I believe folks saying that you need xx tractor hp to run a pto genny are overstating the case. I run a 50kw Winpower with my 35hp tractor. Its doesn't even burp when the house AC units kick on. All you need is enough wattage capacity to run the basics for heat, water, a/c, garage doors, cell chargers, TV, microwave, video games and maybe a blender.
I suggest you get to a farm auction where one is being sold. A dairy farm always has a 50 to 75kw alternator for water, grain drying and milk parlor operation. The Winpowers often have 3phase taps, too. Yeah, they will commit a 100 hp tractor to the job, but you don't really need that much grunt on hand to run that unit. Remember: I have one. I am underpowered (theoretically), I use it for all kinds of jobs (even portable welding and pressure washing). But the tractor has never even dropped 20 rpm momentarily during any usage. I sure have no inclination to buy a 110hp tractor "because its a 50kw genset". (BTW: Its an ALTERNATOR). The surge requirements are well handled by the rather large rotating inertia. The rest is all steady state rpm maintenance.
Think of it as a 1500 AH battery for which you only have 650 AH battery cables for use on an ATV. That pretty much covers it. The auction prices are usually 2/3 of new. Make sure you get a trailer for it. Hauling it over to your relatives in an emergency is worth some points, especially if they already have a tractor. Just tow it over with something having a hitch...
