Aides publiques à l’efficacité énergétique. Mérites respectifs des subventions ad valorem et spécifiques

In France, subsidies in favour of energy efficiency are numerous and diverse. Most of them are ad valorem ? proportional to the price of the targeted good or service ? as the income credit for energy transition, the reduced rate VAT for building thermal retrofitting, the zero-rate loan or the ANAH subsidies. Others are specific i.e. independent from the price: automobile bonus and energy efficiency certificates. We review the arguments for each subsidy type. Compared to specific subsidies, ad valorem ones suffer from four drawbacks: they cause more public spending for a given impact, they distort goods? quality, they benefit more to wealthier households and they encourage more fraud. However, specific subsidy are not without drawbacks either: the fiscal basis must be defined for every type of good and in case of an unexpected drop in the production cost of the subsidised good, the price of the latter risks becoming virtually zero.