Does solar + battery installation improve sound quality vs "the grid"?

I am not an expert on solar systems, but we did install solar in our SoCal home a few years ago. My knee jerk reaction to your questions is maybe but I wouldn't expect to hear a positive difference, In fact, I would have been happy had the converse been true.

There are a lot of ways to implement solar, and a ton of obscure options. Solar systems contain a lot of parts and there are quality differences between parts that look and are described the same but are NOT the same.

Long story short: most home electrical systems are a mess, designed at the cheapest price point and hacked and modified over the years since installed. Adding solar to your home can potentially add additional problems to your system. If I were doing it all over again I would have completely rewired my home, from service point of entry to every outlet. I probably wouldn't have opted for off-grid (difficult here in SoCal) but I would have insisted on a bypass switch of the very best quality. The problem is that doing solar the right way is unaffordable for most folks, including me. Unless you are willing to pay up-front for a custom-designed solar system you are at the mercy of your installer or state/local regulating body for most subsidised system packages.

OK, having said all that did I notice a large difference in the sound of my audio systems? Yes, until I got the grounding issues resolved. No after that, as far as I can tell.

br3098:
Thanks for your reply. I have a 40 year old house that hasn't had a ton of electrical work done from what I can tell. Not planning to go off-grid, nor even to install batteries right away. But I am interested in doing the solar installation the best way. Can you tell me more about the bypass switch issue? Should I do anything else? 

There's a decent amount of improvement to be had running off batteries. But only if running directly off batteries, and only while the battery system is off-line. Otherwise if any part of the system remains connected to AC, via the charging system or whatever, then all that same noise gets conducted right through the batteries and into your system. You're no better off and indeed may even be worse.

This is not by the way my conjecture, guess, best estimate, or regurgitation of someone else's guesses. Its from actual experience. I ran my turntable motor off a battery and even just this one small part being battery powered was an improvement. But only when disconnected from the charger. The system used had a relay switch that would automatically disconnect the charger whenever the motor was running. 

That's what you need. Even then it might not be such a great idea. A lot will still depend on the quality of your inverter. The inverter converts the battery DC to AC. If this is the least bit noisy it can easily wind up being worse than normal AC.

There's nothing magical by the way about solar. It doesn't matter where the electricity originates. Its all down to the wires and connections. I've got a lot of hands-on experience running power to my system. https://systems.audiogon.com/systems/8367 But I make no bones about caring for sound quality and sound quality alone. Solar tends to have more to do with virtue signaling, a subject others are much, much better at than me.