You read that a flat rated A to C sells for €1,400 per square metre more than a flat rated F or G, and you conclude that the energy class is “worth” that amount. The reasoning is tempting, but it confuses correlation with causation. After looking at the gap between theoretical and actual energy performance, this article explains why the price gaps observed between classes do not measure the effect of the DPE (diagnostic de performance énergétique, the French energy performance certificate) on its own, and how I go about not overstating that effect.
The figures that raise the question
A study published in 2025 by a Luxembourg bank reported the following price gaps between homes rated A to C and homes rated F or G, by region of the Grand Duchy:
- South: +€1,407 per m²;
- Centre: +€1,304 per m²;
- West: +€979 per m²;
- East: +€976 per m²;
- North: +€816 per m².
The implicit conclusion is that buyers value energy performance at these amounts. The figures are accurate as a description of the market. What they do not say is what explains the gap.
Correlation is not causation
Confounding variables
A property rated A to C is, in the great majority of cases, a recent one. A property rated F or G is almost always an older one. Comparing prices by energy class therefore amounts, to a large extent, to comparing new and old buildings. And the age of a building carries many more differences than insulation:
Build quality. Current standards, modern materials, acoustics, accessibility, fire safety, heat-recovery ventilation, home automation. Buyers pay for these regardless of the heating bill.
General condition. A new building has no facade to render, no risers to replace, no roof to redo. The energy class correlates with the absence of forthcoming works, which is a price factor in itself.
Design. Optimised layouts, terraces and balconies, integrated parking, a lift: all features more common in recent construction.
The price gap between classes aggregates all of this. Attributing the whole gap to energy performance alone means counting the same causes several times over.
What the buyer is really buying
For the buyer, the label works as a signal summarising the modernity of the property, its presumed condition, its conformity with current standards and its risk of regulatory obsolescence. The buyer is not paying for a letter on a certificate; they are paying for the whole set of characteristics that the letter suggests.
Isolating the “pure” effect of the DPE
To measure what energy performance alone is worth, one would have to compare two properties identical in every respect (period of construction, condition, location, specification) that differ only in their class. That configuration is rare on a real market. Studies that partly neutralise the other factors through statistical methods (hedonic regressions) find effects markedly smaller than the raw gaps, and highly variable from one segment to another.
A reading by segment
Older residential property. Once condition and location are neutralised, the measured effect of the class generally remains limited. What weighs is regulatory risk: Law no. 2021-1104 of 22 August 2021 has prohibited the letting of G-rated homes since 1 January 2025, and extends the ban to F-rated homes in 2028 and E-rated homes in 2034. A property that is let, or intended for letting, carries that deadline in its price; an owner-occupied property much less so.
New or recent construction. The premium observed is an overall “modernity” premium, of which energy performance is only one component. It is hard to extract, and of little use: these properties are not affected by the renovation deadlines.
Offices and institutional property. The effect is clearer, in the order of 5 % in the available studies, because regulatory constraints (the French décret tertiaire on energy use in commercial buildings), investor criteria and financing conditions are stricter there, and because a non-compliant building becomes obsolete quickly.
The common factor is therefore less energy comfort than regulatory and financial risk: letting deadlines, credit conditions, cost of bringing the property up to standard. The DPE acts as an indicator of future compliance more than as a measure of consumption.
What the standards say
The Charte de l’expertise en évaluation immobilière (the French property valuation charter, 6th edition, November 2025) states in its § 1.17 that “green value” does not exist as such, but that environmental criteria may have a positive or negative effect on value in certain markets. It specifies in Title IV, § 1.6, that the DPE rests on a conventional calculation that does not measure actual consumption.
The European Valuation Standards 2025 published by TEGOVA take the same line. EVS 6 distinguishes the case where no legal deadline weighs on the property, where comparison is enough, from the case where a deadline exists, where the valuer estimates the value of the property as if renovated and deducts the cost of the works. In both cases the approach starts from observed transactions, not from a coefficient applied to a letter.
How I proceed
Distinguish actual energy value from “signal” value. Bills for recent years, where they are provided, tell me about actual consumption. The label tells me about the rights and constraints attached to the property. Both go into the analysis, separately.
Choose comparables of the same generation. For a 1970s flat rated F, the useful references are flats from the 1960s to the 1980s in the same area, whose class and price can be observed. Comparing it with a new development next door says nothing about the effect of the label.
Cost the works case by case. Where the residual method is required, an energy audit or contractor quotes replace generic ratios. Heritage constraints (protected area, listed facade) or co-ownership rules may make some works impossible or more expensive; the report says so.
For buy-to-let, reason in cash flows. The cost of compliance works, their date and any period without letting go into the projected cash flows; yield and internal rate of return are calculated on that basis, not on a gross yield adjusted by a flat-rate discount.
Keep watching the market. Bank lending practices, court decisions on energy-inefficient homes (landlord and tenant disputes, liability of certifiers), changes in selling times by class and by area: these data move, and the valuer must update their reference points.
The essentials
Price gaps between energy classes are real, but they mainly measure the age, condition and design of the properties. The effect of energy performance itself is smaller and depends above all on the regulatory constraints attached to the property. A sound valuation does not convert a letter into a percentage; it observes what the market does with comparable properties and explains why.
Further reading
The Market value page describes the comparison method as I apply it. On the same theme, you can read Energy renovation: why the promised savings do not always materialise and Energy certificate reform 2026: what impact on market value?.
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