This paper presents power quality analysis and impact of power solar rooftop on distribution system of the Provincial Electricity Authority (PEA) in Thailand. The case study used in this paper is a 996 kWpeak solar photovoltaic (PV) distribution generator (DG) system which connected to 22 kV at Pluak Daeng 3 substation in Pluak Daeng, Rayong, Thailand. Experiment and simulation are used in power quality analysis. The simulation is conducted through the DIgSILENT PowerFactory program to analyze the behavior of the DG system on the PEA power distribution. Experimental results show that all qualities of power from solar rooftop meet the PEA’s standard criteria while the simulation results show that over 4 MW of solar rooftop generation, the voltage of utility grid system would be affected during cloudy periods. However, if the PV system produces 2-3 MW of power, the distribution system would be benefit.