Intelliworks Energy Saver

I cant see how it can reduce energy if it reduces it it could harm some products and invalidate your warranty

Actually loo at the site is says "reduce your electricity bills by up to 30%"

There is another one on market

http://www.primrose-london.co.uk/energy-reducer-p-2211.html?cPath=309&source=googleads&gclid=COmYnu21o5QCFQyD1Qodr3fbtA

As moonrakerz and I have stated.

All domestic customers pay for a kWH and these(power factor correction) devices - even if they worked - make no difference to the kWh displayed on your meter.

In theory the power station operators might gain a tiny benefit, but in practice they allow for domestic properties.

Now if you are in charge of a huge factory producing, say, cars, then there is value in similar devices - except they are the size of your house!

Cardew wrote: »

For domestic customers it doesn't matter about your power factor as you are only charged for the kWh you use.

Are you sure that domestic electricity meters measure true power (kW) rather than total power (kVA)?

I know that we all talk about electricity being measured in kWhr, but there are a couple of things that make me think that it's quite likely that domestic electricity meters actually measure kVAhr.

(1) It's easier to measure kVA than it is to measure kW. To measure total power you just need to make measurements of the voltage and the current and then multiply the two numbers. To measure true power you also need to measure the phase difference.

(2) It's to the electricity companies' advantage to define a "unit of electricity" as a kVA rather than a kW, because the kVA value is always greater than or equal to the kW value.

Here's another piece of evidence. I've recently been using a smart electricity meter to investigate the electricity use in my own home and in some of my neighbours' houses. (If you're not familiar with them, a smart electricity monitor gives a real-time display of the total power being used in the house. A sensor clips around the main incoming live cable, and the power reading is transmitted wirelessly to a hand-held display unit.) On one recent occasion I noticed that turning on a fluorescent light caused the monitor reading to go down. It wasn't just that something else in the house switched off just as I turned the light on. I was able to make the monitor reading change consistently as I turned the light off and on. Turning the light on made the reading go down. Turning the light off made the reading go up. My interpretation of this is that there was an inductive load in the house --- probably the freezer --- and the capacitor in the fluorescent light starter was doing some power factor correction.

The point is that if the smart electricity monitor reading was affected by the power factor then it must have been measuring kVA rather than kW, and why should we expect an electricity meter to be doing anything different?

While I'm on this subject, I'd like to respond to another couple of arguments against the possibility of getting practical advantage from domestic power factor correction.

(a) It's been stated that domestic loads are mainly resistive, so there's little scope for power factor correction. That may be true in the evenings, when lights are on and people are watching television, but it's not true in the middle of the night or during the day when everyone is out at work. During those periods the only loads --- apart from things like mains-powered clocks and devices left on standby --- are fridges and freezers, which are largely inductive. For example, my own fridge typically operates at a power factor in the range 32% - 38%. So, for long periods of the day and night the load in a typical house will have a significant inductive component.

(b) It's been pointed out that a device that plugs in to a 13 amp socket can't measure the power factor for the whole house. I believe that that is true. However, who says that you need to measure the power factor in order to improve it? Yes, you need to measure the power factor if you want to apply exactly the right correction to bring it back to unity. However, if you know that you have an inductive component to your load then adding some capacitance will almost certainly make things better.

My belief is that the domestic power factor devices on the market simply --- or at least mainly --- consist of mains-rated capacitors. They're not going to do proper power factor optimisation (as would be done on a large industrial site) but they should make the power factor "a bit better" when an inductive load is active.

Anyway, the key question is whether domestic electricity meters measure true power (kW) or total power (kVA). Until someone comes up with a proper, definitive answer to that question --- and it's not definitive to say that "we all talk about kW" or "everyone knows that electricity is charged in kWhr" or "it says kWhr on the meter" --- then I would suggest that it would be wise to be a bit cautious about stating that domestic power factor correction is necessarily a scam.