How geofencing changes your thermostat temperature
Geofencing uses your phone's location to switch a smart thermostat between home and away temperatures. When every phone in the household leaves a boundary around your home, the thermostat sets back; when the first phone returns, it goes back. Sensi uses a fixed 3 mile boundary and a 3 degree setback, while Honeywell Home lets you draw the boundary.
What is geofencing on a thermostat?
A geofence is an invisible circle around your home. The thermostat's app watches your phone's location, and when the phone crosses that circle, the app tells the thermostat to switch to its away or home temperature. Honeywell Home describes it as a feature of the Resideo app that uses the GPS on your smart device to tell whether you are home or away.
The thermostat itself senses nothing here. Everything depends on the phone: its location setting, whether the app is allowed to run in the background, and whether the phone is signed in to the right account.
What changes when you leave and come back?
Each brand handles the setback differently:
| Brand | Boundary | What happens when everyone leaves | What happens when someone returns |
|---|---|---|---|
| Emerson Sensi | Fixed at 3 miles | Setpoint drops 3 degrees in heat or rises 3 degrees in cool; in Auto, the range widens by 3 degrees on each side | Setpoints go back to where they were before you left |
| Honeywell Home (Resideo app, T9 and others) | You drag the radius on a map | Switches to your Away settings; the T9 shows "Using Away Settings" | Switches to your Home settings |
| Google Nest | Not stated | Switches to Eco temperatures after a short wait, when phone location and Nest device sensors agree nobody is home | Returns to the normal schedule |
On Honeywell Home, the setback is whatever you put in your Away settings. On Sensi it is always 3 degrees from where you were. On Google Nest, phone location is one input to presence sensing rather than the whole story; the Nest Eco temperatures page covers the limits it switches to.
How does it handle more than one person?
All three brands follow the same rule: the house is "away" only when the last person leaves, and "home" as soon as the first person returns.
- Honeywell Home. The geofence event triggers when the first person arrives and when the last person leaves. Every phone needs its own Honeywell Home account; someone with a work phone and a personal phone should use two accounts. Tablets are excluded automatically.
- Emerson Sensi. All geofencing-enabled devices must be outside the 3 mile boundary before the thermostat switches to away. Each person logs into the Sensi app on their phone and turns geofencing on.
- Google Nest. Each home member turns location sharing on for their own phone in the Google Home app, under Home settings, then Presence sensing. You cannot do it for someone else.
The flip side is that a person who is home but not enrolled does not count. That is the most common reason for a setback while the house is occupied.
What happens if you change the temperature by hand?
The thermostat accepts it, but geofencing has the last word on Honeywell Home and Sensi when you cross the boundary.
- Honeywell Home T9. The guide says a manual change made while location-based control is active "will remain in effect until you cross the geofence."
- Honeywell Home T5, T5+ and T6 Pro Wi-Fi. Honeywell says permanent hold is disabled when geofencing is enabled. Temporary holds still work. See Honeywell hold vs permanent hold.
- Emerson Sensi. A setpoint change made at home while you are away is allowed, but when you come back inside the boundary the setpoint returns to what it was when you left. Switching between heating and cooling is different: Sensi says that overrides geofencing, and it then carries on from the new mode and temperature.
Can you use geofencing and a schedule together?
It depends on the brand. Sensi says you can use a programmed schedule or geofencing, not both: "Only one option can be turned on at a time." The Honeywell Home T9 can combine them: its Smart Scheduling adds a Sleep period to location-based control, and the guide says you can use geofencing, a time-based schedule, or a combination. On Google Nest, Eco when away runs on top of the schedule. How to choose between the two approaches is covered in schedule vs geofencing.
Why does geofencing switch at the wrong time?
Honeywell Home lists the phone-side causes. Location access must be set to "Always" on iOS or allowed precise location on Android, the app must be allowed to run in the background, and battery optimization apps should exclude it. Honeywell also suggests keeping the boundary away from roads and highways you drive past without heading home, and notes that the actual boundary varies slightly with GPS accuracy.
On Google Nest, Google says the thermostat can wait up to 2 hours before switching to Eco when device sensors see activity around the time everyone leaves. And on Sensi, geofencing is one of the reasons Sensi gives for setpoints that change without you touching them. If you see a setback while home, Nest Eco turning on by itself and thermostat not following its schedule cover the troubleshooting.
ecobee works differently: its Smart Home & Away feature uses occupancy sensors in the house rather than phone location. See ecobee Smart Away turns on by itself.
Frequently asked questions
- How big is the geofence around my home?
- It depends on the brand. Sensi uses a fixed 3 mile boundary. In the Honeywell Home Resideo app you set the radius yourself by dragging it on a map, and Honeywell says the radius shown is an approximation because GPS accuracy varies.
- Does geofencing work if only one person in the house has the app?
- It works, but only that phone counts. Sensi gives the example of a parent who turns on geofencing: the thermostat sets back when that parent leaves, even if a child is still home. Each person who should count needs their own login with geofencing turned on.
- Why did my thermostat set back while someone was home?
- Usually because that person's phone is not part of geofencing. On Honeywell Home, each user needs their own account with location enabled, and tablets are excluded. On Sensi, only devices logged in with geofencing turned on are counted.
- Does geofencing need Wi-Fi?
- Yes. The Honeywell Home T9 guide says location-based temperature control is managed through the Resideo app and will not function without a Wi-Fi connection. You can still change the temperature at the thermostat itself.