The growth of renewable energy generators in public energy networks demands suitable approaches to simulate future power grids, e.g. low voltage networks. One main distributed energy generator are small power photovoltaic systems interconnected by single-phase inverters. The increasing penetration of such inverters requires models that are suitable for large-scale studies. This study analyses the aggregation characteristics based on time domain simulations. The results suggest that under specific circumstances the aggregation of multiple inverters connected at the same point having similar output power can be approximated by multiplying the individual inverter characteristics. In case the inverters have different output powers a simple aggregation is not possible.