Cost of Christmas Lights

A friend of my had a concern as to the cost to keep the Christmas lights on during this holiday season. As it so happens, I have a specialty in electrical systems. So, how much does it cost?

Let’s assume 5 strands of 150 lights each, for a total of 750 lights. We’re going to be old school and use the regular “white” Christmas lights, not LED’s. Christmas lights use “about 25 watts per 50-bulb strand”12. 750 lights is electrically equivalent to 15 50-bulb strands, or  15 \: \text{50-bulb strands} \times 25 \: \text{watts} = 375 \: \text{watts}. The base rate for electricity in Seattle3 is 3.86¢4 per kWh5.

Thus,  375 \: \text{watts} \times \frac{1 \: \text{kW}}{1000 \: \text{watts}} \times \frac{24 \: \text{hours}}{\text{day}} \times 60 \: \text{days} \times \frac{\$0.036  }{\text{kW} \times \text{hour}} = \$19.40

Remember, that’s if you left the lights on all the time for two straight months. If you left them on for 8 hours a day instead of 24 hours, that would be $6.48.

Similarly, if you only used 2 strands of 150-bulbs each for 8 hours a day, that would be $2.59.

Or, if you used 2 strands of 50-bulbs each for 8 hours a days, that would also be grand total of 86.4 cents.

Point being, it doesn’t cost all that much to run your Christmas lights. It costs an order of magnitude less if you use LEDs, which use about 0.05 to 0.07 watts per a bulb. Move the decimal one place to the left on the above costs and you have a pretty good idea of what it costs to run an equivalent6 LED string of lights.

And that’s how engineering works, folks.

NB: I’m experimenting with using \LaTeX to display equations. It’s really quite spiffy.


  1. HowStuffWorks 

  2. GreenOptions reports consumption for each mini-light at about 0.5 to 1 watt 

  3. http://www.seattle.gov/light/accounts/rates/docs/2009Oct_rsc.pdf 

  4. assuming you’re a residential user and use less than 16kWh/month 

  5. kWh is a funny measurement and is actually not time based. For example, a 100 watt bulb that is on for one hour uses 100 watt-hours of energy. Similarly, a 100 watt bulb that is on for 30 minutes uses 50 watt-hours of energy. 

  6. by number of lights, not output of light 

Who People Think You Are

On the Internet, Nobody Knows You’re a Dog

One of the interesting things about working at a company such as Boeing is how people treat you differently. Specifically how people you interface with on a non-recurring basis (i.e. not my coworkers) respond to me.

As soon as I call someone and say, “This is Andrew Ferguson from The Boeing Company,” I can hear their attitude change immediately. They are instantly interested.

On email, it’s very similar. I’ll be asking a vendor a simple question and they will respond with a resume of their involvement at Boeing1 in an effort to prove that, “Yes, we really do work with Boeing and we know how you guys work and we’ll do whatever it takes to keep your business.”

“You guys”…what does that mean any way?

This is a far cry from when I walk into a business, even today, and practically beg them to sell me something. I think a large part of this is because of my age. I’m a twenty-three years old and people don’t expect me to care serious about their product. It’s unfortunate, but true. The other part is to recognize that how you affiliate with something (a person or an corporate entity) can also affect how people treat you.

I haven’t gotten any comments back yet, but I wonder how shocked (if at all) people are when they finally meet me and I’m the youngest person in the room my two decades?

Perhaps the adage I should be keeping in mind is: “With great power comes great responsibility.”

Image: Copyright © 1993 The New Yorker/Peter Steiner. The New Yorker, (Vol.69 (LXIX) no. 20) page 61 of July 5, 1993 issue.


  1. we supply X to this project and Y to that project and Z to those projects 

Power of the Brain

A little while ago, I was wondering to myself how much power the brain uses. Today, BoingBoing helped me answer that question:
From www.boingboing.net:

The brain consumes 20 percent of your body’s energy, but what for? Turns out a third of the energy is spent on “housekeeping.”

I crossed check this and 20% appears to be dead on (see http://hypertextbook.com/facts/2001/JacquelineLing.shtml). As it turns out, it’s also about 20 Watts of power to run the brain (on a roughly 2000 food calorie diet).

Thoughts on Star Trek: Deep Space Nine as a Commentary on Present Day Issues

I’m just over 80 episodes into Star Trek: Deep Space Nine and there’s a couple of episodes that I think people should watch because they offer a really great commentary on what I see in America today.

To me:

  • Duet is about a persons right to have a fair trial, no matter where they came from or what they did. It echoes some of my feelings about Guantanamo Bay detention camp. I also recommend listening to NPR’s This American Life: Habeas Schmabeas 2007.
  • In the Hands of the Prophets is about Christians demanding that religion be taught in schools and/or decrying the teaching of evolution.
  • Homefront and Paradise Lost are about power, fear, and control. They are about what happens when something you love so much (freedom and America) are taken away from you because a few people threaten you. It’s not a perfect analogy, yet there are definitely a lot of parallels to what has happened over the last six and half years. I think the best quote comes at the end: “If the Changelings want to destroy what we’ve built here, they’re going to have to do it themselves. We will not do it for them.” – Benjamin Sisko. Now, replace Changelings with terrorists.

What I think is interesting is that these episodes are about 12 years old. I don’t think the writers intended this as a commentary on the current events of the time. Yet, somehow, twelve years after their air dates, these shows provide such a great reflection of the current times!

Other thoughts I’m going to throw in:

  • There are a surprisingly large number of sci-fi TV shows with episodes named “Paradise Lost”.
  • I am now 51.59% the way through all the Star Trek episodes/movies made.
  • I have seen 372 episodes/movies with 364 (actually, 365 if you count the upcoming Star Trek movie) left.
  • I have watched about 286 hours of Star Trek thus far in this project.