In a certain city, electricity costs $0.17 per kW·h. What is the annual cost for
ID: 844675 • Letter: I
Question
In a certain city, electricity costs $0.17 per kW·h. What is the annual cost for electricity to power a lamp-post for 7.50 hours per day with (a) a 100.-watt incandescent light bulb (b) an energy efficient 25-watt fluorescent bulb that produces the same amount of light? Assume 1 year = 365 days. c (c) A typical incandescent bulb costs $0.89 and lasts for about a year; a typical energy efficient fluorescent bulb costs about $3.49 and lasts for about 3 years. Is the additional cost of the fluorescent bulb justified?
Explanation / Answer
7 hrs/day * 365 day/yr * .1kW * $0.16/kWh = $25.55
25/100 of above answer: $6.39
In 3 yrs for incandence case you spend: 3*25.55 +0.89*3
compared to 3*6.39 + 1*3.49
since second number is smalleer than cost of bulb is indeed justified