An energy-efficient lightbulb, taking in 24.0 W of power, can produce the same l
ID: 2009879 • Letter: A
Question
An energy-efficient lightbulb, taking in 24.0 W of power, can produce the same level of brightness as a conventional lightbulb operating at power 100 W. The lifetime of the energy-efficient bulb is 10 000 h and its purchase price is $4.90, whereas the conventional bulb has lifetime 750 h and costs $0.46 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 $0.20 per kilowatt-hour.
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Explanation / Answer
Data: For energy efficient light bulb: Power, P = 24 W Time, t = 10000 h Cost of bulb = $4.90 Energy cost per kWh = $0.20 For conventional light bulb: Power, P' = 100 W Life time of eachbulb, T = 750 h Total time of usage, t = 10000 h Number of bulbs, n = 10000 / 750 = 13.33 ˜ 14 Cost of bulb = $0.46 Energy cost per kWh = $0.20 Energy cost per kWh = $0.20 Solution: Energy efficient bulb: Energy, E = P t = 24 * 10000 = 240000 Wh = 240 kWh Total cost for energy efficient bulb = (240 * 0.20) + 4.90 = $52.9 Conventional light bulb: Cost price of 14 bulbs = 14 * 0.46 = $6.44 Energy, E = P't = 100 * 10000 = 1000 kWh Total cost for conventional bulbs = (1000 * 0.20) + 6.44 = $206.44 Total savings = $206.44 - $52.9 = $153.54 Ans: Total savings = $153.54Related Questions
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