The Art of Explaining Power Factor

April 7, 2011


I visit a lot of businesses in Michigan. It’s one of coolest parts of my work in energy efficiency. I get to see a ton of different facilities and work with a lot of interesting customers. Energy efficiency isn’t always the primary language of maintenance managers and business owners so questions are frequent.

In pumping applications, what are the benefits of variable frequency drives versus control valves?” or “How do electromagnetic induction lamps work, exactly?” or maybe even “Why is it easier to increase efficiency in chillers used in HVAC applications as opposed to chilled water process applications?

I get a lot of highly technical questions on a pretty regular basis and typically zip off an answer so quickly that raised eyebrows of surprise and jaws dropped in awe. While it’s not often that I encounter an energy question in the field that I can’t address, when I do struggle to easily explain a certain concept or technology to someone, I research the heck out of it until I can roll an answer off my tongue.

I am a firm believer in Albert Einstein’s philosophy on explaining things: if you can’t explain it simply, you don’t understand it well enough.

One of the concepts that I’ve had a hard time articulating lately to customers is power factor so I’ve been reading and researching like crazy. Apparently I’m not the only one that has a hard time explaining this mysterious and costly energy issue. Most of my research resulted in ridiculous graphs and extremely technical jargon.

Power factor is defined as the ratio of the real power flowing to the load to the apparent power in the circuit – or , using the beer analogy – the amount of Sunset Wheat flowing into your mouth to the maximum amount that can be poured into your Weizen glass, usually in percentage form.

Power Factor Beer Analogy Depicted

Note: I did not craft the analogy itself. I just edited a photo from to illustrate the analogy.

You’ll notice that a portion of the beer in your glass above is froth – reactive power. When you tilt the glass to get the beer flowing into your mouth, the froth jumps in first – creating a delivery delay (or lag) in beer-to-mouth timing. Reactive power does the same: creating a lag in power-to-equipment timing. The more froth, the more lag and interference and the lower (worse) the power factor ratio.

If the true power (beer) is 800 watts and the apparent power (glass capacity) is 1000 watts, you will find your power factor by dividing 800 by 1000 equaling 80%. The less beer and more froth you have in your glass, the lower and worse your power factor will get as demonstrated below:

Both images from

Q: Okay. I understand what power factor is now… but why is it important? Why do I need to improve it?

A: It’s important because businesses are paying for froth – reactive power that they cannot use to power equipment. If you can reduce the froth, you get more beer for your buck.  Additionally, utility companies typically charge customers a penalty on top of consumption charges when customer power factor is less than 95%.

Q: If the power is coming into the building but it’s not ending up fed to the equipment, where does it go?

A: Poor power factor causes power losses (all that froth waste) in your distribution system. As power losses rise, one may experience voltage drops. Excessive voltage drops can cause overheating and premature failure of motors and other inductive equipment. Once power factor is improved, motors will run much more efficiently and at cooler temperatures – extending the equipment life.

Q: This sounds like a no brainer. How do I improve my power factor?

A: We’ll talk about not only how to improve your power factor next week, but we’ll also talk about the financial aspect of power correction’s business case.

Stay tuned!

Want to follow the rest of this power factor series easily? Subscribe to my blog by email or RSS via the toolbar on the right. You won’t regret it – promise.

, , , , , ,

Connect with Madam Energy

Subscribe to our RSS feed and social profiles to receive updates.

6 Comments on “The Art of Explaining Power Factor”

  1. Thomas Says:

    You know Madam, I actually posted about this topic earlier on my own blog. This article has provided me with lots of food for thought, I feel that you made lots of very important points. In fact, I wish I had seen it earlier, before I wrote my own blog post.
    All the best :-),



    • Madam Energy Says:

      I’m glad you walked away with some food for thought! I’ll be posting a follow-up to this post later this week that talks about power factor correction so keep an eye open! 🙂 Cheers!


      • Stefanb2hv Says:

        hello Madam,
        Thank you for this very informative posts.. Like you said, I will keep an eye on this blog. I hope you will have more follow ups on this. Actually, I am really impressed on how you make the explanation easy to understand. I am not really super familiar with power factor
        , I just know how to use my appliances, equipments and my very dear gadgets:)
        Anyway, thank you again… Hope to read more from you!!!

      • Madam Energy Says:

        Stefan, I’m glad you gained something from this post! Before I wrote it, I knew very very little about power factor myself. From the amount of traffic this post has gotten, it seems power factor is a big mystery to most people. I did a ton of research and even spent a couple hours with co-workers working out the explanation so I’m really happy you liked the post!


  1. Tuesdays = Dry Erase Day | Don't Hate Me Because I'm Efficient - April 12, 2011

    […] in a recent post, I promised you folks that I would follow-up this week with a post on how to correct power factor […]

  2. Power Factor Correction – How and Why | Don't Hate Me Because I'm Efficient - April 13, 2011

    […] this week I attempted to explain power factor through an analogy using beer. I promised you that I’d follow it up with an explanation of […]

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: