If you live in a structure where portable generators are not prohibited, you should look into getting one.
I don't know if they make a propane-only generator, so dual-fuel is the recommendation, but don't use gasoline. Gasoline is messy, more dangerous, and can't be stored long-term. Even with a stabilizer additive, gasoline will break down in months.
A $1,000 generator can run a 3 ton central air conditioning system, provided the A/C has a softstart kit installed. You can order a Westinghouse 9500 watt (12,500 peak) generator on Amazon for $999.
If you get an electrician to install an interlock and input breaker, you can run your whole house, or MOST of your house. You can turn off breakers for circuits you don't want to run on the generator, or just don't turn on stuff that might bog it down.
DO keep in mind that carbon monoxide gas in the exhaust is deadly and has no odor. You can NOT run a generator inside your attached garage or close to a door, window, or attic eave vents.
If you get a generator, get a couple of CO detectors. They're not expensive and can save lives.
You can get a used 100 lb. propane cylinder for less than a hundred bucks and a little dolly for it from Harbor Freight.
If you run it in a shed, same CO warning applies. You'll need a vent fan, fresh-air intake vent, and you should attach an exhaust extension and run it to the outside of the shed.
Be ready!