Disco Shower or Consumption Shaming?
Saving water saves energy. A new study shows a fun way to do so.
As the father of a teenager, I appreciate the value of a shower. Positive externalities abound. The post-shower fresh scents wafting through the house! The latest Kendrick Lamar album is blasting on his speakers. The opportunity to switch whatever smelly hoodie on the floor out for a fresh one. But there are of course, some more serious negative externalities from hot water consumption – like energy use and the associated pollution for example. Thirty to forty-five percent of indoor water consumption is used for showering/bathing and much of that water is heated. Because the only person I know who enjoys a cold shower is a post-Sauna Swede. And most of us just aren’t. Heating water takes energy. How much energy one uses per shower depends on how hot and long you like your shower and how efficient your showerhead is. The temperature of the water coming into your shower matters as well, but getting used to a colder shower is a bigger challenge for most of us than trimming off a minute or two.
In the US the average shower duration is eight minutes. The EPA tells us that the average shower head has a water flow of 2.1 gallons per minute, and hence each shower uses more than 16 gallons of water! You can of course be like Meredith and install a low-flow showerhead and not cut down showering duration, but still consume less water! This means that Americans use about two trillion gallons of water each year just for showering. That is roughly a one-mile cube of hot water.
California is (most years) in a serious water crisis. Although 80% of non-environmental water use goes to agriculture, there is usually a lot of pressure to reduce residential water consumption. I try to do my part of achieving savings by yelling at my kid to take shorter showers (intensive margin). But there has to be a better way. Enter a new study (not public yet) by Andor, Götte, Price, Schulze Tilling and Tomberg.
They ran an experiment (RCT) in Germany where they sent a few hundred people a new fancy shower head, which allowed the researchers to remotely measure water consumption, temperature and shower duration. Then they split the households into four groups. One group received a report comparing their water consumption to that of a reference group (“neighbors”). There is an extensive literature in economics that shows that these “Opower” comparisons lead to small, persistent savings – the Allcott effect.
The second group received what I call the Traffic Light feature enabled on the showerhead. The showerhead lights up green up to about 4 gallons consumed (15 liters), then turns blue until you reach 5.8 gallons when it turns purple. At 7.7 gallons it turns red (and starts flashing red at 9.5 gallons), making the fact that you are using an excessive amount of water really salient to the showering individual. A third group received both treatments. The fourth group was a so-called control group that got no intervention.
Figure 1: The Traffic Light shower head.
The first question you might want to ask is did both treatments work? The answer is a resounding yes! In the figure below, which measures consumption liters because science, the vertical blue line shows the days since when the intervention started. The red dotted line shows the drop in consumption for the group receiving the social comparison email. The average savings for this group are roughly 9.3%! This is big. For electricity in the Opower studies, the estimated savings are 2%. I find this not surprising since I can control my water consumption much more easily than my electricity consumption (unless I have air conditioning).
Figure 2: Results of interventions on water consumption and estimated energy consumption. “SC” is the social comparison treatment, “RTF” is the traffic light shower head, and “Both” is , well, both.
The real time feedback via the lit up shower head worked like gangbusters! The estimated savings were 28.6%! Holy moly! Shining flashing lights in people’s faces while they wash works! The pink line shows the consumption effects of stacking the social comparison email on top of the real time feedback for combined savings of 34.8% (statistically bigger than real time feedback alone, even though they look the same in the graph).
The paper then decomposes who does the savings. The figure below shows that the savings are largest for people consuming a lot of water prior to the beginning of the program. Someone send the A’s resident water waster Billy Beane one of these showerheads. It will come in handy in the even drier Las Vegas. Ouch. Too soon?
Figure 3. Estimated savings by baseline group.
The paper also asks respondents how they feel about these interventions. There is a whole bunch of nerdy magic, trying to figure out whether people are actually willing to pay for being part of this program, and the answer is that the vast majority of participants is! The average participant is willing to pay around 10 Euros per month, which adds up to more than 100 Euros per year (more than the cost of the showerhead). This is cool.
So what do we take away here? Max is getting his kid one of these shower heads as his end of the school year present. Also, we learn that really salient information provision is a powerful tool for behavioral change. The cost is low (the showerhead is about $80) and the savings are net positive.
Would this work in California or the US? I am not sure. The sample used in this study is a bunch of Germans during COVID. So whether this translates we can only learn by actually running a similar experiment here – in homes, schools, gyms…Given the significant savings these authors show, this seems like a fun and possibly promising avenue to conserve some scarce water and the embodied energy in it.
Suggested citation: Auffhammer, Maximilian, “Disco Shower or Consumption Shaming?”, Energy Institute Blog, UC Berkeley, April 24, 2023, https://energyathaas.wordpress.com/2023/04/24/disco-shower-or-consumption-shaming/
Keep up with Energy Institute blog posts, research, and events on Twitter @energyathaas.
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Maximilian Auffhammer View All
Maximilian Auffhammer is the George Pardee Professor of International Sustainable Development at the University of California Berkeley. His fields of expertise are environmental and energy economics, with a specific focus on the impacts and regulation of climate change and air pollution.
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In many places, the cost of water is as big a deal as the cost of electricity.
I did some work in Alaska many years ago, and visited Barrow. The water system there extracts water from a brackish lagoon, treats it to drinking water standards, and puts it into a circulating heated distribution system. Water was eight cents per gallon. For the 9.5 gallon shower described in this post, that almost a buck.
But, of course, Jim had to put the trash can under the shower in his motel to measure it — 5 gallons per minute “monsoon” model, from 1977. A five minute shower there was two dollars worth of water. Plus the cost of heating it (Barrow has natural gas, so this is actually a comparatively modest cost).
I wonder how people’s behavior would change if they had coin-op showers, charging them in real-time for water and heating energy. Higher at peak (water and energy) use times.
The water side of this problem is easy to solve in much of the US, and certainly easy here in Olympia (where the annual Rain Festival runs from September to June) but more challenging in the desert Southwest.
Fortunately, the energy side of this equation is relatively easy to solve. CO2-heat pump water heaters )See: https://www.eco2waterheater.com/ ) connected to large storage tanks for hot water (100 gallons or more) will allow us to heat our water when the sun is shining and the wind is blowing, and electricity is cheap and clean, and then take long luxurious showers (I prefer Rachmaninoff) when so motivated.
ps, it doesn’t have to be a shower head, just an inline device and one can keep their existing shower head.
I have a question. Where does one get one of these shower heads?
Coloured shower heads already exist on AliExpress for about US$5, powered by the flowing water. Add a flow meter (~US$4) and some more smarts (ESP8266 ~US$1) and this shower head could be under US$20!
I have a product improvement recommendation. Instead of disco colours, use “none”, “yellow”, “orange” and “red” or make it user selectable.
That said, there is no way in hell I’m going to share my personal data. There are already too many entities collecting data on me. It’s already bad enough with FAANG, every “free” app on my phone, the bank, the grocery store, etc. No, I won’t voluntarily give up my data. Maybe if I RECEIVED 10€ every month I would consider it. What’s next, same device for the toilet and start seeing exlax pop ups?
Shower heads that give you x minutes ie y liters of water at z deg would do the trick. Spaced about 15 minutes apart. Use an app to set up – and charge the ‘children’ in the form of allowance or chores. No need to yell at them.