Your Nest thermostat runs on two AA batteries that last about two years
When your Nest thermostat battery gets low, the display shows a lightning bolt icon and you'll get a notification on your phone. The battery compartment is on the back of the device, behind the round faceplate. You don't need any tools — just two fresh AA batteries, a few seconds, and the ability to pop the faceplate off.
The whole process takes less than a minute. Your thermostat will keep working while you swap the batteries because it has a small backup battery inside, so you won't lose your settings or heating schedule. After you insert the new batteries, the lightning bolt icon disappears within a few minutes.
Nest thermostats come in a few models — the Learning Thermostat, the Nest Thermostat E, and the basic Nest Thermostat — and they all use the same battery replacement method. If your model is hardwired to your home's electrical system, the AA batteries are a backup only and last much longer because they rarely get used.
Key Takeaways
- The battery compartment is on the back of your thermostat, accessed by gently pulling the round faceplate straight toward you.
- You need two AA batteries; alkaline batteries (like Duracell or Energizer) work fine and last about two years in most homes.
- The thermostat keeps running on its internal backup battery while you swap the AA batteries, so your schedule and settings stay intact.
- A low battery shows as a lightning bolt icon on the display and triggers a phone notification, but the thermostat continues to work until you replace them.
- If your thermostat is hardwired to your home's electrical system, the AA batteries are a safety backup and may last five years or longer.
How to remove the faceplate and access the battery compartment
The round faceplate of your Nest thermostat is held on by a magnet, not screws or clips. Stand in front of the thermostat and place your fingers on the outer edge of the faceplate — the part that sticks out slightly from the wall. Pull straight toward you with steady, even pressure. The faceplate will come free after a second or two.
Don't twist or pry at an angle. If it doesn't come off easily, you're probably pulling at the wrong spot. The magnet is strongest around the outer ring, so grip there and pull straight out. Once the faceplate is off, you'll see the back of the thermostat, which is a flat metal or plastic surface with the battery compartment visible.
Set the faceplate down somewhere safe where it won't get scratched or lost. You'll be putting it back on in just a moment.
Removing the old batteries and inserting new ones
The battery compartment holds two AA batteries side by side. You'll see a small rectangular slot with two metal contacts at the bottom. The batteries sit with their positive ends (the flat end with the + symbol) facing down toward those contacts.
Push down gently on the top of each battery and it will spring up slightly — this is the easiest way to get them out. Grab each battery and pull it straight up and out of the slot. If a battery is stuck, push down a little harder; the spring mechanism will release it.
Take your two fresh AA batteries and insert them with the positive end facing down into the contacts. You'll hear or feel a small click when each battery seats properly. Make sure both batteries are pushed all the way down and sitting flat in the compartment. If one battery is higher than the other, it won't make good contact and your thermostat may not turn on.
Putting the faceplate back on and checking the battery status
Align the faceplate with the body of the thermostat. The magnet will pull it into place as you push it gently back onto the device. You don't need to force it — the magnet does the work. Push straight in until you hear a soft click or feel the faceplate seat flush against the wall.
Within a few seconds, the display will light up and show your current temperature and settings. If the lightning bolt icon is gone, the battery replacement was successful. If the icon is still there, one of the batteries may not be making contact — remove the faceplate again and check that both batteries are pushed all the way down.
Your phone will receive a notification within a few minutes confirming that the battery is now good. If you don't see this notification after five minutes, restart your phone's Nest app by closing it completely and opening it again.
What type of batteries work best
Any standard AA alkaline battery works in your Nest thermostat. Duracell, Energizer, Amazon Basics, and store brands are all fine. Alkaline batteries last about two years in a thermostat that's not hardwired, or much longer if your thermostat is hardwired and the batteries are only a backup.
Rechargeable AA batteries (NiMH) can work but are not recommended by Nest because they have a lower voltage and may cause the thermostat to show a low battery warning even when they're fully charged. Stick with alkaline batteries for the most reliable performance.
Don't buy premium batteries thinking they'll last longer — a standard alkaline battery is all your thermostat needs. The device draws very little power from the batteries, so the difference between a basic battery and an expensive one is not worth the extra cost.
Why your thermostat has batteries even if it's hardwired
If your heating and cooling system is hardwired to your home's electrical system, your Nest thermostat still has AA batteries inside. These are a backup power source in case your home loses electricity. The batteries keep the thermostat running long enough to maintain your schedule and settings until power returns.
In a hardwired setup, the batteries rarely discharge because the thermostat draws power from your home's wiring almost all the time. This is why hardwired thermostats can go five years or longer without needing a battery change. You'll still see a low battery notification eventually, but it's much less frequent than in a battery-only setup.
If you have a hardwired thermostat and the low battery icon appears, replace the batteries anyway. Even though they're a backup, a dead backup battery means your thermostat has no protection if the power goes out.
Troubleshooting if your thermostat won't turn on after battery replacement
If the display stays dark after you put the faceplate back on, the batteries probably aren't making good contact. Remove the faceplate again and check that both batteries are pushed all the way down into the compartment. They should sit flat and flush with the top of the slot.
If one battery is sitting higher than the other, push down on it until it clicks into place. Sometimes a battery gets inserted at a slight angle and doesn't seat properly. Once both batteries are fully seated, put the faceplate back on and wait 10 seconds for the display to light up.
If the display still doesn't turn on, try removing the batteries, waiting 30 seconds, and reinserting them. This resets the thermostat's internal circuits. If it still won't turn on after that, one of your new batteries may be defective — try replacing one battery at a time with a different one to find which one is the problem.
Frequently Asked Questions
How often do I need to replace the batteries?
In a battery-only thermostat, you'll replace them about every two years. In a hardwired setup, the batteries last much longer — often five years or more — because they're only a backup and rarely get used. Your Nest app will notify you when the battery is low, so you don't have to guess.
Will I lose my temperature settings if the batteries die?
No. Your Nest thermostat has an internal backup battery that keeps your settings and schedule safe even if the AA batteries are completely dead. You may lose the display temporarily, but once you replace the batteries, everything comes back.
Can I use a 9-volt battery or a different size?
No. Your Nest thermostat is designed for two AA batteries only. Using a different size or type of battery can damage the device or cause it to malfunction. Stick with standard AA alkaline batteries.
What if my thermostat is hardwired — do I still need to replace the batteries?
Yes, eventually. Hardwired thermostats use the AA batteries as a backup only, so they last much longer than in battery-only setups. But they will eventually run low, and you should replace them when the low battery notification appears to keep the backup protection active.
Why does my thermostat show a low battery icon if I just replaced the batteries?
The batteries probably aren't making good contact with the metal contacts in the compartment. Remove the faceplate and push both batteries down firmly until they click into place. Make sure they're sitting flat and level with each other. If the icon persists after that, try a different brand of battery.