BB. said:

I think they are saying the average home uses >>300 Watts of energy... Obviously, you would be powering the minimum loads with a 300 Watt inverter (LED lighting/security lighting, USB loads, small radio, etc.).

Not "ground referenced" AC output--Just means you should be able to connect to a (typically) ground bonded AC Neutral main panel (and battery bank negative bus is also tied to the same "AC safety ground") without issue. MSW inverter, generally, will see a ground bonded neutral and dc battery bank as a "short circuit" and trip fuses and/or blow the inverter's switching transistors.

And "prepping" -- You are going to be spending money you don't want too... For decades, had an old genset I inherited. 3,000 Watt B&S--Noisy as heck. Never really needed it except for remote operation when no utility power was available.

Now have 4 gensets. First one now ~50 years old, not sure even will start. Second cheap one got for Y2K--I was not worried, wife was. A 3rd nice Honda eu2000i because don't trust California utility power any more 15 years or so ago. And a new Honda eu genset because of California blackouts last year and this and first times I ever need a genset in 65 years at my home(s) in California. Even turned my 93 year old father-in-law immigrant into a bit of a "prepper" (really my wife did, by talking about what we did with gensets and food storage).

The other old saying... One (operating power source) is 'none'. Two (one spare) is one. Three (one running, two spares) is 'one spare'. Coast guard would install 3 redundant power systems at a lighthouse (in decades past, not sure now). And would "rotate" the operation of 3 engine systems to ensure all where functional.

What ever you chose, "one" backup is not really enough. Choose two different brands/models--Then hopefully a common fault won't take the prime/backup 1/backup 2 all at the same time.

Really depends on what you need the power for... Assuming LED lighting and a portable radio is the "minimum"--Even a 12 volt solar battery system works great--And a couple (3?) USB chargers for cell/USB power packs/etc.

For short term 120 VAC power--A genset or two (with preserved gasoline, or possibly a propane genset) will allow emergency repairs while "other power" (solar, utility, etc.) power is not available.

Obviously fuel (gasoline, diesel) eventually goes bad. And eventually you run out (no further fuel available if SHTF).

Batteries have limited life (especially the small USB/Li Ion packs)... Back to looking for grandfather's (or now great grandfather's) hand cranked drill, hand saw, etc. to do repairs.

The big loads always ended up being the fridge and freezer... Me, I was tending towards dried foods/shelf stable foods for longer term emergency supplies (if the panels/batteries/inverters don't fail, there is always the chance the compressors will).

Now--To play with my wife--Talked about Pemmican as a stored food (nothing hi-tech there):

https://en.wikipedia.org/wiki/Pemmican

I don't see living in a "city/suburban" home for more than a few months (no water, no gas, no power, no sewage) before it become untenable (either my own living conditions, or those around me--Most who probably could not go 2 weeks without help).

COVID has certainly changed much of life--No need for offices(?). Can telecommute for many jobs (certainly not all). Being on properly with well water/septic/etc. makes prepping "easier" and part of the daily lifestyle anyway (further from stores, fewer "utilities").

-Bill