Another year has passed in which the European Commission announced that an integrated energy market for all European Union (EU) Member States is closer than ever before.1 And yet, in 2015, a functioning single European energy market has not been fully accomplished.2 Further regulatory measures have been considered necessary and have been promoted by the Commission and national regulators, now under the banner of the ‘Energy Union’ of the Juncker Commission. This ‘Energy Union’ marks another milestone in the development of the regulatory framework of energy markets in the EU. It has become one of the top three political priorities of the Commission and is prominently represented by the Commission's Vice-President Maroš Šefčovič and Commissioner for Climate Action and Energy, Miguel Arias Cañete. In 2015, a key focus of the Commission's activities was the enforcement of EU State aid rules, most importantly with regard to national subsidy measures for energy generated from renewable resources (renewable energies) and so-called capacity mechanisms, which several Member States implemented to close perceived gaps in their electricity supply. National regulators remained the main drivers of the enforcement of competition law in terms of prohibition of cartels and abusive behaviour.