All I can find is this:
"I can't be sure about meters in other parts of the world, but as far as I know here in the US mechanical meters were calibrated for an average 0.85-0.88 power factor which is/was typical for residential loads. This meant that the meters were accurate when the pf of the home was near 0.85 but slightly inaccurate at other pf's. I've heard that the modern digital meters are more accurate over a wider range of pf's so that might be why some customers notice an increase in their bill. Either way, they're only supposed to meter kWh, not kVA"
From
Looks like digital meters (like mine) aren't so susceptible, but spinning disk ones were more accurate at a certain power factor (preset to what they think you will probably use). I don't know how much it would read wrongly....