Adaptation, Experimentation or Conservation? The Use of Differentiated Implementation Under the Energy Efficiency Directive

In this article, we introduce an innovative theoretical framework to analyse the use of differentiated implementation in the implementation process of European Union (EU) Directives. We identify rationales for offering flexibility in EU Directives as well as motives for policy‐makers to make use of the discretion. We analyse patterns and drivers of differentiated implementation under the Energy Efficiency Directive (EED) in four member states in order to assess whether practices of differentiated implementation conform to the rationales for offering flexibility. We show that member states mainly use the flexibility offered to retain existing policies. In addition, the EED led to some mutual learning based on experimentation, although this effect is limited. Whilst the EED offered a high potential for mutual learning, the member states did not use this opportunity. Overall, the implementation of the EED offers mixed evidence for the use of differentiated implementation to support differentiation.