It’ll be only as good as the inverters that change the DC to AC. If they aren’t quality inverters, they could introduce troublesome over voltage, under voltage, and/or noise. He may have installed hundreds but were any installed in an audiophiles home that would notice poor power?
I’d look at the specs on the inverter he’s using. Check the voltage regulation and distortion specs.
https://blog.se.com/power-management...power-quality/