What Power Supply Does a Nest Thermostat Need?

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A Nest thermostat is a smart electronic device that not only allows users to remotely control the temperature of their homes but also can learn your schedule and temperature preferences. Because they can be controlled via mobile devices or laptops. But all these smart features will be useless to you if you do not have the correct power supply, so what does the Nest thermostat need to function?

The nest uses a rechargeable lithium-ion battery, but what is really important for the user to know is that this device does not operate without an AC power supply (110V/120 VAC ~ 50/60Hz). If AC power is lost for too long, the battery will deplete itself, the device will lose all your settings, and your Nest thermostat will need to be reconfigured.

In this article, we will discuss the type of power supply that the Nest Thermostat uses, how your thermostat communicates to your HVAC system and the ramifications of moving your Nest Thermostat to a different location.

How Is a Nest Thermostat Powered?

The Nest Thermostats have two main power supplies: the battery itself and the common wire that runs from your thermostat all the way to your heating, ventilating, and air conditioning unit outside, in your attic, or wherever you have it installed in your home.

How Does the Nest Thermostat Battery Work?

The battery supply comes from a rechargeable CR2 lithium-ion battery, which is included in when you purchase your Nest Thermostat. Here’s how it works:

  • The lithium battery, though necessary to run the thermostat, is not the main power source.
  • This included battery simply gains its charge from the common wire which is connected to your HVAC system (which we will learn about shortly).
  • If for any reason the system loses power, the battery will be able to keep your home set at your requested temperature for about an hour or two. 

Now, let’s learn a little more about the true main power source: the HVAC system. 

How Does the HVAC System Work with the Nest Thermostat?

The main power supply for the Nest Thermostats is the common wire that runs to your unit. When your HVAC system was installed initially, a special electrical line made up of a collection of wires, was run from the unit to the ideal location for your thermostat or thermostats, usually near your HVAC return registers (the place where you put your air & furnace filters).

This electrical line is usually installed alongside your ductwork, and sometimes in it, for easier location of the line and access to it in the future. The other wires attached to the common wire directly connect a thermostat to the HVAC unit to control its operation based on the temperature setting for the house.

If you were to cut the common wire, remove the Nest Thermostat from its wall mount, or cause any interruption in the circuit for too long, the rechargeable battery in the Nest Thermostat would shut down from lack of power. This would cause your Nest Thermostat to reset and you would lose all your saved temperature data that it uses to intelligently manage your home temperature while saving you money on your energy bills.

Will Moving the Nest Thermostat Impact the Power Supply?

The location of your Nest Thermostat is extremely important to your temperature settings and the performance of your system. After the initial installation, some people might consider moving the thermostat to a different location in the house to fit their needs. However, you should think twice before attempting a move, as you could encounter one or both of the following problems.

  • You could confuse the thermostats communication with the HVAC system itself. The Nest Learning Thermostat will need some time to acclimate to the new location before it can efficiently heat and cool your home to your desired temperature.
  • You may need to rewire the entire system. There is a special type of electrical line made up of several wires that connects your thermostat to your HVAC unit. Moving your Nest Thermostat might require you to run a new electrical line from the HVAC unit to the new thermostat location.

Instead of moving the thermostat itself, you may want to invest in a Nest Temperature Sensor. Nest Temperature Sensors can be placed in different areas of your home and will communicate with your Nest Thermostat to help meet your comfort needs while saving you on energy bills,

If you decide to move the location of your Nest Thermostat, you should contact a licensed HVAC professional to inspect your in-home setup and the new proposed location of your thermostat. HVAC professionals will make calculations based on the size of your house, where the rooms are situated, and where the air return registers are located to provide the best location for the thermostat. They will also be able to run the new line for you.


Nest Thermostats are one of the best options for smart home automation for your HVAC system. The only real drawback of a Nest is that it requires an AC power source and a direct connection to your HVAC unit to function properly. If you are thinking about buying one, make sure you can run AC power to the location you wish to install it in.

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