The battery in your Honeywell Home Thermostat Pro Series sits behind the faceplate and takes about two minutes to swap out
The Honeywell Home Thermostat Pro Series uses two AA batteries to keep your settings and clock running if the power goes out. When the battery icon appears on the display or the screen goes dim, the batteries are low and need replacement. You do not need tools, a technician, or special knowledge — you can do this yourself by removing the faceplate, sliding out the old batteries, and inserting new ones.
The whole process takes less time than it takes to find the batteries. Your thermostat will stay connected to your Wi-Fi and keep all your schedules intact because the batteries only power the display and backup functions, not the main system.
Key Takeaways
- The Honeywell Home Thermostat Pro Series uses two AA batteries located behind the faceplate on the front of the unit.
- You can remove the faceplate by hand — there are no screws or clips to undo, just a gentle pull at the bottom edge.
- Replace both batteries at the same time with fresh AA alkaline batteries, even if only one appears dead.
- Your Wi-Fi connection and saved schedules remain active during the battery swap because they are stored separately from the backup batteries.
Locate the battery compartment behind the faceplate
The battery compartment is not visible from the front of your thermostat. The faceplate — the plastic cover you see when you look at the unit — covers the batteries completely. To reach them, you need to remove this faceplate by hand.
Stand in front of your thermostat and look at the bottom edge of the faceplate. Place your fingers under the bottom edge and pull gently toward you. The faceplate will slide down and away from the base unit. It is held in place by friction, not by screws or latches, so a steady pull works better than a hard yank.
Once the faceplate is off, you will see the battery compartment directly behind where the display was. It is a small rectangular slot with two AA battery positions marked inside.
Remove the old batteries and note their orientation
Before you take out the old batteries, look at which direction they are facing. Each battery has a flat end (negative) and a bumpy end (positive). The compartment is marked with a plus and minus symbol to show the correct direction. Most AA batteries in the Honeywell Home Thermostat Pro Series are installed with the positive end facing up, but check your unit to be sure.
Slide each battery out by pushing it gently from the side. If a battery is stuck, do not force it — wiggle it slightly side to side as you push. Once both batteries are out, set them aside. Do not throw them away when ready; keep them until you confirm the new batteries work, in case you need to troubleshoot.
Install two fresh AA alkaline batteries in the correct direction
Use two new AA alkaline batteries. Alkaline batteries last longer than rechargeable or carbon-zinc types in backup applications like this. Do not mix old and new batteries, and do not use batteries of different types in the same compartment.
Insert the first battery with the positive end (the bumpy end) facing the direction marked with a plus sign in the compartment. Push it in until it sits flat and snug. Repeat with the second battery in the adjacent slot. Both batteries should be inserted in the same direction — positive end first.
Push each battery firmly but gently until you hear or feel a small click. The battery should not move when you tap the compartment lightly.
Slide the faceplate back into place and check the display
Align the top edge of the faceplate with the top of the base unit. Slide it upward until it seats completely. You will feel it click or snap into place when it is fully installed. The faceplate should be flush with the base — no gaps or edges sticking out.
Look at the display. The screen should light up within a few seconds. If it does not, remove the faceplate again and check that both batteries are pushed in fully and facing the correct direction. The positive end should always face the plus symbol marked in the compartment.
Once the display is on, your thermostat will show the current time and temperature. All your saved schedules and settings remain unchanged because they are stored in the thermostat's main memory, which is powered by your home's electrical circuit.
What to do if the display does not turn on after battery replacement
If the screen stays dark after you install new batteries, the most common cause is incorrect battery orientation. Remove the faceplate again and check that the positive (bumpy) end of each battery faces the plus symbol in the compartment. Flip any battery that is backward and try again.
If both batteries are oriented correctly and the display still does not light up, try removing and reinserting each battery one more time. Sometimes a battery does not make full contact on the first try. Push each one in firmly until you feel resistance, then check the display.
If the display remains dark after these steps, one of the new batteries may be defective. Replace one battery at a time with a different AA alkaline battery from a different package to rule out a bad battery. If the display lights up after swapping one battery, the original battery was faulty.
How often to replace the batteries
AA alkaline batteries in the Honeywell Home Thermostat Pro Series typically last two to three years under normal use. You will see a low battery icon on the display when the batteries are running down — this gives you time to replace them before they die completely.
If your thermostat loses power during an outage, the backup batteries keep your clock and settings intact for several hours. After power returns, your thermostat resumes normal operation. This is the main reason the batteries are there — not for everyday operation, but for backup during electrical failures.
Mark your calendar or set a phone reminder for one year after you install new batteries. This helps you remember to check the battery status before they run too low.
Frequently Asked Questions
Can I use rechargeable batteries in my Honeywell Home Thermostat Pro Series?
Rechargeable batteries work but are not recommended. They have a lower voltage than alkaline batteries and may not power the display as reliably, especially as they age. Alkaline AA batteries are the standard choice and will work longer without needing replacement.
What happens to my schedules if the batteries die completely?
Your saved schedules stay in the thermostat's main memory because they are powered by your home's electrical circuit, not the backup batteries. The backup batteries only keep the display and clock running during a power outage. Once you install new batteries, everything will be exactly as you left it.
Do I need to turn off the thermostat before changing the batteries?
No. The backup batteries are separate from the main power circuit, so you can swap them out while the thermostat is running. Your heating and cooling will not be affected, and you will not lose any settings.
Why does the display go dark if I remove the batteries for more than a few seconds?
The display is powered by the backup batteries, so removing them cuts power to the screen. This is normal. Once you install new batteries, the display will light up again within a few seconds. Your thermostat's main functions remain powered by your home's electrical system the entire time.
Can I replace just one battery instead of both?
You should replace both batteries at the same time, even if only one appears dead. Mixing old and new batteries can cause one to drain faster than the other, and you will end up replacing them again sooner. Two fresh batteries cost very little and will last much longer together.