Power Consumption of Hanging Clothes out to Dry

I had a section to do for Kai to become a Wolf in Cub Scouts...luckily, the pack has decided to go out and do some neighborhood cleanup. Still, I was interested in completing my fact finding mission anyway. My goal was to create a set of information on how "little things" add up to "big things" (remember "think globally, act locally").

There is a lot to choose from in my life, I figured I would take them one by one and see if a little "group think" can help me fix any logic problems. After the Jack Johnson Curious George Soundtrack song, I figured I would categorize into:

  • Reduce
  • Reuse
  • Recycle

And I would take a few simple tasks a child could complete with their parents:

  • Encourage your parents to hang out 2 loads of clothes a week
  • Stop using 5 plastic bags a week
  • Use refillable water bottles instead of purchasing bottles of water
  • Walk to school

I haven't dug up all of the facts yet, but I'm committing to it here on the blog!

First task: Encourage your parents to hang out 2 loads of clothes a week.

(Yes, that's one of the loads I hung out today)

I have an LG Tromm Dryer (courtesy of a good quarter or two here at Sun Microsystems). It runs at 240 Volts / 30 Amps, ouch. That's about 7200 Watts per hour. A load of laundry takes about an hour to dry. I've committed to hang out 2 loads per week of laundry, 14,400 Watts per week \* 52 weeks = 748,800 Watts saved per year.

I was browsing around the web trying to find the conversion and I found the Ask a Scientist Web Site that said 1gm of coal could power a 60w light bulb for 550 seconds (let's do some rounding and just say 9 minutes). Now we have to do some normalization.

A 60 Watt light bulb with 1 gm / 9 Minutes = 6.67 grams / hour.

My two loads of laundry actually use 14,400 Watts per week (that's two hours of power), for 1600 grams of coal per week \* 52 weeks = 83,200 grams which, for my fellow U.S. citizens is 182 pounds.

Another site estimated the creation of 1 Kilowatt for each pound of coal (roughly), which would bring us to about 748.8 pounds instead of 182. The first calculation was in an ideal world, the latter appears to not be in an ideal world.

Doesn't seem like very much does it. I'll use the 182 figure to be conservative. Each of those pounds of coal produces about 3.7 pounds of CO2 so on the conservative chart, I am stopping about 673 pounds of CO2 from going into the atmosphere.

That's quite a bit, but is it worth the trouble?

My little suburb has about 80,000 folks in it, let's say there are 20,000 homes and each one of those families could save 136 pounds of CO2 from going into the atmosphere. That would be about 13,460,000 pounds of CO2 that does not enter our atmosphere each year.

Is that interesting yet? Probably not in the context of all of the CO2 created in a year, but I think that is starting to get interesting.

For a child, what is 13,460,000 pounds?

I saw on Yahoo Answers that a Pontiac Vibe is approximately (and conveniently) 2,700 pounds.

(Image borrowed from Edmunds)

My little suburb of Highlands Ranch, if each family would hang 2 loads of wash out per week rather than dry them, would keep about 4,985 Pontiac Vibes from entering our atmosphere and hanging over us each year. Imagine what a country like the U.S. could do by hanging their clothes out to dry?

If you see any MORE logic errors, please let me know and I'll keep trap and fix them.

Note: I was off by a power of 10 (sloppy night time work) and my dryer was 240 volts. Michael Lyle sent the correction and also noted that I should use an ammeter to get an actual measurement. Stay tuned!


It looks to me like a couple of orders (2 and 10) of magnitude got dropped in the process: 30 x 120 = 3600, not 360, and I haven't seen an electric dryer yet that was 120 volts, so the actual value is 30 x 240 = 7200 watts. Now, without measuring the actual value, you won't know, because even if the circuit is rated for 30 amps, it is highly unlikely that the appliance actually draws 30 amps continuously.

My suggestion is to borrow an ammeter from the hardware guys that accumulates the KWH (kilo-watt hours) and the power factor. Wikipedia has a pretty good discussion of power factor. KWH is pretty self-explanatory.

Posted by Michael Lyle on April 14, 2008 at 03:57 PM MDT #

I think I got it...I'm still groggy this morning and have to catch a plane. Thanks Michael ... and the ammeter will be coming, good call.

Posted by Paul Monday on April 14, 2008 at 08:42 PM MDT #


interesting post. I think you have an issue with units though. Watt measures power (ie energy (joules) per unit of time). So in most places you probably mean watt hour instead of watt.

Posted by Marc on April 16, 2008 at 02:48 AM MDT #

I studied up on this a bit...you are right about the implication of a watt hour. I read up on the rating of a 60 Watt light bulb and the calculations made for it implied that 60W was 60W / hour. Hopefully I can refine this when I get equipment in the house to do a closer metering. I just flew out of San Francisco today and I can't help but wonder why solar isn't more pervasive than it is...there is SO MUCH real estate open. I did see SFO has a pretty large distribution of solar panels on one of the buildings...good start.

Posted by Paul Monday on April 16, 2008 at 05:56 AM MDT #

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