The number of the domestic power plants is increasing rapidly. Most of these are photovoltaic (PV) systems. It is worth examining the effects of the PV units on the network, because the spreading of these units is expected. This paper presents a solution how the effect of numerous photovoltaic inverters on the power quality can be simulated and examined if these are connected to the same low voltage (LV) network. The harmonic effect of domestic PV systems is discussed with the application of the so called Double Domain Simulation method. However the distribution network is modelled in the frequency domain, the PV systems are simulated in the time domain. The calculations are performed by different polluted upstream network configuration. Our goal was to build an adequate simulation environment and to examine the effect of numerous PV systems on the power quality of the LV network.