How to Charge Nest Thermostat with & without C-Wire


Today we will learn how to charge Nest Thermostat and fix low-battery issues. The Nest Thermostat receives power from your HVAC system and you can control it from your phone.

You can control the temperature setting by using a simple app in two different rooms. As a homeowner, I personally use Nest Thermostat but after a couple of years, it starts causing a little trouble.

I observed that my Nest Thermostat constantly gave me indications of low battery and was not charging. But the good part is you don’t need to call a professional to fix the issue you can do it on your own by reading this article.

You can try troubleshooting the HVAC system and Nest by powering the thermostat with a C-type wire adopter. Or else you can charge the inbuilt battery.

How to Charge Nest Thermostat with USB

When your thermostat indicates the sign of battery is low, use the USB port back of the Nest Thermostat. 

  • Remove the thermostat display.
  • Plug it into the USB port which you use to charge your phone or in your computer device. 
  • A light will start blinking in front of your thermostat and that’s the confirmation of charging. And, the color of the light depends on the percentage or level of charging of your thermostat. It normally takes half an hour to charge the battery but if the batteries are fully drained, it may take up to 2 hours to charge fully. 

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How Does the Nest Thermostat Battery Work?

Nest Thermostat Battery

The Nest Thermostat battery is charged by pulling the power from the HVAC system and it contains a 380 mAH lithium polymer battery. It works when there is no power in the HVAC system or a power outage that charged battery keeps the thermostat running. A backlit display and wi-fi activity are two other features the nest thermostat comes with. 

Does Nest Thermostat Come With In-built Battery?

Nest thermostats have three generations and all of them come with in-built batteries. You can charge these batteries with Rc or Rh wires directly from your home’s HVAC system.

One common C-wire is used to complete the circuit. The HVAC system continuously charged the in-built batteries and Nest Thermostat will work continuously even when the HVAC system is off for a longer period of time.

In some cases, the thermostat batteries are not charged because there is no power in Rh or Rc wire. In-built batteries are very helpful in a long power cut or when there is no direct supply to the HVAC unit. 

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When Does Your Nest Thermostat need to be Charged?

In some models of Nest Thermostats red light blinks and which indicates of low battery, some flashes a message on the screen device battery is low. When you find these indicators that clearly means you need to charge your Nest Thermostat right away. You can charge this with a USB cable. If you don’t plug in the charge, you will face these issues:

  • The Nest’s display will be unresponsive or won’t work.
  • Your device won’t be able to manage the cooling or heating functions of your HVAC. 
  • Your home’s Wi-Fi connection with your Nest will be disturbed. 
  • You can’t operate the Nest from your app or can’t adjust the temperature. 

To keep away from this kind of issue, you have to charge your Nest device once you get an indication of a low battery. 

Battery Life of Average Nest Thermostat

The in-built battery for Nest Thermostat can run from a few hours to a couple of days. The battery life of Nest Thermostats depends on the power supply they receive from the HVAC system.

If these in-build batteries charge on constant steam power continuously, these batteries can last 5 to 10 years. In some cases when batteries do not receive a sufficient charge, the batteries start falling in two years. Nest device comes with replaceable AAA batteries which can last up to two years. 

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How to Charge Nest Thermostat

We can charge our Nest Thermostat in many ways but it’s important to check a few things before charging. Your Nest Thermostat should charge automatically when working properly with HVAC power.

#Check the Switch On or Off

Nest Thermostat Switch

First and most important you must check if the switch is on or off, I know this sound very simple but trust me many people whom I know thought, their thermostat has broken. The HVAC system has its own switch which controls the power, you must check that is on.

When this switch is on the Nest starts charging itself. This is a simple and common problem that happened to thousands of people. If in your area power has been off for two or three days then Nest may take a couple of hours to recharge. 

#Remove & Charge

If your Nest Thermostat is not charging then you take off the Nest from the wall and try to charge off the wall. This will help you to detect any issue in the Nest (loose or cut Nest wiring, HVAC problem).

If your Nest is still not charging, then try with your phone charger to charge the Thermostat. You will need just a Micro USB Cable or Cable & Charger for your Nest. Put the USB cable in the charging port of the Nest and once it starts charging, hang the Thermostat on the wall.

#Use a Common Wire

Nest Thermostat C-wire

Take off your Thermostat from the wall and plug the wire manually but make sure your HVAC system is on. Put your Thermostat back on the wall and check the status now, if your Nest is not charging or showing a battery low indication that means you will need to add a common wire transformer. When your HVAC system is not providing enough power to your Nest then a common wire transformer is used. 

#Battery Replacement

In extremely rare cases, you will need to change your Nest batteries. I will never suggest you replace your Thermostat battery until you went through all the troubleshooting and confirmed that only the battery is the solution. Here is the entire guide on how to replace your Nest Thermostat battery.

You can purchase a new battery from Walmart

How Long to Charge Nest Thermostat

The simple answer to this question is, it would take only 30 minutes but

sometimes it can take up to 1 hour if the battery is completely drained. If the battery level is below 3.6V then your Nest might lose its wi-fi connection.

When the power is on Nest start charging itself but if you are going outside for a few days it may lower the battery level. Suppose your power goes out, in this case, Nest Thermostat can work for up to 2 to 3 hours (it depends on the model of the Nest).

One of the most common questions is when it should be charged? The simple answer is when you operate your Nest via a mobile app, you get a notification to charge the Nest. Simply put the charger into the USB port and charge your Nest.

How to Charge Nest thermostat without C Wire

Nest Thermostat requires a C wire for consistent power but Nest is designed to work without a C wire in most homes. The Nest Power Connector is the best and alternative option to a C wire.

And, the important thing is it will cost you less than hiring an electrician and installing a new C wire in your walls. Another alternative to charging your thermostat with C wire is buying a new Nest Thermostat without C wire.

  1. Google Nest Thermostat E
  2.  Ecobee Lite SmartThermostat
  3. Google Nest Learning Thermostat
  4.  Sensibo Sky


Anyone can use Nest at their home for an enjoyable experience and you can control it with just one click from your phone. Nest thermostat provides you with a new option to control or maintain the warm or cool temperature within your house.

The thermostat allows you to know when you are economical and help you to save money. Nest also helps you to control house temperature when you are not at home. From outside of your home, you can just simply control it with one app. 

Questions & Answers

Does Nest thermostat need charging?

Yes, its needs charging the thermostat battery is charged by pulling the power from your HVAC system. It works when there is no power in your HVAC system. It also contains a 380 mAH lithium polymer battery.

How do I fix my Nest thermostat with low battery?

You should charge your inbuilt batteries if that’s not working then you should try to troubleshoot the wire connection between your Nest and HVAC system by powering the thermostat with a C-type adapter. 

How do I charge my Nest thermostat battery?

There is a USB port on the back of your Nest when a battery is low put the charger in that USB port. First, take off the Nest display and plug it into the USB port on the wall that you use for your phone. 


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