Rent reduction for heat: when it applies and what cools faster
What German tenancy law offers when your flat overheats, why deducting too much can backfire, and the permission-free way to get cool this summer.
German tenancy law does give you a lever when your flat turns into an oven: rent reduction, or Mietminderung. If heat impairs the use of your flat significantly, the law treats that as a defect, the rent is considered reduced for that period, and German courts have accepted heat-based reductions in individual cases. What the law doesn't have is a fixed table saying 'above 30 °C you get 20 percent'. Every case turns on its own facts, disputes drag on for months or years, and plenty of claims fail. So this guide covers both halves: how the legal route works, and how to get the flat cool this summer rather than the summer after the verdict.
Is there a maximum legal temperature for flats in Germany?
No. The 26 °C figure you sometimes see quoted comes from a German workplace regulation written for offices, not homes. Some courts have used it as a rough reference point. Others have explicitly refused to. What the German Civil Code (BGB) does say, in general terms, is that a landlord must keep the flat fit for the use agreed in the contract. If that use is significantly impaired, there's a defect (Mangel), and heat can qualify.
Context matters a lot here. A top-floor flat in an unrenovated Altbau is expected to get warm in July, and courts have said as much. A new build marketed with modern thermal insulation that still hits 32 °C indoors is a different story. What you could reasonably expect when you signed the lease shapes what counts as a defect.
What have German courts decided about heat?
The case law is mixed, and that's the single most useful thing to know. One example that gets cited a lot: a Hamburg district court reportedly found a 20 percent reduction appropriate for a new-build flat where indoor temperatures climbed above 30 °C. Other courts have dismissed heat claims entirely, treating summer warmth as part of the deal in that particular building. There's no binding scale. The percentages you find online come from single cases with very specific facts.
How much can you deduct without risking your tenancy?
This is where renters get hurt. Deduct too much, have a court disagree later, and you've built up rent arrears. Once arrears cross a certain threshold, the landlord can terminate the lease. The safer route, the one tenant associations routinely recommend, is to keep paying the full rent 'unter Vorbehalt' (under reservation of reclaiming it) and to demand the money back once the defect question is settled. Your claim survives. Your tenancy is never on the line.
Step one: put the defect in writing
Nothing works without a Mängelanzeige, a written defect notice. Your landlord has to know about the problem before the rent can realistically be reduced for it. Write down which rooms are affected, what temperatures you measured, since when, and what it does to daily life: no sleep, an unusable home office, a child's room too hot in the afternoon. Ask for a remedy, set a reasonable deadline, and send it in a way you can prove arrived. Registered mail (Einwurf-Einschreiben) is the standard move.
Measure properly while you're at it. Several readings a day, over several days, taken mid-room and out of direct sun, each with date, time and the outdoor temperature next to it. That log is your strongest piece of evidence later, whether things settle amicably or end up in court.
The faster fix: cooling that needs no permission
Do the maths before you commit to a long fight. Twenty percent of a 1,300 euro warm rent is 260 euros a month, possibly awarded a year or more after the heatwave. In the meantime you were still sleeping at 30 °C. A rent reduction compensates you for the heat. It doesn't remove it.
Cooling, on the other hand, is something you can sort out today, usually without asking your landlord, as long as you change nothing about the building itself. Mobile monoblock units, window units and permanently sealed mobile splits (the refrigerant line is sealed at the factory and never opened) need no drilling and no facade work — a fitted window seal is all it takes. Classic and quick-connect split systems are a different category: EU F-gas rules put their installation in the hands of certified firms, and a DIY job can mean fines running into five figures.
If you'd rather not buy a unit and haul 30 kg up an Altbau staircase, KlimaLegal rents permission-free ACs for the season in Berlin and Brandenburg. The Standard Sommer-Abo (Summer Rental) costs €89 a month with a 4-month minimum term, plus a one-off €189 for delivery, setup and collection: €545 for the whole 2027 season, with a quiet monoblock sized to your room and the window seal fitted for you. The Premium 'Leise' plan, a mobile split with the compressor hanging outside on a window bracket and always installed by KlimaLegal's team, runs €199 a month plus a one-off €299, so €1,095 for the season. There's no deposit, a broken unit is replaced within 3 working days, and only 30 subscription slots exist for 2027.
| Pursuing a rent reduction | Permission-free cooling | |
|---|---|---|
| When you feel it | months to years, if at all | the same day |
| What you get | money back; the flat stays hot | a cool flat; it costs money |
| Biggest risk | termination if you deduct too much | electricity, roughly 30 to 40 cents per hour of use |
| What you need | records, a written defect notice, usually legal advice | a socket, a window, a fitted seal |
Your documentation checklist
Whether you reduce, pay under reservation or just want to be prepared, this file makes your case solid.
- Measure the indoor temperature several times a day (morning, around 2 pm, evening), mid-room, for at least one to two weeks
- Note date, time and the outdoor temperature for every reading, for example with a weather-service screenshot
- Photograph the thermometer in the room with enough context visible, not just a close-up
- Record that you ventilated and shaded correctly: windows open at night, blinds down during the day
- Send the written defect notice with a deadline and keep proof of delivery
- Keep every reply from your landlord and confirm verbal promises briefly by email
- Before deducting a single euro: get your case checked by a Mieterverein or a tenancy lawyer
FAQ
- At what temperature can I reduce my rent in Germany?
- There is no legal maximum temperature for flats in Germany and no fixed threshold above which rent reduction applies. The 26 °C figure often quoted comes from a workplace regulation for offices. Courts assess each case individually, asking whether the heat significantly impairs the use of that specific flat given its age, position and what the tenant could expect when signing.
- How many percent rent reduction is typical for heat?
- There is no standard percentage for heat-based rent reduction in Germany. One reported example is a Hamburg district court decision granting 20 percent for an overheated new-build flat above 30 °C indoors, while other heat claims have been dismissed entirely. Deducting too much creates arrears and can put the tenancy at risk, so get advice before reducing anything.
- Do I have to notify my landlord before reducing the rent?
- Yes, a written defect notice (Mängelanzeige) to the landlord is a precondition for any heat-based rent reduction in Germany. The landlord has to know about the defect and get a chance to fix it. Send the notice in writing with your measured temperatures and a deadline, and keep proof of delivery, for example registered mail.
- Can I set up an air conditioner without my landlord's permission?
- Mobile air conditioners can usually be set up without the landlord's permission: monoblocks, window units and permanently sealed mobile splits change nothing about the building itself, a fitted window seal is enough. Classic split systems that require drilling and an open refrigerant circuit are different, they belong in the hands of certified installers and generally need the landlord's consent.
