How do you control smart home devices with Google Assistant voice commands?

You control a smart home device by voice in two parts. First, the device is set up in the Google Home app. Second, a Google speaker or display is set up in the same app, because that speaker or display is the one that hears your command. When both are in place, you say "Hey Google" followed by the command. Google's examples for smart-home control are "Dim the living room lights." and "Set the heat to 70." ¹

This page gives the steps in order, says which devices and homes the setup depends on, and lists what to do when a command does nothing. For the full list of commands by device, see our guide to Google Assistant voice commands.

Add each device to the Google Home app before you speak to it

A device has to be in the Google Home app before any voice command can reach it. Google says you can control over 50,000 smart home devices, such as TVs, lights, appliances, plugs and thermostats, once you add them to the app ². That number is Google's own count of devices the app can control. It does not promise that each one takes voice commands, so check the device's listing before you buy.

1. Set up the device in the Google Home app, following the steps that came with it.
2. Check that the device has synced. Google's steps are to open the app, tap Home, then All devices, and find the device's tile.
3. Set up a Google speaker or display in the same app.
4. Say "Hey Google," then the command.

Google's page on controlling devices gives those steps for the app ( Google's help page on devices added to the Google Home app).

A speaker or display is what listens for the command

Voice commands run through the speaker or display, not through the device itself. Google says that once you set up a Google smart speaker or display in the Google Home app, you can use voice commands to control your linked smart devices ³. Google's examples for smart-home control sit under speakers and Smart Displays, not under phone commands, so a phone alone is not the place to test them.

Your phone can still control devices from the app. Google says that after you set up a device in the app, you can control it from your phone or tablet. Use the app when a command cannot reach the device, or when you want to check its state.

If your home uses Gemini, the change is one way

Gemini for Home can replace Google Assistant on compatible speakers and displays. Google says that once a home switches to Gemini for Home, it cannot switch back to Google Assistant ⁴. Check this before you switch the home, because a command that works today may not work after. The question on switching back explains the limits on phones.

Basic smart home control is free in Gemini for Home

Google says basic Gemini for Home features are free, including smart home controls, alarms and timers, calendars, notes, lists and reminders ⁵. So you do not need a subscription to turn on a light or set the heat. The guide to Google Assistant voice commands covers the commands themselves.

Some devices need a hub when you are away from home

Devices that use the Matter standard have one extra condition. Google says you need a Matter hub inside your home to set up, control and automate Matter devices while you are away from home ⁶. So if you want to turn on a heater before you arrive, check for a hub first.

When a command fails, check the home and the network first

A command can fail when the device is off or not on the same Wi-Fi network as your phone. Google's troubleshooting checklist starts with whether the device is plugged in and powered on, and then asks whether your devices are connected to the same Wi-Fi network ⁷. Then check these in the Google Home app:

1. Open the app, tap Home, then All devices, and check that the device appears in the same home.
2. Swipe down on the All devices screen to resync your linked smart home devices.
3. For a device from another brand, tap your profile picture or initial, then Home settings, then Works with Google, and reconnect the account.

If a command still fails after those steps, use the device's tile in the Google Home app to control it directly.

Keep locks, alarms and safety devices on a control you can check

Use voice for lights, the thermostat and routine tasks. Do not make voice the only way to lock a door, silence a safety alarm or control anything that protects people. Google says the home controls in Gemini are for convenience only, not for safety-critical or security-critical purposes ⁸. Keep a physical key, a switch or the app you can check in your hand for those devices.

Before you test a command, check which assistant answers it, as described in the question on which voice commands Google Assistant understands. If you are using the wider setup with another hub, see whether you can control Home Assistant with Alexa or Google. For the wider picture of spoken input, see speech to text and AI. For the meaning of the wake phrase, see wake word.