An energy efficient lightbulb, taking in 28.0 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 10000 h and its purchase price is $17.0, whereas the conventional bulb has a lifetime of 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 lightbulbs over the same time interval. Assume an energy cost of $0.80 0 per kilowatt-hour.
Explanation / Answer
You need to compare the total cost of both bulbs. The efficient bulb is more expensive, however only needs to bebought once. The conventional bulb is less expensive but has to be boughtseveral times in order to have a total burning time of10000h. Both bulbs burn a total of 10000h leading to a higher (energycost) cost for the conventional bulb [price per kWh]*[burn hours]*[power consumption] The total cost for each bulb is: [number of times bought]*[bulb price]+[energy costs] Compare these two total costs and your done Good luck!