The Building Modernisation Act (GModG, Gebäudemodernisierungsgesetz) sets out how heating systems in buildings are to be installed in future and how the costs are shared. For tenants the key question is who bears the CO2 costs and gas network charges from 2028 when a heating system is replaced. This guide explains the rules for rented flats, the transition periods and the exceptions, as far as they are described in the ministry’s statement.
Short answer: According to a statement from the Federal Ministry for Economic Affairs, tenants and landlords share the carbon dioxide costs and gas network charges equally from 1 January 2028 for newly installed heating systems. From 1 January 2029 the equal split also covers the price component for biogenic fuels under the biomass staircase. Last updated: November 2026. Check promulgation and entry into force in the Federal Law Gazette.
The most important points
- According to the statement, the Bundestag adopted the law in July 2026. Sources give the exact date differently, so check it in the Federal Law Gazette and in the Bundestag documentation system (DIP).
- From 1 January 2028, tenants and landlords share the CO2 costs and gas network charges equally for new heating systems.
- From 1 January 2029, they also share the price component for biogenic fuels in levels 1 to 3 of the biomass staircase equally.
- New buildings with a building permit application before 13 May 2026 are protected by grandfathering.
- If a heating system fails beyond repair, the rules in force at the time of the failure apply for twelve months.
What applies to rented flats from 2028?
The basic rule is simple to describe. For newly installed heating systems, tenants and landlords each bear half of the carbon dioxide costs and of the gas network charges. The CO2 price is therefore no longer passed on entirely through the heating cost statement. In practice, what matters is whether a heating system was installed after the cut-off date, because the rule is tied to the installation.
The statement distinguishes between building types. Anyone living in a single-family house or in a flat with a gas single-room heating system counts as a self-supplier. According to the statement, such a person can have half of the costs reimbursed by the landlord. Tenants in a flat with a central system receive the split through the landlord’s statement.
Which transition rules apply?
The law works with stages. The table below summarises the cut-off dates and exceptions as the statement presents them. The entries are summaries and do not replace the law text. The key dates of 1 January 2028 and 1 January 2029 are also given by the Federal Ministry for Economic Affairs in its press release on the cabinet decision of 13 May 2026 (at that time a draft bill). The cut-off date for grandfathering, the hardship rule and the deadline for occupancy by the end of 2029 are not in that press release. They rest only on the statement on the later decision and must be checked in the law text.
| Case | Rule according to the statement | From when |
|---|---|---|
| New heating in a rented flat | Equal split of CO2 costs and gas network charges | from 1 January 2028 |
| Biogenic fuels (biomass staircase, levels 1 to 3) | Equal split of the price component | from 1 January 2029 |
| New building with building permit before 13 May 2026 | Grandfathering, equal split does not apply | permit before 13.05.2026 |
| New building with later permit | Split applies if the flats are occupied by 31 December 2029 and the biomass staircase is applicable | occupancy by 31.12.2029 |
| Heating failure beyond repair | Rules at the time of failure apply for twelve months | twelve months |
The table describes the basic line. Whether an individual case falls under it depends on the year of construction, the permit, the heating type and the tenancy agreement. A tenancy agreement that does not address these questions is not automatically wrong, but it must be read in light of the law.
What does this mean in euros? A worked example
Assumption: the annual CO2 costs of a gas heating system in a rented flat amount to 1,000 euros, and the system was installed after the cut-off date. Under the equal split, the tenant then bears 500 euros of these CO2 costs, and the landlord bears the other 500 euros. The gas network charge follows the same logic, but the statement names no amount for it. The example shows only the division, not the actual size of the costs.
Are there exceptions for landlords?
Yes. According to the statement, there is a hardship rule. Landlords of unrenovated buildings with low rents can, in special cases, avoid the equal share of costs. When exactly such a case applies must be read in the law text. As a tenant, check whether your landlord relies on such a rule, and ask for the reasons if they are not comprehensible.
What happens if the heating fails?
If a heating system fails beyond repair, the rules in force at the time of the failure remain decisive for twelve months. This protects against a situation in which new rules suddenly apply during a transition phase. For tenants it is important to document the failure, for example with a dated report from the heating contractor.
Frequently asked questions about the heating law for tenants
Does the law already apply to my current heating?
The split is tied to the installation of a new heating system after the cut-off date. According to the statement, an existing heating system is not automatically covered by the equal split. Existing systems follow the earlier rules, which this statement does not describe.
Do I have to agree to the new heating?
The statement does not answer this question. It governs the division of costs. Whether a landlord may install a new heating system and how the modernisation proceeds is a different matter. The answer lies in tenancy law and the law text, not in the cost rule alone.
What about biogas or biomass?
From 2029, according to the statement, tenants and landlords share the price component for biogenic fuels in levels 1 to 3 of the biomass staircase equally. What belongs to which level must be checked in the law text.
Where do I find the binding wording?
The binding wording will be in the Federal Law Gazette once the law is promulgated. Until then you can check the decisions of the Bundestag and the Bundesrat. The ministry’s statement is a summary and not a legal source.
What you should do now
- Check your tenancy agreement and your latest heating cost statement, and note how CO2 costs are currently shown.
- Ask your landlord in writing whether and when a heating replacement is planned and how the cost split will be applied.
- If a failure occurs, document it with a date and a report from the heating contractor.
- If there is a dispute over the split, get advice from the local tenants’ association before withholding any payment.
Related guides
- Climate, energy and living costs 2027: the overview for tenants and students (hub for this topic)
- CO2 price 2027: what the price corridor means for heating and fuel
- Checking the heating cost statement: deadlines, distribution and typical errors
- Reducing heating costs: what tenants can do without renovation
- Housing benefit for students: who is eligible and how to apply (in German)
Sources: Federal Ministry for Economic Affairs and Energy, statement on the adoption of the Building Modernisation Act (copy, status July 2026); Federal Ministry for Economic Affairs and Energy, press release on the cabinet decision of 13 May 2026 (retrieved 2 November 2026, in German).
Last updated: November 2026. This guide is general information, not individual advice.
