Question

. A circulating pump consumes 450 W for 24 hr a day. a. Determine the energy consumed for a one-year period. b. Calculate the utility energy charges for this period at a rate of $0.12/kWh. c. Determine the energy saved for a one-year period, if the pump is switched off 8 hr a day. d. Calculate the energy cost savings for this period at a rate of $0.12/kWh, if the pump is switched off 8 hr a day.

Answer 1

a. 3942 kWh

b. $473.04

c. 1314 kWh

d. $157.68

Explanation:

a.

There are 1000 W in 1 kW, so 450 W = 0.450 kW. The energy used per day is ...

(0.45 kW)(24 h) = 10.8 kWh . . . . energy per day

Then in a 365-day year, the energy used is

(365 da/yr)(10.8 kWh/da) = 3942 kWh/yr

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b.

At the rate of $0.12/kWh, the cost of running the pump is ...

($0.12/kWh)(3942 kWh/yr) = $473.04/yr

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c.

Switching the pump off for 1/3 of the time will save 1/3 of the energy found in part (a):

1/3(3942 kWh) = 1314 kWh . . . . energy saved by switching off the pump

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d.

The savings will be 1/3 of the cost of running the pump full time:

1/3($473.04/yr) = $157.68/yr