I've been considering a back up generator. Currently I drag a 10 kw "portable" out of the garage to the house and run extension cords through a couple slightly raised windows (then we tape up the gap to keep out most of the cold air.)
Works the refrigerators, freezer, lights, TV, etc. Working on a way to hook up the 240 volt outlet so we can run the well pump, too (next time).
Won't run the heat pumps though (maybe one, but then it won't run the rest of the stuff.) The propane gas fireplace on this side of the house kept this side warm.
My youngest son works on generators for a living. Whole house size to the big ones that run government buildings, schools, server farms, etc. He has his preferences based on how often they have to drive somewhere to work on the generators.
Some of them are easier to work on because they are pretty computerized and he can connect his laptop and "see" trends in the information the computer collects while the generator was running or trying to start. Big heads up on what to start checking. But, the ones he really likes are the old diesels with the John Deere and Perkins engines. Not so fancy, not as electronically enhanced as the new ones, but some of them are 20 to 30 years old and still running. Sure, they need maintenance now and then, but they just keep going.
A frequent issue with the natural gas and propane powered units are the gas pressure regulator valves. In cold weather they'll freeze up, restricting gas flow from the tank to the engine. The generator gets the signal to start (when utility power shuts off/goes down) but it can't fire up and run because the pressure regulator valve won't open up enough to supply the necessary volume of gas to run. Then there's the piping issues. If you've ever messed with water pipes, or pressurized are pipes with the number of joints, elbows, pipe diameters, etc. then understand gas/propane can have the same issue. Gas pressure when the unit isn't running is no guarantee of gas pressure (or supply volume) once the unit tries to start up/run.
The kid likes diesel generators. He's about got me convinced to go diesel.
Look up some info before you decide on power source/fuel. What little bit of looking I've done seems to tell me (right now today):
A diesel back up generator will cost me more than a propane/natural gas generator (buying one).
Same money to install one.
Diesel is cheaper than propane around here, right now. Off road diesel is cheaper than what you buy at the gas station for you truck/car, right now.
The diesel generators seem to use less fuel per hour. Confirm that based on size of the unit you buy.
My first step is go install a solar cell system. Way more expensive than a back up whole house generator, but I can run it pretty much daily. It will make more electricity than we use on the average day (average day of power generator/average day of electricity use). The size/number of battery plates we're having installed will run things all night and more as long as the previous day or two were sunny/bright enough. A solar power system/batteries won't start heat pumps, well pumps, etc. due to the start up amps required, but will run them (as long as it's less than a 30 amp draw) once they start up from the utility power (if you have utility power).
Not going to tell you I understand solar cell power generation. The more I hear, the more questions I have. I will tell you we talked to three companies. I was told contrasting things by different sales/technical reps. As I talked to the next company rep. I had questions based on what I'd previously heard. I didn't get answers from some of them. I got promises to look into it and get back to me with delays of a week or so to no replies at all. The company we went with had a sales/technical guy (the one that visited our house) that would respond to my e-mails within 30 minutes to a couple hours every time I sent him an e-mail with questions. Impressed me greatly and we went with that company.
As I type, more things come back to me. One is a propane/natural gas generator warranty is likely longer than a diesel generator warranty (based on the ones I've looked at.)
One funny thing, one of the companies we looked at for solar was a Generac company (seems all of them we talked to use Generac batteries though) and that company told me they could also install a propane/natural gas back up generator. When I asked about a Generac diesel generator he told me he knew they sold them but his company didn't install them.
Good luck with whichever type of back up power system you go with. When you need it, you need it. Hope is works for you. Me? Dragging that 10 kw "portable" generator out of the garage through the snow/ice/mud last Saturday and hooking it up just about wore me out. Good thing it started on the 2nd pull of the rope (battery died sometime between Saturday and November when I started it up and let it run for about 30 minutes on the concrete in front of the garage) as I wasn't in the mood to pull the rope a bunch of times trying to get it started.