Google Nest Thermostat Error Code E25: How to Fix It

Q: Why does my Nest thermostat show E25 error after a power outage?

After a power outage, the internal battery may be drained. Simply remove the thermostat and charge it via USB for 30-60 minutes. Once charged, it should work normally.

Q: Can I use any USB charger to charge my Nest thermostat?

Yes, a standard USB charger (5V, 1A or higher) works fine. Avoid using a fast charger that outputs more than 2.4A unless the thermostat is designed for it.

Q: How do I check if my Nest has a C-wire?

Remove the thermostat from its base and look at the wire labels. If you see a wire connected to the 'C' terminal, you have a C-wire. If not, your thermostat is not receiving constant power from the HVAC system.

Q: Will the E25 error damage my thermostat?

No, the error is a low battery warning. However, frequent deep discharges can shorten battery lifespan. Ensuring proper power via a C-wire or regular charging can prevent this.

Q: How long does the Nest thermostat battery last on a full charge?

If properly connected to a C-wire, the battery stays charged indefinitely. Without a C-wire, the battery may last several months depending on usage and power harvesting efficiency.

Abstract

Error code E25 on your Google Nest thermostat means the battery voltage is too low for normal operation. This often happens due to insufficient power from the HVAC system or after a loss of power. Follow these steps to recharge the battery and ensure your thermostat stays powered.