Looking at the options you list the time they give you will be hugely increased if when there is a power cut you turn off the aircon and use fan or fans. Your power hungry aircon is the problem...can you do without and manage with fan/s? That will reduce the cost hugely and the 1.5 kw inverter battery setup could suffice for at least 12 hours. Using just the basic needs excluding aircon you should be able to manage on an average consumption of ~100 watts or less for fridge, lights and fan.
Looking at the options you list the time they give you will be hugely increased if when there is a power cut you turn off the aircon and use fan or fans.
Your power hungry aircon is the problem...can you do without and manage with fan/s?
That will reduce the cost hugely and the 1.5 kw inverter battery setup could suffice for at least 12 hours.
Using just the basic needs excluding aircon you should be able to manage on an average consumption of ~100 watts or less for fridge, lights and fan.