17.5KW is way too much for any type of home emergency preparedness (if you can get unlimited fuel, it's not an emergency). Don't plan on running a whole-house AC system in a long-term power outage. If you absolutely must have AC, put a high efficiency window unit in one room and have everyone stay in that room during the hot parts of the day (it's not so bad). 1KW is enough for that. 17.5KW is for running a hospital or something like that.

I like the idea of propane because of storage stability and because gasoline may be very scarce and hard to hold onto. A 400lb propane cylinder is less likely to walk away.