The Clean Energy Package laid the foundations of a more sophisticated unbundling regime for distribution system operators (DSO’s) for electricity. In this article, I propose a systematic analysis of this new regime. I first distinguish vertical from horizontal unbundling. The latter is then further divided in those activities explicitly governed by EU energy law, and a residual category. This residual category amounts to a core business test on behalf of the DSO. Moreover, I propose to extend the EU unbundling regime for DSO in two ways. First, the scope should also cover entities in the same corporate group. Second, it should apply to specific financial burdens on the grid infrastructure for goals other than distribution activities.