Important: This article only applies to the Nest Thermostat. Learn how to tell which thermostat you have.
The Nest Thermostat receives power from your HVAC system. It also uses 2 AAA alkaline batteries as a backup, or to supplement if your system can’t deliver enough power.
You can’t replace the batteries for the Nest Thermostat E or Nest Learning Thermostat. Instead, charge the thermostat with a USB cable.