Home Assistant Power Outage Automation

Automatically turn on lights when a power outage is detected using a UPS battery status sensor in Home Assistant.

Overview

This automation pattern uses a UPS (Uninterruptible Power Supply) as a power outage detector. When the UPS switches from "Online" (OL) to "On Battery" (OB), it triggers a boolean sensor that can then be used to control lights or other devices.

Prerequisites

Hardware Requirements

1. UPS with network monitoring - Must report status to Home Assistant (via NUT, APC, etc.)
2. Smart lights on UPS power - The lights you want to control must:
   • Be connected to power through the UPS (so they have power during outages)
   • Be smart-enabled (either smart bulbs or regular lights on a smart plug)
   • The smart plug/bulb must also be powered by the UPS

Why This Setup?

During a power outage, your smart home hub (Home Assistant) and network equipment need to stay powered to execute automations. Similarly, the lights you want to turn on must have power available. By connecting both your HA server and target lights to a UPS, the automation can function during outages.

UPS Battery Backup
├── Home Assistant server
├── Network switch/router
├── Smart plug → Light (e.g., lamp)
└── (Optional) Other critical devices

Components

Entities Required

Entity	Type	Purpose
sensor.server_ups_status_data	Sensor	UPS status from NUT integration (reports OL/OB)
input_boolean.power_outage	Input Boolean	Helper to track outage state
binary_sensor.power_outage_detected	Binary Sensor	(Optional) Template sensor based on the boolean
light.nymane	Light	Target light to turn on during outages

UPS Status Codes

• OL = Online (mains power available)
• OB = On Battery (power outage detected)

Setup Instructions

1. Create the Input Boolean Helper

In Home Assistant, go to Settings → Devices & Services → Helpers and create:

• Name: Power Outage
• Entity ID: input_boolean.power_outage

2. Create the Automations

Automation 1: Power Outage Detected

Triggers when UPS switches to battery power.

alias: Power outage in progress
description: ""
triggers:
  - trigger: state
    entity_id:
      - sensor.server_ups_status_data
    to:
      - OB
conditions: []
actions:
  - action: input_boolean.turn_on
    target:
      entity_id: input_boolean.power_outage
mode: single

Automation 2: Power Restored

Triggers when UPS returns to mains power.

alias: Power outage over
description: ""
triggers:
  - trigger: state
    entity_id:
      - sensor.server_ups_status_data
    to:
      - OL
    from:
      - OB
conditions: []
actions:
  - action: input_boolean.turn_off
    target:
      entity_id: input_boolean.power_outage
mode: single

Automation 3: Turn On Light During Outage

Triggers when the power outage boolean turns on.

alias: Nymane on when power out
description: ""
triggers:
  - trigger: state
    entity_id:
      - binary_sensor.power_outage_detected
    to:
      - "on"
conditions: []
actions:
  - action: light.turn_on
    target:
      entity_id: light.nymane
mode: single

Optional Enhancements

Additional Helper Sensors

You can create template sensors to track:

• Power outage started - Timestamp when outage began
• Power outage duration - Time elapsed since outage started
• Power outage ended - Timestamp when power was restored

Alternative Detection Methods

Instead of relying on a single UPS sensor, you can group multiple UPS binary sensors together for more robust detection across multiple UPS units.

Architecture Diagram

┌─────────────────────────────────────────────────────────┐
│                    Power Grid                           │
└─────────────────────┬───────────────────────────────────┘
                      │
                      ▼
              ┌───────────────┐
              │      UPS      │
              │  (Battery)    │
              └───────┬───────┘
                      │
        ┌─────────────┼─────────────┐
        │             │             │
        ▼             ▼             ▼
   ┌─────────┐  ┌──────────┐  ┌──────────┐
   │   HA    │  │  Router  │  │  Smart   │
   │ Server  │  │  Switch  │  │  Plug    │
   └────┬────┘  └──────────┘  └────┬─────┘
        │                          │
        │    ┌──────────────┐      │
        └───►│ NUT Sensor   │      ▼
             │ (OL → OB)    │  ┌────────┐
             └──────┬───────┘  │  Lamp  │
                    │          └────────┘
                    ▼
           ┌────────────────┐
           │ input_boolean  │
           │ power_outage   │
           └───────┬────────┘
                   │
                   ▼
           ┌────────────────┐
           │ Automation:    │
           │ Turn on light  │
           └────────────────┘

Troubleshooting

UPS Sensor Shows "Unavailable"

• Check that NUT (Network UPS Tools) integration is properly configured
• Verify the UPS is communicating with your server
• Check USB/network connection to the UPS

Lights Don't Turn On

• Verify the smart plug/light is powered by the UPS
• Check that the entity IDs match your setup
• Test the automation manually in Developer Tools

License

MIT License - Feel free to adapt for your own Home Assistant setup.