December 01, 2025

Turn on bathroom fan when starting shower

Remembering to turn on the ceiling fan when taking a shower early in the morning isn’t always easy. Automate it to prevent mirror fog, reduce humidity, and improve air quality without thinking about it.

Use cases

Convenience & Comfort

Morning Shower - Automatically turn on fan when starting your morning shower
Prevent Mirror Fog - Keep bathroom mirrors clear during showers
Multi-User Households - Everyone gets fan benefits without remembering

Health & Safety

Humidity Control - Reduce excess moisture to prevent mold and mildew
Bathroom Ventilation - Improve air quality automatically

Products needed

Essential Equipment

Smart Fan Switch

Popular brands: Lutron, GE, Leviton, Inovelli
WiFi or Zigbee • Works with existing fan • Load rating sufficient for fan motor

Trigger Option (choose one)

Smart Light Switch: Trigger when shower lights turn on (easiest method)
Contact Sensor: Trigger when shower door opens (best for glass enclosures)
Humidity Sensor: Trigger when humidity rises (most accurate - Aqara, Sonoff, Zigbee)

Optional Enhancements

Multi-Sensor

Combines temperature, humidity, and motion for advanced control

Smart Speaker

Announce "Fan turned on" or play shower music

Basic automation setup

IF shower lights turn on THEN turn on bathroom fan

Triggers (choose one method)

Method 1 - Light-based: Shower lights turn on
Method 2 - Door sensor: Shower door opens (contact sensor)
Method 3 - Humidity-based: Bathroom humidity rises above 75%

Conditions (optional)

Time-Based: Only between 5 AM and 11 PM (quiet hours at night)
Home Mode: Only when someone is home

Actions

Turn on bathroom fan switch
Optional: Set fan to specific speed if multi-speed fan
Optional: Send notification "Bathroom fan activated"

Platform-specific examples

Home Assistant

Trigger Shower lights turn on

Condition Time is between 5 AM and 11 PM

Action Turn on bathroom fan switch

Alt trigger: Humidity rises above 75%

SmartThings

IF Shower lights turn on AND Time is 5 AM - 11 PM

THEN Turn on bathroom fan switch

Hubitat

Trigger Shower light turns on

Condition Time 5 AM - 11 PM

Action Turn on bathroom fan

Setup: Use Simple Automation Rules or Rule Machine

Apple HomeKit

When Shower light turns on

Condition Time is between 5:00 AM and 11:00 PM

Do Turn on bathroom fan

Alexa

When Shower light turns on

Condition Time between 5:00 AM - 11:00 PM

Action Turn on bathroom fan

Google Home

When Shower light turns on

Condition Time between 5:00 AM - 11:00 PM

Action Turn on bathroom fan

Advanced features

Automatic fan shutoff

Turn off the fan automatically after the shower ends:

Trigger: Shower lights turn off for 10 minutes
Action: Turn off bathroom fan

Humidity-based shutoff

Turn off when humidity returns to normal:

Trigger: Humidity drops below 60% for 5 min
Condition: Fan is currently on
Action: Turn off bathroom fan

Bonus automations

Since your smart home now knows when you're showering:

Play Music: Start shower playlist on speaker
Flash Lights: Alert when doorbell rings
Lock Front Door: Secure home while showering
Adjust Thermostat: Increase bathroom temp

Common issues and solutions

Fan doesn't turn on

Problem: Smart fan switch not responding or automation disabled.

Solutions:

Test fan switch manually through app
Check automation triggers - simulate shower start
Verify automation is enabled in your platform
Ensure physical fan switch is in "on" position
Check fan switch load rating matches fan motor

Fan turns on at wrong times

Problem: Multiple triggers firing or humidity sensor triggered by other sources.

Solutions:

Review automation logs to see what triggered
Add time-based conditions to limit hours
Increase humidity threshold (try 80% instead of 75%)
Add delay: Only trigger if condition persists for 2-3 min
Use multiple conditions: Light ON + Humidity rising

Fan doesn't turn off

Problem: Auto-off automation not created or humidity not dropping.

Solutions:

Create separate automation for fan shutoff
Increase shutoff delay if humidity drops slowly
Check bathroom ventilation - fan may need cleaning
Add manual override button
Set maximum run time: Off after 30 minutes regardless

Related automations: