Smart meter margins

[odysseus2000]

There is a lot of media advertising about the benefits of Smart Meters, that they allow any consumer to know exactly what they are spending on gaz and leccy.

As advertised this is a no brainer, but for electric users it has a sting and likely much better margins for electric suppliers.

Power in Watts is measured by multiplying voltage by current which is simple and tells you e.g. how how hot a heating element will get.

But if you have, as do e.g. most LED lights, capacitors, then voltage and current no longer give you power. Indeed it is possible with a capacitor to have both a high voltage and a high current and yet consume no Watts.

The reason being that the capacitor will take current to charge on half of the AC cycle and then return that current on the other half of the AC cycle, so that the net current consumed is zero.

All non smart meters calculate real power and as such LED lights are very low consumers.

But smart meters can be set to calculate not the real power but VA apparent power, i.e. voltage times largest current. Such that the capacitor in an apparent power measurement will leave the consumer with a bill that would not exist with a standard meter.

http://www.electronicdesign.com/energy/ ... lt-amperes gives a discussion of the two ways of measuring power.

One might argue that apparent power is not worth anything, but it is useful as it allows one to size cables correctly as in the capacitor example the cables must be able to cope with the current coming in and then coming out and it is likely this argument that the electric suppliers will use to justify ramping up your bill and if this happens it will be significant.

Under apparent power what in real power would be a 2 watt led lights would be billed as something like a 20 W light. Multiply that by a typical house of many led lights and one can see a big potential windfall and that is why smart meters are generally free. The scope for margin expansion is substantial which is bad for consumers, but good for share holders in electric suppliers.

The uncertainty is whether the politicians will let the suppliers use apparent power as a way to bill you. For the moment it looks like they will but it is likely going to become a very contentious issue and I am currently not welcoming the smart meters that are apparently coming to my properties.

Regards,

[TUK020]

two points to this:

a) Apparent power varying form real power is caused by either leading/inductive loads, or negative/capacitative loads. The place where this power factor is significant and causes major problems for the power companies is in large scale inductive loads on an industrial scale, rather than domestic (I think, can't point to any evidence). E.g. electric motors in a water/sewage pumping station. Don't think domestic/capacitative is an issue.

b) Power factor and also Harmonic Distortion (caused by rectified power supplies for electronic equipment - e.g server farms?) add to the power company costs. You are going to pay for them one way or the other. Economically more efficient to load the bill where the cost is incurred.

[odysseus2000]

As fas I can tell the rational for smart meters is so that the power companies get a new nice large earner with these installed domestically billing for apparent power for very little cost to them, hence much better margins.

Of course one can say how smart meters make consumers able to see there minute by minute power consumption, but that is like setting your car to show instantaneous mpg, fun for a few minutes then ignored.

Smart meter also don't need meter readers or inspections which is a plus, but it is the potential charging for apparent power that is the hidden gem for shareholders in these utilities.

Regards,

[csearle]

But if you have, as do e.g. most LED lights, capacitors, then voltage and current no longer give you power. Indeed it is possible with a capacitor to have both a high voltage and a high current and yet consume no Watts.

The reason being that the capacitor will take current to charge on half of the AC cycle and then return that current on the other half of the AC cycle, so that the net current consumed is zero.

This reason is incorrect. The phase of the current as compared to the voltage cycle is altered with large inductive (or capacitive) loads so the instantaneous power (the product of the instantaneous voltage and instantaneous current) is less. Traditionally meters read this and so the consumer was under-billed unless measures were taken to get the phases re-aligned.

Regards
Chris

[odysseus2000]

This reason is incorrect. The phase of the current as compared to the voltage cycle is altered with large inductive (or capacitive) loads so the instantaneous power (the product of the instantaneous voltage and instantaneous current) is less. Traditionally meters read this and so the consumer was under-billed unless measures were taken to get the phases re-aligned.

Traditional meters measure real power, i.e. Watts.

Smart meters can measure apparent power, the VA rating which is used to size conductors as even with net zero power devices like capacitors, there is substantial current both in and out, and smarter meters can be set to charge for this even though the real power as measured in watts is zero.

Regards,