What's common for Beer Mug and Power Factor?

What's common for Beer Mug and Power Factor?

Understanding power factor is not that hard. We have some very common example from the real life you will understand for sure, but first let’s start with some introduction of power factor.

To understand power factor, we’ll first start with the definition of some basic terms:

kW is Working Power (also called Actual Power or Active Power or Real Power). It is the power that actually powers the equipment and performs useful work.

kVAR is Reactive Power. It is the power that magnetic equipment (transformer, motor, relay etc.) needs to produce the magnetizing flux.

kVA is Apparent Power. It is the “vectorial summation” of KVAR and KW.

Example From the Real Life ;)

Power factor - Example from real life

Ok, these folks must've been running some heavy reactive power compensation - 'cause there's no foam P.F.=1 ;)

Let’s look at a simple analogy in order to better understand these terms….

Let’s say it’s friday evening, and you are with your friends at your favorite pub after really hot day. You order up a big mug of your favorite beer for you and for your friends. The thirst-quenching portion of your beer is represented by KW (the big pic on top).

Unfortunately, life isn’t perfect. Along with your ale comes a little bit of foam. (And let’s face it…that foam just doesn’t quench your thirst.) This foam is represented by KVAR.

The total contents of your mug, KVA, is this summation of KW (the beer) and KVAR (the foam).

So, now that we understand some basic terms, we are ready to learn about power factor:

Power Factor (P.F.) is the ratio of Working Power to Apparent Power.

Power factor formula

Looking at our beer mug analogy above, power factor would be the ratio of beer (KW) to beer plus foam (KVA).

Power factor formula - Analogy with beer mug

Thus, for a given KVA:

  1. The more foam you have (the higher the percentage of KVAR), the lower your ratio of KW (beer) to KVA (beer plus foam). Thus, the lower your power factor.
  2. The less foam you have (the lower the percentage of KVAR), the higher your ratio of KW (beer) to KVA (beer plus foam). In fact, as your foam (or KVAR) approaches zero, your power factor approaches 1.0.

Our beer mug analogy is a bit simplistic. In reality, when we calculate KVA, we must determine the “vectorial summation” of KVAR and KW. Therefore, we must go one step further and look at the angle between these vectors.

Power Triangle

The “Power Triangle” illustrates this relationship between KW, KVA, KVAR,  and Power Factor:

Power Triangle

Note that in an ideal world looking at the beer mug analogy:

  1. KVAR would be very small (foam would be approaching zero)
  2. KW and KVA would be almost equal (more beer; less foam)

There are dosen of tools and technical articles/guides published at EEP that can help you to understand power factor and its controlling. Hope these can help:

Resource: powerstudies.com

About Author //


Edvard Csanyi

Edvard - Electrical engineer, programmer and founder of EEP. Highly specialized for design of LV high power busbar trunking (<6300A) in power substations, buildings and industry fascilities. Designing of LV/MV switchgears. Professional in AutoCAD programming and web-design. Present on


  1. Vidyadhar Joshi
    Dec 11, 2014

    Good Illustration. Hope people donot forget after having a beer. Cheers

  2. Romona Davidson
    Sep 15, 2014

    merci d’un million de… Really appreciate this example……..

  3. […] utilities meter both the real and reactive power consumption of a facility. The real power consumption, and its integral – energy, usually […]

  4. Dejan
    Jun 22, 2014

    Jelen Beer FTW.
    Srsly guys, you could’ve picked some less catastrophic Serbian beer :D

    • perendev
      Jun 23, 2014

      Palindrome: Jelenovi pivo nelej.

  5. […] peak or fully asymmetrical short circuit current is dependent on the power factor (cos φ) of the busbar system and its associated connected electrical plant. The value is obtained by […]

  6. Gaudencio Toto
    Mar 10, 2014

    Excellent example, served me to explain the power factor to my clients.
    We need more examples applicable to real life. Thanks

  7. Barbara Kerr
    Feb 12, 2014

    Is it correct to say that the equipment itself ‘eats’ a bit of the electricity that can be generated? So there is always a bit of loss in the generation process, lost to the equipment itself? Thanks much for this helpful article!

  8. Loh Kon Min
    Feb 03, 2014

    Great job….I love your power factor analogy using beer as an example!!!

  9. lenin pugal
    Feb 02, 2014

    i need more very common example from the real life like this.

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