How Long Can Batteries Last In a Thermostat?

A thermostat is a device that automatically controls the surrounding temperature or activates a device when the temperature hits a certain point. The device detects temperature changes in an enclosed area to maintain it constantly.

The device generates electrical signals when the temperature is above or below the desired level. Thermostats are also included as components of fire detection systems. 

Like most appliances, a thermostat gets its power supply from a battery. The most common types of batteries used to power thermostats are AA batteries, AAA alkaline batteries, or 3V disc-style lithium batteries.

Four Types Of Thermostats 

There are four types of modern thermostats which are;

  • Non-programmable thermostat
  • Programmable thermostat
  • WiFi thermostat
  • Smart thermostat 

Non-Programmable Thermostat

This thermostat is manually programmed and best for those rarely away from the house. It is essential and simple to use. Anytime you want to adjust the surrounding temperature, simply adjust the setting on the thermostat.

A high-quality non-programmable thermostat efficiently communicates with the heating system to maintain your preferred temperature. 

Programmable Thermostat

You can pre-adjust it to a certain temperature for night and day. Most programmable thermostats can be set daily or weekly. It works well for you if you are not always home. For example, if you are out from Monday to Thursday, you can set the thermostat to keep your home at a moderate temperature on these days. It reduces the energy bill you have to pay, and decreases wear and tear on the device.

A programmable thermostat is suited for the home in regions where the temperature changes drastically. Without adjusting it manually, you can have a warm home on a chilly morning and a cool surrounding on hot afternoons.

WiFi Thermostat

The WiFi thermostat is a type of programmable thermostat that connects to a wireless network. You can easily access it via your smartphone, tablet, or PC to remotely adjust the temperature. This type of thermostat is perfect if you want to control home temperature while away from the house. 

Smart Thermostat  

This modern thermostat is primarily found in tech-savvy homes for optimal comfort provided by AI. It is integrated with automation tools and equipment, learning your day-to-day habits to adjust its function.

The thermostat observes when you arrive home and offers maximum heating and cooling as needed using the information it gets from your activity. It also has the feature of a WiFi thermostat in that you can access it via other devices with an internet connection. Most have voice recognition and control features and can work with Google Assistant or  Amazon Alexa. 

They are more expensive but save you heating and cooling expenses in the long run, so they are a good investment overall. 

How Long Do Thermostat Batteries Last?  

Most thermostat batteries can last up to a year, but some highly durable ones deliver for up to five years. You should keep in mind the lifespan of your battery before choosing one for the thermostat.

Depending on the type of battery your thermostat uses, they have different compositions and efficiency levels, and in turn, their life span may vary. Some thermostats also come with backup batteries should incase a power failure occurs. The backup batteries usually need regular replacement. 

Different Types Of Batteries Compatible With Thermostats  

AA Alkaline Battery   

AA alkaline batteries are what most people use as a standard in thermostats. It consists of two electrodes: the metal or carbon anode and the cathode, the positive electrode. The electrons flow across the electrodes, causing current flow and energy, which powers the thermostat. In case of interrupted power, the AA battery can continue to power the device as a backup source.

Other devices that use AA alkaline batteries include remote controls, clocks, radios, etc. Popular recommended brands that produce good AA batteries are Duracell and Energizer batteries. 

AAA Alkaline Battery 

Also known as the triple-A battery, they are low voltage alkaline batteries. They are small in size and fitting for thermostats because they can easily be installed or removed. Although not rechargeable, they are long-lasting with long shelf lines, and can power many appliances. 

3V Disc-Style Lithium Battery 

This battery type does not store all of the electrical energy, only about 80% of it. It is often used for wristwatches, calculators, fitness devices, etc. 3V disc-style lithium batteries are used with the temperature sensor and controller board to store energy for the device’s use. 

It is long-lasting, with a low discharge rate and a voltage of 3 volts that drops over time. 

Can A Thermostat Work Without Batteries? 

Modern thermostats can work just fine without batteries. Modern smart thermostats are connected to the grid and wired to the house’s power source. The thermostat will usually run on AC power, without batteries.

Also, most modern thermostats are hardwired and come with a backup battery. The purpose of a  backup thermostat battery is to retain programmed settings in case of a sudden power outage. 

How To Change The Batteries In A Thermostat

Typical battery-powered dial, switch, and digital or programmable thermostats use regular AA or AAA alkaline batteries, button-style 3V lithium batteries, or 9-volt batteries.

Changing the batteries in your thermostat at least once a year or as needed is good. The beginning of the fall season is a good time to replace thermostat batteries. 

To replace the batteries, here are simple steps to follow;

  • Ensure the thermostat is turned off
  • Slide the thermostat casing up and off the wall mount plate. Some casings do not slide up or off, so you can pull it off.
  • Using a screwdriver, gently lift off the cover and pry out the battery
  • For AA, and AAA batteries, take note of the direction of the negative and positive ends and insert the new batteries accordingly. 
  • Check if the mounting plate is firmly attached to the wall by wiggling it gently. If it is loose, use a screwdriver to tighten it till it is firm. 

Note: If your thermostat uses mercury, you must take extra care as mercury is a dangerous neurotoxin. You should consider changing to an energy-saving programmable thermostat instead. 

How Long Do Thermostats Last? 

The average lifespan of most household thermostats is about ten years. This depends on the make, the model, and the quality of the thermostat. Some even last slightly longer than a decade if properly maintained.

Over time, it begins to wear out due to rust, dust, wiring problems, and normal deterioration. The best time to use a thermostat is to buy it with the rest of your home heating and cooling systems. The HVAC systems last for ten years or more, so when you buy them around the same time, they can decline at the same pace, saving you money and future faults. 

Signs You Need To Replace Your Thermostat.  

Faulty Readings 

If your thermostat begins to read incorrect temperatures, it is time to get a new one. This can happen because the thermostat is old, has manufacturing problems, a faulty sensor, or has been misused. You can test the read by comparing it with a thermometer’s reading. 

Frequent Temperature Shifts 

If the thermostat does not maintain the setting and changes the temperature without any warnings or external trigger, it indicates a fault. By lowering the settings to observe and test, you can confirm if it is a recurring problem. If it is recurring, consult a technician for proper diagnosis or simply replace the thermostat. 

The Thermostat Does Not Respond To Settings. 

Your thermostat should respond and change to your desired setting when you operate it. You would hear clicks, and then your HVAC system starts instantly. If your HVAC system does not respond, it is a sign to replace the thermostat soon. 

The HVAC System Does A Short Cycle. 

In this case, the heating, ventilation, and cooling system goes off earlier than it should or fails to complete a full cooling or heating cycle. You can consult your technician or get a replacement if this keeps occurring. 

Unusually High Energy Bills 

If your thermostat does not correctly read the temperature, it will mount unnecessary pressure on your HVAC system and affect your energy bills. The more the unit cycles per hour, the more power is consumed.

The Thermostat Has Been In Use For Over A Decade. 

Thermostats can last for up to ten years or more, so if it begins to malfunction nearing this age or beyond, it is a strong indicator that the thermostat has served its time and needs to be replaced soon. 


Why does my thermostat battery drain quickly? 

If your thermostat drains the battery fast, it might be due to old age or the thermostat has a fault. You can consult with a technician to diagnose the issues and fix them for you.

Do all thermostats require batteries?  

Not all thermostats need batteries, and some older models require you to rotate the housing or move a lever to adjust the settings. However, most modern thermostats use batteries, especially as a backup in case of a power outage. 

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