How to Choose a Thermostat for Electric Underfloor Heating: Manual, Digital or Wifi?
Why choosing the right thermostat is just as important as choosing the heating element itself
When customers are looking into electric underfloor heating, most of the attention goes to choosing the heating cable or mat – what output, what laying density, what brand. The thermostat tends to stay in the shadows, and many people choose it based on price or on whatever the installer on site recommends. That's a shame, because it's actually the thermostat that determines whether the heating will be truly comfortable, energy-efficient, and reliable in the long run.
From experience, I know that a poorly chosen or poorly configured thermostat can double electricity consumption compared to the same system with proper regulation. And conversely, a well-configured wifi thermostat with a weekly program and smart floor temperature limiting can realistically save 20–35% in costs compared to a cheap simple regulator set to a fixed temperature.
This article will help you understand how different types of thermostats work, how they differ, when it's worth investing in a more expensive model, and when a simpler device is perfectly sufficient. If you're still thinking about what type of heating element to choose, first check out our article How to choose electric underfloor heating: cable, mat, or foil? – deal with the thermostat only once you have a clear idea about the whole system.
Basic principle: how a thermostat controls underfloor heating
A thermostat for electric underfloor heating works as a simple temperature-controlled switch. When the temperature drops below the set value, it turns the heating circuit on; when it reaches the target temperature, it turns it off. This cycle repeats throughout the day.
A key parameter that's rarely discussed is hysteresis – the temperature difference between switching on and off. Cheap thermostats have a hysteresis of 1–2 °C, which causes frequent switching. Higher-quality models work with a hysteresis of 0.3–0.5 °C, which extends the lifespan of both the relay and the heating cable.
Temperature sensor: floor or room sensor?
This is a technical question that matters more than it might seem. Most thermostats for underfloor heating have a floor sensor – a thin cable with an NTC temperature sensor that's built directly into the floor (typically into a protective tube between the heating loops). The thermostat then regulates the temperature of the floor itself.
Some models also have a room sensor (built into the thermostat body or external) and allow a combined mode: the room sensor sets the desired air temperature, while the floor sensor acts as a safety limit so the floor doesn't exceed the allowed maximum (usually 27 °C for living rooms, 35 °C for bathrooms).
For bathrooms, where underfloor heating is the primary heat source, the combined mode is ideal. For a living room with tiles, where heating is more of a supplementary comfort feature, regulation based on the floor sensor alone is sufficient.
Three main categories of thermostats: overview and comparison
On the market, you'll basically find three generations of thermostats, which differ not only in price but also in the philosophy of control and programming options.
Manual (analog) thermostat
This is the simplest type – a rotary potentiometer or bimetallic regulator where you set the desired temperature and the thermostat maintains it. No programming, no display, no wifi. Turn it on, set the temperature, done.
When it makes sense: A manual thermostat makes sense in situations where heating is truly supplementary and irregular – for example in a cottage or holiday cabin that you visit irregularly, where you simply turn on the heating manually before arrival. Or in a bathroom, where you turn it on every morning the same way and turn it off when you leave.
Disadvantages: A manual thermostat has no memory and can't adapt the temperature to the daily rhythm. If you forget to turn it off, it stays on at full power all day. Without programming and without the ability to lower the temperature at night or when you're not home, consumption is unnecessarily high.
Price category: €15–40 including VAT, installed in a standard wall box.
Digital programmable thermostat
This is where real regulation begins. A digital thermostat has a display (LCD or LED), buttons or a touch panel, and most importantly – the ability to program a weekly temperature schedule. You can set different temperatures for different times of day and different days of the week.
A typical 7-day program looks like this: weekdays – morning 6:00–8:00 heating to 22 °C (waking up), 8:00–16:00 setback to 16 °C (work), 16:00–22:00 back to 22 °C (evening at home), 22:00–6:00 setback to 18 °C (sleep). Weekends according to your own needs.
A good example of such a product is the HAKL TH 900 digital thermostat – a robust device with a clear display, floor sensor, and programmable weekly mode. For most typical underfloor heating installations, this is the right choice that will pay for itself within half a year through lower consumption.
Price category: €40–90 including VAT, depending on functionality and display quality.
Wifi (smart) thermostat
A wifi thermostat is a digital thermostat with added value – it has a built-in wifi module and communicates with a smartphone or tablet via an app. You can control it from anywhere in the world, receive notifications, track consumption history, and in some cases integrate it into smart home systems (Google Home, Amazon Alexa, Apple HomeKit).
HAKL offers two wifi versions that differ in output and wiring: HAKL TH 951wifi and HAKL TH 952wifi. Both support programmable weekly schedules, a floor sensor, and remote management via the app. The difference between them is in the maximum load – for more powerful installations (for example, extensive underfloor heating in a living room with an output above 3 kW), the 952 model is suitable, while the 951 is intended for smaller circuits, such as bathrooms or hallways.
Price category: €80–150 including VAT. The difference compared to the digital model pays off faster in terms of consumption than most people think – if the heating actually follows your movement patterns rather than a fixed schedule, the savings can be significant.
Comparison table: manual vs. digital vs. wifi thermostat
| Feature | Manual | Digital | Wifi / Smart |
|---|---|---|---|
| Programming | No | Yes (7-day) | Yes + cloud-based |
| Remote control | No | No | Yes (app) |
| Floor sensor | Yes | Yes | Yes |
| Maximum floor temperature limit | Not always | Yes | Yes |
| Consumption statistics | No | No / limited | Yes |
| Smart home integration | No | No | Yes (some) |
| Approximate price | €15–40 | €40–90 | €80–150 |
| Suitable for | Cottage, holiday home | Apartment, house | Apartment, house, rental |
Technical parameters to watch out for when choosing
Maximum switching capacity (current load)
Every thermostat has a stated maximum output it can switch – typically 3,500 W or 3,600 W at 230 V, corresponding to 15–16 A. For typical bathroom circuits (up to 600–800 W) or hallways, this isn't an issue. But for a larger living room with an output of, say, 2,000–2,400 W, it's a good idea to check whether the thermostat can cover the full output with a margin.
If you have the HAKL TCX 10/1230W heating cable installed, we're talking about an output of 1,230 W – that's easily within the range of any standard thermostat. But if you were to connect two circuits to one thermostat (which is sometimes done for larger areas), always check the total power draw against the thermostat's maximum load.
IP protection class
For bathrooms and wet areas, a thermostat with a protection rating of at least IP21 is essential, with IP44 being recommended. IP44 means protection against foreign objects larger than 1 mm and protection against splashing water from any direction. Standard thermostats for living rooms usually only have IP20 or IP21.
Temperature regulation range
Most quality thermostats allow you to set the floor temperature within a range of 5–40 °C. This is important especially for protecting floor coverings – for laminate and vinyl, the maximum recommended floor surface temperature is 27 °C, while for ceramic tiles it can be higher (up to 35 °C). The thermostat should allow you to set this limit. You can find more on this topic in the article Electric underfloor heating under different types of flooring: tiles, vinyl, laminate.
Sensor type and sensor cable length
The floor sensor is usually included with the thermostat, with a cable length of 2–4 m. The sensor is inserted into a protective tube built into the floor so that it is positioned exactly halfway between two heating loops, not directly above or below the cable. If the sensor measures the temperature directly on the cable, the reading will be higher than the actual average floor temperature, and the thermostat will switch off before the floor is evenly heated.
Practical scenarios from real installations
Scenario 1: 5 m² bathroom – supplementary heating
The most common case. A customer has a bathroom with a radiator but wants a warm floor. The output of the heating circuit is 200–400 W. In this case, a manual thermostat isn't enough – most people don't turn it off, and the heating runs unnecessarily all day. I recommend a digital thermostat with a simple daily program: on in the morning 6:00–8:00 and in the evening 19:00–22:00. If you want convenience – for example, turning on the heating earlier when you get home later – a wifi model really makes sense.
Scenario 2: 30 m² living room – primary heat source
Electric underfloor heating as the sole heat source in a living room (standard insulated panel building, output approx. 1,500–2,000 W). Here a wifi thermostat is almost a necessity. Reason: your movement patterns are irregular – sometimes guests arrive, sometimes you're away for the weekend. A fixed 7-day program isn't enough – remote control lets you change heating schedules on the fly. Moreover, at this output level, every hour of unnecessary heating is visible on your electricity bill.
Scenario 3: A cottage with irregular visits
Here, paradoxically, a manual or simple digital thermostat wins. A wifi thermostat needs a stable wifi connection, which you might not have at the cottage. You'd call a neighbor before arrival, or invest in a GSM thermostat (a different category). For a typical holiday cottage, a simple digital thermostat with the option to set frost protection (5–7 °C) during absence is ideal.
Scenario 4: Rental apartment
A very interesting case. The apartment owner wants to keep control over the heating even though the apartment is rented out – so that tenants don't heat it to 30 °C and so the thermostat can't be blocked or reconfigured. Wifi thermostats allow you to set a maximum temperature and lock manual control directly from the owner's app. This is a real prevention against inflated electricity bills (if the owner pays) or against damage to the flooring from overheating.
Installing a thermostat: what the customer needs to know
A thermostat for electric underfloor heating is installed in a standard wall box (60 mm) at a height of 80–150 cm from the floor. For bathrooms, restriction zone rules apply – the thermostat must be outside zone 2 (min. 60 cm from the edge of the bathtub or shower), or it must have IP44 protection.
The electrical wiring is simple: the live wire (L) and neutral wire (N) from the mains go to the thermostat's input, and from the thermostat's output the live wire goes to the heating cable (N goes directly). The floor sensor is connected to terminals marked "sensor" or "NTC." A detailed procedure can be found in the article Installing a heating cable: spacing, embedding, and connection.
Important notice: Electrical installation work must be carried out by a person with electrical qualifications in accordance with regulation No. 508/2009 Coll. – at minimum §21 (informed person for own equipment); in practice we recommend an electrician with §22 or higher qualification. The thermostat is subject to electrical installation inspection.
Wifi thermostats and their real-world benefits
A wifi thermostat isn't just a marketing gimmick. From real experience with installations, I know the added value is genuine in several cases:
- Irregular lifestyle: When your schedule changes from week to week – different arrival times, travel, working from home alternating with the office. A wifi thermostat can respond to your actual movements, not a fixed schedule.
- Multiple apartments or spaces: The app allows you to manage multiple thermostats from one place. For property managers or owners of multiple apartments, this is a significant simplification.
- Consumption monitoring: Some wifi thermostats record operating hours, giving you at least approximate consumption data. After a few months, you can compare how much your setting changes have paid off.
- Fault notifications: If the sensor stops communicating (indicating a fault), the app will notify you. This is important, for example, for an empty apartment during winter, where a thermostat fault could mean freezing.
- Vacation mode: Instead of manually reconfiguring the program before leaving, you can simply activate frost protection or a low-temperature mode from the app and cancel it upon return.
On the other hand, wifi thermostats also have weaknesses. They depend on the functionality of the manufacturer's app: if the manufacturer stops maintaining the cloud server, remote control will stop working (the thermostat's basic functions will remain, but not the app). That's why it's important to choose established brands with long-term support.
Energy savings: real numbers
Many customers ask how much they'll actually save with a better thermostat. The answer depends on the specific situation, but here are some approximate figures:
Let's assume a 6 m² bathroom with an output of 600 W, a heating season of 6 months (180 days). Without programming – thermostat set to 22 °C, running 24 hours: 0.6 kW × 24 h × 180 days = 2,592 kWh/year. At a price of €0.20/kWh = approx. €520/year.
With programming (heating only in the morning for 2 h and evening for 3 h = 5 h/day at full output + the rest at a setback of 16 °C, which corresponds to approx. 15% of output): 0.6 × 5 h + 0.6 × 0.15 × 19 h = 3 + 1.71 = 4.71 kWh/day × 180 = 848 kWh/year = €170/year. That's a saving of more than €300 per year on just one bathroom. A digital thermostat costing €50 pays for itself in 2 months.
This is of course a simplified model, but the proportions are realistic. For a large living room with an output of 1,800 W, the savings from programming are even more significant. We discuss the topic of output sizing in detail in the article What output of electric underfloor heating do I need for my space?
Most common mistakes when choosing and installing a thermostat
- Underestimating the maximum output: A customer buys a thermostat for 2,000 W, but the cable draws 2,400 W. The thermostat's relay is permanently overloaded, shortening its lifespan and risking a fault.
- Incorrect sensor placement: The sensor directly on the cable or too close to it – the thermostat switches off prematurely and the floor isn't evenly heated.
- Missing protective sensor tube: If the sensor isn't in a tube, it can't be replaced without breaking up the floor. Always insert the sensor into a flexible protective tube with a closure near the thermostat box.
- Ignoring IP protection in the bathroom: A standard IP20 thermostat in a bathroom – this is an unnecessary risk, also from an insurance perspective in the event of a claim.
- Wifi thermostat without a stable signal: The router is too far away or the signal is unstable. The thermostat repeatedly disconnects and behaves erratically. Check the wifi signal strength at the installation location before installing.
- Incorrectly set floor temperature limit: For laminate floors, the maximum is 27 °C – many customers skip this setting and the flooring becomes deformed over time. More in the article Electric underfloor heating under different types of flooring: tiles, vinyl, laminate.
How to choose a thermostat: step-by-step decision process
If you're not sure which thermostat is right for you, follow this simple decision tree:
- Determine the output of the heating circuit – check the label on the cable or mat. The thermostat must be able to handle at least 10–15% more.
- Find out where it will be installed – a bathroom requires IP44, other rooms IP20/21.
- Decide how you use the heating:
- Irregularly (cottage, holiday home) → manual or simple digital
- Regularly according to a schedule → digital programmable
- Irregularly + you want control from your phone → wifi thermostat
- Consider whether it's a primary or supplementary heat source – for primary heating, it's worth investing in a wifi model for maximum flexibility.
- Check the availability of spare parts and sensors – established brands have replacement sensors available separately, so in case of a fault you don't have to replace the whole thermostat.
Frequently Asked Questions (FAQ)
Do I need to buy the floor sensor separately from the thermostat?
Most thermostats for electric underfloor heating are sold including a floor sensor – a cable-type NTC sensor is usually included in the package. Before buying a thermostat, check the product description to see if a sensor is included. If you're buying a replacement thermostat for a broken one, it may turn out that the original sensor is still functional and the new thermostat can be used without a new sensor – but only if the sensor is physically accessible and compatible with the new thermostat.
Can one wifi thermostat control multiple heating circuits?
No. One thermostat switches one electrical circuit. If you have, for example, a bathroom and hallway with separate circuits, you need two thermostats. However, wifi thermostats from the same manufacturer are usually managed from a single app, so control remains convenient from one place.
What happens to a wifi thermostat if the internet goes down?
The thermostat continues to operate according to the programmed schedule even without an internet connection. Wifi is only needed for remote management via the app and for syncing changes. So if the internet goes down, the heating won't stop working – you simply won't be able to control it remotely at that moment.
Can a manual thermostat be replaced with a digital or wifi model without changing the wiring?
Yes, in most cases the replacement is straightforward. Thermostats are installed in the same wall boxes (60 mm), and the wiring is the same (L, N, output, sensor). The only complication may arise if the original sensor isn't in a protective tube and can't be pulled out – in that case you can sometimes use the air sensor included with some thermostats, or you'll need to either arrange access to the sensor or choose a model with an external room sensor.
What is the lifespan of a thermostat and when should it be replaced?
A quality thermostat should last 10–15 years under normal use. The relay (mechanical switching) most often fails due to repeated switching of high currents or long-term overload. The display and electronics are generally more durable. If the thermostat doesn't hold the temperature accurately, reacts with a delay, or restarts, it's time for a replacement. Replacing the sensor (without replacing the whole thermostat) is a cheaper option if the sensor is accessible in a protective tube.
Does a thermostat guarantee protection of the heating cable?
A thermostat is primary protection against overheating the floor surface, but not against mechanical damage to the cable. If the cable is installed correctly, embedded at the correct depth, and not mechanically stressed (for example by sharp objects or heavy furniture placed directly on it), a thermostat with a floor sensor and a set temperature limit is sufficient prevention. That's why setting the maximum floor temperature is always mandatory – even more so for heat-sensitive flooring. All common faults and their causes are discussed in detail in the article Common faults of electric underfloor heating and how to fix them.
Conclusion: invest in the thermostat, not just the cable
Electric underfloor heating is an investment where it's worth thinking through the whole system – from the output of the heating element, through the laying method, to the control. The thermostat is the heart of the whole system and determines whether the heating actually works efficiently or just warms the air and wastes electricity.
For typical apartments and family homes, I recommend a digital programmable thermostat as a minimum – an example is the HAKL TH 900 digital thermostat, which covers the vast majority of typical needs. If you have an irregular schedule, multiple spaces, or want control over the heating even while traveling, invest in a wifi model such as the HAKL TH 951wifi or HAKL TH 952wifi – the price difference really pays off through lower consumption and greater comfort.
A manual thermostat has its place in specific situations, but for year-round occupied spaces, an underprogrammed regulator is a needless waste of money on electricity. Remember: the best heating cable paired with the cheapest thermostat can end up more expensive than an average cable with the right smart regulator.
Do you have a question on this topic?
Not sure what to decide, or dealing with a specific situation in your household? Write to us - we're happy to help.