The waveform of the power output of a solar panel inverter could hardly be any more noisy.
Some are just 60hz square waves, some are "three step" and even the best have major power output at multiples of 60hz, up to and beyond 2,000hz. Waveform quality is just not a priority.
If your equipment is sensitive at all to noise in the power mains, a regenerating power conditioner could be required.
At the same time, the inverters broadcast all sorts of RFI.
This guy wrote it up pretty well :
http://www.rocketroberts.com/techart/inverter.htm