here's my .02 for your solid insider info,
going to "go to the bathroom" on the northstar recommendations
we bought a northstar 8k watt generator from northern tool for work. i think i posted here about it within the last year. has a gcv-whatever honda engine. we unboxed it, started it and it ran for about 5 minutes before we shipped it to another location to be used. when it got there, it never restarted. bad cdi ignition coil. one of the guys managed to buy thru napa a replacement and that was bad out of the box. said f it and bought a troy-built from home depot as a replacement. i got the northstar back and tried to get warranty work on it... there are no northstar dealers and northerntool said any honda small engine dealer will warranty it based on serial number. well that is true, however real world the shop i took it to first said you didn't buy from us so i had to explain everything. they agreed on warranty work but it sat for a month next to string trimmers and lawn mowers in their shop. i took it back before it disappeared or got lost, and rewired the thing with a $10 mail order traditional coil vs the $70 oem replacement. that northstar just got used recently for 2 weeks straight at 8 hrs a day and had no problems. so maybe my ordeal was a fluke, take it for what it's worth regarding northstar/honda quality, point is make sure you have some reliable method of service and obtaining parts because everything breaks.
other things i can tell you from first hand knowledge is that northstar along with the home depot troy-built and an old 5kw dayton genhead turned by a tecumseh engine all ran computer equipment and monitors along with refrigerators and water pumps in a trailer.
THD is a selling point nothing more, it means nothing when you are running things like refrigerators, well pumps, and lights... only when you want to run high end audio equipment or something like hospital equipment that then requires "clean power".
not saying you shouldn't check what equipment you plan to run but nearly everything will run fine as long as voltage and frequency are maintained which really has nothing to do with THD. Most devices labelled for power will say 50-62 hz.
on cheap portable generators it is directly related to engine rpm. so like was said having a generator that is easily serviceable and adjustable is a plus. I would take the old tecumseh generator over the northstar and troy-built because i can adjust the governor screw on it while having a multimeter measure AC frequency and adjust engine rpm till i see 60.0 hz. i can't easily do that on the others because they're newer and you have to disassemble half the thing to access that linkage.
and that old dayton/tecumseh 5k my sister used for over a week at her house running well pump and oil fired furnace during a snow storm power outage couple years back (don't even ask how it was wired) so you don't need much in terms of generator power rating. your heavy hitters are electric motors starting up like old refrigerators, big well pumps, and igniters on oil fired furnaces. i remember telling them make sure not to run the water and have the heat kick on while well pump was running to be safe, whether that happened i don't know knowing them it probably did. so biggest thing is to a survey and plan on what you want to run, when and how.
other thing i can tell you is about inverter boards.
had the pleasure of getting around $10k approved to have capacitors replaced in a 80kva UPS. those capacitors and inverter boards have a life span at least when it's in a UPS. so i would read the fine print on warranty for them on generators. MGE tech told me a common failure for them is to blow up, that's in a large ups system. whether that can happen in a 5kw genset i don't know but it's just one more thing to break down and be an expense that you don't need.
in your case, i would strongly look at serviceability of a unit as a whole, and for the engine and generator head separately.
can the generator be easily separated from the engine?
and what fuel best serves you- gas, diesel, natural gas or propane. be aware most gas is 10% ethanol wreaks havoc on anything carburated so you don't want to leave gas in a generator on indefinite standby it most likely won't start when you need it. it may not be relevant if you are considering only portable generators less than 10kw in which case they are all powered by small gas engine.
