Enrogen always rates our generators at 1.0PF on single phase equipment. This is because in our opinion most of these generators will enter service running a near 1.0PF load.
1.0Pf means the KW and KVA ratings are the same. You pay household electric bills measured in Kilo Watt Hours (kwh), not KVA.
So for example from Enrogen you would see a rating of:
14kVA, 14KW, 1phase, 1.0PF
But typically our industry sells generators in KVA output, so a competitor may use to portray a "bigger" machine:
17.5KVA, 14KW, 1phase 1.0PF
Nothing, both are exactly the same "power" output, the PF is not a function of the generator, but set by the load.
For 1phase applications our opinion is to compare apples with apples, the KW rating must be used as that is a direct reflection of the true power and therefore the horsepower of the engine you buy.