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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Thom, I think the issue is the cost of these things. They're like $500. Most consumers dont have an unlimited amount of money to spend on energy conservation. My hole point is that you have $500 to spend, you can make much better energy saving purchases that have a much greater impact on the environment. Like Ecobee thermostats, TED 500s, retrofitting your whole home's lighting, insulation, etc.... If they were free then I would highly recommend them, but they're not and there are much better purchasing options for the consumer out there.
To add a little to the above posting, we are dealing with a lack of understanding of power factor. I have written an article explaining why <a href="" rel="nofollow">power factor correction </a> does not save consumers any money on the electricity bill. In simple terms, electricity suppliers bill consumers for real power, the amount actually consumed and not apparent power which is volts x amps. It is true that electricity suppliers need to manage their distribution networks, and that power factor IS one of the factors that impacts their distribution losses. It is also true that large industrial users are charged a penalty for a net power factor of less than 85%. But distribution losses will not be solved by consumers. They are aggregate issues that can only be solved by the utility companies (the smart grid) in partnership with industry and device manufacturers.
I studied for a degree in Electrical and Electronic engineering and while altering the power factor will cause less watts to be read by the meter 1 - it is illegal, 2 - the power companies add up all the consumption on a zone of houses and when it does nto add up they will pay a visit to check that your meter is functioning 'correctly' is they see a change in the PF you go to jail for defrauding them - simple enough for you to comprehend. They use the same technique for finding faults in cables without digging up the whole road.
Ralph You will not go to jail for helping the utility company be more profitable. They will love you and will not send the electric police to your home.
@ralph 1. It is not illegal to improve your power factor 2. The meter records true power, which you will be billed for 3. You will not go to jail You need to read <a href="" title="" rel="nofollow">this</a>
If the energy box were to work,why is it illegal? The energy box is installed in the houses breaker panel. Who owns the breaker panel and who owns the electric meter? Thank you in advance for your answer.
How does one explain the benefits of residential power factor correction with the new Smart meters vs. the older analog meters for measuring kwh? They measure and sense pf differently, and the newer tech also rely on an internal calibration and 'software CT settings' that may have been implicated in billing errors when not set correctly... A side by side analysis of how these old vs. new digital metering devices and how they measure kwh under various PF and CT conditions and settings would be most enlightening and perhaps clear up some of the misunderstandings ongoing in various utility districts in California... Your 2cents/kwr on this appreciated.
Theoretically increasing the power factor does increase the real power of a system. However, to what extent the real power is affected may show up very little in a consumer’s bill. If we look at an equation for real power (simplifying it to single phase for illustration purposes), real power equals voltage times current times the power factor: P (Real Power, Watts) = V (Voltage, Volts) x I (Current, Amps) x Power Factor. (P = VI * PF) So as the equation theoretically illustrates increasing the power factor increase the real power, and thus allows system requirements to decrease. The power factor can also be a contributing factor in fewer losses, because less current is required. The lower the losses of a system the more the source power is reaching the load (the consumer). There are more equations into improving the efficiency of a system that are generally already implemented to save the supplier money. It can be really involving, but I agree do a background check on things before purchasing any products that promise savings.
Believe or not it is up to you all. I had no doubt on this and it really work and reduce my monthly bill for at least 10%. And i even built it myself to compare it with the one i bought. It does the same, my current flowing to my house dropped from 4.6 to 3.8 amps. does save my bill on the next coming months. It just really simple, i've collected some capacitors from my workplace scrap centre then make a parallel connection and directly connect to wall socket and it does the job. Its worthy..not talking for those mentioned company but i see and did it myself. Anyone with electrical background will not object on this. Theres a theory and how to solve low p.f.
Good discussion as always, so have taken to building a list of the different names these "things" are being marketed under, and hopefully reducing their sales. It makes me really frustrated, as one dependent on quality advertising to fund the time I spend blogging and etc. - to see I am servings ads from Google for the exact scam I am trying to eliminate. On this, there is a new version of the magniwork out there - goes by the name of "Free Power Blueprint" web site is hxxp:// - and another "Motormagnet" hxxp:// - I have to believe they are making sales or how could they pay for the ads on Google.


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