Our editors pick the products & services we write about. When you buy through our links, we may get a commission. Learn more.

How To Change Honeywell Thermostat Battery

Heating and cooling systems employ thermostats and controllers to manage the system. These units often have batteries inside them. Sometimes the unit is battery operated. In others, the batteries provide a backup system if the mains power goes off.

Over time, the batteries will go flat and need replacement. This brief article describes checking and changing the batteries for many popular Honeywell thermostats.

Do All Honeywell Thermostats Need Batteries?

The quick answer is no, but of course, you need to determine if yours does! So how do you do that?

If your Honeywell thermostat is programmable, then it will need a battery. Some non-programmable thermostats also need batteries. Another sign is if your thermostat has an LED display, as this type usually has batteries.

A quick way to check is to look for a battery compartment cover, but not all thermostats will have them. On some models, you may have to remove the front panel to access the battery.

You could switch off the mains power and check if the thermostat remains on. But if the batteries are flat already, this proves nothing.

If you are really unsure and cannot find a battery, visit the Honeywell website. Here you can find the manual for your particular model.

Some thermostats are powered by the furnace and don’t use a battery, so it is essential to find out.

When to Replace the Thermostat Battery?

As with all equipment, it requires regular maintenance. Checking your system annually is an excellent habit to get into. It’s also a great time to change the thermostat battery. In that way, you should always have a good battery in your system.

The other method is to check the battery level indicator regularly if your thermostat has one.

Lastly, if the thermostat screen goes blank, this is a good indicator that your batteries are dead.

How to Replace Honeywell Thermostat Battery?

Honeywell produces an extensive range of thermostats, and the method for changing the batteries will vary. Here, we will cover the primary examples, but visit the Honeywell website if yours is not listed.

Honeywell Thermostat 1000 Series & 2000 Series

Battery replacement for both the 1000 and 2000 Series vertical thermostats and 2000 Series horizontal thermostat is the same.

There is a low battery indicator on the unit. When the battery indicator illuminates, the batteries have approximately 60 days of life remaining. They recommend that you replace the batteries annually or if you will be away for over a month.

The thermostat is in two parts, the control unit, and the wall plate. To replace the battery in either series:

  • Pull gently at the bottom of the thermostat to remove it from the wall plate.
  • Turn the thermostat over.
  • Replace the two AAA batteries.
  • Refit the thermostat to the wall plate.

Honeywell Thermostat 3000 Series & 4000 Series

The 3000 Series and 4000 Series are similar products, except that the 4000 version is programmable. Batteries are optional, as the thermostats can be hard-wired, but they provide a backup if the power goes out.

A “Replace Batt” warning will flash on the display when the batteries need replacing. You should have around 60 days before the batteries are completely dead. The batteries should be replaced annually, or if you are going away for a month or more.

The thermostat is mounted on a wall plate and changing the batteries is the same for both series:

  • Gently pull at the bottom of the thermostat to remove it from the wall plate.
  • Turn the thermostat over and replace the two AA batteries.
  • As long as the batteries are changed within 60 seconds, the time and date settings are kept.
  • Refit the thermostat to the wall plate.

Honeywell Thermostat 5000 Series and 6000 Series

The 5000 and 6000 Series of thermostats are very similar, but the 6000 version is programmable. Changing the batteries on both is the same process.

You should replace the batteries when the “Replace Battery” warning flashes on the display. The batteries will last for around 60 more days before dying completely.

The method for replacing the batteries is identical for both the 5000 and 6000 series:

  • The battery holder is on the right-hand side of the thermostat.
  • Press down the release catch on top of the unit and remove the battery holder.
  • Replace the batteries and refit the holder to the thermostat.

Honeywell Thermostat TH8000 Series

The TH8000 Series has the option of backup batteries if the unit is connected to mains power. They provide a backup if the mains power fails.

The batteries should be replaced when the “Lo Batt” warning is displayed or during annual maintenance. It’s also recommended to change the batteries if you are going away for over a month.

Replacing the TH8000 Series batteries is very simple:

  • Pull the thermostat away from the wall plate.
  • Turn it over and replace the three AAA batteries.
  • Refit the thermostat to the wall plate.

Honeywell Thermostat RTH2300/RTH221 Series

These instructions relate to the RTH2300/RTH221 Series Honeywell thermostat. Battery replacement is required when the “Lo Batt” indication flashes on the screen. At this point, the batteries have approximately 60 days of life remaining.

  • Move the power control switch to the “Auto” position.
  • Move the heat / cool switch to the “Off” position.
  • Gently pull the bottom of the thermostat to release the catches.
  • Lift the thermostat forwards and up to unclip it from the top mounting points.
  • Replace the two AA batteries.
  • Locate the top of the thermostat on the two catches.
  • Gently lower the bottom of the thermostat.
  • Carefully push the bottom of the thermostat home until you hear a click.

Honeywell Thermostat RTH230B

The RTH230B is a battery-powered thermostat. When the batteries are getting low, a battery icon will flash on the display. You will have around 120 days of battery life from the time the icon comes on. Replacing the battery is a straightforward process:

  • Move the system switch to the “Off” position.
  • Remove the faceplate by pulling it towards you.
  • The battery compartment is on the front of the thermostat at the top.
  • Pull the battery cover out towards you.
  • Replace the batteries.
  • Refit the battery cover. There will be a click when it is fitted correctly.
  • Fit the thermostat back to the wall plate.
  • The thermostat performs a series of tests and will then display the ambient temperature.
  • Reset the time and day settings. Program settings are saved in the memory chip and don’t need to be re-entered.

Honeywell Thermostat RTH7000 Series

These instructions cover battery replacement on the RTH7000 Series of Honeywell thermostats.

When the batteries are due for replacement, the screen will display the “Lo Batt” warning. You then have around 30 days before the batteries become completely dead.

Replacement of the batteries is straightforward:

  • Pull the thermostat towards you to remove it from the wall plate.
  • Turn the thermostat over.
  • The batteries are located at the top of the thermostat.
  • Replace the two AA batteries.
  • Push the thermostat back onto the wall plate.


What kind of battery does a Honeywell thermostat take?

Honeywell thermostats generally use two types of battery, the AA size or the AAA size. Refer to your user manual to check which type you need.

If you don’t have the manual, visit the Honeywell website to find the online user manual.

How do you take the cover off a Honeywell thermostat?

Removal of the battery cover varies from series to series. Many thermostats do not have a battery cover, and the batteries are simply fitted in the unit’s back. Where a cover is fitted, it simply clips into place.

Honeywell thermostat says low battery with new batteries, what should I do?

The first thing to do is to use another set of fresh batteries. It’s not entirely unknown for batteries to go bad in storage.

If the problem persists, then contact Honeywell if the unit is still under warranty. If outside the warranty period, then contact your heating installer.


Most Honeywell thermostats contain batteries, either to run the system or for backup power.

The batteries must be checked and changed regularly. Honeywell recommends that the batteries are changed annually or if you are going away for over a month.

Changing the batteries is a simple process. We hope this short article has given the information you need to change your Honeywell thermostat batteries in the future.

Leave a Comment

Your email address will not be published. Required fields are marked *

Scroll to Top