Article Summary:
Sometimes you might turn off the power to your heating and cooling system in your home or in your vacation home to save energy. The Nest Thermostat relies on the power from your heating and cooling system to keep its battery charged, so if you turn off the power, your Nest Thermostat won’t work.

When you turn off the power to the heating and cooling system (or when it is off because of a power outage), your Nest Thermostat loses the ability to charge its battery and will eventually shut down to prevent the battery from being fully drained.

Before it shuts off, you will likely see one of the following error messages on the Nest display:

• E3
• E4
• E23
• E24

When your heating and cooling system is turned back on, your Nest Thermostat should start right up. However, if your system was turned off for an extended period of time, when you restore power to your heating and cooling system the Nest Thermostat will need to recharge before it turns on, possibly up to 3 hours.

While the Nest Thermostat is recharging its battery, you’ll see a blinking red LED in the lower right of the Nest display.

My Nest won't wake up and has a red blinking LED on the display