How to Reset a Thermostat: Nest, ecobee, Sensi, Honeywell

By Ray Bennett · Updated 2 October 2026 · 5 min read · Checked against the sources at the end

How to Reset a Thermostat: Nest, ecobee, Sensi, Honeywell

Short answer

A restart keeps your settings and helps a thermostat that is frozen or offline. A factory reset wipes them, and ecobee says a full reset will not fix heating, cooling or internet problems in most cases. Before either, work through Honeywell's list for a blank or unresponsive thermostat: the breaker, the switch on the furnace, the furnace door, the batteries, and a five minute wait.

When a thermostat misbehaves, a reset is the first thing people reach for. There are two very different kinds. A restart is like switching a phone off and on: it keeps everything. A factory reset wipes the thermostat back to how it left the box, including how it is set up for your heating and cooling.

This page brings together what Google, ecobee, Sensi, Honeywell, Trane and Lennox say in their own help pages. Most of the time, the fix is not a reset at all.

Before you start

What to carry: a torch, a pen and fresh batteries if your model takes them. Ten minutes.

Gas or electric? Either. The reset steps are the same whether the thermostat runs a gas furnace, a heat pump or an air conditioner.

Write the wiring down. Google says to write down the wire setup before a reset, and to save a copy of other settings like the heating type. A photo of the wires on the base helps too.

What a factory reset costs you. Your system settings. ecobee says a full reset loses the heating and cooling system settings, and a technician may be needed to set them up again.

It rarely fixes the heat. ecobee says that for heating, cooling or internet problems, a full reset will not help in most cases.

Setting it all up again. Google says that after a factory reset, the Nest has to be set up and added to your home in the app again, just as when it was first installed.

Before any reset

Honeywell's own list for a blank or unresponsive thermostat. None of it is a reset.

Check 1Free, ten minutes

Work Honeywell's list first

A blank display. Honeywell’s T6 Pro guide says to check the circuit breaker, the power switch for the heating and cooling system, that the furnace door is closed securely, and that fresh AA alkaline batteries are in correctly.

It shows but nothing runs. Set Heat above the room or Cool below it, then check the same breaker, switch and furnace door. Then wait five minutes for the system to respond.

Cool On or Heat On flashing. Honeywell says the compressor protection is engaged. Wait five minutes for the system to restart safely.

The setting will not change. The T6 Pro only accepts heat from 40 to 90°F and cool from 50 to 99°F.

More on a thermostat that will not work. The full checks are here: when the thermostat is the problem.

Restart or reset: which one

A restart keeps everything. A partial reset clears one part. A factory reset erases the setup, and you configure the thermostat again.

Check 2

Choose the right one

Restart. Google says a restart keeps all your settings, like restarting a computer or phone. It helps when the thermostat is stuck or frozen, cannot connect to the internet, or does not work properly.

A partial reset. ecobee’s Reset Schedule and Preferences erases the schedule and your preferences, but keeps the equipment setup and the account. On the Nest Thermostat E and the Learning Thermostat up to the 3rd gen, Google lets you reset just the schedule, the network or the account connection.

Moving house. Google says a factory reset is useful if you move, or want to leave the thermostat behind, and to remove it from your account in the app first. ecobee says its Reset Registration is the one for moving home, and it keeps the schedule and the equipment setup.

Factory reset. Everything goes back to default. Write your wiring and settings down first.

Where the reset is, by brand

Thermostat	Where the maker puts it
Nest Thermostat, Nest Learning (4th gen)	Settings, then Restart or Factory Reset
Nest Thermostat E, Nest Learning (3rd gen or earlier)	Settings, then Reset, then Restart or one of the reset options
ecobee	Main Menu, General, Settings, then Reset. Lite and Essential: Main Menu, Settings, Reset
Sensi smart thermostat	Hold up, down and Fan together until the display flashes and reboots
Sensi Lite	Hold up, down and menu together for over a second until the display resets
Trane XL824, XL850, XL1050	Menu, Settings, Reboot, with the heating and cooling idle
Lennox E30, S30	Advanced Settings, Restart: the smart hub, the thermostat or both

When the screen is frozen

Check 3Free, two minutes

Restart it by hand

Nest Thermostat. Google says take it off its base, take out both AAA batteries, put them back and press it onto the base until it clicks.

Nest Thermostat E and Learning. Press the thermostat down until the screen turns off, about 10 seconds, then press and release the ring to turn it back on.

Only when it is frozen. Google says a manual restart can lose unsaved information. Use it only when the thermostat is stuck and the menu restart is not possible.

Sensi. Sensi recommends a reset only when its support instructions say to. Afterwards, reconnect Wi-Fi and allow 30 to 60 minutes for it to recalibrate the room temperature: the Sensi checks.

When a reset does not help

Check 4Free to a service call

Look past the thermostat

Heating or cooling still does nothing. The equipment may be locked out rather than the thermostat: how to reset a furnace.

A heat pump that will not start. Rule out the waits first: how to reset a heat pump.

A Nest showing a code. The code names the fault: Nest error codes. With no code, the Nest checks are here: a Nest that is not working.

A Trane or a Lennox. Trane says a reboot keeps your settings: a Trane XL thermostat not working. A Lennox shows numbered alerts: Lennox alert codes.

A Honeywell that still will not respond. The Honeywell checks, batteries to wiring: a Honeywell that is not working.

Questions people ask

How do I reset my thermostat?

First decide whether you want a restart, which keeps your settings, or a factory reset, which erases them. Nest and ecobee thermostats have both in their settings menu. Try a restart first.

Will a reset fix my heating or cooling?

Rarely. ecobee says a full reset will not fix heating, cooling or internet problems in most cases. Check the breaker, the furnace switch and door, and wait five minutes first.

Why is Cool On flashing?

Honeywell says the compressor protection is engaged. Wait five minutes and the system restarts safely.

What do I lose with a factory reset?

Everything, including how the thermostat is set up for your system. ecobee says a technician may be needed to set that up again.

My Nest screen is frozen. What do I do?

On a Nest Thermostat E or Learning, press it down for about 10 seconds until the screen goes off, then press the ring. On a Nest Thermostat, take out the AAA batteries and put them back.

How do I restart a Sensi?

On the Sensi smart thermostat, hold up, down and Fan together until the display reboots. You will need to reconnect it to Wi-Fi afterwards.

Sources: Google Nest Help "Restart or reset a Nest thermostat", ecobee support "Resetting your ecobee thermostat", Sensi (Copeland) support "How to reset your Sensi thermostat", the Resideo (Honeywell) T6 Pro installation guide troubleshooting table, Trane Home support "How to Reboot Your Trane XL824/850/1050 Thermostat", and the Lennox iComfort E30 / S30 user guide