A Nest Thermostat (2020) that shows as offline in the Google Home app, with a thermostat that works at the wall but cannot be reached from a phone, has a connection or power cause, and the first fact is that a blank display is not a fault. The Nest Thermostat has a 2.4-inch display behind a mirrored glass lens, so it looks like a mirror when asleep, and the motion sensor wakes it. A thermostat in a corridor that nobody walks past may look dead for long periods.
The checks in more detail
Touch or press the ring to wake it before you assume anything. If it is awake and shows no Wi-Fi, check the connection. The thermostat joins 2.4 and 5 gigahertz networks, plus Bluetooth Low Energy. Check that your router is working and that the thermostat is within range; look in the thermostat's settings for the Wi-Fi status and signal. Restart the router, and restart the thermostat by pressing and holding the thermostat's ring button for about ten seconds until the display turns off, and then release it so that it restarts.
A changed Wi-Fi name or password, or a router that now uses a combined band name or blocks new devices, leaves the thermostat offline; reconnect it from the settings by choosing the network and entering the password. Then power. The thermostat is powered mainly from your HVAC wires and has a battery backup of two AAA alkaline cells, which are user-replaceable, so replace them as a first step if the display is dead or the thermostat keeps restarting.
Google designs it to work without a C wire, but adds that heating-only or cooling-only systems or zone controllers may need a C wire or a power accessory; an underpowered thermostat drops its Wi-Fi to save energy, which looks like offline. Check the Google Home app for a battery or power message. If the thermostat is online on the wall but the app shows offline, sign out and in, update the app, check that the right Google account and home are selected and remove and re-add the thermostat if needed. It is Matter certified and can be controlled from other Matter platforms. Contact Google support with the model if it stays offline.
Differential
Likely causes of “Nest Thermostat is offline or unavailable”, and how to tell them apart
- 1
A sleeping display
What separates it The screen looks blank but the thermostat is fine
How to confirm Touch the ring to wake it
- 2
Wi-Fi changes or a weak signal
What separates it The thermostat shows no network
How to confirm Reconnect to the network and improve the signal
- 3
A frozen thermostat
What separates it It does not respond
How to confirm Restart it by holding the ring button
- 4
Low power or no C wire
What separates it It restarts or drops Wi-Fi
How to confirm Replace the AAA batteries; check wiring
- 5
The app showing the wrong home or account
What separates it The wall unit is online but the app says offline
How to confirm Check the account and the home
Before you touch a setting
Record this first — changing settings destroys the evidence
- What the thermostat's display shows when touched
- What the Wi-Fi status says
- Whether the batteries are fresh
- What the app shows
Try in this order
0 of 6 completedWake the display
ReversibleTouch the ring.
Check Wi-Fi status
ReversibleIn the settings.
Restart the router
ReversibleAnd the thermostat.
Replace the AAA batteries
ReversibleAs a first power step.
Reconnect the network
ReversibleIf it changed.
Contact Google
ReversibleIf it stays offline.
Model-specific
What is true of this model and not of its siblings
- A mirrored display
- It looks blank when asleep.
- Wi-Fi
- It joins 2.4 and 5 gigahertz networks.
- Power
- HVAC wires plus AAA backup.
- The C wire
- Heating-only systems may need one.
- Matter
- It can be controlled from Matter platforms.
- Google help
- Quote the model.
Stop boundary
When this stops being a self-service repair
- !Switch off the HVAC breaker before touching wires
- !Do not remove the thermostat's wires without noting them
- !Contact an HVAC technician for power problems
Evidence ledger
Sources behind this answer
Exact questions
Common questions
Why is my Nest Thermostat offline?+
A connection or power problem.
Is a blank screen a fault?+
No, it looks like a mirror when asleep.
How do I restart it?+
Hold the ring button about ten seconds.
Are the batteries replaceable?+
Yes, two AAA alkaline cells.
Does it need a C wire?+
Usually not, but some systems do.