They are rated at .8pf which is taking into account of the inefficiency of and inductive motor. Wasted energy to magnetic field. Heaters are 1PF resistive load. No lost energy. As chart shows below 15amps at 120vac will have a different watt load due to PF.
15A to watts calculation with voltage of 120V AC
For AC power supply, watts are equal to the power factor times amps times volts.
watts = PF × amps × volts
For resistive load without inductors or capacitors, the power factor is equal to 1:
watts = 1 × 15A × 120V = 1800W
For inductive load (like induction motor), the power factor can be approximately equal to 0.8:
watts = 0.8 × 15A × 120V = 1440W
I hope you don't mind using your post to add a bit more clarifying info.
Power factor is something we use to characterize the difference between how much energy there is in the electrical system versus how much
WORK we can get that energy to do. Regardless of the power factor 1 watt of electrical energy is 1 watt of electrical energy. Depending on the type of load we are engaging (motors versus computer power supplies versus baseboard heaters) there are differing amounts of work that can be realized from that 1 watt of input energy. We still had to put enough mechanical energy from the engine to make that 1 watt of electrical energy BUT we can't always get 1 watt of work back out of it. In the case of resistive load, you can. Restive loads are perfect consumers. They use it all. To go into the specifics of why will require a lot of forum space but if you are interested you can do some light reading on reactive loads in power distribution systems and the mitigations for them. You'll be asleep in no time.
So.. What this means is that if we are trying to drive a load that requires 1440w of energy and has a PF of 0.8, that means we will have to generate 1800w of energy with the difference being lost as heat in the system. Yep, 360w of diesel fuel out the window for nothing.
BUT.. Motors now are much better and they have higher power factors. That is good news. Some older types of motors such as shaded pole motors have horrific power factors. The plus side there is they are all low power motors and you'll most commonly see them in old fans. Sorry.. About to go on a tangent there. All of that isn't important for this discussion.
If we take most modern devices we should be between 0.9 and 0.95 PF. Unfortunately these generators have been around for a long time and the standard PF for the gauges has been 0.8 so we are stuck with gauges that read 20% off when measuring a pure resistive load and 5-10% off when measuring normal mixed loads.
What that means to the generators.. In a nut shell it means that the gauges lie. The gauges aren't of the type that can adjust themselves based on the PF of the load. They are calibrated for a PF of 0.8 and thats it. And thats OK so long as you (the generator operator) know the kind of loads you are engaging and can temper in your mind when the generator is working too hard. And this brings me around to tying all this back up.. The best thing to go by here is engine load. If we had a fuel flow meter or a strain gauge on the coupling between the engine and generator head we would have a much better measuring system to know what is going on. Since we don't you need to go by knowing your machine and know when its laboring. This is because the mechanical work of the engine rolls all of the complicated electrical stuff into a single and easy to understand thing - Engine power. That is the true sum of everything downstream.
What were we talking about again?
Some day i feel like I might be in a reverse power situation, but that is another story......