Proof that Power Factor Correction devices save little energy!

I wrote about the Plug and Save power factor correction device last year and I opened with :

I was so surprised when I Googled “Save Electricity” and it turned out to be the second hit. I question the validity of a search engine if a company can simply “game” their search ranking to get high on the rankings and then offer no insight on to how their product works. The device claims “Save Electricity Bills by up to 40%”. This is complete and utter b.s.! So what is the Plug and Save?

I also explained why these power factor correction devices don't work as advertised in residential settings in our post "Can improving power factor help your energy bill?":

To go a little deeper, the formula for Power Factor (PF) is below:

PF = Real Power (Watts) ÷ Apparent Power (VA)

- or -

Watts = PF*Amps*Voltage = PF * Apparent Power

The power factor correction devices are said to improve the second half of the above equation, the Apparent Power. However you don’t pay your utility for Apparent Power. You pay them for Real Power (Watts). Apparent Power is defined as the total power in an AC circuit, both dissipated AND returned! (scroll to the bottom of this link to view the power triangle and description of Apparent, Real and Reactive power). This means that if you currently have a poor power factor, your Apparent Power is higher, but all this means is that you are returning more unused electrons to the utility! But since they only charge you for used electrons (dissipated electrons = Real Power = Watts) you don’t give a hoot about your Apparent Power!

When people claim their energy bills have gone down after they install a power factor correction (PFC) device, I always ask how they know it was because of the device, or because of their own behavioral changes, or because of factors outside of their control, like the weather. The only real way to test one of these devices is in the lab, like I advocated in Oct. of 2010 in reply to a comment that said that PFC do reduce line loss:

You’re right. I think I have finally realized that the extra electrons on the line (resulting from a poor PF) reduce efficiency of the wire…but now my question is how much does this really have an impact? The sellers of PFC devices would have us believe it is 20-40%, but I think it is closer to 2-5% (if that). As you say, most new appliances already have some form of power factor correction.

The only solution to this issue seems to be to build to identical houses right next to eachother (so they experience the same weather). Or build two model homes in a temperature chamber. And have a PFC device on one and see how much it saves when you run them through the exact same test scenarios.

Luckily this type of test has been done!

WGAL TV in Lancaster, PA did a controlled lab experiment back in 2009 that compared a sample residential electrical circuit consisting of 2 kW of electricity demand (see video below). Their results after running the test for 8 hours with and without a power factor correction device: 17.67 kWH without the PFC device vs. 17.28 kWh with the device. That's a savings of 2.2%. Ideally, I'd like to see this type of test repeated several times, and with several different configurations of electronic devices as the load, but I think this is a great start.

The PFC device may have saved a few percent in electricity, but this is hardly the 40% that Plug and Save once claimed and the 12% energy savings on average that the Zap Box claims.

Watch the video of the Power Factor Correction test!

http://www.youtube.com/watch?v=V_ooTeO_Tq8

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power factor correction

Power Factor Correction scam

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Comments

Anonymous (not verified) Wed, 07/27/2011 - 13:22

Chris/Powell. Thanks for addressing this topic. We need to rid this industry of hoaxes, overpromises and scams. There is too much very real energy saving potential for homeowners today to have fly by nighters erode the integrity of the opportunity and of legitimate products and solutions. Keep up the good work.

Anonymous (not verified) Sun, 09/18/2011 - 17:04

.. This saving of 2.2%, where does it come from? I'm surprised there are any savings at all. I would venture to say in a real life home situation there would be a slight increase of power usage. Like any electrical device capacitors are not perfect and they have losses. I saw a video on youtube measuring the true power used by the device itself and it was in the area of 20 watts. Maybe low quality capacitors. Still some watt confused, I am.

Anonymous (not verified) Thu, 10/13/2011 - 08:18

I understand what you are saying and you are rite about 90% of these people scaming , but at the Same time the theory is to get the equipment in your home not to pull so,many amps at startup. Everyone your a/c starts it pulls about 40 to 80 amps, the job here is to get that equipment not to have to work so hard and pull that much energy, witch would save you a good amount on your bill each month in the summer, but that's about the only time, you can do the same thing with a hard start hooked directly to your a/ c unit, so what I'm trying to say is that these boxes are not for everyone, if you have multiple a/ c units then yes get one, otherwise its not worth it, now with bussiness its a whole differant story

ckmapawatt Thu, 10/13/2011 - 17:14

Where are the economic numbers to prove that "if you have multiple a/c units then yes get one" ?

Anonymous (not verified) Tue, 12/13/2011 - 06:34

Art, will the power correction device work if I have big bowlcutters and frozen meat grinders that takes a lot of power to start up +- 7 times a day and cookers that boil water to cook polony's

Anonymous (not verified) Thu, 01/05/2012 - 17:04

You cannot return power to the plant. That's non-sense. Electrons do not move long distances. They move back and forth 60 times per sec or 60-hz (AC); furthermore, you're implying that the KVARs produced are free for both the customer and utility company. Why would the utility company take the loss? Electricity needs fuel, so those KVARs you claim returns right back to the utility company use fuel such as coal and natural gas. Who pays for those fuels? If you don't produce KVARs, no one has to pay additionally which is the point of PF correctors! Homes naturally don't produce many KVARs, so there won't be a lot of savings, but to imply that KVARs are reusable power is rediculous. Power is energy. Here's an analogy. If you go jogging, you will use energy (KW) to move, but through the act of simply moving, you have to generate energy to overcome gravity, friction, etc (KVARs). That additional energy is produced by electrolytes just like KVARs are produced by coal and natural gas, so why would you think the utility company can send you energy and get it back from you without using additional fuel?

Anonymous (not verified) Thu, 01/05/2012 - 17:19

I would like to also add why KVAR isn't usable power, nor can it be returned to a plant. When an inductive load is energized, it induces an opposing voltage into the line which causes the phase shift. So, KVAR whole purpose in life is to create a phase shift. Its a natural phenomenon in nature. You can't send it back to the plant because it originates at the load! For everyone asking how do you know if it saves money, simply plug it up then measure, then unplug, then measure. If you plug your refrigerator into it, everytime that refrigerator comes on, it will use less energy (maybe 20% or so) even if that's equivalent to 50 cent a year. If you plug your lamps into it, you will probably see something like .05% saved or .00001 cents saved, so the product does work, it just depends on the application. And, the companies are overstating how much money you'll save by overstating your inductive load use in your house. 40% of $10,000 is a lot better than 40% of $20. Residential savings will be more like 40% of $20 bucks, but its still 40%.

Anonymous (not verified) Sun, 02/12/2012 - 17:05

To Brenton. Quote: "For everyone asking how do you know if it saves money, simply plug it up then measure, then unplug" There are several web sites that have done just that. Guess what they proved. You don't save money with these scam devices.

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