Distributed renewable energy sources (RES), such as photovoltaic systems (PV), can contribute to a reduction in the power quality in distribution grids due to higher power oscillations both in absorption and generation. In this work, by means of a statistical approach, the quality of supply at the point of common connection is evaluated for different PV sizes and also for different levels of aggregated loads sharing a single PV installation as can happen in multi-occupancy building. The role of incentive schemes in Switzerland and UK in driving the choice for the installation of a specific PV size is evaluated.