Generally batteries are used to power gizmos for a short time period, then a generator is used for longer periods.
I imagine you have refrigerators with food and heating which needs power to operate - perhaps a security system, night security lighting, along with the fire system?
Might be best to install an "electronics friendly" generator to come on automatically in the event of a power failure. Or purchase a manually operated generator and set your security system to notify someone if power goes out. Then they can connect it.
Also some generators will run on natural gas. Then it will run forever without needing to go get gasoline.
Note that regular construction generators put out "dirty" "noisy" electricity and electronic control boards like in a heating system, new refrigerators, and other electronics might not even run on it or could be damaged. So best to get an "electronics friendly" generator which produces "clean" electricity.