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 ;)

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*).

*Along with your ale comes a little bit of foam. (*

**Unfortunately, life isn’t perfect.***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.**

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

*).*

**KVA****Thus, for a given KVA:**

- 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. - 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***, and*

**KVAR***:*

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

- KVAR would be
(**very small***foam would be approaching zero*) - 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:

- Power Factor Correction Calculation (MS Excel Spreadsheet)
- Size of Capacitor For Power Factor Improvements
- How Power Factor Corection Works
- Capacitor Banks In Power System
- Economic advantages of power factor correction

**Resource:** powerstudies.com

Fernando

Thanks for the simple and easy explanation by the author and by the corrections by readers.

Olga Neiman

Man, there is a Mistake. PF with the sin is kw/kva=cos(Θ)=sin(90°-Θ)

Alun Williams

The p.f. shown here with sin is indeed correct. SinΘ = perp/hyp = KVAR/KVA

Server Room UPS

What a great way to describe and explain the power factor. I like this style of learning.

WALTER MARTINS DA JUNIOR

The correct unit for reactive power is kvar, not kVAr.

Engr.I.F.Ogbuty

Well said,good job

Ramakrishna

Very clear answer . Thank you

Dinu Alex

good

Stuart

Instructions unclear. Beer now empty.

Robin Koffler

It is amazing how this how often this graphic turns up when you need to discuss reactive power and explain how it can affect electricity bills. With the ESOS deadline on the horizon it is even more relevant.

Jason Koffler

been using this way to explain kva and real power since the mid 90’s.

Alex Damaso

I would like to ask what is the appropriate KW rating of a generator set to used for 5 tonner aircondioning unit? Thanks

Jagdish Aggarwal

this is so simple and interesting. examples are just from day to day life.

Denis mchau

Am student and iwant to know the way of achive my goal to be a engineer .

nick

VERY EDUCATIVE

jorge mosquera

Excelente analogía. Interesante el portal

Saravanan

I didn’t see like this example wow its very help full

ezhil

Analogy of Kirchoffs law

sontakke

Dear Sir,Greetings.

Its a really interesting Practical Example.

Congrants for \an \idea.

Lui

Greatest description ever! ;) Thanks..

PETER

Very good example

Vidyadhar Joshi

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

Romona Davidson

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

Dejan

Jelen Beer FTW.

Srsly guys, you could’ve picked some less catastrophic Serbian beer :D

perendev

Palindrome: Jelenovi pivo nelej.

Gaudencio Toto

Excellent example, served me to explain the power factor to my clients.

We need more examples applicable to real life. Thanks

Barbara Kerr

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!

Loh Kon Min

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

lenin pugal

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

MANI NV

Good approach to teach a topic in a simple way.

SKuchle

Great article I will never be able to look at me beers the same way again.

elbf2801

Took into this extent, the PUB is the Substation and the Brewerei is the Power Plant.

PowertothePeople

Good article. Easy to read and great analogy. However, the equation P.F. = KW/(KW + KVAR) needs to be corrected to P.F. = KW/(KW^2 + KVAR^2)^(1/2) since KVA=(KW^2 + KVAR^2)^(1/2). I understand how the author wanted to keep it simple by associating his beer equation (P.F.= Beer/(Beer + Foam) ) with the actual power factor equation, but this is misleading and will lead to errors. People who aren’t comfortable with this topic will use P.F. = KW/(KW + KVAR) and will not obtain a correct answer.

laxmi

cool…. yesterday only i was questioned on this by laboratory viva examiner!! wish i read this before….