The new Building Modernisation Act
Since 29 July 2026, the Building Modernisation Act (Gebäudemodernisierungsgesetz) has applied, replacing the previous Building Energy Act (GEG). The so-called 65 per cent rule for new heating systems has been dropped. New oil and gas heating systems are permitted again, but must use rising shares of climate-friendly fuels over the years. Because the law is new, we recommend seeking advice from an energy consultant before any decision.
The energy performance certificate
For a sale or letting, you generally need a valid energy performance certificate. Key figures must already appear in the advertisement, and the certificate must be available at the viewing. It is valid for ten years. Listed buildings are exempt. There is the consumption-based certificate, which relies on actual consumption, and the demand-based certificate, which assesses the building technically.
Obligations after purchase
If you buy an older detached or two-family house, you generally have to insulate an uninsulated top-floor ceiling and uninsulated heating pipes in unheated rooms within two years. Check the exact scope with an energy consultant before you buy.
Renovation roadmap and subsidies
An individual renovation roadmap (Sanierungsfahrplan) shows the sensible order in which to renovate your house. It is subsidised and can unlock additional funding for the individual measures. Grants and loans are available through BAFA and KfW; applications usually have to be submitted before work begins.
Energy and property value
Buyers factor in heating costs and upcoming renovations very carefully, and banks take energy efficiency into account when lending. A good efficiency rating therefore has a noticeable effect on the price. Before a sale, it is often worth preparing quotes and documents rather than carrying out a full renovation.
This guide provides a general overview and does not replace legal, tax or financing advice.
