www.lesswrong.com/posts/LHAJuYy453YwiKFt5/the-salt-in-pasta-water-fallacy

French public guidance in 2022 did use a “1°C less = 7% less consumption” rule of thumb, but the official wording was specifically about heating in a dwelling: ADEME’s advice says “19°C, c’est la température idéale moyenne à l’intérieur d’une habitation” and, in that same heating section, “1°C de chauffage en moins = 7% de consommation en moins.” That is not a claim that lowering thermostats cuts all energy use in France by 7%.

Official French energy statistics also show why the 185 TWh/year figure is not a valid implication. France’s total final energy consumption in 2022 was 1,664 TWh, and only 28% of that was residential consumption and 16% tertiary. Separately, ADEME reports that heating accounts for 66% of residential building energy use. So the 7% rule applies to a heating subset of building energy, not to the country’s total energy use. Multiplying that rule by nationwide energy consumption to get 185 TWh/year is therefore a category error and greatly overstates the savings.

Using the official sector shares for 2022, residential energy use was about 466 TWh (28% of 1,664 TWh), and 66% of that is about 307 TWh for residential heating; 7% of that is roughly 22 TWh, not 185 TWh. Even if one incorrectly applied 7% to all residential + tertiary energy, that would be about 51 TWh, still far below 185 TWh.