The widespread use of power electronics in various domains has raised concerns about power quality, particularly the issue of harmonics caused by nonlinear loads. The progressive integration of solar photovoltaic (PV) generation and electric vehicles (EVs) has further emphasized the need to address harmonics to maintain network stability and optimize efficiency. This study examines the propagation of higher harmonics within medium- and low-voltage distribution networks, including nonlinear residential loads, PV inverters, and EV chargers. The harmonic distortions have been evaluated across different penetration scenarios of PV generation and EVs, ranging from 25% to 100%. Results demonstrate that at high penetration levels of PV inverters and EV chargers, the power quality can be severely compromised, prompting the exploration of mitigation strategies for harmonic distortions.