APC UPS Bridge
An ESP32-S3 USB-host bridge that reads an APC Back-UPS or Smart-UPS directly over USB HID and streams 30+ live metrics — battery, load, runtime, input/output voltage and status — into Home Assistant over MQTT with auto-discovery. No apcupsd, no NUT, no cloud.
What it does
Talks to the UPS over USB
A USB HID host driver speaks directly to APC Back-UPS (VID 051D) hardware — no apcupsd or NUT daemon required. Tested on Back-UPS XS 1000M and Smart-UPS C 1500.
Auto-discovers in Home Assistant
Publishes 30+ entities over MQTT with Home Assistant auto-discovery — battery %, load, runtime, input/output voltage, transfer reasons, self-test and more. Zero YAML.
Built-in web interface
An on-device web UI shows live status and handles setup, alongside a unique device ID per bridge and automatic WiFi + MQTT reconnection.
Live in Home Assistant
The companion dashboard surfaces battery and load, voltage trends, and predictive runtime — all from a $9.99 ESP32-S3 plugged into your UPS.
Monitor your UPS in Home Assistant
Get the pre-built, flashed bridge — plug it into your APC UPS and it appears in Home Assistant in minutes. Firmware is MIT-licensed if you'd rather build your own.