How about a battery without solar as a power backup? And  can you keep everything on existing circuits and just reduce load? Or do you need to hook up batteries to only the essential parts of the system? My essentials would a water system (well pump and house pump) two refrigerators and a couple of floor fans.

Unless you have a very large inverter / UPS you will need to split off your essential load.

 

Dependant upon the inverter / charger you pick you may or may not need some form of transfer switch.

 

You absolutely must not allow your inverter and the grid to be connected together, ever!

On 9/1/2022 at 5:35 PM, islandguy said:

My essentials would a water system (well pump and house pump) two refrigerators and a couple of floor fans.

Batteries would be on the "rather large" end also.

Without any kind of off grid recharging, run time would be limited and dependant on bank capacity.

Motors of most types are reliant on larger than normal capacity to allow for starting.

On 9/1/2022 at 2:35 PM, islandguy said:

My essentials would a water system (well pump and house pump)

Would suggest a water storage tower would be a more effective use of your money.