5 Easy Steps to Fix Nest Thermostat Low Battery Problems

by Phil Borges // in Nest

How many times have you walked into your living room and seen that the Nest Thermostat battery is off? You frantically try to turn it back on, only to find out that the battery in your Nest Thermostat died.

You are probably wondering then, why does your Nest thermostat have low battery problems, or why your Nest thermostat won’t charge?

Many people have been complaining that charging a Nest Thermostat doesn’t work for as long as it used to.

The good news is that there are easy things to check and fix right at hand.

So what can you do, once Nest low battery problems have been identified? Fixing the problem is actually pretty simple.

The purpose of this article is to explain why your Nest thermostat battery won’t charge or could be draining so quickly, and more importantly what steps YOU can take to resolve the problem immediately.

Understanding the Use and Features of a Nest Thermostat

Nest thermostats are a smart home device that is popular in the market today which can control the temperature of your house, as well as turn off or on at certain times. It is designed to be easy to use and allows you to control your heating and cooling system at home.

The Nest thermostat has been designed with great features that will help you keep your home at the right temperature even when you are at work or out of town.

These features range from a remote control, energy monitor, and auto-schedule. Most Nest thermostats have a battery back up which will allow the device to continue to function when there is a power outage.

They are easy to install and program, so if you’re a techie person, you’ll be able to have it up and running in no time.

What to do when it displays a low battery warning?

One of the most frustrating things about this is when your Nest says low battery or when it displays that dreaded low battery warning. And while there are many reasons for this, they all boil down to one big problem: your base unit isn’t fully charging your thermostat.

When it displays a low battery warning, you should do the following:

Step 1: Find out why your Nest thermostat battery won’t charge. This could be the result of a faulty rechargeable battery, but there are other possibilities as well.

It is not a difficult process to replace the batteries in your original Nest Thermostat.

To do so, detach it from its base and then simply swap out two AAA alkaline quality cells for the old ones with new energy-efficient power sources. Make sure you only purchase high-quality replacement products as anything else could cause damage or malfunction of this device which may be costly to repair.

Step 2: Try to manually recharge the faulty battery before trying anything else as an alternative way to test.

You’re in luck if the warning has gone and if this remains off for a few hours. The sealed unit usually lasts at least five years.

Nest Thermostat: Power Source

The Nest Thermostat, in the simplest of terms, is a programmable thermostat that learns your habits and adjusts accordingly. One of the most frequently asked questions about the device is “where does it get power?” The answer might surprise you.

The Nest Thermostat has an electrical plug that is attached to the wall of the room in which it is installed. When you install a nest thermostat, make sure you know where your fuse box and main circuit breaker are located so that there will be no surprises when you need to restore power.

As soon as it is plugged into a base unit, the Nest thermostat battery recharge begins or it receives power and sends out an electric signal to let you know that everything’s in working order.

The Nest is designed to be an energy-efficient device, and so it takes power from the HVAC control connections in your home.

5 Easy Steps to Fix Nest Thermostat Low Battery Problems

1.Charging the Nest Thermostat Manually

You may need to charge manually if the nest thermostat has low battery, has been kept in the storage, or when the HVAC is not functioning.

Nest units are usually pretty good about staying charged, but sometimes they need a little boost to get ’em goin’. If the Nest thermostat battery voltage drops below 3.6 volts (not so much of an issue if it’s not in use), your Nest unit may be too out-of-it for you to utilize its features and recharge from the base unit.

In this case, we recommend getting some extra juice going by giving your nest that extra push with one brand new charger.

With the help of a phone charger and micro or mini USB cable, it’s easy to recharge your battery by using its charging point on the rear. Just simply, pull the unit away from its base, plug a phone charger into an outlet and connect it with a cable that goes on both sides of the device until the red light stops blinking. This process should take roughly thirty minutes or two hours.

2.Installation of a C wire also known as a common wire

To ensure the safety of your furnace during installation:

  • turn off the power and remove Nest
  • check if there is a wire connected to the C connector; make note of color for future reference. Now, look at connections on the furnace.
  • make sure you have the same color wire connected to both the thermostat and furnace C terminals or else it will not work properly unless there’s a new cable run in between them.
  • when a new cable has been installed, make sure to connect the C connector on your Nest thermostat and the C terminal of your furnace. Reattach the Nest before making sure that it is working correctly with power from an electric source.

3.Solution when C wire is missing

If you find no common wire connected to the bottom of your Nest base unit, maybe there’s an easy solution. Older HVAC systems required a fan control cable and modern ones don’t need it. We can take advantage of this design by using that cable for our battery charging circuit! We can use the fan cable to connect your battery and give it a power boost.

4.Use a C wire transformer as an alternative option

If you remove the Nest from your base unit and find no C wire, it is possible to get a reliable power supply by using an inexpensive 24Vac transformer. This will allow the thermostat to keep working by performing the following:

  • It is important to switch off the power for safety reasons. Carefully detach the Nest thermostat from its base unit and insert its transformer cables behind it and out through a hole in the center of its backside. If there are any other cords connected, disconnect them as well-and tie anything that needs be safe away with their own cord ties.
  • Attach one cable of the transformer to the Rh connector, connect the other one to the C connector and plug the transformer into the outlet and try it on.
  • Don’t forget to test it out. Check the indicator light on. If everything is working properly, this should start flashing shortly.
  • You don’t want to find out the hard way that those tangled cables are a fire hazard. You should tidy them up so they’re not running in your wall or wadded behind furniture.

5.Reset and Restart Setting

The Nest thermostat, which is known for its sleek design and easy interface, had an error with the software that caused it to stop working. The battery stopped charging and eventually drained out.

Here’s what you will do if the above happens:

  • If the battery is drained out, you have to recharge it.
  • From the main menu, choose the reset or restart function.
  • Just remember, If you are not sure which option to choose, the restart will keep your data. If this does not work for you or if it is just a short-term fix and want everything deleted then choosing factory reset may be what’s needed.


When the power goes out, how long will the Nest thermostat last?

A single charge lasts between one and two hours while offline.

What is the Voltage for a Nest Thermostat?

For the Nest Thermostat to work correctly, you need a 24-volt AC power supply that can usually come from HVAC system or an extension cord plugged into your wall outlet.

How can I tell that I am charging Nest thermostat correctly?

A quick glance at your thermostat will let you know if it is charging. A blinking red light indicates that the battery is being charged. Blinking stops when it is fully charged.

When to consider Nest thermostat battery replacement?

Thermostat battery replacement maybe required when your thermostat regularly displays low battery warnings.


The Nest thermostat is a great device that can save you money on your energy bill.

It is one of the most technologically advanced and helpful devices you can buy, fast, accurate, easy to use – it gives you everything that you need to be comfortable at home.

Nest thermostat battery problems can be frustrating to deal with but ignoring it can be more costly. The next time your Nest thermostat says low battery check it once, conduct test regularly and you’ll never have to worry about being put out in the cold by a device that refused to work for you.

We hope that this article has helped you to resolve some issues with Nest Thermostat low battery problems.

About the author, Phil Borges

Phil Borges is a battery aficionado. He's written extensively about batteries, and he loves nothing more than discussing the latest innovations in the industry. He has a deep understanding of how batteries work, and he's always on the lookout for new ways to improve their performance.