A few deep cycle batteries hooked in series/parallel as needed to deliver your voltage/ampere needs would go a long way to meet your preparedness for loss of light and cooking. A 12 volt charger and solar cell might be all you need to keep the batteries charged. Further details could be had from a local electrician, which I am not.
Knowing how batteries connected in series/parallel work is very important as incorrect selection and or wiring can causes catastrophic damage to both batteries and whatever equipment you connect to them.
2 - 12 volt batteries connected in
series will give you 24 volts which will not work with any 12 volt equipment. Yes there are 24 to 12 volt reducers but decent one's are not cheap and really defeats the intended purpose for household backup battery preparedness.
2 - 6 volt batteries connected in
series will give you 12 volts but the amp hour stays the same.
2 - 12 volt batteries connected in
parallel will give you 12 volts but doubles the amp hour capacity. This is the best solution for most household battery backup preparedness.
2 - 6 volt batteries connected in
parallel still only gives you 6 volts but doubles the amp hour capacity.
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Yes there are ways to connect batteries in both parallel and series but is probably beyond the scope of this thread's intended focus.