This paper analyses patterns of differentiated implementation in four member states (Czechia, Germany, Ireland and the Netherlands) under the 2012 Energy Efficiency Directive (EED). The EED is a directive that potentially offers considerable room for differentiated implementation. It offers broad discretion to member states in choosing and specifying targets and measures related to energy efficiency. The paper seeks to analyse what use member states made of the room offered to them, what explains these choices, and what effects the resulting implementation pattern has on the effectiveness of the EED. The analysis shows that the four member states have made extensive use of the discretion in the EED. They have predominantly done so in order to retain domestic measures that were already in place prior to the EED. This pattern is driven by a combination of inertia and the wish not to disrupt well-working policy approaches. Overall, the pattern of differentiated implementation that resulted has arguably had a positive effect on goal-achievement under as well as domestic acceptance of the EED. At the same time, the Directive’s impact on domestic policies and approaches has been limited and the potential that differentiated implementation offers for cross-border learning has not been realized.