Is the energy performance diagnosis (DPE) really reliable?

Over the years, it has become one of the elements most scrutinized by buyers during a real estate sale. Established in 2006, the energy performance diagnosis (DPE), a tool which estimates the theoretical energy consumption of a home, is nevertheless regularly criticized by real estate players. In question : its supposed unreliability. If it attracts so much criticism, it is because the owners are in the obligation to carry out a DPE to have the possibility of putting their property up for sale or rental since 2021.

Concretely, diagnosticians certified by the State have the mission of assigning a label, which varies from A for the most efficient housing to G for the thermal strainers. However, an erroneous or poorly carried out DPE can cause the price of a property to drop by several thousand euros. Therefore the Is DPE a truly reliable tool?, or are the criticisms on the contrary justified? A study carried out by the Economic Analysis Council (CAE), an independent organization attached to Matignon, provides some answers to this question.

To estimate the reliability of the DPE, the Economic Analysis Council measured the gap between the theoretical energy consumption of a property according to its DPE, and its actual consumption. To achieve this, the CAE relied on the anonymous banking data of more than 150,000 Crédit Mutuel customers. These data make it possible to precisely estimate the energy consumption of these households, and to compare it to the predictions of energy consumption indicated by the DPE. “Theoretical consumption predicted by the DPE is a central measure for modeling energy savings and therefore the decarbonization expected from a renovation», Specifies the CAE.

Now that the stage is set, it is time to look into the question of the reliability of the famous DPE. And according to the study, the recurring criticisms are justified. “If we observe a progression of real consumption depending on the energy performance of housing, however, it is much lower than the theoretical consumption of DPE, alert the CAE. The increase in energy consumption per square meter between housing classified A/B and housing classified G is six times lower than that predicted by the DPE.» In other words, the DPE largely underestimates the energy consumption of housing supposed to be the most energy efficient, namely properties rated A and B.

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Household behavior is not taken into account by the DPE

In detail, low consumption housing (rated A or B) is supposed to consume 83 kilowatt hours (kWh) per square meter each year according to DPE estimates, compared to 548 Kwh for a thermal sieve. But in reality, the gap is much smaller since the energy bills of households housed in an efficient property are “only » 85% lower than those of families living in thermal colanders. Note that this gap is even less pronounced for housing of more than 100 square meters (55% difference between the amount of an energy bill for a housing classified A and that of a property classified G).

So how can we explain these differences between theoretical energy consumption and reality? “Theoretical consumption, calculated by the DPE, and actual consumption may differ because the first does not incorporate household behavior», affirms the CAE. We are talking here about the famous “rebound effect”, which is explained as follows: a household which has renovated its property tends to increase the heating for comfort, ensured by the fact that energy losses are lower in a efficient housing. Furthermore, the model underlying the DPE may be an imperfect predictor of energy efficiency, which may lead to overestimating theoretical consumption gains. The DPE estimates can in fact vary significantly depending on the quality of the diagnosis carried out by the professional.