Shouldn't it be easy to just figure out how long a battery can keep your house going - essentials vs. entire house - and figure out if it's worth it based on average time without power in your immediate area?

I think if you have a propane tank for the kitchen or water heater it's a no-brainer to get a propane powered generator; you're already paying for its fuel.

If you live in a rural area that routinely loses power for extended periods and have a wood stove for supplimental heating, do you need a small source of energy to run the home water heater and fridge for a while?

There's tons of variables, and you can keep going with a long list of what-ifs.

It'd be smart to talk to people that live off the grid full-time. I know of one family that did it for decades with lots of solar panels, huge battery banks of old-school batteries, propane powered appliances, incinerator toilets, a wood stove, lots of insulation, and a big backup gasoline generator for when the sunlight in the winter wasn't enough to sufficiently charge the battery banks.

In the end, as they got older, it became less fun to maintain their energy needs, so they paid to have the utility company run power to the house.