1. Overview of the new heating law
In 2026 the black-red coalition (CDU/CSU and SPD) agreed on a reform of the controversial heating law originally introduced by the previous government. The core changes focus on making climate policy more affordable for tenants, adjusting rules for new and existing heating systems, and introducing a green gas quota for existing heaters. The coalition describes the law as more technology-open, flexible, practical and simpler, and it is expected to be decided by the cabinet soon.
Key themes in this reform include a rent cap-style cost sharing between tenants and landlords for certain charges, removal of the 65% renewable rule for new buildings, continued large-scale funding for heating replacements, and protections for particularly vulnerable landlords. The law addresses CO2 prices, gas network charges (net tariffs), biogenic fuels and the phased introduction of biomethane or synthetic fuels for fossil heating systems.
2. Rent cap and cost‑sharing: what changes for tenants and landlords
The most important immediate change is a clear cost-sharing rule intended as a costs brake for tenants. Cost risks from CO2 prices, gas network charges and biogenic fuels are to be split 50/50 between tenants and landlords. SPD parliamentary leader Matthias Miersch emphasized: ‘Klimaschutz muss für die Mieterinnen und Mieter bezahlbar bleiben. Wir konnten erreichen, die Kostenrisiken bei CO2, Netzentgelten und Biogas konsequent zu halbieren.’ This shares risk and limits one-sided burden on renters after a heating replacement.
How the cost split works in practice
This cost-sharing applies to all existing and future rental relationships following a heating swap involving gas, oil or liquefied gas. For tenants, this functions like a rent cap on certain energy-related variable costs: the landlord cannot pass on more than half of those specific cost increases. For landlords it introduces new responsibilities and partial exposure to volatile CO2 and net tariff costs.
- Costs covered: CO2 price, gas network charges (net tariffs), biogenic fuel costs (biogas).
- Split: 50% tenant / 50% landlord for the listed categories.
- Applies: after heating replacement with gas, oil or liquefied gas for existing and new rental contracts.
For new gas or oil heaters, landlords will for the first time have to participate in paying network charges and fuel costs because, as the coalition puts it, ‘if a landlord creates fossil facts, he must take economic responsibility in the future.’ This represents a shift in cost allocation and is meant to discourage unchecked installation of fossil fuel systems without landlord accountability.
3. Rules for new and existing heating systems, the ‘bio‑step’ and the green gas quota
The reform removes the controversial 65% renewable energy requirement for new buildings, allowing new gas and oil heaters to remain an option. However, from January 2029 a gradual ‘bio‑staircase’ (‘Bio‑Treppe’) will apply to new gas and oil installations. This staircase contains four stages and runs until 2040, requiring increasing shares of biomethane or synthetic fuels for those systems.
| Start / Period | Measure |
|---|---|
| January 2029 | Start of the phased ‘Bio‑Treppe’ for new gas and oil heaters |
| 2029–2040 | Four-stage gradual increase in required use of biomethane or synthetic fuels until 2040 |
| From 2028 | Green gas quota applies to existing heating systems |
| Goal | Reduce emissions from heating while keeping technology options open |
The bio-step (Bio‑Treppe) and timeline
While exact percentages for each stage are part of the implementing details, the law sets a clear roadmap: new fossil heating installations are permitted until a staged transition toward biomethane or synthetic fuels is enforced by 2040. This intends to keep options open for building owners while creating a predictable path for decarbonisation of heating fuels.
Separately, for existing heating systems the law introduces a ‘green gas quota’ starting in 2028. This quota requires a certain share of biomethane or other approved green gases in the fuel mix for existing installations, incrementally increasing the demand for renewable gas without mandating immediate system replacements.
4. Funding, hardship clause and tenant protections
The coalition kept the large-scale funding program for heating replacements in place. Financial support for exchanging old heaters remains available to lower the barrier for modernisation and to support the shift to low‑carbon heating options.
Tenant protection and the rent-cap effect
By halving the exposure of tenants to CO2 price changes, net tariffs and biogas costs, the law creates a de facto cap on how much of these variable energy costs can be shifted to tenants. The German Mieterbund still sees risks for tenants, but the reform was explicitly framed to keep climate protection affordable for renters.
Importantly, the reform includes a hardship clause that protects landlords of unmodernised buildings with very low rents. This clause aims to avoid undue burdens on owners who cannot afford comprehensive renovations and to limit adverse effects on affordable housing supply.
5. Criticism, risks and reactions
The reform generated mixed reactions. On one hand, Unionsfraktionschef Jens Spahn welcomed the changes: ‘Wir schaffen Habecks Heizungsgesetz ab und geben im Keller wieder die notwendige Freiheit. Gleichzeitig braucht es einen fairen Ausgleich zwischen Vermietern und Mietern.’ On the other hand, environmental groups warn that delaying transition away from fossil fuels could raise long-term costs as CO2 prices and net tariffs rise, and could set back climate protection efforts.
- Environmental NGOs: warn of long-term higher costs and slower decarbonisation.
- Deutscher Mieterbund: continues to see risks for tenants despite cost-sharing measures.
- Some analysts: describe the reform as repackaged but still restrictive and costly.
Critics argue the law still leaves elements of paternalism and ongoing biogas costs. Some analysts called the package a ‘black-red heating hammer with better marketing’ (Kettner‑Edelmetalle analysis), suggesting that despite cosmetic changes, substantive controls and costs for biogas and other measures remain.
6. What happens next and practical considerations
The coalition intends to send the revised heating law to the cabinet soon. Once approved, implementing regulations and concrete percentage steps for the bio‑staircase and green gas quota will follow. Those details will determine how quickly the market for biomethane, synthetic fuels and related infrastructure must scale up.
For tenants and landlords the immediate practical takeaway is to watch for the final cabinet decision and subsequent implementing rules. The law changes the economic balance by sharing CO2 and network risks and by setting staged fuel requirements; its real-world effects will depend on detailed thresholds, timing and enforcement that are still to come.
