Okay, here's the plan. A generator with an electric start option will be connected to the supply of natural gas.
Whenever your power goes off for several seconds, (you select the timing), the generator will automatically start up, and provide power to the circuits you have designated as emergency.
I would advise not using air-conditioning in this manner, but it's a matter of taste, (and cost).
It's also wise to have a few circuits not connected to the generator, so that you know when the power comes back on.
Privately, if you can, try to acquire a generator that is water-cooled, (this would allow you to use that heated water as an emergency source of domestic heat and hot water).
As a cost-saving measure, occasionally one can become the proud owner of a welding rig m=eant for service trucks. They often have everything you would need.
Just for comparison purposes, here is the kind of system that I am talking about.
Wow! That's some system! Do you often have need for a back up system (I'm assuming that you'd use a generator for a back up system) where you live? This is the first time that our power has been out for more than an hour.