You could use a classic dead man switch: Place several buttons around the whole place - basically everywhere except in the shower. Once you stop pressing any of these buttons for - let’s say - 30 seconds you can assume you’re taking a shower.

Without trying something similar yet, here are some ideas:

• motion sensor on top of your shower
• trying to detect the vibration of the water flow
• a simple switch that you hit before you get into the shower

Also think of other times you “use” the shower, like cleaning it. Some methods will also be triggered then.

Are u nekkid, but warm, and wet? You’re in the shower.

I would just go with special button, the most straightforward simple solution you have direct control over. Also sometimes you might need to use the shower without mood lights and then system based on humidity or water flow will just be annoyance.

If you use some tools when showering, like brush or spung, you can make a contact sensor into the hook/holder (more work, probably need a custom 3D print), but should also work and you don’t need to press anything

I bet you can rig up something microphone-based, there’s tons of software nowadays for analyzing audio, and you don’t need to run the analyzing software on the device with the microphone anyway. Though the analyzing would likely take a little bit longer that you’d want it to.

Crossposted from showerthoughts

I use a humidity sensor, motion sensor and a helper that shows the change over a period of time. If the humidity raises fast (+2%/5m) and goes over a certain amount (unique, depending on your room’s climate) the bathroom automation changes tracks to hold the light at 100%, turn the extractor fan on, and well, how you stop the automation depends on you. I let it stay on for 15 minutes before waiting for motion. Small tips: For me the humidity triggers the automation within 15s-1m of showering, which is okay for me. Motion sensors typically use IR to see movement. If the room is too steamy it might struggle to see you. Also, it cannot penetrate glass. It must have a line of sight to you.

The best alt I think would be mmwave presence sensors, but they’re pricy and require a wired connection.

How about a simple on off toggle inside your shower handle? Stupid simple and works anytime the waters turned on.

Not sure if you have access to the pipes leading to the shower, but the droplet does what you’re looking to do.

https://hydrificwater.com/

Flowmeter on the shower head or down in the supply lines to the tub/shower?

Would a battery powered smart switch be an option?

Hit the switch and let HA do a command series.

mmwave sensor, humidity sensor, and/or monitoring your water heater power usage. any of those 2 should work.

I am actively working on a bunch of ML algorithms for home assistant for exactly this type of thing, detecting ‘activity’ per room.

I’m using just humidity and its working great. I put the sensor away from my sink so it isn’t triggered by washing my hands.

This will only consider you showering if humidity goes 9% above the 1hr average humidity:

You need a ‘Statistics’ Helper, call it “Average Bathroom Humidity” and base it on whatever humidity sensor you have. Make it “average linear” then set Max Age to 1 hour. (leave other options default)

Make this Template Binary Sensor called “Showering”:

{{ (states('sensor.bathroom_sensor_humidity')|float - states('sensor.average_bathroom_humidity')|float) > 9 }}

This is a fun question.

I have to assume the absolute ideal would be some sort of water flow detection right in line with the shower head. Likely hard wired. But like I said, that’s an ideal.

I think the other suggestions in the thread are reasonable. The microphone one seems most appealing to me since that could theoretically just occupy an outlet anywhere in the room.

Motion sensor positioned really close to the shower controls so it doesn’t see anything but them/your hand moving.

The bigger question might be how do you turn it off? I like the vibration sensor on the shower head