an estimation algorithm that includes i
On which note, I expect that once modern electronic meters are sufficiently rolled out, energy companies will start billing domestic customers for reactive power.
Which is fair enough in my book - the only reason they aren't is that traditional electromechanical meters only measure real power, and in the days when most domestic loads were resisitve it made a vanishingly small difference. But it's going to come as a bit of a shock when people discover how nasty the power factor of their cheap shitty LED lighting from China is. Expect power-factor correction to be the new eco ratings.
Could you translate this into English for those of us who only got a B in GCSE physics?
Resistive power is what you'll remember from your GCSE: Current flows through a Mk 1 tungsten light bulb or similar, makes it get hot, and electrical power becomes heat and light. Power dissipated is current multiplied by voltage. Simples.
Alternating current makes things more complicated, because with AC some things don't act like resistors. The usual culprits are things with coil windings like electric motors, which have some inductance, or things like switched-mode power supplies, which have some capacitance. This causes them to store energy (in a magnetic field, or as charge on the capacitor plates), and then return it back to the supply at a different point in the AC cycle. Imagine a suspension spring compressing and then expanding - you get the energy back, but not when it's useful.
The overall effect is that you have real power - that which the electric motor converts into mechanical work (and heat), and reactive power, which just causes a bit more current to flow. The apparent power - what you'd actually measure if you put a voltmeter and ammeter on the wire and multiplied the readings - is the combination of the two. 'Power factor' is simply the ratio of real power to apparent power. It's a measure of how reactive the load is.
The apparent power matters because the supplier has to generate that electricity, and it causes real transmission losses. As such, industrial customers who are powering massive motors (or whatever) are billed accordingly. Domestic customers (with their tungsten lamps and heating elements) historically had very little reactive load, and the traditional mechanical domestic meter (which can only measure real power) was considered to be 'close enough'.
The difference is that domestic users now have more reactive loads (typically capacitive things like DC power supplies, rather than inductive motors), and - critically - with an electronic meter, it's possible to measure apparent power cheaply at point-of-use.
The good news is that it's possible to design devices to have a better (ie. less reactive) power factor, by adding components that cancel out the effect
[1] (which obviously increases cost). Historically, that's been the domain of industrial users, but if domestic customers start to get billed accordingly, there will be an incentive to design things like domestic LED lighting and consumer electronics power supplies with power factor in mind.
Here's another question: if a smart meter works by sending signals over the mobile cell network or wifi, presumably that means it is itself using power, so am I getting charged for that power use? If so... Chiz!
I don't *think* you get billed for the energy required to run the meter, other than indirectly as part of the standing charge for having an electricity supply. Obviously if you use the energy usage display thinger, that's powered from your side of the meter, and would cost you a few pennies a year.
[1] Inductive and capacitive loads shift the power factor in opposite directions, so you can for example correct the power factor of a motor by adding capacitors.