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Best Radiator Thermostat 2019 • 0 Radiator Thermostats Reviews

What is a radiator thermostat and how does it work?

Thermostats themselves are available in different forms for use in different areas. All types have the basic function in common: a thermostat measures the temperature, via a temperature probe and makes it possible, via a so-called actuator, to reach and maintain as constant a preset temperature as possible. Thermostats are therefore also referred to as temperature controllers.

The most common type building heating, is that of hot water heating. Here, water is heated in a heating system, which can be found in different designs depending on the type of heating, and pumped through pipes to the individual radiators. The basic principle is the same for all H types of stimulation and associated energy sources. Radiators distribute the previously heated water inside them over as large an area as possible, thus enabling heat exchange with the ambient air and heating the surrounding room.

A radiator thermostat usually regulates whether hot water is introduced into a radiator, or in what quantities and at what intervals. This is located in the inlet of the radiator and can thus open or close the water inlet, usually steplessly. The temperature-dependent control is carried out via a so-called actuator. This is a expansion element filled with wax, liquid or gas, which expands when heated and presses a plunger called transfer pin onto the actual valve, thus reducing the cross-section of the inlet pipe to the radiator and thus the water flow. The position of the adjustment head determined by rotation determines the distance between the expansion element and the heating valve and thus the maximum flow rate. If, for example, a medium setting of the radiator thermostat is selected at level 3, this corresponds to a target room temperature of 20 °C. The temperature of the room in which the radiator is to be used is 20 °C. As long as this is not reached, the flow of hot water into the radiator remains open. Once the temperature is reached, this corresponds to a degree of actuator expansion sufficient to close the valve completely.

Benefits and applications of a radiator thermostat

Radiator thermostats provide convenient temperature control for each individual room in which radiators are located. Operation is uncomplicated and can be carried out at any time without major effort. Especially in residential situations where there is no direct access to the actual heating system and therefore the heating output cannot be regulated, as is the case, for example, with rental apartments connected to a central heating, thermostats are usually the only way to influence the room temperature.

With radiator thermostats the heating output can be precisely adapted to individual requirements. Frequently used rooms can be heated continuously, while rarely used rooms can be lowered accordingly.

Once a temperature has been set, it is held permanently without the need for readjustment. This prevents overheating of the room as well as a noticeable drop in room temperature. In addition to the thus guaranteed pleasant room climate, a radiator thermostat also helps to save energy, since never more heating output is called than absolutely necessary or desired.

Heater thermostats are easy to install, can be easily removed at any time without extensive tools or technical knowledge and skills, and reused on other heaters.

Benefits of a radiator thermostat

  • most economical solution
  • available on all radiator models
  • easy to mount
  • easy to operate
  • allows an individual room climate for each individual room
  • help to save energy
  • reusable, for example after moving

Disadvantages of a radiator thermostat

  • each radiator must be adjusted separately
  • Change of setting requires presence
  • Inaccuracy due to temperature measurement directly on the radiator
  • medium-term susceptible to wear

What types of radiator thermostats are there?

There are different types of radiator thermostats for different applications. In their basic function, mechanical flow regulation based on presetting and measuring the ambient temperature, all types are the same.

How this setting, measurement and control is implemented in detail distinguishes it and determines advantages and limitations.

mechanical radiator thermostats

The classic radiator thermostat described here works purely mechanically and is manually preset via the shaping adjustment head.

pre-settable radiator thermostats

Simple radiator thermostats are mounted on the existing radiator valve and operate it temperature-dependently via the rotary control as well as actuator and plung. The choice is made in stages between complete closure and complete opening of the valve and thus of the water flow. In some cases, this adjustment range is not optimal for an existing combination of room size, desired room temperature and type and size of radiator. In these cases, a preset thermostatic valve is often used.

Presettable Thermostatic valves are not visible at first sight. Differences to classic valves only become apparent after dismantling the adjusting head and looking at the screwed-in valve.

A closer look reveals the differences: a presettable thermostatic valve, like the radiator thermostat itself, has an adjustment option along a scale with, for example, six steps (1 – 6). Adjustment is made by means of a special key which is placed on the valve and turned to the desired level.

The default setting enables a permanent limitation of the maximum flow rate and thus the maximum temperature, independent of the setting of the radiator thermostat. If, for example, a six-stage presettable thermostatic valve is set to stage 3, only half of the maximum design flow rate will still be reached at the maximum position of the radiator thermostat.

Authority models

A so-called authorities model resembles a normal radiator thermostat at first glance, but has more in common with the described preset radiator thermostat.

As the name suggests, the authority model is mostly used in public institutions. Here the influence on the heat settings should be limited or even completely prevented if possible. For this reason, such models have a minimum adjustment range, which allows temperature adjustment in a small range, for example between 17 and 21 °C. The temperature range can be adjusted to suit the application. In addition, the setting heads are usually manufactured to be particularly robust in order to prevent damage due to improper operation.

Thermostat controller with remote control

A significant disadvantage of a classic radiator thermostat is the temperature measurement directly on the radiator. Depending on the size of the room, the position of the radiator and the number of individual radiators in a room, the temperature measured in this way and the actual average room temperature may differ significantly. In order to find the individually correct setting, a room temperature measurement on the opposite side of the room to the radiator is therefore also recommended.

Moreover, some radiators are not easily accessible. Thus, even if this is not recommended very much, pieces of furniture are regularly placed in front of radiators and radiator claddings are still to be found at least in individual cases. In all these cases, it is a considerable effort to make settings on the radiator thermostat.

With thermostat controllers with remote adjuster, the thermostat and valve are separated from each other. Otherwise, this variant is also similar to the described technical principle: an expansion element reacts to the ambient temperature, but does not operate a plunger and consequently the valve, as is the case with a normal radiator thermostat, but moves the hydraulic fluid in a cable-like capillary tube, which in turn moves a hydraulic cylinder that opens or closes the valve. The manual setting as well as the temperature measurement can thus be carried out as far away from the radiator as the cable length permits.

Advantages of the thermostat control with remote adjuster

  • more accurate temperature measurement
  • Operation of even hard-to-reach radiators

Disadvantages of thermostat controller with remote adjuster

  • additional installation effort
  • only useful for single radiators

Electric, programmable radiator thermostats

Normal radiator thermostats and thermostat controllers with remote control are set in steps. Most models give five levels, partly with scaling between the individual levels. In addition, there is a defrost setting which prevents damage to the heating system in winter at temperatures below six degrees.

Although each stage corresponds to a temperature that is intended to be reached and maintained by the valve position dependent on it, the setting is not self-explanatory and precise in this respect. For example, as a guide value, a room temperature of 20 °C is applied at level 3 with a medium setting, and an adjustment by one level is associated with a temperature difference of around 4 °C.

A setting made once is retained until it is manually changed again. This also means that a radiator heats even when there is nobody in the house or vice versa, the room is unheated when you enter it again after a long time. Alternatively, only a low medium setting can be selected here, which promises lower losses during absence and at the same time keeps the duration for heating up the room as short as possible after setting a higher stage.

Convenient remedies promise electrical, programmable radiator thermostats. The basic principle of these devices is similar to that of simple, manual radiator thermostats, but the valve adjustment is motorized. A small electric motor, usually operated with standard batteries, rotates a shaft which pushes out or retracts a plunger which in turn determines the position of the radiator valve.

The setting is here, analogous to the purely mechanical radiator thermostat, usually also possible directly via a controller on the device. In contrast to simple thermostats, however, it is also possible to program heating cycles digitally. Electrical radiator thermostats usually have an LCD display for this purpose. Several heating cycles can be programmed via this. As a rule, a heating temperature (day) and a set-back temperature (night) are set. Subsequently, time windows can be set separately for individual weekdays or also for weekdays and weekends, to which one of the temperatures is assigned in each case. Based on the set current time and date, the temperature control is then fully automatic.

In addition, most models have a “Open Window” function: if the built-in sensor measures a sudden, significant drop in temperature, the thermostat interprets this as an indication of an open window and adjusts the radiator down.

Advantages of the programmable radiator thermostat

  • all the advantages of the classic radiator thermostat
  • individual adjustment of heating times
  • precise adjustment of target temperature in °C
  • Additional energy and cost savings through targeted heating

Disadvantages of programmable radiator thermostat

  • functional only with sufficient battery capacity
  • optimally usable only with predictable weekly planning

Remote controlled radiator thermostats

Home automation is a term that has become increasingly important and interesting for property owners in recent years. In principle, even simple programmable radiator thermostats are already elements of such home automation, as described, but the possibilities of spontaneous influence are limited in such models.

Radio remote controlled Heating radiator thermostats extend the operating possibilities considerably. In addition to setting the heating cycles on the device, they offer the possibility of remote access.

Access to the radiator thermostat and all setting options is usually via Bluetooth. Although there is often talk of WLAN radiator thermostats, the individual devices usually only have a Bluetooth interface via which they can either be addressed directly or connected to a central control unit, which in turn can be integrated into a network via WLAN.

Thus there are different possibilities to operate a remote controlled radiator thermostat:

  • programming directly on the device, as with conventional electric radiator thermostat
  • Setting the current heat output or programming via Bluetooth, from a short distance
  • Access via a router connected to the Internet, which in turn is connected to a control unit, which in turn accesses individual radiator thermostats via Bluetooth

Remote controlled Heating radiator thermostats usually work in conjunction with an app that can be run on a tablet computer or smartphone. In addition to the possibility of longer-term programming, conveniently from the sofa, in conjunction with a control unit, in a network with Internet access, from anywhere in the world, at any time, the domestic heating can be accessed. The only requirement is an active Internet connection.

Advantages of a remote controlled radiator thermostat

  • convenient operation via App
  • Access also possible from the greatest distance
  • spontaneous change in room temperature at any desired time
  • optimal energy saving option
  • can be combined with other elements of home automation

Disadvantages of a remote controlled radiator thermostat

  • further components required (central control unit, network router, Internet access, smart phone or tablet)
  • additional installation effort (network integration)
  • Operation requires basic knowledge in dealing with modern communication technology
  • significantly higher initial investment
  • Remote control dependent on active power and Internet supply (problem: power failure or network failure)

So we have tested radiator thermostats

A radiator thermostat test refers mainly to two areas: the operability of a model and its accuracy.

The question of operability begins with the necessary assembly and, if necessary, installation.

Assembly and installation

A classic Heating radiator thermostat is screwed onto the built-in valve with a union nut. As a rule, this is done hand-tight, which is why assembly should always be possible without tools. However, a simple water pump pliers is often required to carefully loosen a tight connection. When mounting a new thermostat , tools can be dispensed with as long as a stable and correct fit can be guaranteed. Since the actuating pin is completely pushed out by a return spring without an attachment and the valve is thus completely open, a new thermostat should be set to the highest possible level when mounting is used.

A radiator thermostat Test checks all necessary connecting elements for operability and reliability. It is also checked for which radiator models a thermostat is suitable, for which adapters may be included in the scope of delivery or must be purchased additionally.

With classic radiator thermostats no further installation is necessary.

In addition to the installation described above, an initial installation is also required for electrical thermostats. Starting with inserting the necessary batteries, setting the current time and date, up to programming the day and night temperature. The radiator thermostat Test also assesses how such an initial installation is to be carried out, how understandable the display and the menu structure are. Most models have to be programmed directly on the device, while individual manufacturers also offer devices that can be connected to a computer via USB and can thus be programmed easily.

The installation effort for remote-controlled radiator thermostats is considerably higher than for other types. These must also be mounted. However, the actual programming only takes place after a connection to further control components has been established. This means at least establishing a Bluetooth connection to a suitable terminal device, such as a smartphone or tablet.

For radiator thermostats that are coupled with a control unit, their integration into a network is also required.

Ease of use

With the simple radiator thermostat, a test of the operability is limited to the ease of movement of the adjustment head, its scaling and, as far as possible, clearly legible labelling. In addition, some models have comfort features such as individual setpoint limitation which can be used to limit the controller's setting range.

For all types electronic radiator thermostats special attention is paid to the control elements and the necessary programming procedure. How self-explanatory is this process, how comprehensible is a necessary operating manual designed and how easy and precise are buttons, switches and controllers to operate? What information does a display provide and how well can it be read? What types of batteries are needed and how easy is it to change them?

In the case of remote-controlled models, the necessary control software is also evaluated. For which platforms is this available? How easy is it to install and, above all, to use by amateurs?

What to look out for when buying a radiator thermostat?

Before choosing a specific manufacturer or model, you have to decide on a type of construction. If only a single, perhaps defective Thermostat is to be replaced, the choice usually depends on the otherwise installed models. If a heating system is newly installed or a conversion of several radiators is considered, the general conditions and heating habits should be reconsidered in order to make a sensible long-term decision.

How many radiators should be controlled in total?

In addition to the question of an overall necessary investment, the number of radiators to be controlled regularly also determines the choice of the appropriate radiator thermostat for other reasons. The more radiators that need to be controlled, the greater the effort involved in using simple mechanical thermostats.

How constant are your lifestyle habits?

The more constant the daily routine, the less often a radiator has to be readjusted. If you use the same rooms in the same room at the same time every day, you rarely have to change the thermostat, which also keeps the effort within limits when using classic, mechanical radiator thermostate. If these habits change from day to day or at least within a weekly rhythm, an electrical, programmable Thermostat can provide good services. This allows automatic adjustment for each day of the week in several heating cycles.

The optimal solution for irregular heating habits is remote control. This enables convenient, long-term programming as well as spontaneous remote access.

What are the technical requirements?

In addition to spatial conditions that can limit the use of classic radiator thermostats, such as radiators that are difficult to access, technically advanced systems in particular require an appropriate environment. Thus a remote controllable radiator thermostat can also be operated exclusively from a control device such as a smartphone or tablet, via Bluetooth, at close range, but this only represents a greater ease of operation compared to electrical, programmable thermostats without remote control. Such models, especially when used with a complete heating system, can only play out their real added value if they are connected to a network and operated remotely via the Internet. For this, however, the corresponding technical prerequisites must be available.

Leading manufacturers


The brand Buderus originates from the company Buderus founded in 1731 and, after various takeovers and mergers, is distributed today by Bosch Thermotechnik GmbH, based in Wetzlar, in addition to the brand Junkers. The product range includes all components of complete heating systems of all sizes. The heating accessories also offered include radiator thermostats.

Although numerous products of modern control and regulation technology are sold under the Buderus brand, the range of simple radiator thermostats is limited to some models of classic, mechanical thermostats.


Danfoss A/S, a public limited company founded in 1933 and based in Nordborg, Denmark, manufactures heating and refrigeration products in 21 countries. The company founder Mad Clausens already invented the thermostatic radiator valve in the 50s. The range includes classic radiator thermostats as well as design models and radio-controlled thermostats and control units required for remote access.

Honeywell/ Rondostat

Honeywell International Inc., Morristown, New Jersey, USA, founded in 1885, is active in numerous fields. These include chemicals, aerospace, transportation, armaments and automation. The basis for this is above all a series of acquisitions and mergers. The business segment Automation and Control Solutions (ACS) produces equipment from the building technology segment.

Under the name Honeywell, both classic radiator thermostats and electrical, programmable models are sold.

The Rondostat brand is also part of the Honeywell International Inc. program and offers individual models of electric, programmable radiator controllers.


Oventrop GmbH & Co KG is one of the leading manufacturers of valves and control systems for building services throughout Europe. Oventrop sells classic radiator thermostats as well as components of modern central control systems for building services engineering.

Sources of supply for radiator thermostats – specialist trade vs. Internet

The various radiator thermostats are mainly found in DIY stores and in specialist heating and plumbing retailers.

In particular, electric, programmable thermostats are offered again and again also in the simple retail trade and are found even in the temporally limited, seasonal offer of well-known discounters. However, a truly comprehensive range can be found above all in online trading. On the one hand the manufacturers themselves offer an overview of their product range and in some cases a direct ordering option, on the other hand the products of most manufacturers are offered via well-known trading platforms.

The Internet offers the possibility to inform oneself comprehensively and to compare different offers with each other, to compare and to select the individually suitable model.

Things to know and advice

The history of the radiator thermostat

The first known hot water heating dates back to 1716 and was used to heat a greenhouse. From the beginning of the 20th century, castles and villas, a noble and wealthy minority, increasingly brought the system into private residential construction.

In the beginning the influence on the heating power was limited to a simple switching on or off. Graduated or even room temperature-dependent control was not possible.

Already in the 1930s, the founder of the company known to this day Danfoss designed the first versions of a thermostat. However, it took more than a decade, until 1946, before the product was ready for production and market launch. Although the radiator thermostat already worked according to the principle still in use today and was therefore reliable, interest was initially low. The main reason for this was the widespread lack of insight into the need to save energy at that time.

Only the oil crisis of the 70's and the resulting Heating plant regulation, from the year 1978 led finally to a surface covering spreading.

At the turn of the millennium, the trend towards home automation, represented by the catchword Smart-Home, begins to attract more and more public attention. Since then, the number of manufacturers and models for the automation of temperature control has been increasing steadily.

Simple installation of a radiator thermostat

Before a new Thermostat can be installed, its predecessor usually has to be dismantled. The assembly is comparatively simple and harmless. Since the radiator thermostat is an attachment to the screwed-in radiator valve, the system remains closed, even when dismantled, so that no heating water can escape. In order to avoid burns, the radiator should cool down as much as possible before disassembly and assembly.

  • Open the Heating radiator thermostat completely.
  • loosen the knurled screw or union nut of the thermostat. This should not be very tightly tightened and can therefore be loosened without effort with a simple water pump pliers.
  • After loosening the screw connection, the radiator thermostat can simply be pulled off. Occasionally a slight jolt is required but even here you should not work with force.

The installation of a new thermostat is always carried out in reverse order.

When buying, you should make sure that the connection is correct, as there are different thread types depending on the radiator model and manufacturer.
For electrical, programmable Thermostats the connection usually consists of adapters with plastic threads. As a rule, these are included in the scope of delivery in different versions for different radiator types. They should be handled with special care, as simple plastic threads can be more easily damaged.[/box]
  • Set the new Thermostat to the maximum temperature level before installation.
  • Plug the radiator thermostat or, for many electric models, the device holder onto the radiator valve.
  • Tighten the knurled screw or union nut carefully by hand. You can then tighten the connection carefully with a water pump pliers, but without using too much force.

FAQ – Frequently Asked Questions

How do radiator thermostats save energy?

A house or an apartment consists of several rooms, each of which fulfils different functions. Depending on their use, a different room temperature is also regarded as sensible. Bathrooms, for example, are usually warmer than living rooms and these, in turn, are warmer than bedrooms.

Without radiator thermostat and thus without room-related temperature control, there would only be a choice between heating to full capacity and not heating for a heating system.
At most, the maximum capacity of a burner could be regulated in this way. This would either overheat individual rooms or heat others too little. As a rule, one would certainly rather accept the overheating of individual rooms, which would ultimately lead to unnecessary energy expenditure. The individual temperature control, for each individual room, allows an exact adaptation to the own needs and preferences and thus an optimal efficiency.[/box]

May I exchange the thermostats in my rented apartment?

Yes, there is nothing to prevent you from replacing existing thermostats at your own expense. For example, you can replace conventional radiator thermostats with programmable or remote-controlled models as a simple tenant. However, the thermostats available at the time of moving in are generally the property of the apartment owner. You should therefore store them and replace them before moving out.

Why are only numbers indicated on a radiator thermostat, no temperatures?

The actual room temperature reached at a certain position of the radiator thermostat depends on several factors. The thermostat measures the ambient temperature and thus determines the valve position. When the set temperature (or better temperature level) is reached, the thermostat closes the heating valve. The measurement is carried out directly on the radiator.

Depending on the room design, the temperature measured here does not have to correspond to the actual, average room temperature.
An exact indication of a temperature on the controller would only be misleading in this respect. However, an intermediate level 3 corresponds to a temperature of approximately 20 °C measured on the thermostat.[/box]

How to operate a radiator thermostat most effectively?

Who enters a cooled down room, tends frequently to turn on a radiator thermostat immediately fully, in the assumption this would warm up the room as fast as possible. However, this is a mistake. Radiators function according to the principle of heat transfer: Water is heated to a predetermined temperature of up to 90 °C in a heating system, usually by a burner. This water then passes through a radiator made of a material with good thermal conductivity, releasing the heat to the ambient air, which in turn heats up, increasing the overall room temperature.

A higher level of the radiator thermostat does not change this basic principle and does not accelerate the heat dissipation and thus not the increase of the room temperature.
The setting on the radiator thermostat only determines until which room temperature hot water is continuously introduced into the radiator.[/box]

A further point of contention is the question of the sense or nonsense of lowering the room temperature during a planned, prolonged absence. In a nutshell: the faster a room can cool down, which mainly depends on its insulation but also on its location, the more sensible it is to lower the room temperature during long periods of absence.

In practice, a reduction to about 16 degrees is recommended, as this saves energy on the one hand, but on the other hand does not cool a room down to such an extent that there is a risk of mildew or subsequent heating takes excessive time.

Woran you can see a defect of the radiator thermostat?

Like almost all technical and mechanical devices, a radiator thermostat is subject to natural wear. However, this is not always noticeable to the user at first glance. If, however, a thermostat is clearly stiff or makes unusual noises during adjustment, an exchange should be urgently considered. The same applies in the event that a radiator becomes or remains hot, even though the controller is at the lowest level or defrost, or conversely remains cold or only moderately warm at the highest level. All this, of course, under the condition that the heating system itself functions correctly.

Defects that only lead to deviations from the optimum heating output are much more difficult to detect. Only a clear deviation of the room temperature from the set temperature provides an indication of a defect or severe wear. However, this also depends on the individual spatial conditions.

In general, it is therefore recommended to consider an exchange after about 15 years. It should always be borne in mind that a new radiator thermostat, perhaps even a more advanced design, allows energy savings that can justify an investment.

How to program an electronic radiator thermostat?

The exact operation of a programmable thermostat always depends, at least in parts, on the manufacturer and model. However, the programming is basically the same for most models from all manufacturers.

For an initial installation, which is usually started automatically after the necessary batteries have been inserted, the current date and time must first be entered. The device then asks for a temperature value for heating operation, which is usually marked with a sun symbol as daytime operation and a second value for set-back operation, which is usually marked with a moon symbol as night setting. The time intervals during which heating operation is activated can then be set, either separately for each individual day or for workdays and weekends. Outside these time periods, the unit switches to lowering mode.

As a rule, manual operation, automatic operation and complete deactivation can be selected on the device. The current setting can usually also be changed during automatic operation via a controller. Such a change is valid until the next cycle change. A key lock prevents unintentional changing of the settings.

Even in the deactivated state (summer operation), most devices carry out a complete valve opening at regular intervals and then a closure, in order to maintain the functionality of the valve and to prevent the tappet from getting stuck.

Alternatives to radiator thermostat

Some heating systems dispense with temperature control directly on the radiator by means of one of the radiator thermostats described. In most cases room thermostats and sometimes outdoor temperature sensors are used.

In the case of room thermostat measurement a single room is usually used as reference room. If the temperature in this room falls below the set temperature, the heating system switches on and works until the desired room temperature is reached. The temperature in the reference room alone counts here. Systems with outdoor temperature measurement also use the values measured here and control using parameters that can also be selected.

Some modern plants work with several reference rooms, up to a measurement in each room. Only when each room has reached the set desired temperature is a heating process interrupted or, if the temperature in a room drops, all rooms are heated again.


Radiator thermostats reduce effort, protect your nerves and the environment and save money. Even simple classic models provide good service and are usually quickly assembled, easy to use and reliable. However, the usually low acquisition costs allow only a small individual adjustment without frequent readjustment and therefore lead to a certain extent either to unnecessary energy consumption or not always optimal regulation of the room temperature.

If you want to adjust the room temperature as precisely as possible to your individual living habits and thus also want to exploit the maximum savings potential, then electric radiator thermostats are clearly to be recommended. Even simple programmable models, which can be retrofitted without great effort and are already extremely inexpensive, enable precise adaptation to individual living habits and thus heating habits.

Those who strive for absolute freedom and cannot or do not want to commit themselves to a week or a daily rhythm will find the support they are looking for in the growing range of remote-controlled radiator thermostats. Spontaneously, still on the way home from an unscheduled appointment, turn up the heating and be greeted by cosy warmth? With Smart-Home solutions, it's not a dream of the future, but lived reality and state-of-the-art technology.

No matter which solution you choose or are interested in, the Internet offers information and comprehensive offers as well as expert evaluations of individual products in the heating radiator thermostat test.

Continuing links and sources

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