An energy-efficient lightbulb, taking in 27.5 W of power, can produce the same l
ID: 1998454 • Letter: A
Question
An energy-efficient lightbulb, taking in 27.5 W of power, can produce the same level of brightness as a conventional bulb operating at power 100 W. The lifetime of the energy-efficient bulb is 10,000 h and its purchase price is $17.00, whereas the conventional bulb has lifetime 750 h and costs $0.420 per bulb. Determine the total savings obtained by using one energy-efficient bulb over its lifetime as opposed to using conventional bulbs over the same time period. Assume an energy cost of $0.0930 per kilowatt-hour.Explanation / Answer
Energy consumed by energy saving bulb = 27.5 W*10000 h = 275 kWh
energy consumed by conventional bulb = 100W*10000h = 1000 kWh
number of conventional bulbs required = 10000/750 = 13.33333
Total cost using energy saving bulb = 17 + 0.093*275 = $ 42.575
total cost using conventional bulb = 13.333333*0.42 + 0.093*1000 = $ 98.6
total savings = 98.6-42.575
= $ 56.025