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Do Smart Thermostats Use Batteries?

We’re all aware of the numerous advantages that come with battery-powered gadgets, which are often worth more than the annoyance of having to replace them every so often. 

Do smart thermostats use batteries?

In general, smart thermostats have internal batteries used to supplement if your HVAC system can’t deliver enough power or are used as backups and maintain constant voltage for the thermostat’s electronics. A backup battery in a thermostat will protect any programmed routines or settings from being erased.

Batteries are, overall, both safe and dependable. Since some thermostats don’t need an external power source to retain their settings, you will never have to worry about data loss due to a power outage again…as long as you choose the right one.

Let’s look at everything you need to know about smart thermostats and which ones have batteries. We’ll look at how to swap the batteries when they need to be changed, as well as some of the best smart thermostats on the market with battery backup. 

If you want to upgrade your home’s HVAC system with a new smart thermostat, this is how you should plan ahead. This will give you peace of mind so that if you decide to upgrade, you’ll be aware of all your choices. 

Read Also: How to Unlock a Honeywell thermostat? Easy Unlocking Hacks

Do Smart Thermostats Use Batteries?

Do Smart Thermostats Have Batteries? 

Smart thermostats receive their power from the HVAC system via the common wire and use internal batteries to regulate power flow as a backup. These batteries are typically not meant to be replaced by the homeowner although there are a few exceptions.

The most popular Smart Thermostats that have replaceable batteries are covered later in this article.

These batteries will not operate the HVAC system when the power goes out, and they’re mostly helpful for storing thermostat settings and diagnosing issues generated by the thermostat.

The “C” or common wire allows the thermostat to power itself instead of being powered by batteries, and it must be connected to the C or common terminal on the furnace control board.

C-wires are often not available in older homes. The majority of houses constructed in the 1980s and after are wired with a common wire. It is pretty simple to determine whether you have a common wire. You may check at your thermostat by removing the front cover to see how the wires are connected.

Most companies provide a C-wire power adapter if you don’t have a C-wire. This adapter is installed at the furnace, where the thermostat is connected. It will give power to your thermostat using the current wiring.

“The C-Wire Power Adapter Quickly and easily powers connected thermostats that require a c-wire (common). It provides a C wire (common wire) to power a thermostat. Only install if you do not have a C wire available to connect to your thermostat.”


Like any other electrical component, there are different types of smart thermostats to choose from according to your requirements. None of the major smart thermostat brands have replaceable batteries, but they all have internal batteries. This includes Google Nest, Ecobee, Honeywell, and Amazon smart thermostats.

What Type Of Smart Thermostats Use Batteries? 

There are many different types of smart thermostats, including basic Wi-Fi connected versions and more complex models with sensors that allow remote control functions, geofencing capabilities, and those that come as a part of a more extensive home automation system.

Almost all the trusted smart device brands, including Honeywell, Google Nest, Amazon, and Ecobee, have highly rated thermostats with backup batteries built-in. These batteries are not intended to be replaced by the end-user.

That said, here is what replacing a battery in a Nest E Thermostat looks like.

Having a battery-backup thermostat ensures that your data will be saved, and there will be no interruption to the thermostat’s function even if there is a power failure in the main power supply of your home. 

Which Smart Thermostats Have Batteries?

Almost all the major brands of smart thermostats have backup batteries included in the design. This includes Google Nest, Honeywell, Ecobee, and Amazon. If you are looking for a reliable smart thermostat with battery backup, these are some of your best options.

While most have batteries that are not meant to be swapped out by the user, there are a few.

Smart Thermostats With Replaceable Batteries

Here are the smart thermostats with replaceable batteries:

Google Nest Thermostat 

The Nest Thermostat is designed to be a budget option, although it is loaded with smart features.

First, it has two-AAA batteries that can easily be replaced. These batteries provide a battery backup and help supplement the thermostat when the HVAC system isn’t providing enough power to the thermostat.

Here are some notable features:

When you’re away from your home, the Nest Thermostat can lower to save energy both away and at home.

In addition, you can change the temperature wherever you are using the Google Home app.

The Nest Thermostat is built to be installed by you. The procedure is typically completed in 30 minutes or less, and it can be accomplished with only one person.

The Nest Thermostat Monitors your HVAC system. Get alerts and reminders about your heating and cooling system, such as when it’s time to change the filters. Also, HVAC monitoring can help identify many HVAC issues early. If something seems wrong, it can send an alert.

 Emerson Sensi Wi-Fi Smart Thermostat 

The Emerson Sensi is a smart thermostat that comes from a little less known brand but is still highly rated.

It has two-AA batteries that can easily be replaced. The batteries must be installed for the thermostat to connect to a wireless network, which is crucial for making it a “smart” thermostat.

The Sensi works with all major assistants such as HomeKit, Alexa, and Google Assistant.

It’s simple to install and requires a C-wire or an adaptor in order to be effectively powered and linked to existing HVAC systems.

Emerson Sensi Smart Thermostat (on Amazon) is capable of sending you maintenance reports on a regular basis, including filter replacement notifications, which will aid you in keeping your HVAC system up and running at optimal performance and help prevent costly repairs.

You also get all the expected smart features with the Sensi – flexible scheduling capabilities, remote access, and accurate usage reports. 

You also get all the expected smart features with the Sensi. It maintains its simplicity while still providing all of the smart features that you’ve come to expect. You get detailed usage data, various control options through your phone or preferred voice assistant, and flexible scheduling capabilities.

Smart Thermostats With Internal Batteries

Here are some of the highest-rated smart thermostats with internal batteries, not meant to be replaced:

Google Nest Learning Thermostat 

With a rotating bezel to control functioning and an impressive energy-saving mode, the Google Nest Learning Thermostat (on Amazon) is one of the best smart thermostats out there. The Nest Learning Thermostat uses internal batteries to operate, and they are charged by the main power supply.

The batteries are continually charged since they are connected to a continuous power supply. If the backup batteries do go bad, you may start noticing problems.

Related Content: Do You Need an Electrician to Install A Nest Thermostat?

The Nest Learning Thermostat is the first thermostat to get ENERGY STAR certified. The Energy Star certification on the Nest Learning Thermostat means that it can help you save energy while also cutting your energy costs and protecting the environment. 

Moreover, if you are into having smart devices in stylish colors, Nest Learning Thermostat comes in seven sleek colors. You can view them on Google’s product page here

Honeywell Home T9 Smart Thermostat 

The Honeywell T9 Smart Thermostat (on Amazon), which has add-on sensors, has all of the outstanding elements of a smart thermostat packed into a sleek-looking device.

The T9 has geofencing capabilities so that your house is at just the right temperature when you get home after a long day of work while also conserving energy when you’re away.

With the Honeywell Home app, you can manage all of your heating and cooling demands that we’ve mentioned, as well as adjust schedules and select temperature targets for specific rooms using the remote sensors.

Honeywell’s smart room sensors may be installed in rooms where you wish to maintain a specific temperature. I have sensors in my kids’ rooms and in my master bedroom. 

There is a multi-room display option in the Honeywell Home app, also viewable on the thermostat itself, that allows you to set up specific schedules for which rooms you want to be heated or cooled and at what times.

ecobee3 Lite Smart Thermostat 

This thermostat is the one I personally prefer and use. It also happens to be one of the most popular thermostats, next to Google’s Nest. 

This smart thermostat is equipped with all the features you could expect, except it does not have a microphone built-in. I prefer this, so I don’t have problems with my other speakers when giving voice commands. 

The Ecobee works excellent with all the popular voice assistants, including Apple HomeKit, Alexa, and Google Assistant. 

With Energy Star approval and monthly usage reports, the Ecobee 3 Lite keeps energy conservation on the mind and helps to guide you on how to save more. 

The device’s vacation mode allows you to control your property’s temperature from wherever you are going. As expected, you may program your heating and cooling needs to meet the times you are at home and away, allowing you to be more flexible with your energy usage.

ecobee3 Lite can send an alert if the temperature drops unexpectedly or gets too hot, allowing you to change the temperature as needed and alerting you to potential problems.

Ecobee thermostats also integrate with a range of sensors they produce, from room sensors to windows sensors. The room sensors detect if you are in the room, the temperature, and humidity, and this allows the thermostat to make smart decisions about if a room needs climate control or not.

There’s also a new feature with the ecobee3 Lite that cuts off the thermostat when a window or door is open. Now you won’t waste energy having the HVAC system on when a window or door is open. Also, you can track which windows are open.

Amazon Smart Thermostat 

The Amazon thermostat is designed to be cheap and does not have all the features as the other thermostats on this list.

The Amazon smart thermostat is manufactured by Honeywell and is based on the same technology used in their Honeywell Home Smart Thermostats. 

The Amazon Smart Thermostat is basic with a simple, minimalist design and an easy-to-use touchscreen display.

It’s simple to set up, configure, and use with the Alexa app and, as expected, works well with Alexa voice commands. The Amazon Smart Thermostat is Not compatible with Google Assistant or Apple HomeKit.

Is there a battery-powered Nest thermostat?

The Google Nest Thermostat is powered by two AAA batteries that can be replaced by removing the thermostat from the wall. This is not to be confused with the Google Nest Learning Thermostat which does not have replaceable batteries.

Do wireless thermostats have batteries?

In general, smart wireless thermostats are powered by the connected wires coming from the furnace. There are a few models that are powered by AA or AAA batteries.

How Do I Change The Batteries In My Smart Thermostat?

If you choose to purchase a smart thermostat that uses replaceable batteries, there will be a time that eventually comes when those batteries need to be replaced.

When the batteries of your smart thermostat need to be replaced, you will usually get a notification in the app and a low battery warning the thermostats. 

When that low-battery warning shows up, there’s no rush. The smart thermostats on the market today provide ample warning well ahead of time, so you won’t have to worry about your battery dying suddenly.

For example, Honeywell battery-operated smart thermostats have a 60-day warning period before the batteries run out. 

While specific thermostats may vary slightly, here are general instructions for replacing the batteries of a smart thermostat:

  1. Use the main circuit breaker to turn off the power to your smart thermostat as a safety precaution.
  2. Remove the thermostat from the wall mount by pulling it straight out from the wall.
  3. Replace the old batteries with new batteries. The thermostat may power on at this point. 
  4. Slide the thermostat back onto the wall mount. 
  5. Turn the breakers back on to supply power to the thermostat. 

The thermostat should be on and function at this point after it boots. Test it out and make sure it works properly. 

Guidelines to replace the battery in a Nest Thermostat:

Here are the instructions from Google:

  1. Pull the thermostat display off the base.
  2. Remove the old batteries from the back of the thermostat display.
  3. Insert the 2 new AAA alkaline batteries.
  4. Push the thermostat display back onto the base until it clicks into place.

Guidelines to replace the battery in an Emerson Sensi Thermostat:

Here are the instructions from Emerson:

  1. Grab the face plate with both hands and pull it straight towards you. After a tug, the face plate will detach from the sub-base.
  2. Remove the 2 AA Alkaline batteries from the face plate.
  3. Allow the front display to go blank.
  4. Insert 2 fresh AA Alkaline batteries, and push the face place back onto the sub-base. You’ll hear a snap when it is pushed on securely.

How Do I Know What Batteries To Put In My Smart Thermostat?

The battery compartment on the thermostat will state which size batteries to use and which direction they should be installed. 

Most smart thermostats use two AA or AAA alkaline batteries. If you are unsure before you begin, make sure you have the correct battery for your device by consulting the manufacturer’s user guide.

With smart thermostats today connected to a mobile app, you won’t have to worry about missing a low battery alert since you’ll receive it as a notification on your phone with information about which batteries should be used.


All leading smart thermostat brands have different models with specific functionalities to match the demands of different uses. Most often, there is an economy version for those getting started, and then there is the premium model with all the features. 

All smart thermostats are going to be hard-wired to a certain extent. They are directly powered by the HVAC system with the help of a C-wire, which provides a continuous power supply. Some smart thermostats have batteries to supplement that power.

There are no smart thermostats that use batteries as their only power source. The wireless connection would drain batteries too quickly.

If your home comes with a smart thermostat, chances are that it is already hard-wired to the system.

If you wish to install a new smart thermostat to your existing HVAC system in a home built before the 1980s, expect to have to install a C-wire adapter to power the smart thermostat.

Recommended read: 

How to Charge the Nest Thermostat? Some Effective Ways

How to Unlock a Honeywell thermostat? Easy Unlocking Hacks