The battery compartment is on the back of the thermostat, and the swap takes about two minutes
The Honeywell Home Pro Series thermostat runs on two AA batteries that power the display and wireless connection when your power goes out. When the screen shows a low-battery symbol or the display dims, the batteries need replacing. You do not have to turn off your heating or cooling system — the thermostat will keep working on your home's wired power while you swap the batteries.
The entire process requires only the two new AA batteries and takes place at the thermostat itself. You do not need to access your breaker panel, remove the thermostat from the wall, or touch any wiring.
Key Takeaways
- The battery compartment is located on the back of the thermostat faceplate and opens by sliding or unlatching a small cover.
- Use two fresh AA batteries, and insert them with the positive (+) end facing the direction marked inside the compartment.
- The thermostat will continue heating and cooling normally during the battery change because it draws power from your home's wiring.
- If the display does not turn back on after inserting new batteries, check that both batteries are seated firmly and facing the correct direction.
Locate the battery compartment on the back of the thermostat
Remove the thermostat faceplate by gently pulling it away from the wall. Most Honeywell Home Pro Series models have a faceplate that slides or clips off the base unit. Pull straight toward you with steady pressure — do not twist or pry at an angle.
Once the faceplate is off, look at the back of it. You will see a small rectangular compartment, usually labeled "BATTERIES" or marked with a battery symbol. The compartment cover either slides to one side or has a small latch you can press to open it.
Remove the old batteries and insert new ones
Open the battery compartment cover by sliding it or pressing the latch. Two AA batteries will be inside, oriented with their positive (+) ends pointing in the same direction. Remove both old batteries and set them aside.
Take two fresh AA alkaline batteries. Look inside the compartment for markings showing which direction the batteries should face — usually a diagram or a + and − symbol. Insert the first battery with its positive end facing the marked direction, then insert the second battery the same way. Push each battery in firmly until you hear or feel a click.
Close the battery compartment cover by sliding it back into place or pressing the latch shut until it clicks.
Reattach the faceplate and check the display
Slide the faceplate back onto the base unit, aligning the edges and pushing it in until it clicks or seats fully. The thermostat should power on when ready, and the display should light up with your current temperature and settings.
If the display remains blank or dim after a few seconds, remove the faceplate again and check that both batteries are pushed in completely and facing the correct direction. Reinsert them if needed, then reattach the faceplate.
What battery type to use
Use standard AA alkaline batteries — the kind sold in multipacks at any grocery store, pharmacy, or hardware store. Duracell, Energizer, and store brands all work equally well in the Honeywell Home Pro Series. Do not use rechargeable batteries or old batteries you have removed from other devices.
Alkaline batteries last between one and three years in a thermostat, depending on how often your heating and cooling system runs and how frequently the thermostat's wireless connection transmits data. If your batteries drain much faster than that, your thermostat may have a wiring problem — contact a technician to check the connections.
Why the thermostat has batteries
The batteries serve as backup power for the display and wireless features if your home loses electricity. When power returns, the thermostat switches back to drawing power from your home's heating and cooling system wiring. The batteries do not power the heating or cooling itself — that always comes from your home's electrical system.
If you remove the batteries and your home loses power, the thermostat will go dark and you will not be able to see the temperature or adjust settings until power returns. For this reason, it is best to replace the batteries as soon as you see the low-battery warning rather than waiting until the display goes blank.
Troubleshooting a thermostat that will not turn on after battery replacement
If the display stays blank after you insert new batteries and reattach the faceplate, first remove the faceplate again and check the battery orientation. Look at the diagram inside the compartment and make sure both batteries are facing the same direction with the positive ends pointing the way the diagram shows. Reinsert them firmly and try again.
If the display still does not light up, try removing the batteries, waiting 30 seconds, and reinserting them. This can reset the thermostat's power circuit. If the display remains off after that, the thermostat may have a deeper electrical problem — contact a heating and cooling technician or Honeywell customer support for help.
Frequently Asked Questions
Can I change the batteries while the thermostat is heating or cooling?
Yes. The batteries only power the display and wireless features, not the heating or cooling system itself. Your system will keep running normally while you swap the batteries. You do not need to turn anything off.
What happens if I put the batteries in backwards?
The thermostat will not turn on. The batteries must be inserted with the positive (+) end facing the direction shown in the compartment diagram. If you insert them backwards, straightforward remove them, flip them around, and reinsert them.
How often do I need to replace the batteries?
Most AA alkaline batteries last one to three years in a Honeywell Home Pro Series thermostat. You will see a low-battery symbol on the display when they are running down. Replace them as soon as you see that warning to avoid the display going blank.
Do I need to reprogram my thermostat after changing the batteries?
No. Your temperature settings, schedules, and wireless connection will remain unchanged. The thermostat keeps these settings in permanent memory that does not depend on the batteries.
What type of batteries does the Honeywell Home Pro Series use?
Two AA alkaline batteries. Standard brands like Duracell and Energizer work fine. Do not use rechargeable batteries or old batteries from other devices.