Again, there are two problems that I believe we can pull out of an entire dirty power discussion and do something about ... THD and Surges.
Unfortunately, talking about THD only from the gen side is making it sound like all problems are cured by getting a low-THD gen. They aren't ... everything in your house is dumping THD back out on the line (smps devices are among the worst by their very design, UPS, etc). If you were to argue that THD is bad, then your electronics are getting eaten up by the THD that is already in your house wiring, and not from the gen (how often do you run your gen, after all?). My belief (IMHO) is that THD is the lesser evil.
Think of the house wiring as a pond, and everything in the house has dirtied up the water already, because almost every device is dumping THD into that pond. Your "clean power" gen is dumping clean water into the pond, which immediately turns dirty (clean + dirty = dirty). Your "dirty power" gen is dumping dirty water into the pond (dirty + dirty = dirty). In commercial/industrial sites, they can clean their entire lake of dirty water with specialized equipment, and end up w/ less dirty water. The grid requires this of them.
When you transfer back to the grid, clean water is getting dumped into your dirty pond by the grid, along with the occasional (and free) instant-death-dealing surge. Kiss that HVAC goodby, not slowly from THD, but instantly, from a single surge event.
What can you do about a THD problem? I'm no EE, but as best I can tell, little to nothing ... what commercial/industrial sites can do, with an army of EE's at their disposal, isn't what we can do at the home level. Can you stick a $200 UPS in front of something that is supposedly susceptible to high-THD? Sure, but now that same UPS is dumping more THD back out on the wiring.
The only clean pool of water I can find is the small puddle that is internal to your device that has an SMPS in front of it; this is a DC puddle. Behind it, that SMPS is dumping THD back out into the AC house pond. Our prevailing codes in the US say that this is a one-way street only ... clean up incoming power, but do nothing about outgoing power.
What can you do about the Surge problem? I'm no EE, but as best I can tell, you simply install an SPD device in your load center, and smaller SPD devices in front of susceptible devices. Have an HVAC that costs 10k? Stick an SPD in front of it. Same w/ little $$$ electronics. No THD being dumped back out on the line, from your SPD effort.
So, do you get a low-THD gen? Absolutely no problem, if you are willing to trade fuel choice, authorized dealer network only, complexity, low-watts, and other issues for the chance to dump clean water into your dirty pond water. Economics-wise, it's better for the economy when you buy a $5000 honda, than a $1000 westinghouse. Ignore those trade-offs (and issues, costs & headaches) behind the curtain ...
As I run my gen's for 1000 hrs / yr, out in rural nowhere, I too, am excited by "inverter technology" ... but I don't know where the marketplace will go with their designs. A "jet-engine complexity" Honda, and other similar designs, are the first iteration, and they don't fit rural applications easily. They are more like a JD tractor that only the dealer can repair, if you can get it there. I've seen only one open-frame gen w/ an inverter panel, but it had none of the features of a westinghouse non-inverter open-frame.
I took the $4000 in savings, bought $300 worth of SPD's, and called it good, as surges were infinitely more fixable than THD. 5 years later, it's still good. If my $300 TV does die a horrible death (and I can somehow trace it to THD, in some form of electronic autopsy), I still have $3700 left over to buy another $300 TV ...
YMMV, and watch out for those marketing folks ...
