Nest Eco mode turns on by itself

Why does a Nest thermostat switch to Eco without being asked?

Because it was asked, just not by you at the thermostat. Google describes several ways a Nest ends up in Eco, and only one of them is a person choosing Eco on the screen:

• Eco when away. The thermostat senses that everyone has left and switches to Eco after a short wait. This is a setting, "Automatically switch to Eco when away", and it relies on presence sensing.
• The home was set to Away. Google says that if you set your home to Away in the Nest or Google Home app, all your thermostats switch to Eco.
• The schedule. On the Nest Thermostat (2020), the Eco preset can be used in the temperature schedule, so a scheduled block can put it in Eco.
• A manual choice you did not see. Eco can be picked in the Nest or Google Home app as well as on the thermostat, and Google says you can also tell Google Assistant to switch a thermostat to Eco.

When it happens, look at the status in the Google Home app. On the Nest Learning Thermostat (4th gen), "Eco when away" means presence sensing triggered it, while "Eco hold" means someone chose it by hand.

How does the thermostat decide nobody is home?

Google says the thermostat uses its own activity sensors, sensor data from your other Google Nest products, and your phone's location to tell when everyone has left or come back. When it concludes the home is empty, it waits a short while to make sure nobody is coming back, then switches to Eco.

That decision can be wrong in a few predictable ways:

• Phones are not sharing location. Each home member turns location sharing on or off for their own phone, and you cannot change it for someone else. If a person who is home has it off, they do not count.
• The phone is linked in the other app. Google says you can share your phone location in the Home app or the Nest app, but not both. Turning it on in one turns it off in the other.
• Only one phone counts per person. Turning on location sharing for a second phone turns it off on the first.
• Too few signals. Google's tip is that opting more devices into presence sensing improves accuracy, and that every member of a household should turn on location sharing.

Presence sensing devices and phone location live in the Google Home app under your Profile picture, then Home settings, then Presence sensing.

Why does Eco sometimes start hours after everyone leaves?

Google explains this one directly. The thermostat will wait up to 2 hours before switching to Eco when device sensors detect activity around the time everyone leaves. That longer wait applies even if phone location is also in use. Google's fix is to use only phone location for presence and turn off the other device sensors in the home's presence settings.

How do you stop Nest from switching to Eco by itself?

Turn off the setting that does it, not the schedule. Google's steps for the Google Home app:

1. Open the Google Home app and tap Favorites or Devices, then Climate, then your thermostat.
2. Tap Settings, then Eco when away.
3. Turn off "Automatically switch to Eco when away".

Turning off learning alone is not enough. Google's page on disabling Auto-Schedule warns that with presence-based automations or Home/Away Assist enabled, the thermostat might still switch to Eco when it senses everybody has left. Auto-Schedule and its behavior are explained in Nest Auto-Schedule.

If you want presence sensing for other devices but the thermostat keeps guessing wrong, review which devices and phones are opted in under Presence sensing before turning anything off.

How does Eco end once it has started?

That depends on how Eco started:

How Eco ends on Google Nest thermostats

How Eco started	Model	What ends it
Automatically (nobody home or home set to Away)	All	Someone comes home, motion is sensed, or you change the temperature in the app
Chosen by hand	Learning Thermostat (3rd gen or earlier), Thermostat E	Only switching the mode back to heating or cooling
Chosen by hand	Nest Thermostat (2020)	The next scheduled temperature change, or the end of a hold of up to 24 hours
Eco hold	Learning Thermostat (4th gen)	The end time you picked

A manual Eco on the older Learning Thermostats and the Thermostat E is the case that looks most like a malfunction: the house stays at Eco temperatures even with everyone home, and the schedule is ignored. Nothing is broken; it is waiting for you to pick heating or cooling again.

Is the house too cold or warm in Eco?

Then the Eco limits are set wider than you want. In Eco, the thermostat only heats when the house drops below "Heat to" and only cools above "Cool to". If either is set to Off, it will not run at all in Eco unless the house reaches the Safety Temperature. The ranges and where to change them are on our Nest Eco temperatures page.

What should you check now?

Does the Google Home app show "Eco hold"?

• Yes

  Someone chose Eco by hand, or used a voice command. Switch back to heating or cooling, or let the hold end.

• No

  Was anyone home when it switched?

  • Yes

    Do you want the thermostat to switch to Eco when the home is empty?

    • Yes

      Keep Eco when away on and fix presence sensing: turn on location sharing for each phone and opt more devices in.

    • No

      Turn off "Automatically switch to Eco when away" in the thermostat settings.

  • No

    That is Eco when away working as designed. If the wait felt too long, use only phone location for presence.

For more Nest settings and messages, see the Google Nest hub. How Eco compares with Away on other brands is in Eco vs Away mode.