Determine the annual energy, water, and cost savings associated with replacing an existing showerhead (having a water flow rate of 2.5 gpm) with a low-flow showerhead (1.6 gpm). An electric water heater is used for domestic hot water heating with an efficiency of 95 percent. The temperature

Question

Determine the annual energy, water, and cost savings associated with replacing an existing showerhead (having a water flow rate of 2.5 gpm) with a low-flow showerhead (1.6 gpm). An electric water heater is used for domestic hot water heating with an efficiency of 95 percent. The temperature of the showerhead water is 110°F. The inlet water temperature for the heater is 55°F. The showerhead use is 10 minutes per shower, 2 showers per day, and 300 days
per year. Assume that the electricity price is $0.07/kWh and that the combined water and waste water cost is $4/1,000 gallons.

Accepted Answer

The annual savings in water usage due to replacing a showerhead using 2.5 gpm by another using only 1.6 gpm can be estimated as follows:

Δm= 2*[(2.5−1.6)gpm]*10min/day *300days/yr = 5,400gal/yr

The energy savings incurred from the reduction in the hot water usage can be estimated as indicated below:

ΔE = 5,400gal/yr *8.33Btu/gal. °F[(110−55) °F]/0.95 = 2.604 *[latex]10^{6}[/latex]Btu/yr

Therefore, the annual cost savings in energy use and in water use are, respectively:

ΔCost =[(2.604x106Btu/yr)/(3.413Btu/Wh)]*1000W/kW*$0.07/kWh = $53/yr

and

ΔCost = 5,400gal/yr *$4.0/1000gal = $22/yr

Thus, the total annual savings incurred from the water-efficient showerhead are $75. These savings make the investment in water-saving showerheads virtually certain to be cost-effective.

Question 15.1: Determine the annual energy, water, and cost savings associa...

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