The responsibility for voltage maintenance and reactive power management is increasingly shifting from transmission to distribution grids. The system operator’s control levers include transformer tap changer positions and, for renewable energy sources, reactive power setpoints and Q(U) characteristic curves. However, the system operators remain uncertain about the interactions among these reactive power and voltage control quantities. In particular, the interplay between Q(U) characteristic curves and reactive power exchanges with neighbouring network operators is causing concern amongst system operators. This paper addresses this issue and establishes the key performance indicators `reactive‐power provision efficiency' and `voltage sensitivity' to rate the suitability for reactive power control schemes. These key performance indicators are used to evaluate the correlations among different operating modes for specific assets in a small distribution network for several study cases and two topologies. The results are then generalised, and recommendations for system operators are derived.