The build

I assume your fridge/freezer will be on the same ring mains as your battery, if full, should be able to keep modern fridge going for at least a week probably 2. We have a 1 kilowatt caravan kettle we can use to draw less power from a battery.

They won't be on that circuit, we had to compromise somewhere and decided with the electrician that we can always run an extension lead to the fridge or freezer if required