Can improving Power Factor help your Energy Bill?

***Update - 4/21/09: An Electrical Engineer friend of mine just send me the most detailed technical and economic analysis I've seen on the topic of residential power factor correction devices.  Check it out after you read the blog below if you are really interested:  NLCPR: Power Factor correction

Part of our goal with the Mapawatt Blog is to review the best products that can save energy and water in your home.  Product developers know that as energy costs rise, consumer's budgets get tightened, and people start to care more about their environment (the trifecta of sustainable drivers), those consumers are going to want products that help them save energy.  But do all these products live up to their claims?

One of these products is a power factor correction device and can be seen here.  This product claims:

Residential customers throughout North America could see a realized savings of 8% - 10% typically and as much as 25% on their electrical usage (and thus power bills).

However, I'm not buying it.  There are two great resources on-line that address this same issue.  One is from the National Institute of Standards and the other is a blogger I've been reading for 4 years and has a great section on electricity, Michael Bluejay. Both of these resources say power factor correction really wont help on your residential bill.  It can make a difference for certain industrial users who may be billed by the Utility for peak demand, but this is another story (and it is addressed in the Bluejay article).

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!

Let's take an example of 2 completely identical motors sitting side by side.  Both of these motors have the exact same efficiency and operate at 1.2 kW. The first motor doesn't have a power correcting device.  The second motors does have PF correcting device.

  • Motor 1: 1.2 kW motor, connected to a 120 V circuit, PF = .7
  • Motor 2: 1.2 kW motor, connected to a 120 V circuit, PF = .999 (this has the Power Factor correction device, thus the excellent PF!)

Using the equation above we can show the amps (current) that will be dissipated in motor 1:

1.2 kW = .7 *120V * A → A= 14.29

And we can do the same thing for motor 2:

1.2 kW = .999*120V*A → A=10.01

But this doesn't mean you'll pay less to the utility!  All this shows as that your power factor increases (gets better) your amperage decreases, but the Real Power (Watts =  what the utility charges you) stays the same!  Therefore no matter your power factor, in residential settings the utility is still going to show that you took the same amount of Real Power off of the power lines, so that is what you pay.

I would like to see more info from the manufacturers of these devices on how improving PF helps save you Watts!  Basically, your utility doesn't really care what your Power Factor is, so I want to see some evidence on how this device impacts your energy bill.

One more thing!  On the product's website there are many customer testimonials.  NEVER believe customer testimonials.  Especially on things like energy saving devices or products that claim they can improve your gas mileage.  The reason people believe these testimonials is because they can't see electricity flowing through their home, so they just take the product's statements at face value.  Even if the "customer" really said the things about the product, how do you know they aren't mentally insane and or compulsive liars?

Also, if your energy bill goes down the month after you install this, how do you know its not just because you didnt have your AC or lights on as much?  You dont! Only believe data and analysis from trusted web sources (Mapawatt, Rocky Mountain Institute, Energy Star, Michael Bluejay, etc.).

I'm not saying this doesn't work, but I am saying that I need more evidence, and until I see more evidence, I think your and my money can be spent on better energy savings

I'm not the only site questioning the validity of Power Factor correction devices.  Open4Energy has a great review of Power Factor correction devices and another post on Energy Saving Scams.  I should note that it is in their "scam" section!

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The simple answer is yes power factor correction is old technology that can save up to 25% of the bill if readings are poor.
ckmapawatt's picture
Lee, considering you linked to a company that sells "power factor correction" solutions and you didnt really provide information as to how power factor correction helps residential customers, I am calling bollocks on your claim.
Hi everyone, ok, we all have our opinions on this topic, on houses, if your energy bill is not all that bad these products will save you, but not as much as a home that has a larger utility bill, if you have a house with a couple of compressors and a pool, and a heat pump pool heater and use your air conditioning more than usual you will save about 20-25% on your utility bill. Everyone that I have sold my product to is happy, I make sure before they buy that they understand really how much they can save. On the big projects schools, hotels, hospitals, etc. I go there and get with the right people, show them how this will work for them, on a project that has a utility bill of say $60,000 a month I can save them quite a bit, after doing a energy survey I can tell them just about how much I can save them,I am always on the money, no problem, most of the time on a $60,000 a month utility bill I can save the customer $12,ooo a month no problem, do it all of the time, on $10,000 it is usually $1,000 to $1,500 and some sometimes $2,000 a month, depends how hot it is and what is going on in the evenings, are the buildings being used or not, there is much more information needed to figure this out that's for sure, not one customer upset and hundreds of customers saving over $1,000 a month on their utility bills. We have large hotels saving over $20,000 a month, this is the truth, no reason to lie or make things up, that's crazy and if someone calls you up on these statements, you neen to be able to back your self up with the proof not just a statement, that will not cut it. Thank's for reading. Patrick.
Patrick, I just started selling this product in Florida. I wonder which brand your are using and would you be open to publishing some testimonials? Our residential sales have been well received but we need to open the commercial market ( condos) which should benefit even more so.
I have been an electrical contractor for over 30 years. I have seen the what the power company has done in our area. The real scam is what the power company has done to make all of us buy the total BS that all customer are billed for KWH(real Power)! All the electrical engineers I have work with over the years still believe what they learned in school and most are not very practical. Some never have wired a house,a commercial building, worked in a nursing home, hospital or school. Most don't get it. Power Companies, Engineer's, and the like have a vested interest and big egos to keep their CASH COW going . AT the common man's expense. Truth is PFC if done correctly does work. Stop the BS !!!! Talk to real world people who have done electrical work and know that fixing line loss will extend the life of all inductive type loads.
I was under the impression that these type of products could save money if the correct sized unit were installed?
Hi Patrick, Sometime last year I was entertaining selling power factor correction devices but was not comfortable with the person in charge. I thought he was a little shady. However, I did think that it was a great idea. I liked the product and felt it was a good fit for me to sell. If you have a minute would you give me your take on it and let me know which companies you would recommend? I would greatly appreciate it. Thanks, Anne-Marie
ckmapawatt's picture
Ed, What does it matter if they're sized right? The utility doesn't punish for poor power factor so it's irrelevant! Until someone can show me that these power factor correction devices save energy based on electrical principles, I can't recommend them.
Well you can have doubts and believe anything. Facts are facts I do sell PFC Units which we make and match them to actual loads. All you need to do is look at electric bills before and after if customer KWH is less than ask what has changed. Real world proof is the only true test. Why do most utility companies in US add PFC to their transmission lines. If it works for them why not the customer?
ckmapawatt's picture
I can only take your comment with a grain of salt considering you sell a PFC device. Your website says that the PFC device could save $50/month. I highly doubt that this has ever happened.


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