Like all the other guys from Florida, my wife and I have had this discussion in the last 10 days without power (we got it back at 5 PM today - Monday). What I did for this storm was to bring the motor home over from the commercial property where I normally park it and put it across the top of the driveway, partly to block the storm, but primarily because I knew we'd need the power.
It has an Onan 4K watt generator that produces 110V power (only) @ 1800 RPM. With it, I powered the motor home itself (TV, a couple of lights, 12V appliances, a fan, etc), two full size refrigerators, numerous chargers (laptop computers, cell phones, lanterns, etc), an entertainment complex (large TV, VCR, DVD player), a couple of interior lamps and another fan, and a desktop computer. I could also run a powerful microwave or my toaster if I unplugged one of the refrigerators. I used 10 guage extension cords to get into the house from the coach, then 12 or 14 guage cords from there to various power strips. I didn't try to run through the panel; I just unplugged the appliances and lamps I wanted and plugged them into the extensions. We shut it down at bedtime and used flashlights and rechargeable lanterns, so it ran about 16 to 18 hours per day for 10 days with no problems.
I've lived in Florida for 32 years, and the longest we were without power previously was for about 1-1/2 days during Hurricane David in 1979. Our only other power outages were due to minor storms or car accidents knocking over a pole, and the longest was maybe 4 to 6 hours. Even those happened infrequently, maybe once every 2 or 3 years.
I guess the point I'm trying to make is that up until now, we've never felt it was worth it to even have a portable standby generator, let alone a serious whole-house system. But, our thinking is changing a bit after this storm.
Not that we expect it to happen again anytime in the next 32 years, but a couple of factors enter in. First of all, what Jared said about running the AC to keep the house dry is absolutely true. After 10 days without power, our house frankly stunk, mostly from the damp, musty conditions. And, although it might be more information than anyone cares to know, when you sleep during very hot nights with no moving air and no AC, you sweat, the bed gets damp, and it doesn't dry out the next day -- and it's tough to do a laundry without power if you aren't set up for it. We toughed it out for 10 days and then I told my wife to just throw the danged sheets away.
Next, we're not getting any younger, it's harder to face the discomfort, and we're moving to a more rural area where the outages are more frequent and last longer, and we're going to have to run a pump instead of the city water system we have now. So, we're thinking seriously about a whole house system for our new house. Our decision may have been influenced by our back yard neighbor, the owner of an electrical contracting business, who ran his whole house system the entire 10 days, powering even his yard lights, pool circulating pump, pool light, air conditioning, water heater and the whole shebang. He also had full TV and internet the whole time because he has a satellite system. It was hard to lay in bed at night and see his whole house ablaze with lights...I don't know how big his unit is, but I'm thinking the easiest way to make the decision on size is just to make it big enough to run everything.
My wife asked what it might cost, and I said I didn't have a clue. Just to throw out a number, I said, "$20,000." She didn't blink an eye; she just said, "Well, it's all about priorities, right? That's about the cost of a new car. If we put off buying a car for a few years, we could have the whole house system."
So, what I want is a system big enough that I don't have to manage it. I'll do a search on the TBN archives and also Google; this subject has been discussed a lot. I'll likely want an automatic switch so it will come on even when we're not home; maybe with a 5 minute time delay so it won't come on with every brown-out.
I suspect it will be propane for the reasons already stated; the fuel lasts the longest and we'll have plenty of it around, anyway. My second choice would be diesel because it holds up better than gasoline, I can use the fuel for the tractor, and I surely don't want to have a large gasoline tank on the property -- LP Gas doesn't scare me 1/10th as much as gasoline.
On the subject of LP gas efficiency, it's about 10% less efficient than gasoline when used to fuel an engine. JoeR's Dad mentioned that he had a 500 lb. propane tank. JoeR translated that to a price per gallon, not per pound. Propane weighs 4.2 pounds per gallon, so that 500 lb. tank holds about 119 gallons when it is completely full. To use it all in 3 days would be about 40 gallons per day, and converting it to gasoline efficiency, that would be the equivalent of about 35 gallons of gasoline per day, or about 1-1/2 gallon per hour. I think that's a lot, even for a 15 KW generator. I suspect that the tank was not quite full or the 3 days might have been 3-1/2 days or some other combination that would bring it down into the realm of 1 gallon per hour or less, which is what I would expect. At that point, it would be less expensive than gasoline because propane is much lower cost per gallon, and comparable to the cost of off-road diesel delivered in bulk.
The other advantages of a propane system are longer engine life, less carbon and sludge build-up in the engine, less polution and much less chance of problems due to moisture in the fuel, etc. There is also less chance of damage to a fuel spill, but a slight more risk with a leak, although completely manageable, especially if the local State LP Gas Bureau Disaster Inspector lives in the same town and is a friend /forums/images/graemlins/cool.gif.
So, it looks like a whole-house system for us. All I have to do is determine the proper size, plumb it and have it wired properly, and I can cross that particular worry off my list for the future.
