Changing the thermostat on the heater: explained step by step

Changing the thermostat on the heater: explained step by step

You want to change a defective thermostat on the heating or switch to a modern controller? With these instructions you can replace the thermostat yourself in a few minutes. We explain step by step how it works and what needs to be considered.

When does it make sense to change a thermostat?

Changing the thermostat when the device is broken is not only useful, but necessary. An old thermostat in particular is prone to defects. After about 15 years, it can therefore happen that it no longer works properly. One possible consequence: the radiator no longer reaches the desired temperature.

But this can also have other causes. So maybe the thermostat isn't bad at all. Before you replace it, you should therefore rule out other causes. Check the following:

  • Are other radiators also staying cold and is there possibly no hot water? Then the entire heating system could have failed.
  • Is the radiator completely cold or only in certain areas? If the heater only stays cold at the top, it probably needs to be vented. If it only stays cold at the bottom, hydraulic balancing is necessary. In this case, you should contact a professional.
  • The radiator valve could also be defective. We will tell you how to check this later in the instructions.

Even if a thermostat is not defective, a change can make sense – for example to switch to a modern or smart model. Programmable thermostats can save energy and cut your heating bills by an average of 10 percent. The investment is usually worthwhile after a heating period, i.e. the cold months in which you heat.

Preparation: You need this to replace an old thermostat


Make sure you are well prepared before changing the thermostat. Image: © AdobeStock/Ralf Geithe 2022

Before you start, you need a new thermostat. It is best to order exactly the model that you have used so far. Normally, the manufacturer and model are noted on the controller. If you switch to a smart device, ask a specialist shop for advice on which thermostat is compatible with your heating system. It is best to bring the product name of the old model with you to the consultation.

Get a pair of pliers ready. A pipe wrench or water pump pliers works best. If you don't have the right tool, you'll find it at the hardware store.

Step-by-step instructions for changing the thermostat

How to change the thermostat on the radiator:

  1. Turn the thermostat all the way up, i.e. to the highest level.
  2. Put the pliers on the ring nut and turn it counterclockwise. If the ring is made of plastic, you should be extra careful not to damage it.
  3. Carefully pull off the controller.
  4. Now the heating valve appears, there you can see a small pin. Push in the pen. If it pops out again, the heater valve is intact. If he doesn't, stop the thermostat change immediately and contact an expert. It could be that the heater valve is defective.
  5. If everything is fine with the valve, set the new thermostat to the highest level as well.
  6. Attach the new thermostat to the valve.
  7. Use the pliers to turn the ring nut clockwise until it is tight again.

You're done in less than ten minutes. Make sure the new thermostat turns freely. Turn the knob up and wait for the heater to warm up.

Once you have a smart thermostat installed, follow the manufacturer's instructions for further setup.

How much does it cost to change a thermostat on the heater?

A new thermostat is available in specialist shops from 10 euros. You can find smart thermostats from 25 euros. If you don't have a pipe wrench, you can get a good model for as little as 10 to 15 euros. If you need it more often, invest a little more.

Smart thermostats Buy now from

Who pays for changing the thermostat in the rented apartment?


You usually have to pay for a new thermostat yourself in a rented apartment. Image: © AdobeStock/M. Schuppich 2022

Who pays for the cost of a new thermostat depends on various factors. It usually looks like this: If the thermostat is defective, you have to pay. If more than the thermostat is defective, such as the heating valve, the landlord usually assumes the costs. It is best to read the rental agreement to find out what it says about repairs in the apartment. If you are unsure or if information is missing, find out about your rights and obligations as a tenant, for example from the Tenant Protection Association.

If you only want to upgrade your thermostat to a smart one, but there is no defect, you also have to bear the costs. Important: Keep the old device. This way you can restore the original condition of the apartment when you move out.

At a glance: How to change the thermostat on a heater

  • Obtain a compatible new thermostat and pipe wrench.
  • A normal thermostat is available in specialist shops from 10 euros, smart models from 25 euros.
  • Follow our guide to change the thermostat step by step. It doesn't even take ten minutes.
  • In rented apartments, you usually have to bear the cost of changing the thermostat yourself. Find out more about this in your rental agreement.

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