If a landlord wants to raise the rent after a heating replacement in a rented flat, the usual legal basis is the modernisation levy in section 559 of the German Civil Code (Bürgerliches Gesetzbuch, BGB). It allows the landlord to pass on part of the costs to the rent every year. This guide explains how high that share is under the statutory text and which limits apply.
Short answer: Under section 559 (1) BGB, a landlord may raise the annual rent by 8 percent of the costs spent on the flat. Within six years the rent may not rise by more than 3 euros per square metre, or only by 2 euros where the starting rent is below 7 euros per square metre (section 559 (3a) BGB). Last updated: November 2026, based on the text retrieved on 2 November 2026.
The most important points in brief
- The modernisation levy is set out in section 559 BGB and allows an annual increase of 8 percent of the costs spent.
- Within six years the rent may not rise by more than 3 euros per square metre, and only by 2 euros where the starting rent is below 7 euros per square metre.
- For certain heating measures under section 555b (1) or (1a) BGB, an additional limit of at most 0.50 euros per square metre applies within six years.
- If a measure covers several flats, the costs must be allocated appropriately among them.
- Changes to the levy are discussed politically, so the wording of the law at the time of the increase always matters.
What a landlord may pass on under section 559
The provision allows the landlord to raise the rent after modernisation measures. The calculation refers to the costs spent on the flat and not to the market value of the building. The legislator has set a fixed rate of 8 percent of the costs per year. On this basis, the landlord can spread the costs over many years and pass them on to the tenant.
A heating replacement can fall under energy-related modernisation, for which section 559 (3a) BGB sets a separate limit. Whether a specific measure qualifies follows from section 555b BGB, not from the name given to the work in a contractor quote. This is where a close look is worthwhile, because not every change in the boiler room is a modernisation in the sense of tenancy law.
How is the increase calculated?
The levy refers to the costs, not to the existing rent. The statutory text speaks of 8 percent of the costs spent on the flat per year. The table below summarises the rules as they appeared in the text retrieved on 2 November 2026.
| Rule | Content | Provision |
|---|---|---|
| Levy rate | 8 percent of the costs spent per year | Section 559 (1) BGB |
| General cap | At most 3 euros per square metre of living space within six years; 2 euros where the starting rent is below 7 euros per square metre | Section 559 (3a) BGB |
| Heating measures | Additionally at most 0.50 euros per square metre within six years | Section 559 (3a) BGB with section 555b (1) or (1a) BGB |
| Several flats | Costs must be allocated appropriately among the individual flats | Section 559 (3) BGB |
The cap of 3 euros applies to increases under section 559 and not to increases under sections 558 and 560 BGB. An increase tied to the local comparative rent therefore runs separately and is not counted against the modernisation limit. Anyone who sees both increases together should check them separately.
Worked example with assumptions
Assumption: the heating replacement costs 20,000 euros, the flat has 60 square metres of living space, and the full costs count as spent on the flat. The calculation is simplified and does not replace a check of the individual case.
- Annual levy: 8 percent of 20,000 euros gives 1,600 euros per year.
- Monthly increase: 1,600 euros divided by 12 gives about 133.33 euros per month.
- General cap: 3 euros per square metre times 60 square metres gives 180 euros per month. The increase stays below this figure.
- Heating limit: 0.50 euros per square metre times 60 square metres gives 30 euros per month as an additional upper limit.
In this example the increase stays below both limits. A lower starting rent, different costs or a different split across several flats leads to another result. What counts is always the calculation for the specific case.
What tenants should check now
Tenants should check the notice of increase for completeness. This includes the type of measure, the costs stated, the levy amount and the conversion per square metre. Anyone who wants to know who decides on a heating replacement and who bears the costs will find the answer in the guide Heizungstausch in der Mietwohnung.
Frequently asked questions
May a landlord raise the rent after every heating replacement?
No. An increase under section 559 requires a modernisation in the sense of the law, and the costs must have been spent on the flat. Which measures qualify follows from section 555b BGB and not only from the description of the works.
How high may the levy be?
The statutory text names 8 percent of the costs spent per year. For the rent itself, a cap of 3 euros per square metre applies within six years, or 2 euros where the starting rent is below 7 euros per square metre.
Is there a separate limit for heating measures?
For certain heating measures under section 555b (1) or (1a) BGB, an additional limit of at most 0.50 euros per square metre within six years applies. This limit comes on top of the general limits and does not replace them.
Can I object to an increase?
If you consider an increase unreasonable, check the calculation and have the information reviewed, for example by a tenants association or a legal adviser. This guide cannot give a legal assessment of an individual case.
Do the rules also apply to several flats?
Yes, if the measure affects several flats. The costs must then be allocated appropriately among the individual flats under section 559 (3) BGB. The allocation is therefore a separate point to check.
What you can do now
- Read the notice of increase in full and note the date, the amount and the costs stated.
- Recalculate the levy at 8 percent and compare the result with the cap of 3 euros per square metre.
- For heating measures, check whether the additional limit of 0.50 euros per square metre is respected.
- If in doubt, have the notice reviewed by a tenants association or legal adviser before you agree to it.
What else matters in an increase
With a modernisation increase, the date from which the higher rent applies matters as much as the amount. The notice usually names that date. It is worth comparing it with the tenancy agreement and with the timing of the works, because errors at this point are not rare.
The law also contains a hardship clause in section 559 (4) BGB. Under it, an increase may be limited where it would mean hardship for the tenant. Anyone who sees themselves affected should examine this provision with an advice centre before agreeing or objecting. There is no general answer, because the personal circumstances decide.
Related reading
- Climate, Energy and Costs 2027: The overview for tenants and students
- Heizungstausch in der Mietwohnung: Wer entscheidet und wer zahlt
- Heizkosten senken: What tenants can do without renovation
Sources: Section 559 BGB, rent increase after modernisation measures (German text reproduced on gesetze.legal, retrieved 2 November 2026). For binding information, the official German text on gesetze-im-internet.de is decisive.
Last updated: November 2026. This guide is general information, not individual advice.
