Five Percent: Conserve Energy

Climate Change Is Important: Energy Conservation is the First Step

December 28, 2008

20.5% Less Hot Water Used From One Cup Of Coffee

Category: Save Water,Tips – Tom Harrison – 6:57 pm

Coffee Saves WaterA single cup of coffee per day has reduced my hot water usage by 20.5% — it seems improbable that such a small amount of liquid could have such a large impact, but I have been taking careful notes and checked them twice: it’s true. Here’s how I figured this out.

My hot water usage is composed of a daily shower, a small amount to wash my face, and one quarter of the dishwasher usage, as I share with my family of four. All our clothes washing is in cold water.

As per an earlier post in which I measured the water usage of various low-flow shower heads and settled on the Oxygenics Elite 700. When on full-blast, it uses 1.6 gallons per minute (GPM); when the lever is turned to low it uses about 9/10ths GPM. I’ll typically turn it on high to get wet, shampoo and rinse my hair (50% of shower time), then turn it on low while I wash my face and body (30%), then on high to rinse off (20%), or 70% at 1.6 GPM, and 30% at 0.9 GPM. Because I have set my water heater to about 115 degrees, it’s almost or all hot water.

Our Energy Star dishwasher uses about 4 gallons per cycle, of which I account for 1 gallon per day.

So how does the coffee affect hot water usage? Since November I have been using the Shower Professor shower timer, and keeping track of my results. When I step in, I set the timer for 5 minutes. When I get out of bed in the morning and stumble into the shower, I often find that I’ll use the full five minutes, or even 15 seconds more. However, if I have had a cup of coffee before, I regularly complete the shower in under 4 minutes.

So to do the math:

Un-caffeinated: (((70% * 1.6 GPM) + (30% * 0.9 GPM)) * 5.25 minutes) + 1 gallon = 8.3 gallons
Caffeinated: (((70% * 1.6 GPM) + (30% * 0.9 GPM)) * 4.0 minutes) + 1 gallon = 6.6 gallons

Difference: (8.3 – 6.6)/8.3 = 20.5% reduction in hot water use when I have had coffee before taking a shower.

Unfortunately, I am not very good at making coffee until I have had a hot shower.

No, seriously, I take a shower about 20% faster if I am awake and aware.


  1. Time to switch from coffee to amphetamines?

    Comment by John — January 2, 2009 @ 4:14 pm

  2. This post has completely blown my mind…. i’m an after shower coffee drinker, maybe i should switch.

    Comment by Mr Green Gear — January 2, 2009 @ 8:12 pm

  3. For me this is an illustration that the quickest, cheapest and easiest steps toward conservation are thoughtful observation, small decisions and new habits

    Comment by Paul Lambert — January 3, 2009 @ 9:01 am

  4. It’s good to see someone taking a serious approach to efficiency and resource usage by measuring and calculating what they do. It’s always a good idea to be able to quantify the difference you make.

    I’ve been keeping a track of my own mileage and efficiency in my lately car but haven’t been so systematic with electricity or water yet, I think I will start doing so.

    BTW, you don’t say if the coffee was decaf???

    Comment by Tony — January 6, 2009 @ 12:38 pm

  5. […] water saving shower head can help you conserve water, and in particular hot water which means you’re also save […]

    Pingback by Low Flow Shower Head Review: HighSierra FCS Works Great | Five Percent: Conserve a Little Energy — February 12, 2009 @ 4:32 pm

  6. […] — it has gotten to be a habit just to press a single button when I get in — unless I haven’t had my coffee yet, I’m in and out in about 4 minutes. My wife shaves her legs, so her showers are longer […]

    Pingback by Shower Timer: Six Bucks Once Saves Water Every Month | Five Percent: Conserve a Little Energy — June 20, 2009 @ 8:30 pm

RSS feed for comments on this post.

Sorry, the comment form is closed at this time.