Energy efficiency class of a house in Germany: what the letter means

On your energy performance certificate (Energieausweis) an arrow above the colour band points to a letter between A+ and H. This article is written for owners of a residential building who want to know where the letter comes from and what it says about their house. The short answer: it is not a professional judgement but the result of a division — with a reference area that many people confuse.

Six questions: what does the class measure, where do the nine boundaries lie, which class is typical in the existing stock, why is the neighbouring house rated differently, what changes in 2027 — and what does a better class bring?

#What the efficiency class says — and how it is calculated

The law allows no discretion: the classes “follow directly from the final energy consumption or final energy demand”, says § 86 (2) of the Building Modernisation Act (Gebäudemodernisierungsgesetz, GModG).2 Two issuers with the same input data necessarily arrive at the same class. Where the letter sits in the overall picture is explained in the German overview of the energy performance certificate.

Its reach is just as clearly limited: certificates are meant “to enable a rough comparison of buildings” (§ 79 (1) GModG).5 The class is a comparative measure, not a forecast of your heating costs.

The most common mistake lies in the reference area. Annex 10 literally heads its numeric column “final energy [kilowatt-hours per square metre of usable floor area and year]”.1 That is not the living space but as a rule larger: if it is unknown, § 82 (2) sentence 4 GModG allows it to be taken as 1.35 times the living space — for buildings with up to two flats and a heated basement, otherwise 1.2 times.3

#Which classes exist and where the boundaries lie

Nine steps, eight upper limits, one open class at the end:

The boundaries are stated in the Act as “less than or equal to”.1 Exactly 100 kilowatt-hours is therefore still class C; only a value above it makes it D.

#Which class a typical German house has

There is no reliable answer to that — and that is the finding. An expert report by the Institute for Ecological Economy Research sets five data sources side by side: the share of buildings in classes G and H ranges in them from 5 per cent to almost 40 per cent.9 The data situation is inadequate, the authors note.

They name three reasons: demand or consumption, counted by buildings or by floor area, and the fact that certificates only arise on specific occasions — so rather for the better buildings.

What is reliable is the look at the age of the stock: 60 per cent of all residential buildings date from construction periods up to 1979.10 Anyone who owns an unrenovated house from that time had better reckon with the rear part of the scale.

#Why the neighbour with the same house has a different class

Because the same letter can come from two procedures. The demand certificate calculates from building components and technical systems under standard conditions (§ 81 GModG),4 the consumption certificate evaluates real bills (§ 82 GModG).3 Which type is permitted is explained in the comparison consumption or demand certificate.

Four adjusting screws shift the result without anything about the building changing:

The weather, by contrast, drops out: heating consumption is weather-adjusted (§ 82 (3) GModG), and the climate factors of the German Meteorological Service are binding per postcode.11 A cold winter therefore does not push you into a worse class.

#Does the scale change to A to G in 2027?

Not for your home.

The origin of the confusion lies in Brussels: Article 19 (2) of the EU Energy Performance of Buildings Directive requires a closed scale “using exclusively the letters A to G”, with A corresponding to zero-emission buildings and G to the worst buildings of the national stock.8 The same paragraph allows a deferral until the end of 2029 for member states that rescaled their classes between 2019 and May 2024. For German residential buildings no rescaling has been decided so far. What the amendment means for commercial property is explained in the German article on the new A to G scale from 2027.

#What a better class brings — and how to get there

First, visibility: as soon as a certificate exists, the efficiency class of a residential building belongs in every property advertisement in commercial media (§ 87 (1) no. 5 GModG).6 It is in the listing before anyone has set foot in the house.

What it moves in the price cannot be quantified seriously. The Federal Institute for Research on Building, Urban Affairs and Spatial Development calls the effect of a building’s energy quality on rent and purchase price “not yet clearly established”.12 The percentages in circulation come from listing analyses by comparison portals.

The physical part is certain: one class better means less final energy per square metre. The way there is shown by the certificate itself, because the modernisation recommendations are a mandatory component. Which measure pays off is covered in the German article on energy-efficient renovation and funding; where the class sits on the form is shown by the sample certificate.

#Conclusion: one division, two procedures, one scale that stays

The efficiency class of your house is the final energy value per square metre of usable floor area, placed into nine fixed steps — there is no more to it. Looking at the reference area is therefore worth more than debating the letter. And for residential buildings the scale remains: A+ to H.