In Germany, from what I understand, when the temperature in apartment falls below a tolerable amount, then the renter can request the landlord for a rent reduction.

This happend to me, and I got a thermo meter, and it showed below the expected temperature. When I went to escalate with the landlord, she told my thermometer is giving wrong values.

Now, what do I do? How could I possibly escalate this?

  • 1
    The way to escalate this is to pay less rent - which may then lead to you getting evicted if you're wrong or can't prove that you're right. So before doing that, you go to a lawyer, the Mieterschutzbund or similar. Ther nure are also Rechtsschutzversicherungen which offer retrospective coverage for Mietrecht, but you'd have to check, whether that applies.
    – DonQuiKong
    Feb 19 at 6:54
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    Based on the question body, maybe "thermostat" in the title should be "thermometer"? Feb 19 at 9:10
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    Thermostat or Thermometer? If it's the thermostat that's broken then surely it's her responsibility to fix it.
    – komodosp
    Feb 19 at 11:07
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    The thermometer vs. thermostat discrepancy between the title and question body needs to be clarified for this to be accurately answered. Is the landlord claiming that the thermostat you used to measure the room temperature is inaccurate or are they claiming that the thermostat used to control the heating system isn't working correctly? And, if it's the thermostat, is it the one that the landlord installed or did you replace it with your own (e.g. a smart thermostat or similar?)
    – reirab
    Feb 19 at 15:53
  • 2
    Thermostats mounted at the heater often enough are analog devices that open or close the water inflow due to a bimetal or expanding fluid pressing the normally closed valve open when the temperature is too low. Generally, those are not set to "temperatures" at all but display numbers that are roughly temperature bands. Other thermostats have actually temperature settings. In either case, the thermostat should contol the heating. Thermometer are devices to measure temperature and not control the heating. Some thermostats contain thermometers of some sort.
    – Trish
    Feb 19 at 18:57

4 Answers 4


This may seem familiar, I have quoted it before:

Quoting § 535 BGB:

§ 535 Inhalt und Hauptpflichten des Mietvertrags

(1) Durch den Mietvertrag wird der Vermieter verpflichtet, dem Mieter den Gebrauch der Mietsache während der Mietzeit zu gewähren. Der Vermieter hat die Mietsache dem Mieter in einem zum vertragsgemäßen Gebrauch geeigneten Zustand zu überlassen und sie während der Mietzeit in diesem Zustand zu erhalten.


§ Section 535 Content and main obligations of the tenancy agreement

(1) The rental agreement obliges the landlord to grant the tenant the use of the rented property during the rental period. The landlord must leave the rented property to the tenant in a condition suitable for use in accordance with the contract and maintain it in this condition during the rental period.

The landlord is responsible for the proper functioning of the Thermostat just as much as for the rest of the heating.

If it doesn't work and that is the reason your apartment is falling below the said temperature for multiple days in a row, you can lower the rent.

Please note that to lower the rent, it must be broken in a way that makes it impossible for you to heat up the rooms using the heating system. So for example if you could heat your rooms to 20° if you set it to 25°, that is still technically broken and surely inconvenient, but not a reason to reduce rent.

When I went to escalate with the landlord, she told my thermometer is giving wrong values.

That seems borderline stupid. The minimum temperature your landlord has to guarantee is 18°C, your heating should easily be able to give you 23-25°C if you put it that way. No thermometer is off or could be read wrong by 7°C. A thermometer that wrong could not differentiate between a life threatening hypothermia and life threatening fever.

I suggest you ask them over and offer them the ability to bring their own thermometer if they don't believe you.

Thermostats are nasty and sometimes not easy to handle. Especially elderly people often have problems adjusting them correctly since they became all touchscreen technological marvels, when back in the day they were a box with a single hardware knob. Last time, the service technician did not set the timezone correctly, and my neighbor had to wake up to their freezing nighttime settings every morning until I fixed it. How do you explain UTC and timezones to someone who wants to turn on their heating that is definetely not travelling across timezones any time soon?

If your themostat doesn't work, ask your landlord to call a service technician if they cannot fix the problem themselves. That is their obligation.

  • 1
    This answer focuses on material law. I think the question concerns procedural law. Feb 18 at 17:15
  • 3
    Feel free to write an answer more in line with what you think.
    – nvoigt
    Feb 18 at 17:22
  • Do all german rooms have a thermostat? I don't think I have one
    – Babu
    Feb 18 at 17:29
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    @PMF But a possibly acceptable 1-2° off is still less than a third of the 7° error the answer talks of.
    – TripeHound
    Feb 18 at 18:53
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    @trystwithfreedom The knobs on German radiators are essentially thermostats, even if they are not calibrated in terms of a numerically indicated temperature. Usually they have the settings cold/1/2/3/4/5, which map to various temperatures, that may be room-dependent; a 3 in the bathroom may be warmer than a 3 in the bedroom. If you open everything to 5 and still cannot get to the minimum acceptable temperature, your heating is broken and your landlord is obliged to fix it.
    – gerrit
    Feb 19 at 8:01

I would argue that, at the moment, the landlord might be correct. So, before doing anything else, I'd gather more data. Buy a couple of extra thermometers, of different makes. They should be within a couple of degrees of each other.

You've then got a reasonable consensus measurement. Next, you want to get more data, using all three thermometers. You're aiming to show a sustained decrease below the permitted temperature. I would record video while taking the measurements, to show you've not just opened all the windows, or something, and take measurements 3x a day for a couple of days. Measure in all the rooms, allow thermometers to acclimatise to each room before reading, and make sure to include the radiator settings in the video each time.

The nice thing here is that it might also help figure out what is wrong - a radiator in one of the rooms might not be working, in which case, bleeding it might fix it.

If there's nothing obvious, but the heating still can't get up to a reasonable temperature, you've got a vastly improved case for taking action - not just a couple of measurements with a possibly accurate thermometer.

At that point, I'd start discussing how they can either fix it or start losing rent.

  • It wouldn't hurt to test the thermometers by dunking in ice-water (zero degrees) then in boiling water (100 degrees) It is a reasonable assumption that if those two points read correctly, then anything in between is correct too. If the thermometer doesn't reach either of those two extremes, it isn't worth relying on in the first place.
    – MikeB
    Feb 20 at 8:24
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    Be careful with the upper bounds. While I like the scientific test, do not put thermometers for measuring room temperature in boiling water or a really cold freezer. They are probably not meant for that and it might not be safe! A cheap room thermometer that goes from -20 to 50 should never reach their respective limits anywhere in Germany naturally and will certainly not be safe for going over those limits.
    – nvoigt
    Feb 20 at 9:04
  • 1
    I'd like to add that the themometer the topic originator bought is probably correct, but before you take action like reducing the rent you pay, you want to have excellent proof of this.
    – lupe
    Feb 20 at 10:54
  • @MikeB unless it's a digital thermometer designed to measure ambient air temperature, in which case immersing it will probably cause it to stop working. Even an analogue thermometer with a bimetallic strip is unlikely to handle immersion very well.
    – phoog
    Feb 21 at 10:51
  • @lupe in jurisdictions I'm familiar with there is a very specific procedure required for paying reduced rent, so it is probably a good idea to check with a local L&T lawyer or at least s tenant's rights organization before reducing rent payments.
    – phoog
    Feb 21 at 10:55

What is the accuracy and precision of the thermometer and when was it last calibrated?

All scientific instruments (including thermometers) have varying degrees of accuracy and precision:

Precission vs Accuracy

Both are sources of inaccuracy in measurement. Calibration can reduce inaccuracy, but precision is a function of the instrument itself and its operating conditions.

You don’t tell us what sort of thermometer you are using but if it is a cheap alcohol filled tube that you might buy in a souvenir store, it has probably never been calibrated and might be out by several degrees. If it’s a reasonable electronic one such as you might buy in a hardware store, errors are likely to be in the order of a degree or so providing it’s new or recently calibrated. If it’s a high precision laboratory instrument with recent calibration errors could be less than a tenth of a degree. Consult the literature that came with the instrument, it will tell you all about its accuracy and precision. If it didn’t come with literature, you might as well not bother.

In addition, how you measure the temperature is also going to matter. You should be measuring in several positions in the room and be using the median temperature. You need to be away from walls, doors, and windows and out of drafts. You also need to repeat the measurements in the same places at the same time over several days.

If you present this kind of robust data, it will be very hard for anyone to argue against it. As the person asserting the fact (it’s too cold), the onus rests on the tenant to prove it.

  • 7
    Why would it be the OP's burden to prove accuracy & precision vs the landlord having to prove the opposite?
    – Greendrake
    Feb 19 at 5:08
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    @Greendrake because the tenant accuses the landlord that he didn't do his obligations. The burden of proof lies with the accusing party.
    – Trish
    Feb 19 at 8:34
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    @Trish that's kinda silly. Thermometers are measuring instruments. What kind of certification are you conceptualizing requiring to prove the accuracy? A thermometer purchased from any store should have an assumption of accuracy and reliability. You say it is cold, you purchase a measuring device to prove it, and it says it's too cold. If the landlord wants to dispute the accuracy of your device, they can purchase their own measuring device and check the temperature themselves. If their device reads different enough, you can both bring them to court. Feb 19 at 22:06
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    @Trish OP says it was too cold. OP got a thermometer showing it was too cold. How is that not 'showing that it is cold in the flat'? OP has provided enough proof. If the landlord wants to say that OP's thermometer is 'showing the wrong numbers', the landlord has to provide some contradictory evidence. Feb 19 at 23:19
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    @JasonGoemaat the OP has provided evidence and the landlord has questioned the reliability of that evidence. As the person making the assertion (it’s too cold) the onus is on the tenant to prove it with robust and reliable evidence. Without that it’s a case of “is” vs “isn’t”. The landlord wins that argument.
    – Dale M
    Feb 19 at 23:37

I am no expert in law, but I do know that precisely calibrated thermometers are a lot more affordable these days than they used to be.

For example, I have this one from switchbot which advertises ±0.2°C accuracy - and the manufacturers of the sensing chip offer calibration certificates to that effect. The range of temperatures people find comfortable is fairly narrow, so you want to know the measurement is right.

My country does not have the same rental protections as Germany has - but when I lived in a rental property with faulty heating and the landlord was unresponsive to my complaints, I brought myself a cheap fan heater which I ran as needed. This kept me warm, and was within my rights as a tenant.

  • Electricity is expensive in Germany. I wouldn't want to run a cheap fan heater on my dime and if electricity was included in the rent the landlord would react by increasing rent. Also, the wiring/breaker might not be able to support it and it might even be a fire hazard.
    – Roland
    Feb 21 at 7:48

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