Germany's Building Modernisation Act: heating rules

What changed on 29 July 2026

The ministry’s page says the Act was promulgated in the Federal Law Gazette on 28 July and that the main provisions have applied since 29 July 2026. It describes the change as leaving the choice of heating technology to the owner: heat pumps, district heating, hybrids, biomass, and also gas and oil heating. The earlier uniform requirement of at least 65% renewable energy is dropped.

The current text of the law at gesetze-im-internet.de confirms this in its structure. Sections 71, 72 and 73 each read “(weggefallen)”, that is, repealed. Section 42 now begins with the principle: where a heating system in an existing building or building network is replaced and the owner picks one of the listed options, sections 43 to 46 apply.

The ten options for replacing a boiler

Section 42(2) lists what an owner may choose:

1. a system fed with gas, heating oil or LPG;
2. an electric heat pump;
3. a solar thermal system;
4. a system using biomass or hydrogen (green, blue, orange or turquoise) and derivatives;
5. a heat-pump hybrid (a heat pump plus a gas, oil, LPG or biomass burner);
6. a solar-thermal hybrid;
7. a high-efficiency combined heat and power plant;
8. direct electric heating;
9. a house connection station for a heat network; or
10. another innovative heating solution.

The bio-fuel steps for new gas, oil and LPG boilers

Section 43(1) is the new central rule for fossil boilers. If such a system is installed after 29 July 2026 in an existing building, the owner must ensure that this share of the heat it supplies comes from biomethane, bio-oil, bio-based LPG or hydrogen and its derivatives:

The ministry calls this the “Biotreppe” (bio-step). Section 43 gives ways to meet the duty without buying fuel: a solar thermal system can satisfy it, and for 2029 to 2034 the duty counts as met with 0.04 m² of collector aperture per m² of floor area in a house with up to two flats (0.03 m² in larger buildings). A ventilation system with heat recovery of at least 73% can also count. A heat-pump hybrid counts as compliant if the heat pump reaches at least 30% of the output of the peak-load generator at the specified test point (40% in a bivalent alternative operation).

If the old boiler fails beyond repair, section 43(7) gives a grace period: a system installed between 1 January and 31 December 2028 is bound by the duty only after twelve months, and from 2029 an existing duty continues for twelve months from installation.

Where the owner is not the operator, the operator must meet the duty (section 43(6)).

Biomass and direct electric heating

Section 45 requires a biomass stove or boiler with water as the heat carrier and only the fuels allowed by the ordinance on small and medium combustion plants. A biomass hybrid meets the section 43 duty through the solid biomass itself.

Section 46 allows direct electric heating in an existing building with flats only if the building’s thermal insulation is at least 30% better than the required level in sections 16 and 19. This does not apply in a building with no more than two flats where the owner lives in one, nor to the replacement of an existing single-room unit.

What did not change for existing systems

The law keeps the duties on operating older systems in larger buildings. Section 60b requires a heating check and optimisation for a water-based system in a building with six or more flats, within a year of its 15th birthday for systems installed after 30 September 2009, and by 30 September 2027 for older ones. Section 60c requires hydraulic balancing after a new system is installed in such a building. Results must be shown to tenants on request.

Fuel quotas still to come

Section 42a says the federal government must submit, by 1 December 2026, a law introducing a green gas and green heating-oil quota under which fuels placed on the market for heating are fully climate-neutral from 2045. The ministry says the details of the quota, which it dates from 2028, will be set in that separate law. That law was not in force when this guide was checked, so treat any figure for it as proposed.

Subsidies

According to the ministry, the federal subsidy for efficient buildings continues with changes from 21 July 2026: an income bonus of 40% for households below €30,000, 30% up to €40,000 and 10% up to €50,000, and a cap of €28,000 on eligible costs, falling by €750 every half year. Applications approved before 20 July are unaffected. Check the lender’s current conditions before signing a contract.

District heating

Under section 109, municipalities may use a state-law power to impose connection and use obligations to a public district heating or cooling network also for climate and resource protection. Whether your street is covered depends on the municipality.

Which professional to consult

A qualified energy consultant or an architect can compare the options and issue the proofs the law requires, such as the proof of the bio-fuel share for larger hybrids. A property valuer can value the effect of a system on a home. See also the energy certificate when buying.