According to a recent study, the average american household contains 40 light bu

Question

According to a recent study, the average american household contains 40 light bulbs. Assume that each of these is a 75 watt incandescent bulb.
a) If all the lights in the house are turned on for 8 hours per day, how much energy would be used in one day? express the answer in kilowatt hours.
b) If energy costs $0.10 per kWh, how much does it cost per day to do as described in part a?
c) According to the General Electric website, a 20 Watt CFL bulb produces the same amount of light as a 75 Watt incandescent. If every incandescent bulb in the same house were replaced with a CFL, calculate the monetary savings over one year, still assuming that all the bulbs are turned on for 8 hours per day.

Explanation / Answer

a.) no. of light = 40
rating of a bulb = 75 W
no. of hours = 8hr/day
Energy used in one day = 40*75 * 8 = 24000 Whr
= 24 kWh

b.) cost = $0.10 * 24

= $2.4

c.) GE 20W bulb

energy used in 1 day = 20*40*8

= 6.4 kWh

cost = 0.10*6.4

= $ 0.64

saving per day = $ 2.4-0.64

= $ 1.76 per day

saving per year = 365*1.76

= $ 642.4

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