12kwh could be a tad small for the battery capacity if you want to minimize or eliminate generator usage (just going on what the typical house would use) We run 20kwh battery. Most nights we are only using around 15 - 30% of that. Though when we have ad bad weather we have seen in hover around 40% SOC for a few days. hasn't got low enough to need a generator yet over several years.
So I feel 20kwh is a good size for the average house.It will still be sufficient capacity as the battery starts to age over time and say 20% of the banks capacity is lost and your living with a 16kwh bank after x amount of years deterioration.
Though some system designers like size there banks to wring every last kwh of capacity out of the lithium battery banks to try and make it the most cost effective (kwh out pr $ spent over it's life ) On paper this sounds good but in practice. I'm still not sold on it and prefer a bit of breathing space.
As mentioned there isn't much you cant run off grid if your inverter is big enough. We run several split system AC units the house has all the mod cons dishwasher, vacuum, coffee machine and so on. I run machine tools in my shed , lathe, 4 ton car hoist, welders, plasma cuter, compressor 15 and 20A units.
Offgrid 2008, Selectronic PS1 6kw/48v inverter, x 2 Midnite solar classic 150 MPPT, 3960w NE PV 24 x 165w BP panels, 4200w NW PV 21 x 200w DAQO PV, 16x400ah lithium.