The Building Modernisation Act (GModG): what has applied since July 2026

Since 29 July 2026, German building energy law has been called the Building Modernisation Act (Gebäudemodernisierungsgesetz), GModG for short. If you own a house, a flat or a commercial property, the same question always lies behind it: which part of it affects my building, and from when? The short answer is that this year it is mainly the heating rules that are new — the energy performance certificate (Energieausweis) only takes its turn on 1 January 2027.

This article puts the Act in order for owners of residential and non-residential buildings (Nichtwohngebäude): what it actually is, which part enters into force when, what has become of the 65 per cent duty for heating systems, what changes for the energy performance certificate, which deadlines run until 2033 and what this means for selling and letting. For the individual questions it points you onwards at the right places.

#What is the Building Modernisation Act — and since when has it applied?

The GModG is not a new Act but the old one under a new name. Article 1 no. 1 of the amending Act replaces the title of the Building Energy Act (Gebäudeenergiegesetz, GEG) with “Act on Saving Energy and Modernising the Heat Supply in Buildings (Building Modernisation Act – GModG)”. The GEG was not repealed; it was renamed and largely rebuilt. That is why the consolidated version is still found at the same address on gesetze-im-internet.de, and why the section numbers on the energy performance certificate have stayed the same.

The amending Act bears the official title “Act amending the Building Energy Act, amending the Building Electromobility Infrastructure Act and amending further provisions in the heating sector”; it was signed on 23 July 2026 and promulgated in the Federal Law Gazette on 28 July 2026 — reference BGBl. 2026 I No. 226.8 An official footnote to the title of the Act gives the reason: the transposition of Directive (EU) 2024/1275 on the energy performance of buildings, known as the EU Buildings Directive or EPBD.

#Why the Act enters into force in stages

Article 9 of the amending Act staggers the entry into force across four paragraphs: paragraph 1 puts the Act into force on the day after promulgation, paragraph 2 postpones Articles 2 and 7 to 1 January 2027, paragraph 3 Article 3 to 1 January 2028 and paragraph 4 Article 4 to 1 January 2030.8 The new energy certificate law is contained solely in Article 2; Article 7 amends the Building Electromobility Infrastructure Act and concerns charging points and parking spaces, not the certificate. That is why two statements are true at the same time: the GModG applies, and nothing changes for the energy performance certificate in 2026.

This staggering is not a formality but the most important reading aid for the whole Act. Anyone reading a news item about the GModG should first check which Article contains the rule described. If it is in Article 1, it applies today. If it is in Article 2, it applies from 2027. The official federal GEG information portal arranges the new rules of the promulgated Act by exactly these four dates.9

#What changes for the energy performance certificate, and from when exactly?

In 2026: nothing you will notice. Article 1 touches §§ 80 to 85 only editorially — it swaps references to other sections and deletes one number from the catalogue of details. The certificate you need today for a sale or a new letting is the same as in 2025, and it remains valid for ten years from the day it is issued (§ 79 (3) GModG).1 When a duty to have a certificate arises at all and which buildings are exempt is set out in detail in When an energy performance certificate is mandatory.

Article 1 does contain one change of substance, but it lies next to the certificate itself: no. 40a adds a no. 5 to § 88 (1) and thereby, since 29 July 2026, extends the group of persons authorised to issue certificates to include persons who, under the rules of the federal states, may issue the declaration of compliance under § 92.8 For you as an owner this changes nothing — there are simply more issuers.

The real rebuild is in Article 2 and takes effect from 1 January 2027. Six points affect owners directly.

The certificate goes digital. The new § 79 (2) requires the energy performance certificate to be issued digitally in a machine-readable format; at the request of the client or the owner, additionally on paper.8 So the paper copy does not disappear, it merely becomes the exception on request.

Non-residential buildings only get the calculated certificate. The new § 80 (3) sentence 2 prescribes for non-residential buildings an energy performance certificate based on an energy balance calculation, and the new § 82 (1) expressly restricts the consumption-based certificate to buildings used exclusively for residential purposes.8 For commercial premises, surgeries, office buildings and mixed-use properties, the cheaper route via consumption data therefore disappears. The GEG information portal sums this point up in the same way: consumption certificates (Verbrauchsausweise) are no longer provided for non-residential buildings.9

Purely residential buildings may choose freely. Today, § 80 (3) sentence 2 prescribes a demand certificate (Bedarfsausweis) for residential buildings with fewer than five flats whose building application was submitted before 1 November 1977 — unless the building already met the requirement level of the Thermal Insulation Ordinance of 11 August 1977 on completion or was brought up to it later (§ 80 (3) sentence 3).2 Anyone who can prove that they have renovated their older building to this level may therefore already choose today. The rule and its exception no longer appear in the new § 80 — from 2027, for a building used exclusively for residential purposes, you decide yourself which of the two methods is applied. Which one is really better for your house depends on criteria other than the year of construction; the comparison Consumption certificate or demand certificate sets the two methods side by side.

Two years of consumption instead of three. The new § 82 (1) requires final energy consumption to be recorded annually, broken down by energy source, over a period of two years. Today it is 36 consecutive months. The rule that the most recent billing period may not lie more than 18 months in the past remains.8

The certificate gets new details. The new § 85 (1) lists 31 mandatory details in a single list.8 Part of this is restructuring rather than addition: today § 85 spreads its catalogue over three paragraphs — 20 numbers for every certificate, of which no. 15 has been dropped since July 2026, plus nine more for the demand certificate and six for the consumption certificate.3 A demand certificate today therefore already carries 28 mandatory details. New in the catalogue are the share of renewable energy generated on site (no. 14), the calculated useful energy (no. 25), a yes-or-no statement on the building’s ability to respond to external signals (no. 26) and the question of whether the heat distribution system can be operated at low temperatures (no. 27). Operational greenhouse gas emissions in kilograms of carbon dioxide equivalent per square metre and year will in future appear in every certificate (no. 16), and from 2028 the life-cycle greenhouse gas emissions are added for large new buildings (no. 17).

The advertisement will state the primary energy value. The new § 87 requires two details, the second of which bundles five values: date of issue, annual primary energy demand in kilowatt-hours per year and square metre of usable floor area, energy efficiency class, year of construction and the main energy sources for heating. The final energy value that advertisements state today thus gives way to the primary energy value.8

#Four smaller changes that are easily overlooked

Four further points of Article 2 each affect small groups, but hit them hard. The exemption for listed buildings is dropped. Today, § 79 (4) sentence 2 GModG exempts a listed building (Baudenkmal) from the duties to present and display under § 80 — so no energy performance certificate is needed there on sale or letting.1 The new § 79 (4) knows only two exemptions: federal defence buildings and small buildings. The consumer advice centre (Verbraucherzentrale) describes the same change for owners.12

The informational advice session is dropped. Anyone who buys a residential building with no more than two flats today must, after handover of the certificate, hold an advice session, provided it is offered free of charge.2 The new § 80 (4) no longer contains this duty.

Extending a contract triggers the certificate duty. The new § 80 (3) expressly names the case in which a rental, lease or leasing contract is extended. Anyone who merely extends today does not need a new certificate; from 2027 they do, if no valid one exists.8

The display duty is restructured. Today it depends on area thresholds of 250 or 500 square metres of usable floor area with heavy public footfall.2 From 2027 it is linked simply to heavy public footfall in a non-residential building — without any square-metre threshold.

#What applies to heating systems now — has the 65 per cent rule really gone?

Yes, and it has been gone since 29 July 2026. Article 1 no. 32 of the amending Act reads, in a single sentence: §§ 71 to 73 are deleted.8 § 71 contained the requirement that a newly installed heating system must generate at least 65 per cent of its heat from renewable energy. It has not been suspended or postponed but removed from the Act. The federal GEG information portal expressly also lists the advice duty when replacing a heating system and the operating bans for certain heating systems among the dropped rules.9

In their place comes a different construction: freedom of choice for the appliance, a quota for the fuel. The new § 42 (2) lists ten permitted options for replacing a heating system — from the gas, heating oil or liquefied petroleum gas boiler through the electrically driven heat pump, solar thermal, biomass and hydrogen, the two hybrid variants, high-efficiency combined heat and power and direct electric heating to the building substation connected to a heat network and an “other innovative heating solution”.8 None of them is banned — but none is unconditional either: § 42 (1) expressly makes replacement subject to the provisions of §§ 43 to 46. Anyone who chooses a gas, heating oil or liquefied petroleum gas system thereby takes on the quota of § 43. Direct electric heating may only be installed in an existing building with flats if its structural thermal insulation undercuts the requirements of §§ 16 and 19 by at least 30 per cent; exempt is a building with no more than two flats, one of which the owner occupies (§ 46).

#The bio staircase: what a new gas or oil boiler costs comes later

Anyone who opts for the fossil option takes on a duty that only bites in a few years’ time. Under § 43 (1) GModG, for a gas, heating oil or liquefied petroleum gas system newly installed in an existing building after 29 July 2026, the owner must ensure that a growing share of the heat is generated from biomethane, bio-oil, biogenic liquefied petroleum gas or hydrogen.6

This duty can also be met in other ways, namely by four routes. What is time-limited is not the route but the simplification — an important difference that is easily lost when reading the Act. A solar thermal system (§ 43 (3) sentence 1) and a ventilation system with heat recovery (§ 43 (4) sentence 1) can each cover the quota without any time limit. Only the deemed compliance — the duty is regarded as met without further proof — is limited to the period from 1 January 2029 to the end of 31 December 2034 and tied to fixed values: for the solar system at least 0.04 square metres of aperture area per square metre of usable floor area, 0.03 where there are more than two flats; for the ventilation system a heat recovery efficiency of at least 73 per cent, a coefficient of performance of at least 10 and supply of the entire building area. Otherwise, for solar thermal, § 43 (3) sentence 3 requires proof by an expert under § 88 or a contractor’s declaration as soon as more than 15 per cent is to be credited. The heat pump hybrid system is the third route: it meets the requirement under § 43 (5) if the heat pump reaches at least 30 per cent of the output of the peak-load generator at part-load point A under DIN EN 14825, or at least 40 per cent in bivalent alternative operation — with proof required above 30 per cent credit, for buildings with at least six flats and for non-residential buildings only for the period after 31 December 2039, for all other modes of operation from 1 January 2029. The biomass hybrid system is the fourth: under § 45 (2), the use of solid biomass meets the duty under § 43 (1); here too, above 15 per cent credit, the share attributable to it must be proven from 2035.6 If the old system fails beyond repair, § 43 (7) gives twelve months’ breathing space: anyone who installs a new system in 2028 because of such a failure is only subject to the quota twelve months after installation; from 2029 the stage that applied at the time of the failure continues to apply for twelve months.6

A second point is often presented as a duty in force and is not one: § 42a GModG merely announces that the Federal Government is to present, by 1 December 2026, an Act on a green gas and green heating oil quota that obliges those placing heating fuels on the market to switch them entirely to climate-neutral fuels from 2045. That is a legislative mandate, not a requirement for your building. From when which quota applies to fuel suppliers is not in the GModG — anyone reading percentages on this is reading about an Act that has not yet been passed.

Two further rules concern the relationship between landlords and tenants. Article 5 amends the Carbon Dioxide Cost Allocation Act and splits the costs arising from the installation and operation of a heating system under § 43 equally between both sides — network charges and carbon dioxide costs from 2028, the additional costs of the mandatory bio share from 2029. Article 6 inserts § 559f into the Civil Code (BGB): after installing a heat pump, the landlord may only apply the full modernisation levy if a specialist contractor proves that the seasonal performance factor is at least 2.5; without this proof, only half of the costs. The proof is not required for newer or well-insulated buildings — built after 1996, built to the Thermal Insulation Ordinance 1994, after renovation to the level of § 38 GModG, or with a flow temperature of no more than 55 degrees Celsius (§ 559f (1) sentence 2 BGB).8

In detail, with grandfathering, the breakdown deadline, municipal heat planning and the fines: Heating Act 2026: what really applies to your heating system now.

#Who is affected: residential, non-residential and public buildings?

The GModG affects the three building groups to very different degrees. For residential buildings the existing system essentially remains; the real tightening lies with non-residential buildings, and the strictest requirements for new buildings apply first to the public sector.

#Residential buildings: no renovation duty for the individual house

The Act contains no unconditional renovation duty for your home. The familiar requirements remain: the retrofit duty for the top floor ceiling and uninsulated distribution pipes, the conditional requirements that only apply when you are renewing the roof, façade or windows anyway, and the rules for extensions and conversions. The Verbraucherzentrale describes the same system: few replacement and retrofit duties, alongside conditional requirements for measures that are planned anyway.12

The reason lies in the EU Directive itself. For residential buildings it does not require a minimum standard for each building but a trajectory for the stock: the average primary energy consumption of the entire residential building stock must fall by at least 16 per cent by 2030 compared with 2020 and by at least 20 to 22 per cent by 2035, with at least 55 per cent of this reduction to come from renovating the 43 per cent of residential buildings with the worst energy performance.10 The obligation therefore lies with the state, not with the individual owner.

Official statistics show how large this stock is: at the end of 2025 Germany had 13.5 million single-family houses, 2.8 million two-family houses and 3.5 million multi-family houses. The multi-family houses alone contained 23.6 million flats; in total there were 44.0 million flats in Germany.11 A duty covering each of these buildings individually would have needed a different design from the trajectory the Directive opted for.

#Non-residential buildings: maximum values from 2030 and 2033

This is where the real innovation lies. From 1 January 2027 the new § 40 GModG, “Renovation requirements for existing non-residential buildings”, applies. It obliges the owner to ensure, by suitable measures, that the annual primary energy demand for heating, hot water, ventilation, cooling and built-in lighting is no more than 3.5 times the value of a reference building from 1 January 2030 and no more than 2.95 times from 1 January 2033.8 At European level this corresponds to the thresholds below which all non-residential buildings are to lie from 2030 and 2033 respectively — measured against the 16 and 26 per cent of the stock with the worst energy performance.10

The duty has exemptions, and they are broad. It does not apply insofar as compliance is technically impossible or economically unreasonable or conflicts with other public-law provisions. It is also deemed met if the building was erected from 1 January 1996 onwards, if it demonstrably reaches the requirement level of the 1994 Thermal Insulation Ordinance, if it is mainly heated with biomass or a heat pump, or if it is connected to district heating. Exempt are, among others, buildings due for demolition, certain listed buildings, industrial plants, workshops, agricultural buildings with low energy demand and small detached buildings.8

The duty therefore affects a manageable part of a very large stock. The most comprehensive survey to date by the Institut Wohnen und Umwelt extrapolates to 21.124 ± 0.445 million non-residential buildings in Germany, of which, however, only 1.981 ± 0.152 million are heated or cooled and thus fully covered by building energy law; the figures date from 2021.13

#Public buildings: zero-emission buildings from 2028

The Federal Government leads the way on requirements for new buildings. Article 3 of the amending Act inserts a § 10a with effect from 1 January 2028: a new non-residential building owned by the public sector and used by a public authority must be built as a zero-emission building. Article 4 extends this to all new buildings with effect from 1 January 2030 — from then on, the same standard applies to anyone who erects a building.8

For existing public non-residential buildings used by a public authority, a certificate based on an energy balance calculation must be issued from 2027; where there is heavy public footfall, it must be clearly displayed. Added to this is the staggered solar duty of the new § 106, which likewise begins with public non-residential buildings and only reaches new residential buildings from 2030.8

#And the new A to G scale?

From 1 January 2027 the Act introduces an efficiency scale from A to G — but exclusively for non-residential buildings. The new § 86 separates the two worlds neatly: paragraphs 1 and 2 refer to Annex 10 for residential buildings, paragraphs 3 and 4 introduce the new Annex 10a for non-residential buildings, and only a building that causes no on-site emissions from fossil energy may enter class A there.8 Unlike for residential buildings, this scale does not measure in kilowatt-hours per square metre but as the ratio of the calculated primary energy demand to that of a reference building — there is therefore no generally valid conversion into kilowatt-hours.

For residential buildings, Annex 10 continues to apply with the nine classes A+ to H and the limits of 30 to 250 kilowatt-hours per square metre of usable floor area (Gebäudenutzfläche) and year.7 Article 2 changes nothing about the scale and its limit values; it merely defines the area reference more narrowly: from 2027 the reference quantity is the usable floor area under DIN/TS 18599: 2025-10 that is heated or cooled.8 Because the denominator can therefore turn out smaller, the stated figure shifts in individual cases — the classification itself is not affected. The report that homes will now get a class between A and G remains wrong.

#Which deadlines will owners face up to 2033?

The following dates are in the Act and can be noted down. Not every one affects every building; the third column gives the provision so that you can look up the point relevant to you.

#What does the GModG mean for selling and letting?

In everyday practice the procedure stays as it is. If you want to sell, let, lease or lease out a building or a flat, an energy performance certificate must be available. It must be presented to the prospective buyer or tenant at the viewing at the latest; if there is no viewing, without delay, and at the latest on request. After the contract is concluded, it must be handed over. The same applies accordingly to letting (§ 80 (3) to (5) GModG).2

Anyone who places an advertisement in commercial media and has a certificate at that time must state five details: the type of certificate, the final energy demand or final energy consumption value, the main energy sources for heating and — for residential buildings — the year of construction and energy efficiency class (§ 87 (1) GModG).4

If the certificate or the details are missing, this is an administrative offence. § 108 (2) GModG distinguishes three ranges. Up to 50,000 euros applies to breaches concerning the building envelope and building services, such as faulty construction, an uninsulated top floor ceiling or missing control devices on the heating system. Up to 10,000 euros applies to the numbers covering all energy certificate breaches: failure to present, failure to hand over, missing mandatory details in the advertisement. Up to 5,000 euros remains for the other cases.5 From 2027 the numbers in this provision shift; the amounts stay the same.

Two things do change here from 2027: the extension of a rental, lease or leasing contract also triggers the certificate duty, and listed buildings are no longer exempt. Which occasions trigger a duty in detail, who is exempt and what applies to owner-occupied flats and inheritances is set out in When an energy performance certificate is mandatory.

#What does an energy performance certificate cost under the new law?

The Act changes nothing about the price itself — it changes what an issuer has to do. At Energieausweis Portal, the consumption certificate for a residential building costs 69.90 € and the demand certificate 119.90 €; anyone in a hurry pays a 39.99 € surcharge for express processing. The full breakdown, including the range for preparation with an on-site inspection, is in What an energy performance certificate costs.

Two points of the new law noticeably affect the effort. First, from 2027 the issuer must inspect an existing building on site or have suitable photographs made available for the assessment. Preparation via an online form therefore remains possible; it gets an additional evidence step. Second, for non-residential buildings only the more computationally demanding calculated certificate is permitted — the cheaper route via consumption data disappears there. What consequence this has for prices, the Act does not say, and we do not estimate it here.

For residential buildings both remain open: you can have the consumption certificate or the demand certificate issued, and from 2027 you may choose freely between the two for a purely residential building without any check of the year of construction.

#Frequently asked questions about the Building Modernisation Act

#Conclusion: one Act, two dates

The Building Modernisation Act is the renamed and rebuilt Building Energy Act, and it arrives in stages. The heating part has applied since 29 July 2026: no more 65 per cent duty, but instead freedom of choice for the appliance and a fuel quota from 2029. On 1 January 2027 the energy performance certificate follows, with digital issuing, a free choice of certificate type for purely residential buildings and considerably more mandatory details.

For owners of a home, the news is therefore calmer than many headlines suggest: no renovation duty, no new efficiency scale, and an existing certificate keeps its ten years. Anyone who owns a non-residential building, on the other hand, has two dates in the calendar — 2030 and 2033 — and should know the starting position of their building before they arrive.