Energy saver

[Refugee]

Those are no use at all on a domestic supply.
Some industrial tariffs do measure power factor and the bills are charged accordingly. These are usually very large installations that in the past had a man that watched a dial and switched capacitors in and out.
On a domestic supply the device will just use a little bit of power to feed the control gear and do nothing.

[pwdrive]

If the motor/cap circuit is resonant then no problem when the motor is connected to the supply but if the supply is switched off and the capacitor is still connected across the motor the voltage generated might overstress something, like wise if the capacitor is connected in the same manner and has a reactance equal to the inductive reactance at a frequency that's less than the supply frequency.

Lawrence.

[Alan Douglas]

According to the site, the device is connected to the mains at all times, not to the load.

As noted, of no use on domestic service. I believe the average connected load is not very inductive anyway.

Interesting, in their instructions "is attached to the top 220v breaker." Perhaps they haven't heard that there is no such thing as "220 volts." The standard here is 120/240 and has been for sixty years, and was 115/230 in 1928, but never 110/220. That's just a figure of speech, dating back to Edison.

[Nick]

Some years ago (2005/6) we rebuilt our house as close to carbon-neutral as we could.

As part of that exercise, I monitored the power usage on every device in the house, including power factor.

All the appliances were new then, so are as efficient as they could be at the time (very well insulated fridges, low energy washing machine/dishwasher, ground-source heat pump etc.). Modern PCs have to have PFC PSUs as part of the Energy Star scheme... The heat pump, which uses about 50% of all our electricity, also has internal PFC (its 3-phase as well).

Almost everything, had a power factor very very close to of 0.9 or better, except the low-energy lighting that we were required to have as a part of the latest building regs and our planning constraints - these lights are very few and limited to rarely used locations.

So overall, in a house with reasonably modern white goods and other electrical items, there is absolutely no point in trying to further correct the PFC - just switch stuff off when its not being used - e.g. leaving a PC on all year without standby costs about 60 quid.

If you have items with very poor PFC which are major consumers of electricity, then the items probably are also very old and inefficient and you'd be better off just replacing them... e.g. old fridges & freezers which aren't well insulated, washing machines that can't do low-energy washes, immersion heaters etc.

However much it may grate, keeping some old stuff going because you can is sometimes not a very good idea... just switching things off when not in use (if they don't have an ultra-low-power standby mode) is by far the simplest thing to do.

[ppppenguin]

As others have said, domestic users are not charged for Volt-Amps reactive (VARs) so no point in power factor correction. As Nick has pointed out, modern appliances have to have a decent PF to comply with regs. What's a bit more iffy is harmonics. The current waveform drawn by a PFC corrected PSU will still be full of harmonics, it's typically a spike of current at the same phase as the voltage peak. I have no idea how domestic metering responds to harmonics, probably it doesn't or it's negligible. The effect on the network as a whole can be significant. Takes you back to the old days of lots of TVs with half wave rectification causing significant distortion of the mains waveform.

Back to the OP. The device is pure snake oil.