A kilowatt-kilovars recording meter will record true power or reactive power on a time-share basis.

Haven't been able to find a definite answer to this. When a capacitor is placed across an AC supply although it draws current it doesn't dissipate power. So a specific example. If a 0.22uf capacitor has a reactance of approx 15k at 50hz then over a year (8760 hours) how many Kwh would a domestic meter clock up ? If it were a resistor it would average out at around 34Kw over the year at 240 Vac. What would the cap clock up ?

No, the domestic meters implement a true vectorial calculation, P=U*I*cosφ Of course, they are relatively crude electromagnetic devices, and the quadrature may deviate slightly, causing a "leak" of the reactive power into the active one. But the leak can work in either direction. If you connect a very large polypropylène capacitor to your mains, you will see some consumption though, because the wiring of your home will introduce a very slight resistive component, but for "normal" values ,like suppression capacitors, this is negligible.

Thanks Elvee... So you are saying that apart from wiring resistive losses the meter would not record the current (power) that has flowed (because no "real" power has been generated). What about the newer all electronic meters which have the capability (but is it used ?) to record reactive power/power factor etc. So the 15k resistor would consume a real 34Kw over a year and cost say £5 a year.

Thanks... Reason for the question was actually to do with "watless droppers" vs small transformer for a particular circuit. A small transformer that gets hot obviously consumes real power and you are charged for it, the cap supplying the same circuit doesn't and from what I gather you don't get charged for it (although obviously the circuit it's powering consumes real power that is chargeable).

Look inside a mains voltage LED lamp bulb. You can see the series cap that "drops" the voltage down to a LED suitable voltage. They tell us on the label it is a 240Vac, 1W or 3W or whatever bulb.

Small transformers are a disaster from an energetic point of view: a typical 1 VA transformer can use 3 watt or more open circuit. (of course, you don't use them without a load, and you have to add copper losses).
From that perspective, capacitive droppers are much more effective, even when most of the quiescent power is dissipated in a zener.

Your meter should only register real power. The current to the capacitor will be limited by the capacitor impedance at the 50 Hz power supply frequency. However capacitors have a residual series resistance (ESR). The current determined by the capacitor will flow through that resistance and dissipate as heat. That is real power and will be measured by the meter. Capacitor life is often determined by the heat generated by ESR. Low ESR means less heat, and more ripple current capability.