateways with a privacy-respecting local solar inverter monitor — real-time power data via MQTT and web UI on an ESP32 with wired Ethernet support.
Overview
OpenDTU (2,100+ GitHub stars) is one of the most successful open-source solar energy projects. It replaces the proprietary cloud gateways (DTUs) that Hoymiles, TSUN, and Solenso micro-inverters require, giving you local-only solar monitoring with MQTT integration, a responsive web dashboard, and zero cloud dependency. Running on an ESP32 with Ethernet (T-Internet-POE or T-ETH-Lite), it provides rock-solid wired monitoring of your solar installation.
Key Features
- Inverter Support: Hoymiles HM/HMS/HMT series, TSUN, and Solenso micro-inverters
- Real-Time Data: Live power generation, daily/total yield, voltage, current, temperature per panel
- Web Dashboard: Beautiful responsive web UI with live charts and inverter status
- MQTT: Publishes all data to MQTT for Home Assistant, Grafana, or any automation system
- Power Limiting: Remotely set inverter power limits via web UI or MQTT
- Wired Ethernet: The T-Internet-POE provides PoE-powered wired connection — install and forget
- Multi-Inverter: Monitor multiple micro-inverters from a single DTU
- OTA Updates: Over-the-air firmware updates
Getting Started
Flash OpenDTU via web installer. Connect an nRF24L01+ or CMT2300A radio module (for communicating with inverters) to the ESP32. Configure your inverter serial numbers in the web UI. Data immediately appears on the dashboard and flows to your MQTT broker.
Why This Project
Solar panel owners want to monitor their generation without sending data to Chinese cloud servers. OpenDTU keeps everything local and integrates beautifully with Home Assistant for energy dashboards. The T-Internet-POE's PoE support means a single Ethernet cable provides both power and connectivity — perfect for rooftop or attic installations where WiFi may be unreliable.
