How to Change Thermostat Batteries

If your home’s spring cleaning list is almost complete, we bet you almost forgot one item — changing the batteries in your HVAC thermostat! Like all batteries, these should be changed once a year to avoid interruption to your home’s heating and cooling. Here we’ll discuss how to tell when the thermostat batteries are low, how often they should be changed, and how to change them in three common thermostat types.

How to Tell Thermostat Batteries are Low

Every HVAC thermostat uses batteries to function, regardless of the thermostat’s features. The batteries are the power source for the electrical relays and wires that let the two talk and create the heating and cooling you want in your home. The vast majority of thermostats have one or more signals when the batteries are running low, such as:

• You see an empty battery icon: You’ll usually see this icon within one or two months of dead batteries. When you see the icon, change the batteries or risk functionality of the thermostat and the HVAC system.
• The display goes blank intermittently: This usually happens as the batteries are close to draining completely out since the thermostat batteries are the display’s main power source.
• The temperature is set, but the air isn’t warm or cool: Without enough power to send messages to the HVAC system, the thermostat can’t tell the system what air temperature to produce.
• Thermostat sensors misread the air temperature: Related to the previous issue, the thermostat sensors need a proper power source to gauge the indoor air temperature.

What Happens If the Thermostat Batteries Completely Drain?

Simply, you won’t have any control over the HVAC system until the batteries are replaced. The system could run continuously, heating or cooling the home when it’s not wanted, or not running at all when a climate controlled indoors is necessary.

What Kind of Batteries Do I Use in My Thermostat?

To be sure, check the thermostat’s user manual as it lists the type, voltage, and how many batteries it needs to operate. The most common batteries found in an HVAC thermostat are:

• One 9-volt battery
• One button-style 3-volt lithium battery
• Two AA batteries
• Two AAA batteries

How Often Should I Change My Thermostat Batteries?

Most homeowners can get away with changing the batteries once a year, though some people change them twice a year when the HVAC system has its bi-annual service appointments. If your thermostat uses batteries for backup power, remember to change them once a year.

How to Change a Wall Thermostat Battery

When wall thermostats were first introduced, they were a relatively simple device with a sliding switch to adjust the temperature. Today, they come in a range of shape, size, and features; most have digital displays and programmable settings. But they all use batteries and all batteries need to be changed at some point.

1. Remove the display housing from the wall-mounted plate.
2. Turn the cover over to view the batteries.
3. Use a small, flathead screwdriver to remove the batteries from their slots.
4. Align the new battery ends with the correct terminal in the slots and press into place.
5. Realign the display housing posts with the wall-mounted plate and press the housing until it clicks in place.

How to Change a Honeywell Thermostat Battery

A well known name in programmable digital thermostats, Honeywell has existed for more than 100 years. Because the brand’s thermostats can have slight variations, we recommend referring to the user manual if you find any variances in changing the batteries.

1. Look on the top right of the thermostat for a push tab.
2. Press the tab down until the battery compartment loosens, possibly slightly dislodging from the thermostat housing.
3. Gently pull the battery compartment toward yourself and tip it so the existing batteries fall out.
4. Align the new battery ends with the compartment markings and insert them into their slots.
5. Gently slide the battery compartment bottom-first into the thermostat and press until it clicks securely in place.

How to Change a Nest Thermostat Battery

Nest thermostats have been a popular brand with homeowners since its introduction in 2010. A product among the internet of things, these thermostats are WiFi-enabled, giving homeowners the flexibility of adjusting the settings through voice commands or programming a heating and cooling schedule on the go through a smartphone app. Be aware the following directions are for standard Nest thermostats; the Nest E and Nest Learning thermostats have an installed battery that’s rechargeable with a USB cord.

1. Begin by delicately pulling the display from the wall-mounted base.
2. Turn the display over and you’ll see two 1.5 volt AAA batteries.
3. Remove the existing batteries from their slots.
4. Make sure the positive and negative ends of the two new batteries are aligned and lightly press into the slots.
5. Press the display onto the wall-mounted base until it clicks, signaling it’s securely in place again.

Why Do My Thermostat Batteries Drain Quickly?

It’s recommended to only use known battery brands as they are usually high-quality and provide thermostat power for at least a year. But, even quality batteries can drain quicker than expect when these situations happen:

• Corroded contacts: Corrosion usually covers the terminal contact and battery end with a discolored, flaky layer. Without a clear connection between the two points, the corrosion causes a short or loose connection, simultaneously decreasing the amperage while still pulling power from the battery.
• Old thermostat: Older thermostats are notorious for using up batteries. The internal parts pull more amperage as they try to operate and keep up with the HVAC system.
• Wrong battery voltage: Double check the batteries you installed — it’s possible you may have accidentally used batteries with the wrong voltage.

Changing the thermostat batteries only takes a few minutes of time but it’s time well spent for year-round heating and cooling comfort. But if your HVAC system still acts up after changing the batteries, Bell Brothers offers comprehensive and professional service. Contact us today to schedule an appointment.