Set Square wrote:

Power factors of less than unity apply to reactive loads - like some type of
electric motors. [It's actually the cosine of the phase angle when volts and
amps are not directly in phase with each other].

That's only part of the story for power factor, non-sinusoidal waveforms
(i.e. harmonic currents) being the other. Any electronic power supply
working from a single-phase supply and using a rectifier with a
capacitor-input filter (reservoir capacitor) - and that's most of them -
will only draw current from the mains near the peaks of the voltage
waveform. This gives a peaky or spiky current waveform which also leads
to poor power factor, despite it only having a small phase shift.

The more general definition of PF is true_mean_power / apparent_power,
the latter term meaning the product of the RMS voltage and RMS current.
Your meter or monitor instrument (& the Maplin one seems to be the
best) will display true power as W (or kW) and apparent power as VA (or
kVA). PF = W / VA. (The electricity company's meter reads kWh, so you
don't pay for the apparent energy you're not actually using - large
users excepted).

--
Andy