It’s impossible to predict with that level of detail. Significantly (and perhaps unintuitively), the power factor of a load is not an indication of how sensitive the load measurement will be to introduced phase errors. The detail that’s missing is the phase of the fundamental (50Hz for me, 60Hz for you) component of the current signal (relative to V). If that’s close to 0° then the measurement will be quite insensitive to introduced phase errors (just like a big fat unity power factor resistive load is). If it’s a long way from 0° like in the two examples above, then it will be quite sensitive.
I’ve previously said it makes no sense to talk about phase when you’re dealing with non-sinusoidal signals, and then went ahead and broke my own rule in the two examples above by declaring the phase differences to be ~90° and ~50°, although I did include a caveat: “but they’re close enough [to a sinewave] that you could at least imagine what the 50Hz component would look like were you to extract it.” I eyeballed an FFT out of the signal. In the Microwave case it didn’t take much imagination at all, the Pool case is a little more challenging. Actually, I cheated a little in that case and asked my energy IC what it made of the signal… it calculated the fundamental phase difference to be 52.3°. There are some signals that I would never even attempt to guess at. Here’s a signal that my energy monitor (and my revenue meter) has to deal with at least twice a day:
That one doesn’t even require drilling down to a per-circuit basis. That’s what your main feed from the street to the house will look like if you’ve got solar panels and the solar panel output is roughly balanced with the house loads. That happens just after dawn and just before dusk every day, and quite a bit throughout the day on the cloudy days.
In summary, there are two pretty-much unrelated causes for non-unity power factors:
- a phase shift between V and I
- harmonics in I (i.e. non-sinusoidal I)
and typically you’ll have contributions from both. It’s the contributions from the first that determine how sensitive your measurement will be to introduced phase errors.
To demonstrate here’s a simple experiment you can try in a spreadsheet: knock up the standard single cycle V and I columns, in-phase perfect sinewaves, say 240V and 1A. Observe how both Apparent Power and Real Power come out at 240W and that the PF is 1. Play around with rotating one of the columns south by a cell or two (introducing a measurement phase error) and note how insensitive the Real Power calculation is to the phase error.
Now add a 10A 150Hz in-phase sinewave into the I column such that the I column is now the sum of a 1A 50Hz sinewave and a 10A 150Hz sinewave. Irms will be totally dominated by the 10A. Apparent power will shoot up to 2412 watts, Real Power will remain unchanged at 240W and power factor will drop down to 0.1. Again play around with moving a column south by a cell or two to introduce a measurement phase error and note how insensitive the calculation is to the error. So in this ridiculously extreme example, we’ve got an extremely low power factor but the Real Power measurement is just as robust as a unity power factor resistive load, when it comes to introduced phase errors.
BTW, this example also shows why it makes no sense to speak of angles when your non-unity power factor is caused by harmonics in I. You could calculate arccos(Real/Apparent) and you’d get 84° but there are no sinewaves here that are shifted by 84°. All the sinewaves in this experiment are in perfect phase with each other. The 84° is meaningless. It’s even a bit misleading, because it might tempt you to think: if the sinewaves are already out by 84° then this measurement is going to be very sensitive to any introduced phase errors. In reality, this measurement is extremely insensitive to introduced phase errors, because the sinewaves are in perfect sync with each other (and the power factor is very very low).
