Low-flow Shower Heads

Dascomb Hall


Summary:

30 inefficient 2.35gpm shower heads in Dascomb were replaced with 1.5gpm shower heads, saving in the conservative scenarios approximately 56,355 gallons of water annually, 34 ccf natural gas, and $866 per year.  The entire retrofit was estimated to cost $900, meaning that the project will payback in less than two years in the conservative scenarios.

Background premise:

Twenty five gallons of water are required for the average American 10 minute shower.[1] Not only will this present problems as the western aquifers become depleted and fresh water becomes scarcer, but fossil fuels such as coal generated electricity or natural gas are required to heat shower water. While natural gas water heaters are far better than electric heaters powered by coal generated electricity, they both contribute to greenhouse gas emissions and climate change. One of the simplest means of reducing personal water consumption and the associated energy costs is installing low-flow shower heads, which are cheap, easily installed, and capable of reducing water use up to 60%. This proposal addresses the possibility of installing low-flow shower heads in a dorm on campus.

Cost-benefit estimation:

Low-flow shower heads provide for slightly trickier cost-benefit calculations than usual, since both water and energy used to heat the water are saved. Required information includes the number of shower heads in a dorm, gpm flow rate of existing shower heads, estimate of the number of showers taken by students, estimate of the average shower length, the number of students living in a given dorm, estimate of the electricity required to heat a gallon of water to shower temperatures, and the cost of Oberlin electricity and water.

Dascomb, our target dorm, houses roughly 170[2] students and contains 30 shower heads. Assuming, as a conservative scenario, that students take 3 showers per week and 78 showers per school year per student (based on two 13-week semesters), showers take 5min (which is half the national average1), with the Dascomb shower head flow rate of 2.35gpm (measured) the dorm consumes 155,805 gallons of water on showers per school year. By using a Niagara Conservation N2912 Earth Massage 1.5 GPM Showerhead we would be able to achieve a savings of 56,355 gallons. Water savings of 86,190 gallons is worth roughly $784 at the Oberlin College water/sewer rate of $0.0139 per gallon (based on data provided by Renee Benjamin).

Based on Koomey et al[3] this would require 32,122 gallons of water heated to a temperature of 139 degrees Fahrenheit for the average shower temperature of 105 degrees. Using a water heater with 60% efficiency, this would save roughly 34 ccf of natural gas per school year, worth $82 at $1.45/ccf. This would create a total yearly savings of $866. For the less conservative estimates of six 5 minute, three 10 minute, or six 10 minute showers/week, the yearly savings would be $1733, $1733, and $3467 respectively

The Niagara Conservation Showerhead comes with a 10-year warranty and costs $15. Assuming that 15 min installation cost per head at $60/hour it would cost $30 per head installed. Based on the $900 it would then cost to retrofit Dascomb, installing low-flow showerheads would yield positive dollar savings for every year after installation, except for the most conservative estimate which would yield positive savings starting in the second year.

With a 10-year life-span and a 10% discount rate, the net present value of this project is roughly $4421. For the less conservative estimates of three 10 min showers per week and six 10 minute showers per week, the net present value is $9749 and $20,400 respectively. Scaled over the ten year life span, these numbers represent 25%, 35%, and 44% yearly rates of return, respectively.

It will only be possible to verify these estimates after installation if a dorm with water monitoring is used. Hopefully, in a dorm of 170 students any behavioral differences between years will level out. If these estimates are verified as accurate after an initial project, with this kind of return on investment it would be wise to outfit all dorms on campus.

Additional benefits:

Low-flow showerheads could be used as an educational tool if signs were posted with information on the purpose of the low-flow shower heads and additional water conservation steps that can be taken (such as shortening shower times). Some shower heads also allow for push-button halting of the water flow while soaping up, which would only help to conserve water if students were educated about it through the signs.


[1] http://www.msnbc.msn.com/id/27720656/

[2] http://www.oberlin.edu/reslife/housing/dorms/dascomb.html

[3] Koomey et al. 1994. Lawrence Berkeley Laboratory. <http://www.enduse.lbl.gov/info/lbnl-35475.pdf>

 

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