Without sapping the life out of a Naim system with a power conditioner a balanced power transformer fitted on the circuit (not in the same room - they large, heavy, and if there is DC offset to clear up from the mains, they hum) may decouple you nicely from the grid.
Equitech are probably the gold standard but there are a few out there. But honestly, unless you are regenerating your own mains and can do it better than a power station just put up with it.
Batteries. Whilst potentially this could be applied to virtually all electronics, it is likely to impractical at least for most items, and against forum rules to discuss for Naim gear. However as an example anything with an external single DC power supply (with non-burndy connectors) at a voltage easily obtainable from batteries, it might be a realistic consideration. In particular, for example, by using batteries a source store and renderer could be completely separated from a other than the data connection to the DAC, preventing any possibility of ground plane modulation. If the daytime mains supply hash is primarily affecting those same components then this approach would also help with that, but not if the problem is more to do with, say, amps (at least in practical and forum discussion acceptability terms).
Solar inverters are generally quite noisy by design, an inverter, panels and battery would cost a fair amount too. If you have a freezer sometimes the inverter types can interfere with the mains - Just remember to switch it back on if you do any trials!
I’m considering the Isotek or Isol-8 range to determine if one of their power blocks or other products will achieve this. Theres a fair few who use them on this forum and results seem positive.
Motor generator sets, nice clean dedicated HiFi supply, can’t understand why no one makes them for HiFi buffs. Park it in your garden or garage and direct connect through the wall to your listening room.
Oh, hang on they are big, heavy, bit noisy (mechanically) and very expensive. but that doesn’t put some HiFi people off.
A chap who I shared a lab with back in the 80’s was working on a new design for one, incorporating UPS functionality, for the UK military. The prototype was encased in a safety cage made of railway sleepers and 1" thick threaded steel bars. I did wonder where it would end up if it had escaped!
And you forgot to add a PITA with respect to being a maintenance burden. Brushgear and commutator maintenance heavy!
But, a greatish way if turning DC to AC. And then back again to DC in your PSU!
Or perhaps just use batteries in your garden.
But yes, the days of 660Mw Parsons or GE rotating plant are almost behind us. Wind and PV chopped to ( sort of ) AC.
Quite right @Thegreatroberto, there is a fair bit of maintenance, although the MOD one went AC to AC and I don’t recall seeing (like I was supposed to be looking in the first place) any slip rings, but I suspect there were!
Another good point why not go AC to LV DC, Direct to the kit!
I also had this ‘great idea’ in the late 70’s to modify an old and obsolete main frame multi-platter hard disk unit into a multi track analogue recorder, imagine that with the digital world hot on my heels, LOL!! Anyway it would have sounded terrible even if you could get it to reliably track a concentric line on the disk.