One of my many income streams is the repair of radio and electronic equipment, and any interferrence from my mains supply would render my workshop useless.. To get an "RF quiet" inverter is difficult, as the EMI filtering is the very first thing left out as a design cost cutting measure. It cannot be added retrospectively.
Most inverters use the "high frequency" approach, where the low voltage DC is chopped at a high frequency to AC, rectified to high voltage DC, then chopped again at 50/60 cycles into some pretence of an AC sine wave.
These are cheaper to manufacture and have a fairly small footprint, the high frequencies mean smaller transformers.
The better type are called "low frequency "inverters, where the initial voltage step up is done at the same frequency as the mains output. These are very much quieter, and use less components as everything is done in one conversion stage, but these require large transformers, lots of copper, lots of iron, therefore more expensive..... but very reliable, the low frequencies minimise commutating losses , less stress in the semiconductors. These are the RFI friendly ones.
Chopping DC using square waves to do a voltage conversion creates harmonics.
50/60 Hz harmonics are unlikely to cause issues above the 4th/5th, or a few hundred Hz at low to medium power levels.
High Frequency chopper harmonics extend well into the HF bands, and the house wiring acts as a very efficient radiator/aerial/antenna, transmitting RFI and hash.for many hundreds of meters.
i have had a good run with the Australian SELECTRONIC brand, my two are low frequency types . are over 20 years old and have never failed despite running 24/7. This company still appears to be in business, but unsure of what design the later offerings use, but there is bound to be other manufacturers using this approach.
To increase reliability with the generic Chinese cheapies, my advice is to divide the building into many self contained circuits, and use a multitude of smaller inverters to run each section independently. Small inverters are cheaper to buy, they tend to die with dignity, generally they just stop working , rather than dramatically catching fire as the bigger ones do, and they will never all fail at once.
But, your gunna be stuck with the RFI problem using these..
Buying expensive inverter equipment is rather like buying expensive power tools, its a great thing at the time, but years down the track, they have become a discontinued model, and either parts are unavailable, Hitachi are very good at this, or the manufacturer has gone out of business.
The smaller Chinese inverters, 300 watts or so will run lights and small appliances well, and will generally last 2/3 years. They hate inductive loads, this is what kills them, voltage spikes caused by poor regulation. The lF types with their big transformers soak up these spikes by virtue of the high inductance between the load and the semiconductors.
Of course, large professional stuff costing megabucks and needing its own building and full time maintenance team is another story entirely.
Im just a little fish.
Our engines may last 100 years, but sadly nothing else we can afford / need will.