Germany's heating law and the GEG: what actually applies

What the heating law actually requires

Behind the buzzword "Heizungsgesetz" (heating law) stands the amended version of Germany's Building Energy Act (GEG). It has been in force since 1 January 2024, and its core rule is quickly explained: anyone installing a new heating system must run it on at least 65 percent renewable energy. The small word "new" carries all the weight here. The rule targets newly installed systems, not the heating system doing its job in your basement today.

And even for new heating systems, the requirement does not apply everywhere immediately. So far, only new buildings in new development areas are directly affected. For existing buildings, in other words for the vast majority of owners and condominium owners' associations, the start date is tied to municipal heat planning and begins no later than 2026 or 2028 respectively. You will find the overview in the section on deadlines.

Grandfathering: your current heating system can stay

Grandfathering is the law's most important relief, and it regularly gets lost in the public debate. It means that existing heating systems may keep running, and they may be repaired. There is no general obligation to replace them right away. If the system breaks down and can be repaired, everything simply stays as it is.

Only one replacement rule exists, and it predates the current amendment by many years: constant-temperature boilers older than 30 years must be replaced. This obligation concerns an older generation of boilers and comes with exemptions. Among those exempt are low-temperature and condensing boilers as well as owner-occupiers of single-family and two-family homes who have lived there since February 2002.

For you this means: as long as your heating system runs or can be repaired, there is no pressure to act. Looking ahead still pays off, because those who know the deadlines, options and subsidies decide confidently rather than hastily when it matters. That is exactly what the next sections are for.

What applies from when: the deadlines at a glance

The law's timetable is tied to municipal heat planning. The idea behind it: before you invest, you should know how your city or municipality plans its future heat supply, for example whether a heat network is coming to your neighbourhood. That is why the 65 percent requirement for existing buildings only takes effect once this planning is in place, but no later than two fixed cut-off dates.

The cut-off dates are upper limits. If your municipality's heat plan designates specific areas earlier, the requirement can also take effect there earlier. It is therefore worth keeping an eye on local heat planning. Incidentally, the same deadlines also apply to new buildings outside new development areas, for example when building on an infill plot.

What "until then" means in practice

Until the requirement takes effect in your municipality, gas or oil heating systems may still be installed. The law attaches two conditions. First, professional advice is mandatory before installation. Second, such systems must later use increasing shares of renewable fuels: 15 percent from 2029, 30 percent from 2035 and 60 percent from 2040.

At the very end stands a fixed final date: from 1 January 2045, heating systems may no longer run on fossil fuels. Every gas or oil heating system installed today therefore has a clearly limited time horizon. The later mandatory shares and the fixed end date belong in every decision about installing a new fossil-fuel system.

If your heating fails for good: the breakdown rule

The scenario that worries many owners: the heating system gives up for good in the middle of winter, and supposedly a brand-new renewable system must be in place within a few weeks. That is precisely what the law does not require. For a total breakdown, meaning a defect beyond repair, transition periods of usually five years apply for switching over.

During this time, a fossil-fuel solution may step in temporarily, for example a used gas heating system. Nobody is left in the cold, and nobody has to rush a decision with consequences spanning decades. This buffer is particularly valuable for condominium owners' associations: five years are enough to obtain quotes, involve the owners' meeting, pass resolutions and prepare the subsidy application properly.

The distinction from a repair matters: if the system can still be fixed, grandfathering continues to apply and no deadline starts at all.

Your options: six ways to meet the 65 percent requirement

When a replacement is due, the law does not prescribe any particular technology. It only defines the target: 65 percent renewable energy. Several compliance options are open to get there:

• Heat pump: heats with electricity and ambient heat, feasible in many apartment buildings too.
• Connection to a heat network (district heating): the heat arrives ready to use, particularly attractive where heat planning provides for networks.
• Direct electric heating: heats directly with electricity.
• Heat pump hybrid system: combines a heat pump with another heat generator.
• Biomass heating: for example with pellets.
• Solar thermal in combination: complements one of the other solutions.

On heat pumps in apartment buildings specifically, the assumption stubbornly persists that they do not work there. In fact, they are feasible in many cases, whether as a central system, as a cascade of several units or as a hybrid solution. What matters are the flow temperatures and the existing radiator surfaces. Often it makes sense to combine the replacement with improvements to the building envelope. Our guide to energy-efficiency renovation shows how to sequence and subsidise such measures wisely.

Which option suits your building depends on its condition, its location and local heat planning. Qualified advice before deciding is therefore money well spent. When installing a fossil-fuel system, it is mandatory anyway.

Heating replacement in the WEG: resolution, costs, schedule

In a condominium owners' association, the central heating system is part of the common property. The decision to replace it is therefore not made by an individual owner but by the owners' meeting through a resolution, and a simple majority is enough. How resolutions come about and which majorities apply to what is explained in our guide WEG and the law.

The association bears the costs: as a maintenance measure, they are generally shared by all owners according to their cost allocation key. Three funding routes are available: the maintenance reserve, a special levy or a loan taken out by the association. Which combination fits depends on the reserve level and the size of the project. Our guide to financing provides an overview.

The process itself follows a well-rehearsed pattern: the property manager coordinates the quotes, prepares the draft resolutions, keeps an eye on subsidies and deadlines, and manages the schedule. This is where it is decided whether the project drags on or runs smoothly. A committed, well-organised property management company turns this mandatory topic into a plannable project.

Special case: gas heating units in each apartment

Many older residential complexes heat unit by unit, with a separate gas boiler in each apartment (known in Germany as Gas-Etagenheizung). For them, the law provides a separate, deliberately long roadmap: once the first of these apartment-level systems in the building is replaced, the association has five years from that point for the fundamental decision on whether the building will switch to central heating or remain decentralised. If it opts for centralisation, a total of up to 13 years remains for implementation.

That is plenty of time, but no reason to shelve the topic: the fundamental decision affects every single apartment and belongs on the agenda early, ideally before the first boiler failure forces it.

Subsidies: grants for replacing your heating system

The switch is supported through Germany's federal subsidy scheme, processed via the state development bank KfW. The basic subsidy is 30 percent of the eligible costs. Bonuses can be added, including a speed bonus and an income-based bonus. In total, the subsidy is capped at 70 percent.

Important for apartment buildings and condominium owners' associations: the eligible costs are staggered per residential unit, with 30,000 euros for the first unit and decreasing amounts for each additional one. The more units the building has, the larger the total from which the grant is calculated.

Frequently asked questions about the heating law

This guide was prepared with great care (last updated: July 2026) but does not replace legal or energy advice for your individual case. What counts is the Building Energy Act in its current version, your municipality's heat planning and the current subsidy conditions. For special situations, specialised advice is the way to go.