Glossary
Gebäudemodernisierungsgesetz (GModG)
Gebäudemodernisierungsgesetz (GModG): The Gebäudemodernisierungsgesetz (GModG, German for 'Building Modernisation Act') has governed the energy requirements for buildings in Germany since 29 July 2026. It replaces the Building Energy Act (Gebäudeenergiegesetz, GEG): the 65% renewables obligation when replacing a heating system and the replacement obligation for old boilers are gone, while new gas and oil heating systems face a 'bio-ladder' (Bio-Treppe) from 2029.
What is the Gebäudemodernisierungsgesetz?
The Gebäudemodernisierungsgesetz (GModG, the Building Modernisation Act) has been Germany's central law on the energy requirements for buildings since 29 July 2026. It evolved from the Building Energy Act (Gebäudeenergiegesetz, GEG), widely known as the "heating law", and was published in the Federal Law Gazette on 28 July 2026 (BGBl. 2026 I No. 226).
What changed compared with the GEG
The obligation to use at least 65% renewable energy when replacing a heating system (GEG § 71) is gone. So are the obligation to replace boilers after 30 years (GEG § 72), the obligation to insulate the top-floor ceiling (GEG § 47) and the ban on running fossil heating from 2045. Instead, anyone who installs a new gas, oil or LPG heating must use a rising share of climate-friendly fuels from 2029, the so-called Bio-Treppe (bio-ladder).
What owners still have to do
The one retrofit obligation that remains is insulating previously uninsulated, accessible heating and hot-water pipes outside heated rooms (§ 69 GModG). In owner-occupied one- and two-family houses it only falls on the new owner after a change of ownership, with a two-year deadline.
What landlords need to know
For a gas or oil heating installed after 29 July 2026 in a rented home, landlord and tenant each pay half of the CO₂ costs and gas network fees from 2028, and from 2029 also half of the cost of the bio share up to 30% (§ 5a CO2KostAufG). To see where your building stands today, try the Energy Efficiency Quick Check.
This page is for information only and does not replace legal or energy advice.
Frequently asked questions
Gebäudemodernisierungsgesetz translates as 'Building Modernisation Act'. Abbreviated GModG, it is the German law on the energy requirements for buildings and has replaced the Building Energy Act (GEG), often called the 'heating law', since 29 July 2026.
It was published in the Federal Law Gazette on 28 July 2026 (BGBl. 2026 I No. 226). Most rules have applied since 29 July 2026. Further parts take effect on 1 January 2027 (including the digital energy performance certificate and a solar requirement for non-residential buildings), on 1 January 2028 and on 1 January 2030 (zero-emission standard for all new builds).
No. The former obligation to replace constant-temperature boilers after 30 years (GEG § 72) has been abolished, as has the ban on running fossil heating from 2045. Existing heating systems may keep running and be repaired.
Not as a legal obligation. You may install a new gas or oil heating again, but it is subject to the bio-ladder from 2029. For the federal heating grant (KfW 458), the 65% threshold remains a funding condition.