Electronic vs. programmable thermostats for underfloor heating: which one is worth it

Electronic vs. programmable thermostats for underfloor heating: which one is really worth it?

When we talk about thermostats for underfloor heating, most people encounter a basic division: simple electronic thermostats and programmable thermostats with weekly or daily schedules. At first glance, it seems to be a simple choice – cheaper vs. more expensive. In practice, however, it is much more complicated, and choosing the wrong type of thermostat can mean either throwing money away unnecessarily or – worse – uncomfortable living and higher energy bills for years of operation.

After years of working with customers who are dealing with underfloor heating, we see the same scenarios again and again: someone buys the cheapest thermostat because "they just turn it on in the morning and off in the evening," and after two months calls to say that their electricity bill has jumped up. Another person pays for a top-of-the-line programmable model but never sets it up properly because the manual is incomprehensible. In this article, we will therefore look at both types in great detail – from a technical perspective as well as from the perspective of real daily practice.

What is an electronic thermostat for underfloor heating and how it works

An electronic thermostat – in common language also called a "manual electronic" – is a device that maintains the set temperature without any time schedule. The user simply sets the desired temperature (either the air temperature in the room, or the surface temperature of the floor, or a combination), the thermostat measures the actual state and accordingly turns the heating circuit on or off.

Technically, an electronic thermostat works with an NTC sensor (a thermistor with a negative temperature coefficient), which changes electrical resistance in proportion to the temperature. The control electronics compares the measured resistance with the desired value and controls the relay – usually with a switching power of 3,500 W (16 A) or 3,680 W at 230 V, which covers standard rooms. Some models work with a hysteresis of ±0.5 °C, which means that the relay does not switch constantly, but switches at 0.5 °C lower and turns off at 0.5 °C higher than the set value.

A typical representative of this category is, for example, SALUS RT10-230V – a compact, low-maintenance thermostat with a rotating wheel or buttons, an LCD display showing the current and set temperature, and a built-in floor sensor. Such a device can handle a room where automatic regulation in time is not needed – for example, a bathroom with an electric heating mat, where you simply want the floor to be warm at all times.

When an electronic thermostat is sufficient

From practice, we see that an electronic thermostat is the right choice in several typical scenarios:

• Bathroom or WC – spaces where floor temperature is desired continuously (or the entire heating can be easily turned off manually when leaving). There is no reason to pay for a program here, because the formula "I shower in the morning and in the evening" is exactly the case where you simplify the program in your mind yourself.
• Supplementary heating in a room with a primary heat source – if the underfloor heating is only a comfort heating of the floor and the air temperature is controlled by another system, the programmability of the underfloor heating thermostat loses most of its meaning.
• Rented spaces, airbnb – where you don't want guests to accidentally change the entire weekly program. A simple rotating regulator with min/max temperature limits is more robust against "creative" interference by visitors in this case.
• Buildings with irregular use – a cottage or weekend house, where you just don't have a predictable schedule. Here it is better to manually turn on the heating before arrival (or via smartphone, if you have a WiFi model) than to rely on a fixed schedule.

What is a programmable thermostat and what gives it an advantage

A programmable thermostat adds a time dimension to the electronic one – you can set different temperatures for different parts of the day and week. The basis is usually a weekly program with the possibility to set several temperature zones for 24 hours (commonly 4 to 6 temperature changes per day). More advanced models allow individual setting of each day of the week separately.

Technically, they work the same way as electronic thermostats – NTC sensor, relay, hysteresis – but in addition they contain a real-time clock (RTC, Real Time Clock) with its own battery in case of power failure and a program memory. It is important that the RTC clock is equipped with a backup battery at least CR2032 – without it, the thermostat would lose time and settings after each power failure.

A good example of a mid-range programmable model is SALUS ERT20 - 230V, which offers a 5+2 daily program (workweek + weekend) with 4 temperature changes per day. For more demanding applications and greater comfort in configuration, the SALUS ERT50 - 230V with a 7-day program and finer hour resolution is used.

Energy savings: concrete numbers, not just marketing promises

We are talking about concrete numbers, not vague "up to 30% savings" statements from promotional materials. Let's say you have an apartment of 70 m² with electric underfloor heating at 100 W/m², which is a total installed power of 7,000 W. At an average operation of 8 hours a day during the winter period (November–March, approx. 150 days), this represents 8,400 kWh for the heating season. The price of electricity in Slovakia in 2024 ranged around 0.18–0.22 €/kWh for households (depending on the distributor and tariff).

If a programmable thermostat reduces the temperature during the night (22:00–06:00) by 3–4 °C, the system consumes 30–40% less energy during this interval. Nighttime reduction lasts 8 hours = 33% of the day. Of the total 8,400 kWh, 33% is therefore made up of nighttime operation, i.e. approx. 2,800 kWh. Saving 35% of that = 980 kWh. At a price of 0.20 €/kWh, this is 196 € per year. A programmable thermostat costs 20–50 € more than a simple electronic one. Return on investment: less than 3 months of operation.

These numbers vary according to the specific installation, but the conclusion is clear: with electric underfloor heating as the primary heat source, a programmable thermostat pays for itself very quickly.

Technical parameters to focus on when choosing

Aside from the basic division of electronic/programmable, there are a few technical parameters that significantly influence the choice of thermostat for underfloor heating. A more detailed discussion is in the article How to choose a thermostat for underfloor heating: what to pay attention to, here we summarize the most important ones.

Switching power of the relay

Each thermostat has a maximum load that it can switch directly. Standard models for households have a relay rated for 10 A (2,300 W) or 16 A (3,680 W). If you have a larger area with higher power (e.g. bathroom + hallway + kitchen on one thermostat), you must either use a thermostat with a higher relay power or install an external contactor. More on this topic in the article Switching power of the thermostat for underfloor heating: how to determine it correctly.

Type of sensor: floor vs. air

A very important choice – the thermostat controls the temperature either according to the surface temperature of the floor (floor sensor), or according to the air temperature in the room (air sensor), or combined. For the bathroom, a floor sensor is ideal – you want the heat under your feet. For the living room, where underfloor heating is the primary heat source, a combination or air with floor protection is better. A detailed comparison can be found in the article Thermostat with floor sensor vs. air sensor: difference and when to use which.

Temperature range and limitations

Most thermostats allow setting from 5 to 40 °C. However, for underfloor heating, it is critical to set the maximum floor temperature – usually 27–29 °C for living areas (standard EN 1264-2), 33 °C for bathrooms and room edges. If the thermostat does not have an adjustable maximum floor temperature limit, incorrect wiring can damage the floor covering – parquet or laminate are sensitive to this.

Hysteresis

Hysteresis is the difference between the on and off temperature. A smaller hysteresis (±0.2–0.3 °C) means finer regulation, but the relay works more often. A larger one (±1 °C) saves the relay, but the temperature fluctuates. For underfloor heating, a hysteresis of ±0.5 °C is usually optimal.

Programmable thermostats in practice: what to pay attention to when setting up

One of the most common problems we encounter is an incorrectly programmed thermostat. The customer pays for a good programmable model, leaves it on the "factory" settings, and then wonders why the floor is not warm in the morning when they get up. Why? Because underfloor heating has a large thermal inertia.

Thermal inertia of the floor: key factor in programming

Unlike a radiator, which heats up in 10–15 minutes, a concrete screed with heating cable or mat under ceramic tiles takes 45 minutes to 2 hours to reach the desired surface temperature. This means that if you get up at 6:30, you need to program the thermostat so that it increases the temperature already at 4:30 or 5:00.

Some more advanced thermostats – for example, Jablotron AC-83 – have an adaptive start function (so-called auto-adapt or optimum start). The thermostat "learns" the thermal inertia of the specific installation and automatically shifts the on time so that the floor reaches the desired temperature exactly at the beginning of the programmed comfort period. It is therefore not necessary to manually estimate when to turn on the heating – the thermostat solves it itself after a few days of learning.

The simpler Jablotron AC-82 does not have an adaptive start, but offers clear weekly programming with 6 temperature changes per day and a reliable design proven in practice. It is an ideal compromise for those who want programmability, but are not interested in smart-home integration or advanced features.

Typical programming for a working family – concrete example

Let's take a real scenario: a family with two adults, both going to work from 7:30 to 17:00, children going to school. An 80 m² apartment, electric underfloor heating as the primary heat source in the living room and kitchen, a bathroom with a heating mat on a separate thermostat.

For the living room/kitchen, an optimal weekly program would look like this:

• 05:00 – 08:00 – 21 °C (morning comfort temperature, family time before leaving)
• 08:00 – 15:30 – 17 °C (reduction during absence – savings)
• 15:30 – 22:30 – 21 °C (comfort after returning, evening)
• 22:30 – 05:00 – 16 °C (night reduction)

For the bathroom on a separate thermostat (a simple electronic one is sufficient, or a programmable one with a simpler program):

• 05:30 – 08:30 – 26 °C (morning washing)
• 08:30 – 20:00 – 20 °C (mild comfort in case someone is at home)
• 20:00 – 22:00 – 26 °C (evening bath for the children)
• 22:00 – 05:30 – 16 °C (night reduction)

This setting in practice saves 25–35% of costs compared to constant operation at 21 °C, while comfort is not reduced at all – in fact, you step onto a warm floor in the morning and return to a warm apartment in the evening.

Comparison of models in practice: electronic vs. programmable

In the following table, we summarize the key differences that emerge from daily practice and technical parameters of specific devices available in the category thermostats for underfloor heating:

Installation and wiring: what to think about during installation

Whether you choose an electronic or programmable thermostat, the installation proceeds in principle the same way – the thermostat is installed in a standard electrical box Ø68 mm, built into the wall at a height of 1.2–1.5 m (recommended height according to the standard). 230 V power is brought to the thermostat and the output leads to the heating mat or cable in the floor.

A detailed installation procedure can be found in the article Installation of a thermostat for underfloor heating: step by step and electrical wiring diagrams in the article Wiring of a thermostat for underfloor heating: diagram and most common errors. Here we highlight a few practical points that are handled a bit differently with programmable thermostats than with simple electronic ones:

• Protection against power failure – programmable thermostats must have a backup battery. During installation, check that the battery is in good condition and note the replacement date (typically 2–3 years). Without a battery, the thermostat will lose time and program after a power failure.
• Position of the floor sensor – the sensor is placed in a protective sleeve (plastic tube Ø16–20 mm) embedded in the screed. It must be in the middle between the heating cables, not over the cable and not too close to the wall. Proper placement is the subject of the article Setting up the floor temperature sensor: correct depth and placement.
• Setting the resistance of the external sensor – before the first start, it is necessary to set the correct type of NTC sensor in the thermostat (10 kΩ at 25 °C is the most common standard, but some sensors have 12 kΩ or 15 kΩ). Mixing up the sensor type will cause incorrect temperature measurement by up to 5–8 °C!

Smart thermostats: where they fall between the two categories

In recent years, a third category has appeared on the market – so-called smart thermostats with WiFi or ZigBee/Z-Wave connectivity. Technically, they are programmable thermostats, but they are controlled via a smartphone, tablet, or voice assistant (Google Home, Amazon Alexa). You can change the schedule remotely, track consumption history, and receive notifications.

For underfloor heating, smart thermostats are very interesting especially in cases where the schedule changes irregularly – for example, when working from home, traveling, or managing multiple households. The disadvantage is the higher price (60–150 €), dependence on the WiFi network, and the need to have the base unit always charged (or connected).

If you are interested in a detailed comparison of specific models from the range, see the article SALUS vs. Jablotron thermostat for underfloor heating: model comparison.

Most common mistakes when choosing and setting up

From practice, we see the same mistakes again and again, regardless of whether the customer chooses an electronic or programmable model:

• Underestimating thermal inertia – a thermostat set to a comfortable temperature from 07:00 is not enough, because the floor heats up from 05:00. Result: the customer gets up on a cold floor and thinks the thermostat is broken.
• Wrong sensor resistance – as mentioned above, mixing up the type of NTC sensor (10 kΩ vs. 15 kΩ) causes a systematic measurement error.
• Thermostat in the wrong position – placing the thermostat (air) directly over the heating element, on the sunny side, in a draft, or behind curtains. This causes false temperature measurement.
• Purchasing an electronic thermostat for a large area – the customer buys a cheap thermostat for a 35 m² living room with 3,500 W and then wonders why their annual consumption is twice as high as the neighbor's.
• Ignoring the floor protection limit – when using a heat-sensitive floor covering (laminate, teak, bamboo), it is essential to set the maximum floor temperature to 27 °C. Some cheap electronic thermostats do not have this function at all.

Problems related to the operation and diagnosis of thermostats are discussed in detail in the article Common thermostat problems for underfloor heating and how to fix them.

Frequently asked questions (FAQ)

Is a programmable thermostat always better than an electronic one?

Not automatically. For a bathroom with a heating mat, where you want the floor to be warm in the morning and evening and the temperature is not important for the rest of the day, a simple electronic thermostat is sufficient – for example, SALUS RT10-230V. If the underfloor heating is the primary heat source in living areas, a programmable model definitely pays off and pays for itself in energy savings within a few months.

What happens if a programmable thermostat loses power and does not have a backup battery?

The thermostat will lose the set time and program. After power is restored, it will either work in emergency mode (constant temperature, usually 15–18 °C) or the entire program will reset to factory settings. Therefore, a backup battery is an absolute necessity for programmable thermostats. Replace the CR2032 battery every 2–3 years.

Can I connect the heating of the entire apartment to one thermostat?

It depends on the total power. If you have an 60 m² apartment with 100 W/m², that is 6,000 W – most standard thermostats switch a maximum of 3,680 W (16 A). For higher power, an external contactor or several separate circuits, each with its own thermostat, are needed. More details in the article Switching power of the thermostat for underfloor heating: how to determine it correctly.

Is it worth buying a WiFi smart thermostat instead of a classic programmable one?

It depends on your lifestyle. If you have a regular schedule and simply want to save energy, a classic programmable model is more cost-effective and reliable. A smart thermostat makes sense with an irregular schedule, travel, working from home at different times, or if you are interested in integration with a smart home. The price difference is 30–80 € and in some cases this investment pays off extra savings due to remote control.

Do I need to buy a separate thermostat for each room?

In principle for comfort and efficiency – yes, we recommend a separate thermostat for each room with underfloor heating. Each room has different heat losses, different usage patterns and different orientations to the cardinal points. One common regulation leads to compromise temperatures in each room and unnecessarily overheats or underheats some areas.

How long do these thermostats last and when should they be replaced?

Quality thermostats from manufacturers such as SALUS or Jablotron have a lifespan of 8–15 years with normal use. The critical component is the relay – it is dimensioned for 100,000 to 200,000 switching cycles. At a frequency of switching once every 15 minutes, this represents about 30–50 years, which is more than the lifespan of the other electronics. The most common reason for replacement is failure of the LCD display, cracked buttons or obsolescence (unavailability of replacement sensors). More information in the article Common questions about thermostats for underfloor heating.

Conclusion: which type of thermostat to choose?

The answer is not universal, but after reading this article, it should be clear for your specific case. An electronic thermostat is the right choice when you want simplicity, low cost and underfloor heating is not the key role in heating the space. A programmable thermostat is an investment that pays off – and with electric underfloor heating as the primary heat source, it pays off quickly.

If you are facing a specific choice, the following simple rule works in most cases: bathroom = an electronic thermostat is sufficient; living room, bedroom, children's room with underfloor heating = a programmable thermostat definitely pays off. For more demanding applications and greater comfort in management, choose a model with adaptive start and WiFi connectivity.

A complete overview of available models can be found in the category thermostats for underfloor heating. Before making a final decision, also read the accompanying articles in the Knowledge Center – especially How to choose a thermostat for underfloor heating: what to pay attention to and Thermostat with floor sensor vs. air sensor: difference and when to use which, which will help you refine your choice according to the specific conditions of your installation.