Basic assumptions
For ease of understanding, let’s calculate that water costs 1 cent per gallon. We are also assuming a two-person household, averaging five toilet flushes per person per day, one 10-minute shower per person per day, four loads of laundry per week and 1 minute of running the bath faucet per person per day. So for a family of four, you can cut these payback periods in half.
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But here’s one caveat: None of these paybacks take into account the energy savings from reduced hot-water use. Hot water costs an additional 1 cent per gallon to produce, thus making payback periods even shorter.
Water rates in Asheville and Buncombe County:
- Basic rate: $3.45/CCF (1 CCF = 748 gallons)
- Sewer treatment MSD: $3.51/CCF
- Total cost for a gallon of water: $6.96/CCF or 9 cents/gallon
Faucet aerator:Â
Standard faucet aerators use 2.2 gallons/minute, and low-flow aerators use as little as .5 gallons/minute with a net savings of .7 gallons/minute. Assuming two people use the faucet 1 minute each every day, that’s a savings of 1,250 gallons of water and $12.50 a year. With a cost of only $1, the payback period is four weeks.
Showerhead:
Standard showerheads use 2.5 gallons/minute, and low-flow showerheads use 1.75 gallons/minute with a net savings of .75 gallons/minute. Assuming two people take 10-minute showers each, that’s a savings of 5,475 gallons of water and $54 a year. With a cost of $5, the payback period is five weeks.
Toilet:
Older fixtures use 3.5 gallons/flush, and new standard toilets use 1.6 gallons/flush. Low-flow toilets use 1.28 gallons/flush. Net savings from installing a new low-flow toilet in place of an old toilet is 2.2 gallons/flush. Net savings for buying a low-flow versus a standard toilet is .3 gallons/flush. Assuming two people flush the toilet a total of 10 times a day, the savings from switching to a low-flow toilet from an old toilet is 8,030 gallons of water and $80 a year. Savings from buying a low-flow versus a standard toilet is 1,095 gallons of water and $11 a year. With a cost of as little as $110 for a low-flow version, the payback period for replacing an old toilet is 16 months. The payback for choosing a low-flow versus a new toilet is immediate, since there is no cost difference.
Washing Machine:
Standard washing machines use 33 gallons/load and front-loading ENERGY STAR washing machines use 15 gallons/load with a net savings of 18 gallons/load. Assuming two people do four loads of laundry a week, that’s a savings of 3,744 gallons of water and $37 a year. With the cost of front-loading washers being $300 more than standard machines, the payback period is eight years.
Source: USEPA consumer calculator spreadsheet.
[Matt Siegel is director of the WNC Green Building Council. He can be reached atmatt@wncgbc.org or at (828) 254-1995.]
