Hello Watt's study relies on data from Linky and Gazpar meters (via Enedis and GRDF) in order to compare them with DPE ratings. Then a correlation was made with the database of the DPE Observatory and INSEE. Hello Watt therefore contrasted the actual energy consumption and the labels of the DPEs. However, the uses of each other concerning its consumption vary greatly from one person to another.
A bit like the theoretical consumption of a car displayed by the manufacturer: the motorist knows it, according to his driving, this consumption often remains purely theoretical, but it is no less valuable for buying a vehicle.
For Yannick Ainouche, President of CDI Fnaim: “The timing is right. While it still takes a little more weight with the first bans on the rental of colanders in force since January 1, this study tries to accredit the thesis that the ECD is not reliable in order to allow those who do not want doing renovations to find a loophole; it's just outrageous. »
Technical analysis :
The 3CL 2021 method (method for calculating the conventional consumption of housing for the development of a DPE) incorporates standard use by occupants in order to have uniform labels: standard use on heating, hot water production etc
The 3CL method does not take household equipment into account.
Without this, the ECD would have the following consequences, for example:
- to have well-classified accommodation, because people would only have few equipment, or very efficient equipment
- to have badly classified housing, example: a large family who would live in a dwelling and therefore would use more showers, sinks, equipment such as dishwashers, washing machines, etc.
- to have disparities between the occupants who heat to 21 or 23°C, while others heat to 19°C, or that others only heat part of their homes...
Hello Watt's survey states:
- Page 2: “in section 4 we show that the ECD is a poor predictor of the energy consumption of a dwelling. »
- In addition, it reads: “Most of the analyzes in this study are not directly based on DPE labels but on energy consumption. »
- Page 8: "The 3CL method itself is reliable, but the professionals who apply it take shortcuts to reduce its complexity, or do not implement it reliably for some other reason.
- Page 9 in conclusion “The DPE is a poor predictor of the energy consumption of dwellings, to the point that a purely random estimate would have similar performance. Even if the DPE is not designed to be an accurate estimator of consumption, since it simulates a normalized behavior and only takes into account a part of the energy consumption, the lack of correlation between DPE and consumption is worrying. and could indicate a problem in its methodology, relevance or implementation”
For Yannick Ainouche: “The DPE is in no way a “predictor” of the energy consumption of a home, since energy consumption is inherent to the lifestyles of each user. The DPE is an indicator that gives a consumption trend, and this trend will be more or less accentuated by the use of housing by its inhabitants. Of course, an energy sieve remains an energy sieve when the apartment or house in question is poorly insulated, with single-glazed windows... This study makes no sense. »