Our local utility gave us a free aerator. I installed it last week in the faucet for the master bathroom. This was easy to do and took about five minutes. The new aerator conserves water but its stream seems just as powerful as its predecessor.
So here’s my question: how much will this small contraption save us in the coming year ?
The math took a while to figure out, but the results are instructive.
The new aerator runs at one gallon per minute (gpm), whereas the old aerator ran at two gpm. Therefore, for each minute the faucet runs, we save a single gallon.
The bathroom serves two people. I estimate the faucet runs about eight minutes each day and generates three income streams for our local utilities.
First, we’re on a city water meter. One thousand gallons of inflow costs $2.55.
Second, a city meter also measures our wastewater. One thousand gallons of outflow costs $5.76.
Third, our hot water heater runs on natural gas, which is measured in Therms. According to our latest Xcel Energy bill, each Therm costs about $0.90, including taxes and fees. And according to this excellent article at FreeBy50.com, the typical gas water heater uses about .0089 Therms to heat a gallon of water.
Streams of Savings
I calculate that our savings for the coming year will total $32.06.
Savings Stream No. 1: Water Inflow
Total Savings: $7.45
Here’s the math: 1 gpm in saved water * 8 minutes per day * 365 days per year = 2920 gallons saved per year. This works out to savings of $7.45 (2.92 * $2.55 = $7.45).
Savings Stream No. 2: Water Outflow
Total Savings: $16.82
Here’s the math: 2.92 (1000’s of gallons) * $5.76 (cost per 1000 gallons) = $16.82.
Savings Stream No. 3: Saved Therms
Total Savings: $7.79
Here the math gets more complicated because the faucet doesn’t run hot water 100 percent of the time. About half the time we use cold water and the rest of the time the water is warm but not steaming hot. If the water heater supplies about one-third of the water that sprays out of the faucet, which I think is a fair estimate, then it uses 973 gallons of heated water per year (2920 gallons * 1/3 = 973). This works out to an annual cost of $7.79 (973 *.0089 Therms * $0.90 per Therm = $7.79).
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If you want to plunge into the lucrative world of low-flow faucet aerators, you can shop a wide variety of inexpensive products at Amazon or Home Depot. Better yet, check to see whether you local utility company offers aerators for free.