For those with interest in current tech, here are a few energy storage / backup systems we've installed locally with a range of hybrid inverters or inverter-chargers, all using li-ion battery systems in the range of 5 to 20 kWh of capacity. Larger ones can run a whole house including pool pump and AC, more typical is auto backup for the essential loads such as fridge, lighting, communications, water pump, .....and whatever else one deems "essential". 😉