What "Off" mode actually turns off
Off stops the thermostat from calling for heating or cooling, but it is not a power switch, and it does not always stop the fan. A fan left on On, an ecobee fan minimum runtime or a Nest manual fan timer can still run. A Google Nest in Off also still heats or cools to hold its Safety Temperatures.
What does Off mode stop?
Off tells the thermostat not to call for heating or cooling. Honeywell's VisionPRO TH8000 manual puts it in one line: "Off: Heating and cooling systems are off." Sensi's guide for the Sensi smart thermostat says much the same thing: "When the Mode is Off the thermostat will not bring on your heating or cooling systems."
What Off does not do matters just as much. Google is direct about it for Nest: "Off mode doesn't turn off the power to your Nest thermostat or your system." Google adds that a Nest in Off stays connected to the internet, so it still takes commands from the app, still records Energy History (with an Off icon) and can still download software updates.
Google's page on Nest temperature modes adds that in Off you cannot change the temperature by hand until you switch to another mode, and that scheduled temperatures are ignored.
So Off is a mode, like Heat or Cool. It changes what the thermostat asks for. It does not shut anything down.
Does the fan still run in Off mode?
It can. On most thermostats the fan has its own control, separate from the system mode. The T6 Pro has a Mode button and a separate Fan button, and the VisionPRO has separate SYSTEM and FAN keys. Turning the system to Off does not change the fan setting, so a fan you set to On keeps running.
What else can run the fan with the system off depends on the brand:
- Google Nest. Google's modes page says that in Off the thermostat only heats or cools for Safety Temperatures and "All other heating, cooling, and fan control are disabled." But its fan help page makes one exception: a fan you start by hand with the fan timer can keep running in Off. Google lists the Nest Thermostat, the Nest Thermostat E and the Nest Learning Thermostat (3rd and 4th gen) as allowing it. A fan schedule is different: it will not start while the thermostat is in Off.
- ecobee. Two fan features ignore the System Mode: the fan minimum runtime, and a Fan Hold (called Fan Timer on the Smart Thermostat Premium, Enhanced and Lite). Both run whichever System Mode you pick, Off included.
- Honeywell Home VisionPRO. If a fan schedule has been programmed, the manual says "Auto" runs that schedule, and a choice of On or Circ stays active until you press FAN and pick Auto again.
If your fan is running and you are not sure why, the fan runs when the system is off page walks through each of these. For the On and Auto choice itself, see fan "On" vs "Auto".
Will a thermostat in Off ever turn the heat or cooling on?
A Google Nest will, by design. Off mode still uses your Safety Temperatures, and Google says that when the home reaches one of them, the thermostat "will start heating or cooling automatically" and sends a Safety Temperature alert to your phone. That is why a Nest set to Off can still come on in very hot or very cold weather.
Google says that to stop a Nest in Off from ever starting the system, you have to set both Safety Temperatures to Off. On the Nest Thermostat and Nest Learning Thermostat (4th gen) that is done in the Google Home app, under Settings, Temperature preferences, Safety Temperatures. On the Nest Thermostat E and older Learning models it is on the thermostat, under Settings, Equipment, Safety temp. Google warns that with Safety Temperatures off, the thermostat cannot help keep the home from reaching damaging temperatures.
The Honeywell and Sensi guides cited here describe no similar safety feature in Off mode.
What happens to your schedule and holds in Off?
On a Nest, Off "disables all regular heating and cooling schedules," and the thermostat no longer holds your Eco Temperatures either. Google also notes that if your system has independent fan control, the fan will not run on its set schedule while the thermostat is Off.
ecobee works differently. A hold stays active even when the System Mode is Off, and ecobee adds a catch: in Off you cannot see whether a hold is active. To check for one or cancel it, you have to switch the System Mode to anything other than Off first. If you set a hold, then turned the system off and back on, the hold may still be in force. Our page on thermostat keeps returning to schedule covers the opposite problem.
On the Sensi smart thermostat and Sensi Lite, choosing Off at the thermostat cancels Auto Mode. Sensi says you then have to turn Auto back on in the Sensi app. How that mode works is on the Auto mode page.
How do you set Off on each brand?
| Thermostat | How to select Off | What the manufacturer says can still run |
|---|---|---|
| Honeywell Home T6 Pro | Press Mode until Off shows, then leave it | Not stated; the fan has its own button (Auto, On, Circ) |
| Honeywell Home VisionPRO TH8000 | Press SYSTEM, choose Off, press DONE | Fan On or Circ until you choose Auto; a programmed fan schedule under Auto |
| Google Nest Learning Thermostat (4th gen) | Press the display, choose Mode, turn the dial to Off | Safety Temperatures; a fan timer you started by hand |
| Google Nest Thermostat | Press and hold the touch bar until "Turn off" appears | Safety Temperatures; a fan timer you started by hand |
| Google Nest Thermostat E, Learning Thermostat (3rd gen) | Quick View menu, Thermostat, Off | Safety Temperatures; a fan timer you started by hand |
| ecobee | Set System Mode to Off | Fan minimum runtime and Fan Hold; an active hold stays in place but is hidden |
| Emerson Sensi smart thermostat | Press Mode (Heat, Cool, Off or Aux) | Not stated |
In the Google Home app, Off is under your thermostat's Temperature mode.
When is Off the right choice?
Google suggests Off for a Nest when the home will be empty for a long stretch, such as a vacation. It compares Off with Eco: Off probably saves more energy, but the house takes longer to come back to a comfortable temperature, because Eco keeps heating or cooling to the Eco Temperatures and Off does not. If you would rather keep the house within a range while you are gone, see Nest Eco temperatures or a vacation hold.
Off is also the simple choice in mild weather when you want neither heat nor cooling, and it is a quick fix if the system keeps flipping between the two. That behavior is explained in thermostat switches between heat and cool.
Off is not the way to make the equipment safe for service. It leaves power to the thermostat and the system in place, so anything beyond the thermostat belongs with a licensed HVAC technician.
Frequently asked questions
- Does turning the thermostat to Off save more energy than Eco?
- Google says you will probably save more with Off than with Eco on a Nest, because Eco still heats or cools to the Eco Temperatures. The trade-off is that the house takes longer to get back to a comfortable temperature when you switch back.
- Can a Nest thermostat in Off mode still turn the heat on?
- Yes. Off still uses Safety Temperatures, and if the house reaches one of them the thermostat starts heating or cooling and sends an alert to your phone. Google says the only way to stop that is to set both Safety Temperatures to Off.
- Why did my Sensi leave Auto mode when I pressed Off?
- On the Sensi smart thermostat and Sensi Lite, changing the mode at the thermostat (Heat, Cool, Aux or Off) turns Auto Mode off. Sensi says you have to select Auto again in the Sensi app afterwards.
- Does my ecobee forget its hold when I turn it Off?
- No. ecobee says a hold stays active while the System Mode is Off. When you switch heating or cooling back on, check whether a hold is still in place before you expect the schedule to take over.