How to Automate Your Air Conditioner With Home Assistant Based on Presence and Temperature

An aircon that runs whether anyone is home or not is the easiest way to waste electricity, and Home Assistant solves it cleanly by tying the unit to a room sensor and a presence signal. The climate entity that represents your aircon switches on when a room crosses a temperature threshold and someone is present, and switches off when the room clears or cools. A short hold timer stops it flapping every time you nip to the kitchen.

Quick Answer

Build an automation around your aircon's climate entity that turns it on when a room temperature sensor exceeds your threshold and presence is detected, then turns it off when presence clears. Add a 15-minute hold so a brief exit does not shut the unit down. Done well, this trims runtime to only the times a room is both warm and occupied.

What you need before you start

This build assumes your aircon already appears in Home Assistant as a climate entity, whether through an integration like Sensibo, a generic thermostat setup, or an IR blaster that controls the unit. You also need a temperature reading for the room and some way to detect presence, which can be a motion sensor, a phone tracker, or a dedicated presence sensor. The smart home range at Evetech covers the sensors and hubs that feed these automations, and the best-selling accessories include the small fittings and adapters that tidy a sensor install.

Step-by-step: automate the aircon

1. Confirm the climate entity works manually. In Home Assistant, open the aircon's climate entity and set it to cool, change the target temperature, and confirm the unit responds. Everything downstream depends on this control being reliable, so prove it first.
2. Get an accurate room temperature. Use the aircon's own sensor only if it reads the room rather than the air at the unit. Otherwise add a separate temperature sensor placed away from the aircon's airflow and direct sunlight, because a sensor in the wrong spot makes every later decision wrong.
3. Set up a presence signal. Decide what counts as someone being in the room. A motion sensor is simplest, a presence sensor is steadier for people sitting still, and phone-based tracking works for whole-home presence. For per-room comfort, a room-level sensor beats a house-wide one.
4. Create the turn-on automation. Trigger on the room temperature rising above your threshold, say 25 degrees, with a condition that presence is detected. The action sets the climate entity to cool at your comfort target. Now the aircon only starts when the room is genuinely warm and occupied.
5. Create the turn-off automation. Trigger on presence clearing, with a condition that the room has been empty for a set period. The action turns the climate entity off. Optionally also turn off once the room drops below a lower temperature, so it stops when comfortable even if you are still there.
6. Add a hold to stop short-cycling. Insert a delay, around 15 minutes, before the off action commits. This means a quick trip out of the room does not trigger a shutdown and immediate restart, which is hard on the compressor and wastes power. The hold is the difference between a smooth system and an annoying one.
7. Set sensible bounds. Cap how cold the target can go and avoid running the aircon when a window or door sensor reports the room is open, if you have those sensors. Small guard conditions prevent the automation fighting reality.
8. Test across a real day. Watch it through a warm afternoon and a cooler evening. Confirm it starts when you enter a hot room, holds through brief absences, and shuts down once you leave for good. Tune the thresholds and hold time to your home's rhythm.

Why the hold timer matters most

The single setting that separates a pleasant automation from a frustrating one is the presence hold. Without it, the aircon reacts to every momentary gap in motion detection, cutting out the instant you sit still or step away, then lurching back on. A 15-minute hold smooths all of that, keeping the unit running through the natural pauses of occupying a room while still shutting down properly when you actually leave. The smart home and appliances range at Evetech has the presence and temperature sensors that make this responsive without being twitchy.

Frequently Asked Questions

Do I need a specific integration for my aircon?

You need the aircon to appear as a climate entity, which can come from a brand integration, a generic thermostat configuration, or an IR controller. Once it shows as a climate entity, the automation works the same way regardless of brand.

What temperature threshold should I use?

It depends on your comfort, but starting around 25 degrees for the on-trigger and a couple of degrees lower as the comfort target works for many rooms. Adjust to taste after watching it run for a few days.

Why does my aircon keep switching on and off?

That is short-cycling, usually caused by no hold timer on the presence-off action. Add a delay of around 15 minutes before the off action so brief absences and motion gaps do not toggle the unit.

Can I use a motion sensor for presence?

Yes, motion sensors are the simplest presence input. For people who sit still, a dedicated presence sensor holds the state more reliably, avoiding the aircon cutting out when no one is moving.

Will this save electricity?

It should, because the aircon only runs when a room is both warm and occupied rather than cooling empty spaces. The exact saving depends on your habits, but eliminating unoccupied runtime is where the gains come from.