If the device is to actually going to correct a poor Power Factor, I would think that knowledge of the load would be essential. Normally capacitors are added to the line to balance any inductive component of the load. The idea is to create as close to a pure resistive load as possible.
Not knowing the load, which in a residential setting could vary alot, I don't understand how the amount of capacitance could be calculated. I don't think the device is using capacitors anyways, how could they know what size? In a factory you can correct PF at the problem, switching in a known bank of capacitors as needed for a known load.
PF correction in appliances allows the manufacturer to use smaller guage wires, less iron mass, have cooler running motors, less over-all build cost. The lower the VA rating of the load the smaller the wires can be. ( oversimplification, but the general idea )
It all boils down to the old saying ELI the ICE man. E ( voltage ) leads I (current) in an L (inductive) circuit. I ( current ) leads E (voltage) in a C ( capacitive ) circuit.
You can use one to cancel the phase shift of the other.