Electrical startup load question (pls check my work!)

I'm looking to buy a backup generator so that I can run the furnace plus a few other things in the event of a power outage in winter. So getting the right capacity is obviously important.

The generator vendor that I'm looking at is suggesting a 1200W power budget for getting the furnace started up when it goes into a heating cycle (less power being required once its done its startup. But I thought Id try to get a better number for my furnace. I dug through some manuals and for my model (sorry I can't post a link) it is recommending 8.8 amps as "a minimum circuit ampacity". The footnote in turn says:

"Minimum Circuit Ampacity = (1.25 x Circulator Blower Amps) + ID Blower amps."

Any idea why the 1.25 is in there? Is that to account for the startup current to get the blower motor started?

They also seem to be using 115V in these calcs where I have 110V service. It's probably not useful to try to get this to a NASA level of precision but if I just go 110V * 8.8A I get 968W so do you think I would be safe assuming that the generator would see a 1000W demand to start up the furnace? Cord from generator to furnace would be 20 feet or so.

Thanks

source https://hvac-talk.com/vbb/showthread.php?2222176-Electrical-startup-load-question-(pls-check-my-work!)&goto=newpost