I listened to an amazingly well tuned wilson/D'agostino/DCS/Shunyata Everest system recently. The owner has 4 Tesla Powerwall in the garage. I asked if he could disconnect from the utility and play on just battery. Not a problem he said. With about 30 seconds of fiddling on his phone, he was able to activate the transfer switch, disconnect the utility and run the house on battery power only. I thought I heard a slight difference. My friend Bob said he could not. Another friend though he heard something too.
At a minimum, a system run off a battery was almost indistinguishable from the street. This system from what I understand only has 1 circuit to the rack. I don't know if its a 12 or a 10. For a single circuit feeding a Shunyate Everest feeding an entire system with a D'Agostino stereo amp, it was pretty darn effortless. I was not hearing a lack of power. The subs in the room were on a standard wall outlet that is most definitely #14 shared across the wall. 2 subs and a TV on the circuit.
I am not sure how all this impact the battery vs utility equation. I don't know if a system feed with multiple large gauge wire circuits would reveal more of the difference between battery and utility. A powerwall has an output of around 40 to 100 Amps depending on the model. With a 200A service and 4 on the wall, I assume these are powerwall 1 and all 4 are providing around 160 amps of power to the service. The branch wire and 20A CB are the limitation to power.
This makes me more interested in putting together a 3000W inverter. The batteries I am looking at have about a peak output of 40A. I would still go for power from the road before a battery. But if you were in a situation where the power to a rack was insufficient and you were in a building that could not be updated with new wiring, a Battery seems to be an option that may have very little limitations compared to the wall. Provided the right batteries and inverter is used.
It also says, if you are on utility power and want to get off the grid thinking its cleaner to not be on it. I don't see adding powerwall as a solution. If I can't really tell a difference and one friend who I trust hears no difference, then the gain of adding $60K in electrical energy storage is not the answer for audio. It is the answer to poor utility power and backup power in blackouts.