Leccy supplied to yer castle is AC alternating current type. The voltage follows the path of a constant sign wave. 0 to 230 to 0 to -230 to 0 to 230... Hence alternating. It does this 50 times per second. Tis why they refer to it as 50Hz hertz. While this is happening the current flows in pulses, timed to the rise of the peaks of the voltage sign wave. Hence yer castle is supplied wiv constant pulses of electrical energy.
In leccy terms yer castle is a load. It loads the leccy supply, meaning it uses the power delivered to it. There's 3 types of load in leccy terms:
- Resistive where the current and voltage are said to be in phase. They match each other on phase angle. Meaning there's no phase shift between them.
- Capacitive where the current arrives earlier than the volts, so theres a bit of an offset. We say the current leads the volts. There's a phase shift between them.
- Inductive where the current arrives later than the volts, so theres a bit of an offset. There's a phase shift between them.
We remember this using CIVIL. CIV capacitive load current leads voltage. C before V. VIL inductive [L] load current lags voltage. L after V.
Yer typical house is an inductive load because of the type of leccy appliances yer have. Leccy cooker, washing machine, hoover, leccy shower etc are all inductive appliances. Office blocks wiv a lot of flourescent lights are typically capacitive loads.
Yer typical house has a supply current lagging the voltage by about 10%. This is factered into the normal cost of a leccy unit, to generate and supply the energy. Houses which are much more heavily inductive will see their power factor value shift more. Fer arguments sake a guess of 20% if they have a big lathe running or 20x henry hovers. With a normal old style leccy meter excessive power factor wasn't measured. So yer still paid the same unit price for the power delivered in watts. Volts x amps = watts. This is not the same for smart meters. They can measure phase shift which allows them to charge for excess phase shift.
In a purely resistive load, the energy delivered (voltage and current) is in phase. So the demand on the network is considered fair. Yer use of the energy network is what you get. For a typical castle where the power factor is offset by 10% because its an inductive load, yer placing a slightly greater demand on the supply network for delivery of the energy yer need, because of it being an inductive load wiv a phase shift. More demand than what whould be needed if it was a pure resistive load wiv no phase shift. This is factored into the normal leccy unit price for say 10% phase shift. Fink of it as putting a bigger strain on the energy supply network, for what you need. The greater the phase shift, the greater the strain. If yer phase shift drops to the above example of 20% because yer run a lot of henry hoovers at the same time, this would put an even greater strain on the supply network, to supply the same energy with a greater phase shift.
The short answer is smart meters measure phase shift and charge yer more for it, because yer putting greater strain/demand on the leccy network to supply the same amount of energy, if the phase shift is greater. Lots of peeps online argue against this as some sort of foul play. Its not. Its a fairer way of charging those who put excessive demand on the network supply. Yer never got charged this way before because they split the cost of energy generation and supply equally across every unit of energy used. Smart meters allow charging of users with greater phase shift due to what their powering in their house.