Power electronic technology has been widely employed in renewable energy systems, like photovoltaic(PV) generation systems, wind generation systems; in home appliances, like compact fluorescent lamps (CFLs), LED lamps, microwaves. However, power electronic based devices are harmonic polluters, which could inject a relatively large amount of harmonics into the power grid relative to their power demand. This article presents a study of the harmonic current characteristics of two kinds of LED lamps and a photovoltaic panel. Equivalent CFL index is used to compare the harmonic effects of different harmonic sources and to quantify their relative severity.