Last updated: 16/10/2022

The function of radiator thermostats is to enable simple and smart regulation of the radiator temperature. Whether the radiator thermostat is to be manually adjustable, programmable or controllable via app, thanks to the different types, all wishes can be covered. Replacing an old or defective thermostat is not only important for your personal well-being at home, but also to save on heating costs. With our large radiator thermostat test 2022 we want to help you find the best radiator thermostat for you. We have compared mechanical and electronic radiator thermostats as well as radio radiator thermostats with each other and listed the respective advantages and disadvantages. This should make your purchase decision as easy as possible.




Summary

  • A radiator thermostat is attached to a radiator and allows you to control the regulation of the temperature.
  • Basically, we distinguish between three types: mechanical and electronic radiator thermostats and radio radiator thermostats.
  • Mechanical models are suitable for the simplest possible operation of the thermostat. If heating costs are to be saved and additional functions are desired, electronic or radio-controlled models will serve you well.

The Best Radiator Thermostat: Our Picks

Guide: Questions you should ask yourself before buying a radiator thermostat

What is a radiator thermostat?

The radiator thermostat is responsible for regulating the temperature of the radiator. The radiator has heating water flowing through it, which gives off heat. When and how much water flows in is determined by the valve built into the radiator thermostat. It is therefore an important component of every heating system. Basically, we distinguish between a mechanical radiator thermostat, an electronic radiator thermostat and a radio radiator thermostat.

Heizkörperthermostat-1

With mechanical radiator thermostats, the temperature is set on the basis of various stages.
(Image source: pixabay.com / ri)

All types of radiator thermostats have the same function. The only difference is that they are designed to meet different needs and their operation varies. In the Decision section, we will go into more detail about the three types and show you the advantages and disadvantages of each.

How does a radiator thermostat work?

Mechanical radiator thermostat

The radiator thermostat consists of an upper and a lower part. The valve is located in the lower part. In the upper part, called the thermostat head, there is a liquid or gas which adjusts its volume according to the temperature. The valve pin is controlled with this and with manual adjustment on the temperature controller.

The desired room temperature is set by means of the temperature controller on the thermostatic head and thus also the position of the valve pin.

The valve pin extends from the thermostat head to the valve. Its position determines the size of the valve opening. If it presses on the valve, the opening is reduced and less heating water flows into the radiator. If it presses little or not at all on the valve, the valve opening becomes larger and more heating water flows in. If the temperature controller is turned to a lower setting, the valve pin is pressed onto the valve. If it is set to a higher level, it pulls the pin away from the valve. If the desired temperature is reached and the same heat would continue to be emitted, it could become too warm as a result. Therefore, the valve pin is still controlled by the liquid or gas in the thermostatic head. If the room temperature is too high, the liquid or gas expands and this causes the valve pin to press on the valve. Conversely, if the temperature is lower, the volume is reduced, the valve pin no longer presses on the valve and it can open.

Electronic radiator thermostat & radio radiator thermostat

With an electronic radiator thermostat & a radio radiator thermostat, the heating water supply basically works the same as with the mechanical type. However, the room temperature is measured by an electronic sensor and an electric motor controls the valve.

When do you need to replace a radiator thermostat?

Two reasons for replacing your radiator thermostat are that the thermostat is defective or that you want a new model. In most cases, the valve can still be used and only the thermostat head must/could be replaced.

The radiator thermostat is broken

When you should replace a radiator thermostat depends entirely on how well it works. Signs of a defective radiator thermostat would be, for example, that your radiator no longer cools down properly or if the temperature controller can no longer be moved properly. Then, at the latest, it would be time to replace the model.

If no problems occur over a longer period of time, the rule of thumb is that radiator thermostats should be replaced about every 15 years. However, there is no obligation to replace them.

One way to determine whether it would be necessary to replace the radiator thermostat is to unscrew the thermostat head and check whether the valve pin is already worn. If this is the case, the pin can no longer press properly on the valve, which no longer guarantees proper functioning.

Saving heating costs

Another reason for changing your radiator thermostat would be the desire to save heating costs. On the one hand, higher costs may be incurred if the heating valve no longer functions properly. For example, if it continues to heat without a higher room temperature being desired. On the other hand, you may have a need for a programmable model. If you are often away from home and you do not want to heat the room to the same extent when you are away.

What types of connection are there for a radiator thermostat?

Basically, all different radiator thermostats can be attached to the radiator. However, you may still need an additional adapter.

It is important to note which thread size your valve has and how your radiator is positioned. You may need an adapter with a special fit for your desired model (such as an angle adapter).

To avoid finding out after buying a new radiator thermostat that the model does not fit the thread, you can consider the following points before buying:

  • If you want to replace a faulty radiator thermostat, you can look for similar models.
  • Consider the location of your radiator or where the radiator thermostat will be placed. Ask yourself how the thermostat can be removed.
  • Measure the thread size of your valve before buying.
  • Check whether a suitable adapter is included with the radiator thermostat.

What are the alternatives to a radiator thermostat?

If you heat your home with the usual boiler, the use of a thermostat is inevitable. However, it is possible to control the heating system (the boiler) directly. Room thermostats or outdoor temperature sensors are usually used for this purpose. Alternatives to heating with a heating system would be electric radiators or heating with wood. In the following section, we provide you with a brief overview of the alternatives.
Type Description
Room thermostat The desired temperature is set on the thermostat. It measures the room temperature and if this is lower than the specified value, the radiators heat until the actual room temperature is restored.
Outdoor temperature sensor Is attached to the outside wall of the house. It measures the outside temperature and adjusts the temperature of the heating water according to the circumstances. This ensures that the radiators always provide enough heat.

Alternatives to heating with a heating system

Electric heating systems such as convector heaters or infrared heaters are both available in the form of individual radiators. If you cannot or do not want to use a heating system, this is a good alternative. The electric radiators are easy to set up in the desired location and can also be moved again without much effort. Depending on the model and your needs, they can also be attached to the wall in a suitable place. https://www.instagram.com/p/B316M87IXa3/ A second alternative would be to heat with wood using stoves and fireplaces. They are now available in many different designs. They serve as heat producers and heat accumulators and are also used specifically as a stylistic device. This alternative can be used as whole-house heating and, depending on the model of the stove or fireplace, can also be used for cooking.

Decision: What types of radiator thermostats are there and which is the right one for you?

If you want to buy a new radiator thermostat, there are three alternatives to choose from:

  • Mechanical radiator thermostat
  • Electronic radiator thermostat
  • Radio radiator thermostat

The operation and functions of the three different radiator thermostats each have advantages and disadvantages. Depending on what you prefer and what your thermostat should be able to do, a different type is suitable for you. In the following section, we would like to make the decision easier for you.

What distinguishes a mechanical radiator thermostat and what are its advantages and disadvantages?

The mechanical radiator thermostat is still the most commonly used control for the radiator. We distinguish between four types of thermostatic heads.

  • With built-in sensor: The temperature is measured by the built-in sensor in the thermostat head.

A mechanical radiator thermostat with a built-in sensor is easy to install and operate. In addition, with this type of thermostat you have very low purchase costs.

Advantages
  • Easy to install and operate
  • Low initial cost
Disadvantages
  • One radiator thermostat per radiator is necessary
  • No programming possible

With all four types of mechanical radiator thermostats, one thermostat is required per radiator and programming of the heating times is not possible.

  • With remote sensor: A remote sensor is a temperature sensor that is outside the thermostat head and connected to it by a capillary tube. The remote sensor is used when the thermostatic head is in an unfavourable position (for example, behind a curtain). To ensure that the temperature measurement is not influenced by this, the remote sensor is placed where it can be freely flowed around.
  • With remote adjuster: If the thermostat head is in an inaccessible place (for example behind a panelling), a remote adjuster is used. The remote adjuster is a thermostatic head that can be placed in a suitable location. It has a built-in sensor and is also connected to the valve by a capillary tube.
  • With central adjuster: The central adjuster has the remote adjuster and the remote sensor separately and both are connected to the valve by capillary tubes.

The advantages and disadvantages of the three variants compared to the mechanical radiator thermostat with built-in sensor are as follows:

Advantages
  • More accurate temperature measurement possible
  • Enable operation of hard-to-reach radiators
Disadvantages
  • Additional installation effort
  • May be more expensive than those with built-in sensor

These three types of mechanical thermostats promise more accurate temperature measurement than those with built-in sensors. In addition, they make it possible to operate radiators that are difficult to reach. However, they entail additional installation work and, depending on the model selection, they may cost more.

What characterises an electronic radiator thermostat and what are the advantages and disadvantages of it?

With electronic radiator thermostats, one thermostat is needed for each radiator, which is set separately. The temperature settings are made directly on the thermostat head, usually via a digital display. This allows you to precisely set your desired temperature. Electric thermostats are programmable. You can set the temperature you want depending on the time of day or day of the week. As a rule, it is programmed to heat during the day and lower the temperature at night. In addition, you can individually determine on which days of the week it does not need to heat during the day. However, if you want to return to a warm home, for example after work, you can set it to start heating before you arrive.

Advantages
  • Programmable (energy saving option)
  • Precise setting of the temperature in °C possible
  • Heating cost savings possible through additional functions such as “open window” function and Smart System
Disadvantages
  • High purchase costs
  • One radiator thermostat per radiator is necessary
  • Only work with sufficient battery capacity

Another feature that most models are equipped with is an “open window” function. A sudden and strong drop in temperature is interpreted by the thermostat as an open window and it lowers the heating temperature. Meanwhile, some radiator thermostats also have an intelligent control (Smart System). This means that the thermostat is able to analyse what is actually happening in the environment. It perceives how much sunlight is in the room and how intensively the room is used. Based on these factors, it adjusts the temperature. This enables intelligent heating. With these additional functions, you can save some heating costs if you use it correctly. Electronic radiator thermostats usually have higher purchase costs than mechanical ones. They are only fully functional when batteries with sufficient capacity are used.

What distinguishes a radio radiator thermostat and what are its advantages and disadvantages?

A radio radiator thermostat basically has the same functions as an electronic thermostat. However, it has some additional features. Here, too, one radiator thermostat is used per radiator and the settings/programming can be made on the thermostat head itself. However, with radio thermostats, all units can also be set via a common control unit. The control unit can be placed anywhere in the room. This is made possible by the Bluetooth function and an Internet connection.

Advantages
  • Have all the advantages of an electronic radiator thermostat (programmable, precise temperature setting, heating cost savings through “open window” function and Smart System)
  • Control of several thermostats via one control unit
  • Operation via an app possible/operation over long distances possible
  • Can partly be integrated into a Smart Home system
Disadvantages
  • Additional installation effort
  • Additional components are required for use
  • Significantly higher purchase costs
  • Remote operation only possible with active power and internet supply (network and power failures can cause problems)
  • Some knowledge of modern communication technology is advantageous

Some models can even be controlled via an app. This allows you to operate and set your radiator thermostat conveniently and spontaneously. If you are in a network with Internet access, you can control the thermostats even from a great distance. Furthermore, more and more models allow you to establish them in the Smart Home System. Compatibility with Apple HomeKit, Alexa or Google Assistant, for example, even allows you to control your heating with the voice control system. The installation of a wireless radiator thermostat requires an additional effort to the previous types (network integration). You should also be aware that other components are needed for full functionality, such as a network router (internet access), a mobile phone, laptop or tablet or a central control unit. The purchase costs of a wireless radiator thermostat are usually significantly higher than for the other types. Remote operation is only possible with an active power and internet supply. Depending on this, network and power failures can cause problems. To make full use of this thermostat, you should have some knowledge of modern communication technology.

Buying criteria: Use these factors to compare and evaluate radiator thermostats

In the following, we will show you which aspects you can use to decide between the many possible radiator thermostats.

Heizkörperthermostat-2

You can buy radiator thermostats in different designs. The classic colour of a thermostat is white, but some models are also available in black.
(Image source: pixabay.com / Gelly___)

The criteria you can use to compare thermostats include:

In the following paragraphs, we will explain what is important in the individual criteria.

Operation & Function

With the help of the decision section, you have become acquainted with the different types of radiator thermostats. This is the first and most important purchase criterion. This is how you decide which functions you want for your radiator thermostat and how you want to operate it.

Simple and uniform operation

If you are looking for the simplest and most uniform operation possible, we recommend a mechanical radiator thermostat. Here you should distinguish between the four models of thermostat heads. If you want the lowest possible purchase costs, the thermostatic head with the integrated temperature sensor would be the right one for you. If your radiator thermostat is located behind a curtain or in a place that is difficult to reach, you should choose one of the other models. For another overview of these four types of mechanical radiator thermostats, read the decision section again

Programmable and save heating costs

If you want to save on heating costs and programme your thermostats individually, you are well served by an electronic model. If you want the functions of an electronic radiator thermostat and would also like to be able to control the thermostats via an app, you should go for a radio radiator thermostat. You can read about the exact advantages and disadvantages of all options in more detail in the section above.

Connection type

This criterion is somewhat related to the one above. With mechanical and electronic radiator thermostats, all settings can only be made on the thermostat head. If you want to be able to control your radiator thermostats all from one device and possibly even adjust them via an app, our advice would be a wireless radiator thermostat. These models have Bluetooth and internet connection and can do this for you.

Heizkörperthermostat-3

Meanwhile, some radiator thermostats are integrated into a “smart home” system. Compatibility with Apple HomeKit, Alexa or Google Assistant, for example, allows you to control your heating even with the voice control system.
(Image source: pixabay / geralt)

Here you can also take into account whether the radiator thermostat is integrated into a home system. Compatibility with Apple HomeKit, Alexa or Google Assistant, for example, allows you to control your heating even with the voice control system.

Smart System

Some models of radiator thermostats work with a smart system or also called intelligent heating system.

A smart system optimises your temperature settings and thus helps to save heating costs.

A model with a Smart System may be more expensive to purchase, but it will automatically optimise your pre-programming. Even if this only makes a slight difference, you can still save on heating costs. Mechanical thermostats do not have a Smart System. If you want a model with this function, we recommend an electronic or radio radiator thermostat.

Power supply

Mechanical radiator thermostats do not need an additional power supply. They only need to be connected to the radiator. After you have connected it, you should not have to worry about this. Electronic and radio thermostats, however, need batteries to work. Usually these are AA batteries and often two of them are already included in the delivery. As soon as the batteries are empty, you should replace them for further full functionality. Most thermostats show on the display when the batteries are empty or almost empty. An automatic mechanism should then open the valve of the radiator thermostat to a certain degree so that heat can continue to be emitted.

Child safety lock

Radiator thermostats are usually located in places that are within reach of children. It can happen that children change the settings of the thermostat while playing. This could, for example, give the false impression that the radiator thermostat is broken, or it could also result in higher heating costs. In other words, if you have children and want to avoid the problems mentioned, we advise you to buy a model with a child lock.

Type Childproof lock
Mechanical radiator thermostats
Electronic radiator thermostats
Radio-controlled radiator thermostats

Mechanical radiator thermostats do not have a child safety lock. But electronic and radio-controlled thermostats now usually have one. You can activate them with a special key combination. You should find this in the operating instructions for your model. If you do not have your operating instructions at hand, you can search for a version of them on the Internet.

Facts worth knowing about radiator thermostats

How do you change a radiator thermostat?

  1. Preparation: Set the thermostatic head to the highest setting. This makes it easier to remove because it sits so loosely.
  2. Loosen the retaining ring: The thermostatic head is secured by a retaining ring or clamp. You can loosen the retaining ring with pliers and the clamp with a screwdriver. If your model has a retaining ring, put a rag or cloth around it so as not to damage it when removing it. Loosen the regulator by turning it anticlockwise with a pair of pliers. If it is the clamp instead, loosen the screws with a screwdriver.
  3. Remove the radiator thermostat: Once the first two steps are done, you can remove the radiator thermostat. Sometimes this requires a slight turning. If it does not work well, check again if the retaining ring/clamp is loose. If this is the case, pull on it a little harder to overcome the safety lock, which some models have integrated.
  4. Check the valve pin: The valve pin should now be visible. To check whether the thermostat is actually broken, try to push the pin inwards. If this is not possible, it means that the valve and not the thermostat is broken.
  5. Put on the new radiator thermostat: Now you can put on your replacement model. Make sure that the thermostat is mounted in the same way as it was when it was removed. The highest setting should be in the same place (fully turned up).
  6. Fasten: Now you can reattach the retaining ring or clamp with pliers or a screwdriver.

If you have a model with a remote sensor or remote adjuster, you must also replace them.

Additional functions also require correspondingly more installation effort.

If you have chosen a radio-controlled radiator thermostat, you will have to do a little more work. For example, the central control element must be replaced and network settings made, or additional functions (e.g. Smart Home System) must be installed. Generally with programmable devices, you should not forget that you also have to allow time for your individual settings.

What do the numbers on a radiator thermostat mean?

A mechanical radiator thermostat is equipped with a temperature controller. This means that the temperature is set in five stages. Depending on the model, these steps are marked with numbers, dashes or symbols. Contrary to popular belief, the five stages are not related to how quickly the radiator heats up. They stand for a specific temperature.

Stage temperature in °C
* = frost protection approx. 7°C
Stage 1 approx. 12°C
Stage 2 approx. 16°C
Stage 3 approx. 20°C
Stage 4 approx. 24°C
Stage 5 approx. 28°C

It only makes sense to set the radiator thermostat to the highest level if you want to reach a room temperature of approx. 28°C and not so that it gets warm faster. We recommend that you do not use any levels above four, as they consume a lot of energy and can increase your heating costs.

How can you make a radiator thermostat that is stuck work again?

Your radiator no longer heats, even if you have set the radiator thermostat to the highest level? Then it’s probably because your heating valve is stuck. In the following section we will show you how to make the valve work again

  1. Dismantle the thermostat head as described above.
  2. Then the heating valve with the valve pin comes to light. Ideally, the valve pin should protrude 5mm. If it does not stick out that far, it will be stuck. There are three possibilities that could help you to loosen it again.
  3. Try to pull the pin out carefully with pliers. Normally it should come out this way.
  4. If this doesn’t work, you can use a hammer or the back of a screwdriver to gently push on it. This will apply pressure, which may loosen the pin.
  5. If this is not the case, carefully tap the side of the valve body with a hammer.
  6. If the pin still does not come loose, try using a multi-functional product to remove dirt, adhesive residues and other things.
  7. If one of these options has worked, it is a good idea to use a special tap grease.
  8. Apply the fitting grease around the valve pin and press it in several times (again, with a hammer or the back of a screwdriver) and let it come out again. This allows the grease to spread well.
  9. Now you can reattach the thermostatic head. Again, follow the instructions above.

If the valve pin cannot be loosened in any way, you should consult a specialist. To give you a better idea of the whole process, we have selected a video that shows you how to make your radiator thermostat operable again.

Image source: Raths/ 123rf.com

Reviews