Great topic.
Sorry this is long winded, but my research and gained advice has changed my outlook on emergency preparedness. I always wanted a larger 5000-7000w generator, 240v, run everything, no hassles, etc. Maybe Natural Gas Unit, etc. thought this was the right way... After last winters storm and many people were without emergency power after 1-2 days having burned up all their stock pile of 5 gallon cans of gas... Others generators wouldn't run due to lack of maintenance, forgot to refill that 5 gallon can after cutting lawn all summer, etc. I began to reconsider... We only have a small McCulloch 1800watt inverter generator from our camper. in our old house it would only power the sump pump or the furnace, or the fridge at a time. I would constantly run between each, switching every half hour, getting no rest or sleep at night constantly switching off extension cords.
We recently moved and renovated our new place. After much research on the internet and talking with a few electricians and generator sales guys, we wired the house specifically with dedicated "emergency" circuits through a 60A generator sub-panel (uses a double pole breaker to switch between gen & utility feeds). This panel is fed off the main house panel (200A) via a 30A breaker (up to 60A) and 8g wire for all we needed. This is the proper and safest way to power your house in an emergency, when on generator power, there is absolutely no risk of back feeding the grid. No utility disconnects were necessary to install the panel and it runs all my emergency circuits via extension cord to generator. Easy for my wife to figure out if I'm away, and the additional wire was minimal cost (maybe $60) and the panel was around $300 including breakers. Our biggest improvement was the newer more efficient appliances and addition of all Natural Gas appliances.
With the house being wired following a plan for which circuits would be necessary for emergency situations, we were able to run sufficient lighting throughout the entire house, Heat via the furnace (gas), the deep freezer, the fridge to keep food from spoiling, cook on the stove (gas), and TV/entertainment circuit to keep informed and kids entertained. This past Saturday evening I tested the new set up using our old 1800 watt (peak) 1600w nom portable inverter gen ($350 at flea market). Much to my surprise, it powered EVERYTHING
but the old sears deep freezer at the same time with
no troubles at all. Ran for about 4hrs on half tank of gas (maybe 1-2L of fuel??). We couldnt' believe the difference with modern efficient appliances and the fuel savings with the smaller inverter style generators. Outdoor temps were around 0*C, our kids watched TV, surfed internet on the Ipad, wife fired up stove and baked a casserole, fridge was cold and the house was lit up and warm. Unfortunately the ice cream started to melt in the deep freezer after the 4+hr test
I had actually turned off the main panel powering the rest of the house, just to see if our plan was sufficient. My family didn't even realize until it was time to run the dishwasher
Pleasantly surprised with energy efficiency, simplicity, and more importantly, fuel efficiency, I determined a 3000 watt Honda inverter would be just perfect to power "everything" we need, including the deep freezer, with no switching between appliances (fridge or furnace to freezer, etc.). My 1800W will do for now while we save up.
I strongly suggest taking some time to consider your needs in an emergency vs what you think you need. We live in town so don't need a well pump which helps... Deciding/wiring necessary circuits is easier than you think, by simply moving the wire from main panel, over to the new panel... With some planning, you can have all the necessities and fuel efficiency too. A 2000-3000w inverter generator will burn 1/2 the fuel a 5000w coleman/briggs will use, way less noise, and will get you by for days or weeks. This means half the gas to keep on hand/cycle through.
We considered natural gas generac also, but like the portability and reliability of a portable unit.
Future plans also include a wood stove for enjoyment, and emergencies.
Hope this helps.