The German Building Energy Act (Gebäudeenergiegesetz, GEG) has been in force since 2020 and was substantially tightened with the amendment of 1 January 2024. For owners of existing buildings, this gives rise to concrete obligations – and many overlooked exceptions. This article summarises the duty regime in 2026, with a focus on what most commonly triggers discussion in NRW.
Legal basis
- Building Energy Act (GEG) in the version of 1 January 2024 (heating law amendment), most recently amended in 2024 (BGBl I).
- Ordinance on Energy-Saving Thermal Protection and Energy-Saving Plant Technology in Buildings – repealed in 2020, contents consolidated into GEG.
- Federal Subsidy for Efficient Buildings (BEG-EM) – the flanking subsidy regime.
The five central obligations for existing buildings
1. Boiler replacement obligation (Section 72 GEG)
Constant-temperature boilers installed before 1 January 1991 may no longer be operated. Transitional rules:
- Owner-occupiers of single-/two-family houses in continuous self-use since 1 February 2002 are exempt, as long as they live there themselves.
- On change of ownership (sale, inheritance, gift): the replacement obligation applies within 2 years from registration of the new owner.
- Low-temperature and condensing boilers are not, in principle, subject to this replacement obligation.
2. Insulation obligation for the top ceiling (Section 47 GEG)
If the top ceiling (or the roof above it) does not meet at least the minimum thermal protection under DIN 4108-2, insulation is mandatory – U-value no higher than 0.24 W/m²K.
- Exception: owner-occupiers (cut-off date as above).
- On change of ownership: 2-year period after the transfer.
- Practical relevance: affects virtually all uninsulated houses up to construction year around 1995.
3. Insulation obligation for heating and hot water pipes (Section 71 GEG)
Freely accessible heat distribution pipes and fittings in unheated rooms must be insulated. Minimum thickness depending on pipe diameter; for cross-sections up to DN 22 at least 20 mm.
- Immediate obligation, no transitional period for uninsulated existing lines any longer (applied until 2009).
- Common breach points: boiler room, cellar corridor, attic.
4. 65% renewables requirement for new heating systems (Section 71 GEG)
This obligation applies to newly installed heating systems from the following cut-off dates:
- In new development areas: immediately since 1 January 2024.
- In existing buildings in large cities (> 100,000 inhabitants, including Düsseldorf): once the municipal heat plan is in place, no later than 30 June 2026.
- In smaller municipalities: no later than 30 June 2028.
This can be met by: heat pump, connection to a district heating network, pellet/wood heating, hybrid heating with a renewable share of at least 65%, H2-ready gas heating combined with secured hydrogen supply.
Important: existing fossil-fuel heating systems may continue to be operated and repaired. In case of irreparable defect, there is a 5-year transitional period (in existing buildings) during which a stop-gap heating system may be installed.
5. Energy performance certificate requirement on sale/letting (Section 80 GEG)
On sale, letting or leasing, the owner must present a valid energy performance certificate to interested parties no later than at the viewing. Breach: fine up to 10,000 EUR (Section 108 GEG).
The most important exceptions
Owner-occupier exception
Owners of single-/two-family houses who personally occupied the building on 1 February 2002 and have been using it themselves ever since are exempt from the obligations in Sections 47 and 72 GEG. On a change of ownership (sale, gift, inheritance outside the household), this exception lapses – the new owner has two years to retrofit.
Economic unreasonableness (Section 102 GEG)
An obligation lapses if the required investments cannot be recovered through savings within a reasonable period. Assessment follows a strict economic standard; in disputed cases an expert report is required. Practically relevant almost only in listed or heritage-worthy buildings.
Heritage protection (Section 105 GEG)
Protected monuments and buildings in heritage ensemble areas are exempt from many obligations or can be released on a case-by-case basis. Application to the local heritage authority.
Hardship rules under the heating law
Owners aged 80 and over are exempt from the 65% renewables requirement on heating replacement. For recipients of social benefits (SGB II/XII), in cases of proven insufficient financial means or in extreme economic situations, hardship applications are possible under the federal subsidy.
What to check when buying a house
From my practice as a buyer support consultant – the GEG obligations trigger the 2-year deadline on change of ownership. Consequence: any existing-stock purchase should include the following on the inspection list:
| Check item | Source | Consequence |
|---|---|---|
| Boiler year of construction | type plate, maintenance log | replacement obligation if pre-1991 |
| Top ceiling insulated? | visual inspection of attic | if applicable, insulation to 0.24 W/m²K |
| Pipe insulation in boiler room | visual inspection | immediate |
| Energy performance certificate present, valid? | seller | mandatory disclosure; fine risk for seller |
| Connection to Düsseldorf heat plan | City of Düsseldorf, municipal heat planning | heating cut-off at the latest 30 June 2026 |
This check should be made before the notary appointment, because the investment obligation changes the effective purchase price. In substance reports I typically quantify these obligations at 10,000–35,000 EUR of investment backlog.
Municipal heat planning in Düsseldorf
Under Section 71 GEG, the City of Düsseldorf is obliged to submit a municipal heat plan no later than 30 June 2026. This divides the urban area into zones for:
- District heating expansion (district/local heat)
- Hydrogen network expansion (in Düsseldorf, presumably not in residential areas)
- Decentralised heat supply (heat pump etc.)
In each zone, the planning result determines which heating system is still permissible from the cut-off date. Owners should await the heat plan result before heating decisions – or work with their energy consultant on a heat-pump option as default, which is GEG-compliant regardless of the heat plan.
Fine framework
Section 108 GEG provides for fines up to 50,000 EUR (e.g. for intentional operation of a boiler that should have been replaced) and up to 10,000 EUR (e.g. for breach of the energy performance certificate or insulation obligation). In administrative practice, fines are rare; the obligations are largely enforced via market and bank-financing mechanisms (mortgage lending value!).
Bottom line
GEG 2024/2026 is not a general refurbishment mandate for existing buildings, but a targeted duty system with significant exceptions – particularly for owner-occupiers. On change of ownership, however, many exceptions lapse, and the buyer takes on a 2-year investment obligation. Anyone buying should know this obligation, quantify it and factor it into the purchase price. Quantifying it is only possible on the basis of a solid building survey and groundwork assessment – they are essential to estimate costs and risks sensibly before the purchase.
Related articles:
- iSFP 2026: Refurbishment Roadmap, BAFA Subsidy and Bonus
- What Does Energy Consulting Cost in Düsseldorf?
- Buying a House in NRW: The 12 Hidden Defect Risks
Next step: Advice on GEG obligations at house purchase – within my buyer support engagement the GEG duty status is quantified as standard.
Next step
Would you like this topic assessed for your property in concrete terms? I offer a free initial consultation — fee ranges, scope and available subsidies discussed openly.