Primary energy demand and final energy demand: what separates the two figures

Your energy performance certificate shows two energy figures one above the other, both in kilowatt-hours per square metre and year, and one of them is usually considerably larger. That is not a mistake: the two figures measure different things. This article is written for owners of a residential building who want to know which of the two counts for them.

In order: what the two terms mean, why both appear in the certificate, what the primary energy factor does, which figure determines the efficiency class and which belongs in the advertisement — and which renovation measure moves which of the two.

#What is final energy, what is primary energy?

Final energy (Endenergie) is the amount of energy that has to be supplied to the building at its boundary: the gas at the meter, the oil in the tank, the electricity for the heat pump. Primary energy (Primärenergie) is the same amount plus everything that was needed beforehand to get it there — extraction, power station, grid losses, transport. Both relate to one square metre of usable floor area (Gebäudenutzfläche) and one year.

Before that comes a third quantity: useful energy (Nutzenergie), the heat that arrives in the rooms. It becomes final energy when the losses of the heating system are added; final energy becomes primary energy when the factor of the energy source is applied to it. Where the chain appears in your certificate is shown in the overview of the energy performance certificate.

#Why are there two figures in your energy performance certificate?

Because the Act requires both. § 85 (3) of the Building Modernisation Act (Gebäudemodernisierungsgesetz, GModG) prescribes for the consumption certificate (Verbrauchsausweis) the “final energy and primary energy consumption of the building for heating and hot water”.3 In the demand certificate (Bedarfsausweis) both appear as calculated demand. That is why the colour band of the form has one arrow above and one below the scale — which is where is shown in the article on the official template.

The calculation runs in one direction only. § 82 (3) GModG says: “The primary energy consumption is calculated on the basis of the final energy consumption and the primary energy factors under § 22.”4 Primary energy is not a second measurement but a value derived from the first.

#What does the primary energy factor do — and why does electricity fare differently from gas?

The primary energy factor is not the result of a calculation but a set number: Annex 4 to the Building Modernisation Act lists it for each energy source.1 Grid electricity carries the highest factor, because behind every kilowatt-hour delivered lie the losses of power station and grid; wood the lowest, because only the non-renewable share counts there.

On 1 January 2027 the table is replaced — by Article 2 of the amending Act of 23 July 2026, whose entry into force Article 9 (2) sets for that date.8 Grid electricity falls to 1.5, in line with the growing share of renewable electricity: in 2025 it stood at 55.1 per cent of gross electricity consumption.11 Wood rises from 0.2 to 0.7, and district heating gets its own table value for the first time.

District heating is the special case: under § 22 (2) GModG the factor that the supply company has published itself applies, with a lower limit of 0.3 under paragraph 3.2 Two houses with the same final energy can carry very different primary energy values here.

#Which figure determines the efficiency class — and which must go in the property advertisement?

For the class the answer is clear. § 86 (2) GModG provides: the energy efficiency classes under Annex 10 “follow directly from the final energy consumption or final energy demand”.5 The primary energy value changes nothing about the letter, even if it is twice as high. What lies behind the nine levels from A+ to H is explained in energy efficiency class of a house.

For the property advertisement the same applies today — but no longer from 2027. § 87 (1) no. 2 GModG currently requires “the value of the final energy demand or final energy consumption for the building stated in the energy performance certificate”.7 The new version introduced by Article 2 of the amending Act instead requires from 1 January 2027 “the annual primary energy demand stated therein in kilowatt-hours per year and square metre of usable floor area”.8

#Which values are typical, and where does your house stand?

The dena Building Report 2026 provides a point of reference: climate-adjusted heat consumption in 2024 was 149 kilowatt-hours per square metre of living space and year, and 128 without climate adjustment.9 That is final energy, related to living space (Wohnfläche) — the certificate calculates on the larger usable floor area, for a one- or two-family house with a heated basement alternatively 1.35 times the living space. The figure in the certificate therefore turns out lower than a rough estimate based on living space.

#Which measure lowers which figure?

The distinction tells you what a measure can achieve. Everything on the building envelope lowers useful energy and thus final energy; primary energy follows, because the factor stays the same. Switching the energy source works the other way round: it leaves the heat demand as it is and swaps the factor.

The heat pump is the case where both come together. Electricity carries the highest factor, but final energy is smaller by the seasonal performance factor: Fraunhofer ISE measured 77 systems in existing buildings and found an average of 3.4 for air-to-water units and 4.3 for ground-source units.10 The divisor clearly beats the factor.

Whether your building shows the values as calculated demand or as recorded consumption depends on the type of certificate: the demand certificate calculates the building, the consumption certificate evaluates three years of bills. For the question of which figure counts for what, that changes nothing.

#Conclusion: one figure describes the house, the other the energy source

Final energy tells you how much energy your building needs; primary energy additionally tells you what it is heated with. That is why insulation moves both values, while replacing the heating mainly moves the second. For the efficiency class only final energy continues to count — anyone placing an advertisement from 1 January 2027, on the other hand, uses the other figure than today.