Go for copper windings. You didn't say if you wanted an inverter model or not, nor what voltage you wanted. I would keep in mind that the inverter models while quite and more fuel efficient have more to go wrong, and less of a chance that they will be repairable in the moment.
Is it mission critical? Does your son/daughter in law have issues that absolutely require it to work? If so, buy a Honda, a bigger Generac, or a Northern Tool. If not, and they don't plan on using it frequently, and their neighbors will tolerate the noise, buy a cheap one, or two, but I wouldn't cheap out to the point of aluminum wiring. Is there a local service center for a brand that you like?
Unless they can keep gasoline fresh, someone is going to need to think about getting sealed cans of fuel for it, or at least consider getting a propane unit.
I have three;
- One Onan 5kw (5000+ hours). Routine maintenance only. 120V only. Happiest when it has 2.5-5kw of load. That makes it a bit of diva, but it always starts and runs, and then leans into the load when it gets dumped on.
- One ancient Coleman 4kw gasoline generator that came with house and looks to be fifty years old. No idea on the hours. Replaced the fuel hose, and the spark plug short to stop it. The crankcase vent mists a little oil, so you don't want it some place that you care about when you are running it. I think that these sell for more now than they did when they were new. (120/240)
- One no-name china diesel 6.5kw. (33hrs) (120/240) Threw a push rod once, (probably my bad for not adjusting the valves at ten hours), had the float of the fuel gauge leak, needed a new fuel solenoid (the old one weeped fuel) and vibrated a few screws loose from the Yanmar clone engine early in its life. I bought this for not much from someone who was moving and no longer needed it, with 8 hours on hour meter. I have now gone over it enough times that I think that I understand it and have it in trustworthy shape, but whether it will be a 5000 hour generator is in the castings, and I have no idea. I will never put that many hours on it.
They all produce relatively clean 60Hz power. (120V +/-) The 6.5kw diesel handles the furnace and booster pump, coming on, with the fridge and freezer running. I prefer the diesel because it is easier for me to keep the fuel around, but YMMV. Has it let me down? Yes, but only once was it not repairable (I didn't have a spare push rod).
My observation is that people tend to buy generators, leave them in the back of the garage, and then pull them out for emergencies and expect them to run flat out for a couple of days. That is asking a lot. Regular use and maintenance goes a long way toward making a generator reliable in my opinion.
Just my $0.02 YMMV, of course. For the record, all of these will become standby standby generators next winter, when we install Tesla Powerwall batteries which charge from the solar on the roof.
All the best,
Peter
