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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Chandler, I watched your video, but you don't show how users will save money on their energy bills. All you show is amps dropping...but that doesn't prove anything, because while the amps are dropping, the PF is increasing and kWh (what the utility cares about) stays the same!!! In the YouTube video on your site you say, "The Amperage is what you are paying for." This is wrong. You are not paying for the amperage, you are paying for the cumulative power! It sounds like you need to re-read my article to understand some of the equations above....
Chris, Answer these questions. Does unity is an electrical system improve it or not? If you reduce current draw ( amps) on a conductor does it use kw faster or slower? If I have a PF of .70 at 14 amps , improve it to PF of .99 at 10 amps which is more efficent?
Liston, I don't understand all of your questions. On the last one, you are definitely more efficient at a higher power factor, but again, the utility isnt charging for efficiency, only kWh used. You're right that improving PF helps greatly in an industrial setting, but that is totally different than a residential setting.
For fun, I emailed a supplier of these devices and asked for their feedback on a site that explained as does your site that for home use it made no difference. Wow. Talk about hostile! The message ended with "Do NOT contact us anymore." Not what I call good salesmanship. When I started communicating with the people in Australia who market the LUTEC electricity amplifier, I was called a STUPID DONKEY because I did not accept their claims. I think it is great that sites like yours are there for checking before going further. I always do an internet search for " . . . scam" or ". . . problem" about any product that sounds too good to be true.
I have worked for an electrical utility for over 35 years, about 1/2 that time as an engineer and the balance in charge of our energy conservation programs. Good stuff so far, I won't touch more on the basics of why it won't save residential consumers money other than to agree. I have dealt with reps from two different companies selling these 'magic boxes'. After a year of disagreement, one company actually flew their 'chief engineer'(he never actually mentioned a degree) in to convince me. When I handed him the specifications for how to provide verification of the actual energy savings, he turned to the sales rep and said 'under this protocol we won't show any savings'. Mind you they were the same specifications already used to sucessfully demonstrate savings for everything from compact fluorescent lights to insulation to heat pumps. The second company never replied. Many of these also market a surge protection aspect. If so, ask what UL category they have the device listed in. The ones I have seen list it under Standard 508, which is Motor Controls. The UL standard for Transient Voltage Surge Suppression (TVSS) is 1449. If they list it differently, the surge protection claims are as questionable as the energy savings. At this link the FTC settled with a manufaturer over "falsely representing that its transient voltage surge suppressors would save consumers 20 percent on their electric bills..." At this link the FTC sent warning letters to internet marketers "Making Misleading Claims about the Benefits of Gas-Saving and Other Energy-Related Devices..." including Transient Voltage Surge Suppressors - "the Commission and the states have challenged claims that these products provide significant savings for consumers' energy bills." This link mentions that the Texas AG "issued a temporary restraining order against...they claimed consumers could plug {the device} into the wall to trim electricity consumption by 25 percent...the legal but rather ineffective devices promise to “fix up” a consumer’s power in some way...He warns potential customers to be leery about energy-saving promises from vendors of products that use capacitors to improve power factor."
Hello Jay, I am considering selling energy box. I have very no/very little background in electricity. The consensus I get as I do research is that most people do not think the energy box works in residential homes. My question is this: Lets instead of focusing on a box that is designed to save 10% to 25% onyour monthly electricity bill, we have decided to engineer or design scenarios that would cause monthly increase in monthly electricity bill resulting in a increase in bill. Can this be done?,or is electricity just something that is available no no way of improving or decreasing the efficency of the electricity? Thank you in advance for you answer.
Jay, You have said it better than I ever could have! I think I'm going to feature an excerpt from this comment along with a list of many of the companies selling these products. The sad thing is, I think a lot of people selling this stuff really believe they are helping people. Others know they are scamming people. Thanks for commenting!
One more thing, it will only work if your house mostly using inductive load(coil based) such as fluorescent light using choke, motors on washing machine, refrigerator and so on. What it do is to minimize the angle of current and voltage. Which is known that most of inductive load will tend to make current lags behind voltage. But if the circuit is capacitive, the current will lead the voltage. That is why we used capacitor to correct the angle and reduce amperage. 10% does make a lot of saving if in term of one year. Just my 2 cents...
Hello. I use Power Factor correction on all of my AC motors. They all in the woodworking shop.They work good, no blown fuses. My high power transformer benefit from Power Factor correction capacitor to, that is in DC router table. So what is the problem? I know it dos not lower the energy bill but it help my tools run more efficient. I have to add that I'm not an electrical engineer- but I can do basic algorithmic calculation to get V and A to 90 degrees as close as possible. I someone has a problem with that e-mail me. Paul.
Hey Paul, you're right on track. All this self-centered talk about whether or not there is an individual monetary savings does not change the fact that inductive loads run more efficiently with corrected or at least improved power factors. The bottomline is that the amount of fuel required to generate a given amount of power will be less and electric motors and flourescent ballasts will live longer even though the average home owner's monthly power bill may remain unchanged. Sounds like a worthwhile investment in the environment that should be considered rather than a "rip-off". Seems kind of a no-brainer to an old hippie like me. Incidentally, an improved power factor will lengthen the service lives of a backup power generators for folks like me who occasionally rely on them during power outages after northeast U.S. ice storms. And double incidentally, saving a utility money by using their power more efficiently will not land you in jail. It won't get you any credit either. It just means that they burn less coal, oil, gas, etc. while you pay the same old bill and relish the satisfafction of knowing that you're doing what you can to preserve the environment. -Thom.


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