Google groups E298, E448, and M20 as Nest thermostat no-power alerts on supported models.
What E298 / E448 / M20 means
Google groups E298, E448, and M20 as Nest thermostat no-power alerts on supported models.
What you may notice
- The display shows a no-power alert
- Heating or cooling is unavailable
- The thermostat may use battery power
- The app may report the device offline
Most likely causes
- 01The HVAC breaker is off
- 02The service switch is off
- 03A common-wire or power-connector issue
- 04An equipment safety switch opened
- 05A transformer or control board failed
Safe checks, in order
Start with the simplest non-invasive check. Stop as soon as the error clears; repeated resets can hide a condition without correcting it.
Verify system power
Check HVAC breakers and the equipment service switch.
Confirm panels are closed
A furnace-panel interlock may interrupt power when a cover is open.
Wait after restoration
Give the thermostat time to recharge and reconnect.
Use the official troubleshooter
Follow Google Nest model-specific guidance before changing wiring.
Know where to stop
Turn off HVAC power before touching wiring. Never bypass a safety switch to make the alert disappear.
When to call a technician or support
Call an HVAC professional if power is present at the equipment but the thermostat still reports no power.
When you call, have the exact product or vehicle model, model year where relevant, the complete code or symbol, and when it appeared.
Where this information came from
We use the manufacturer's current published guidance as the starting point, then organize it into a safer, beginner-friendly sequence.
Google Nest Help — no-power alert Source last checked August 16, 2026. Manufacturer instructions and model manuals take priority over this independent summary.