How to Maintain and Update the Firmware of a Smart Thermostat

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How to maintain and update the firmware of a smart thermostat – a complete practical guide

A smart thermostat is now a full-fledged computer connected to the home network. It has its own processor, a miniature operating system, and – most importantly – firmware, i.e., software written directly into the device's memory. This firmware is not static. Manufacturers regularly update it: they fix bugs, improve Wi-Fi connection stability, add new features to the app, and address security vulnerabilities. If you do not update the thermostat's firmware for several years, it may gradually happen that the app stops communicating with the device correctly, integration with Google Home or Amazon Alexa fails, or the thermostat starts behaving unpredictably – it restarts, loses settings, or does not respond to commands.

During the years I have been working with heating technology, I have seen dozens of cases where a customer called with the problem "the thermostat is not working" – and all it took was a firmware update. Not always, but surprisingly often. This article will show you how to systematically maintain the firmware, what can go wrong, how to prevent updates, and when it is better not to perform an update at all.

What is thermostat firmware and why it matters

Firmware (from English firmware) is a set of instructions permanently stored in the device's memory (usually flash EEPROM or NOR flash memory). Unlike regular software on a computer, it is not stored on a hard drive but directly in the chip. As soon as you connect the thermostat to power, the firmware runs immediately – without an intermediate operating system.

For a smart thermostat, firmware ensures:

Control of relays (turning the boiler on and off)
Temperature measurement and deviation evaluation (hysteresis, PID regulation)
Wi-Fi communication with the manufacturer's server or local API
Interface for the mobile app (MQTT, HTTP REST, WebSocket)
Management of time schedules and zones
Integration with external platforms (Google Home, Alexa, HomeKit)
Communication encryption (TLS/SSL certificates)

Each of these functions can contain errors. Manufacturers continuously fix them and release new firmware versions. Neglecting updates means your thermostat is running with old bugs – and sometimes with security holes that someone could exploit to control your heating system illegally.

Types of firmware updates – OTA, manual, and factory reset

Not all firmware updates proceed in the same way. We distinguish three main types that you will encounter with smart thermostats available on the Slovak market.

OTA update (Over-The-Air)

This is the most common and convenient method. The thermostat is connected to the internet, and the manufacturer's server automatically detects a new firmware version. The device downloads it, verifies its integrity (checksum, digital signature), and installs it – usually at night when the thermostat is not actively receiving requests. Some models will notify you via the app, while others will do it without any notification.

OTA update is standard for most modern devices. For example, Elektrobock PT32 GST communicates with the manufacturer's server and supports remote management – the update proceeds transparently for the user, provided the device is online and has a stable Wi-Fi connection.

Manual update via the app

Some models do not perform OTA automatically but offer a "Check for updates" button directly in the app. The user must start the update manually. This is a safer approach in terms of control – the device does not restart at an inconvenient moment – but it requires active attention.

Manual update via USB or serial link

This method is less common for commercial thermostats but is encountered with devices using serial interfaces (e.g., RS-485, Modbus) or DIY platforms such as ESP32/ESP8266-based thermostats. In practice, this means connecting a laptop directly to the device and uploading a firmware binary file using a flashing tool. A typical home user will not encounter this, but an installer will.

Factory reset

This is not technically a firmware update, but it is directly related to maintenance. If an update fails, the thermostat behaves unstably, or it is necessary to resolve serious configuration issues, a factory reset will return the device to its factory state. The firmware will remain at the current version, but all settings – schedules, zones, Wi-Fi password, preferences – will be deleted.

When to update – and when to wait

This is a question that customers often underestimate. There are several scenarios in which updating the firmware is clearly the right choice, but also situations where it is better to wait.

When to update without hesitation

Security patch: If the manufacturer announces a fix for a security vulnerability, update immediately. An unpatched hole could allow an attacker to take control of the boiler.
Thermostat shows unstable behavior: It restarts, loses settings, or does not respond to schedules – these are typical symptoms of a bug in the old firmware, which is fixed in the new version.
You want a new feature: A new version may bring, for example, support for a larger number of zones or integrated PID regulation instead of simple hysteresis.
The app requests an update: If the manufacturer's mobile app has stopped communicating properly with an older firmware version, an update is necessary.

When to wait with the update

Immediately after a new version is released: The first release of a new firmware version may contain new bugs that have not yet been discovered. I recommend waiting 2–4 weeks until the user community has "tested" the new release.
During the heating season without a backup: If the update fails, the thermostat may temporarily disconnect. In freezing weather without a backup (e.g., a mechanical thermostat), the risk is too high.
When the device is in a critical phase: During active heating at night, when it is –15 °C outside, is not a good time for a manual update.

Step-by-step firmware update procedure

The following procedure applies to most commercial smart thermostats available on the Slovak market, including models such as EMOS P5623. Specific steps may vary by manufacturer, but the principle is the same.

Step 1: Backup settings

Before every update, write down or take a photo of the current thermostat settings: temperature schedules for individual days, set hysteresis, any zones and frost protection thresholds. Many apps (e.g., Tuya Smart, eWeLink, manufacturer-specific apps) allow you to export settings directly from the menu. If this feature is not available, screenshots from the app are sufficient.

Why? Because in rare cases, a firmware update can erase user settings – especially if a reset of the configuration memory sector occurs. From my own experience, a customer without a backup of settings spent half an hour re-entering a weekly schedule he had painstakingly set up.

Step 2: Check the current firmware version

Before updating, record the current version. You can usually find it in the thermostat menu under „Settings" → „Device information" or directly in the app in the device details. The firmware version is usually in the form X.Y.Z (e.g., 2.3.17). Write this number down – if problems arise after the update, you will know which version you updated from and what to inform technical support about.

Step 3: Ensure stable Wi-Fi connection and power

This is a step that people often underestimate. During the update, there must be no interruption in the Wi-Fi connection or power to the thermostat. If the update is interrupted during the write to flash memory, the thermostat may „brick" – that is, become unbootable. The solution is then a service intervention (USB flash, contact the manufacturer). Therefore:

Check the Wi-Fi signal strength at the installation location (ideally at least –65 dBm)
If the signal is weak, temporarily use a mobile hotspot closer to the thermostat
Ensure that the thermostat's power is stable – do not perform the update during a storm with voltage fluctuations
If the thermostat is powered by batteries, check their status (I recommend at least 70 % capacity)

Step 4: Start the update

Depending on the manufacturer, there are two ways. Automatic OTA: the thermostat downloads and installs the update itself, and you receive a notification in the app. Manual: in the app, select „Firmware update" or „Check for updates" and confirm the installation. The thermostat will automatically restart after the update. A restart usually takes 30–90 seconds – during this time, the thermostat does not communicate and the boiler is turned off.

Step 5: Verification after the update

After the restart, check the following:

Does the app display the new firmware version?
Are all schedules and settings preserved?
Does the thermostat respond correctly to manual temperature changes?
Does it turn the boiler on and off according to the set hysteresis?
Does the integration with Google Home / Alexa work (if you use it)?

If some settings are missing, restore them from the backup. If the thermostat does not respond or the app reports a communication error, try a manual restart (disconnect and reconnect the power). For more detailed troubleshooting, see our article WiFi thermostat not working or not connecting to the internet – common causes and solutions.

Regular maintenance of a smart thermostat beyond firmware

Updating the firmware is only one part of caring for a smart thermostat. There are several other actions that extend the device's lifespan and maintain its accuracy.

Cleaning and physical inspection

The thermostat contains a temperature sensor that must measure the air temperature in the room – not heat from the sun, from the kitchen, or from the fireplace. Therefore:

Check once a year whether the air vent mesh is not dusty. Dust on the sensor causes delayed measurements and inaccuracy of up to ±1.5 °C.
Check several times a year (at the beginning of the season, in the middle of the season) the measured temperature of the thermostat against an accurate thermometer at the same height and location. A deviation of more than 0.5 °C indicates dirt or a sensor fault.
Ensure that the thermostat is not directly exposed to sunlight or located near a heat source – this causes falsely high readings and unnecessary boiler shutdowns.

Wi-Fi and Network Infrastructure Check

A smart thermostat depends on the quality of your home network. A weak Wi-Fi signal causes connection drops, delayed commands, and sometimes failed OTA update attempts. I recommend:

Checking the signal strength at the installation location once a year (via the app or router administration)
If you replace the router, don't forget to pair the thermostat with the new network (new SSID / password)
Connect the thermostat to the 2.4 GHz band, not 5 GHz – most smart thermostats support only 2.4 GHz
Consider a Wi-Fi extender or mesh system if the signal is weak

Account and Cloud Platform Management

Most smart thermostats operate through the manufacturer's cloud. This means your thermostat communicates with the manufacturer's server, from which commands from the app are received. This cloud can experience outages, changes in terms of service, or in the worst case, be discontinued (if the manufacturer goes out of business or stops product support). Therefore:

Monitor communication from the manufacturer regarding platform changes
If the manufacturer ends the cloud service, check whether the thermostat supports a local API (e.g., via Home Assistant)
Always keep a backup of your login credentials in the app
If you receive an email about the end of device support, plan the replacement in good time

Batteries and Backup Power

Many thermostats (including some models we sell) are battery-powered. A weak battery can cause unstable behavior – the thermostat may restart, lose Wi-Fi connection, or fail during firmware updates. I recommend replacing batteries once a year as a preventive measure, not waiting for a "low battery" warning. High-quality alkaline batteries (Duracell, Energizer) last 1–2 years with normal use, while cheap, no-name batteries may last less than 6 months.

Troubleshooting after firmware update

Despite careful preparation, it can happen that a firmware update causes a new issue or reveals an existing one. From practice, I know these most common scenarios:

Thermostat does not connect to the network after the update

Cause: The new firmware version may have different default Wi-Fi settings. Solution: Restart the Wi-Fi pairing manually (usually by holding the button for 5–10 seconds until the LED starts blinking). Then add the device again in the app. If the app reports an error "device offline", restarting both the router and the thermostat may help.

App does not work properly after the update

Cause: The new firmware may require a newer version of the mobile app. Check the App Store or Google Play for an app update. I recommend uninstalling the old app version first and then reinstalling it – the cache from the old version may cause conflicts.

Schedule does not work after the update

Cause: The update may have reset or reformatted the schedule memory. Solution: Re-enter the schedules manually or restore them from a backup. Also check the time zone settings – after the update, it may be reset to UTC, which can shift the schedule by an hour or more.

Integration with Google Home has stopped working

Cause: The new firmware may use different API endpoints that require re-pairing with the platform. Solution: Disconnect the device from Google Home and add it again. More information can be found in the article Integration of Wi-Fi thermostat with Google Home, Alexa and smart home systems.

Thermostat measures a different temperature than before the update

This is a rare but real phenomenon. A new firmware version may include an improved calibration coefficient for the temperature sensor. If the difference is less than 0.5 °C, it is an improvement. If it is larger, check whether manual calibration (temperature offset) is available in the settings. Most thermostats allow setting a correction of –5 °C to +5 °C.

Security of firmware – why ignoring updates can be risky

This topic is often underestimated in the home environment. A smart thermostat is an IoT device connected to the internet – just like security cameras or smart locks. If the manufacturer fixes a security vulnerability and you do not apply the update, your device remains vulnerable.

Typical security threats for smart thermostats include:

Unauthorized access via Wi-Fi: An attacker within range of the network can take control of the thermostat if the firmware contains an unpatched authentication flaw
Eavesdropping on unencrypted communication: Older firmware may communicate without TLS/SSL – the content (commands, temperatures, daily routines) can be intercepted
Exploiting the thermostat as an entry point: A compromised thermostat can be used to gain access to other devices on the home network

Manufacturers such as Elektrobock, EMOS, and others regularly issue security patches for their products. In models like EMOS P5623, OTA updates are integrated directly, which minimizes the risk of the device remaining on an old firmware version for longer than necessary.

Firmware and long-term device support (EOL)

Every smart thermostat has a limited period during which the manufacturer provides firmware updates. This period is called "End of Life" (EOL) or end of support. After this period, the manufacturer will stop issuing new firmware versions – the device will continue to function, but new security vulnerabilities will not be fixed and no new features will be added.

When choosing a smart thermostat, I therefore recommend looking not only at current features, but also at how long the manufacturer plans to provide support. Established manufacturers (Honeywell, Siemens, Hager, as well as domestic brands like Elektrobock) usually support their products for 5–10 years after market launch. Cheap no-name devices from Asian sources may have support ended within 1–2 years.

More on how to choose the right device can be found in the article How to choose a WiFi thermostat – what to watch out for before buying.

If your thermostat has reached EOL but is still working, you have a few options:

Continue using it without further updates (at your own security risk)
Switch to a local API (e.g. Home Assistant) without dependency on the manufacturer's cloud
Replace the device with a newer model that has active support

Special situations – GSM thermostats and firmware

Thermostats with GSM connectivity (e.g. Elektrobock PT32 GST) have a specific approach to firmware updates. Unlike Wi-Fi models, they communicate via a mobile network (SMS, GPRS or 4G), which affects the update process:

OTA updates via the mobile network are slower and can be more expensive (data transfer via SIM)
Some GSM thermostats allow firmware updates only with physical access to the device (USB or serial port)
The GSM module (SIM card) requires separate care – checking credit or the validity of the data tariff

The difference between Wi-Fi and GSM thermostats in terms of management and updates is discussed in more detail in the article WiFi vs. GSM thermostat – what is the difference and which one is worth it.

Automatic updates – turn on or off?

This is a question for which there is no single answer. From practical experience, I recommend the following approach:

Turn on automatic updates if:

It is a security update (most manufacturers label them separately)
You have a backup thermostat or another way of controlling heating
The thermostat is installed in a vacation property that you do not visit regularly
You have reliable backup of your settings

Turn off automatic updates if:

You manage multiple devices and want to test updates on one first
You have a critical installation (server room, medical facility, crisis center)
You are without a backup in winter and do not want to risk a heating failure

Frequently asked questions (FAQ)

How do I find out what firmware version my smart thermostat has?

The firmware version is usually found in the thermostat menu under "Settings" → "About device" or "Information". In the mobile app, the version is available in the device details – most apps display it in the "Device" or "Device Settings" section. Look for items such as "FW version", "Firmware", or "Software version". If you cannot find the version in the app, try the web interface of your router – some thermostats publish their firmware version in the local network as well.

Can a firmware update damage the thermostat?

In extreme cases, yes – if the update is interrupted (power outage, Wi-Fi drop). However, the probability is low, as modern devices use dual-bank flash (a backup copy of the firmware), allowing the device to revert to the previous version. The manufacturer also verifies the integrity of the firmware before installation. I recommend updating only with stable power and a good Wi-Fi signal – the risk drops to almost zero.

What to do if the thermostat "freezes" and does not respond after an update?

First step: Physical restart – disconnect the thermostat from power for 30 seconds and reconnect. If it still does not respond, try a factory reset (usually by holding the button for 10–15 seconds). If that does not help, contact the manufacturer's technical support – most manufacturers have a customer hotline or email. In extreme cases (thermostat does not start at all), it may be necessary to flash the firmware via a service interface (USB), which is a task for an authorized service center.

Does the thermostat lose its settings after every firmware update?

It depends on the manufacturer and version. Most modern thermostats store user settings in a separate memory sector that is not overwritten by firmware updates. However, sometimes an update that changes the format of stored data (e.g., adds new parameters) may require resetting the configuration. Manufacturers usually warn about such changes in the release notes. Therefore, backing up your settings before each update is a good habit, not unnecessary paranoia.

Can I revert to an older firmware version if the new one does not suit me?

Most commercial thermostats do not allow downgrading firmware – it is a deliberate security restriction that prevents returning to versions with known vulnerabilities. Some devices based on open-source platforms (Tasmota, ESPHome) do allow downgrading, but require advanced technical knowledge. If the new firmware causes problems, contact the manufacturer – they may issue a fix or provide a special version. Alternatively, note the version number before updating – if problems arise, you will have precise information for technical support.

Will a firmware update affect the energy consumption of the thermostat?

Directly, no – the thermostat itself consumes a minimal amount of electricity (usually 0.5–3 W). However, a firmware update can improve the regulation algorithm (e.g., transition from simple hysteresis to PID regulation), which can lead to heating savings in the range of 5–15%. Real numbers and energy-saving calculations can be found in the article How much can I save on heating with a WiFi thermostat – real numbers and experiences.

Conclusion – systematic care pays off

The firmware of a smart thermostat is a living software, not something that is set once and forgotten. Manufacturers issue updates several times a year, and each one either fixes a bug or advances the device further. A customer who spends half an hour once a year checking and updating the firmware has a thermostat that works reliably, securely, and efficiently throughout its entire lifespan.

I recommend setting a reminder on your phone – for example, every September, before the heating season begins. At that time, you check the firmware version, review the release notes on the manufacturer's website, back up your settings, and possibly start the update. It is a routine that takes 15–20 minutes and can save you several hours of problem-solving in icy January.

If you are considering purchasing a new smart thermostat with long-term firmware support and a reliable OTA update process, take a look at our full range in the WiFi and smart thermostats category – you will find there verified models for which we also provide expert advice on selection and installation.

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