Natural gas
or
Diesel
Add an automatic transfer switch.
For my home, I used a 2800 watt Kipor inverter generator that I had for my class C diesel. It would keep the fridge, freezer, sump pump and furnace (natural gas) going. I had a manual transfer switch (six breakers). I chose the circuits I powered carefully to provide light in most of the rooms. My stove was natural gas by choice. Water heating was natural gas and required no power. I did keep ten gallons of gas available, which I rotated into vehicles. My office computer and the TV had power too.
Ten gallons was enough to power the necessary items in the house for a few days. I never had to use the system for an extended time frame--but I would have probably done "one hour on, two hours off" to extend the limited fuel supply. There was a natural gas fireplace with a millivolt thermostat. With doors open that would keep the house from freezing up.
The transfer switch was about $100. The installation by a licensed electrician was $350.
I was pleasantly surprized how many items I could power up with a mere 2800 watts.
Solar if you wish to be grid independent with a LARGE battery bank, minimum 72 hours reserve capacity.
I'd have loved to have solar--but I have a beer budget.