A 70 W outdoor security light burns, on average, 10 hours a day. A new bulb costs $5.00, and the lifetime is about 1000 hours. If electricity costs $0.10 per kW·h, what is the yearly price of “security,” per light?

What will be an ideal response?


70 Watts times 10 hours per day is 700 Watt-hours per day or 0.7 kW-hour/day. Multiplying this by 365 days per year gives 255.5 kW-hours/year of electricity use at $0.10 per kW-hour, for a total annual electricity cost of $25.55. If the light is on 3650 hours per year, one will use an average of 3.65 bulbs (each lasting 1000 hours, or 100 days at 10 hours per day) each year, at an average annual cost of $5*3.65 = $18.25/year. So the total annual cost to operate the light is about $18.25 + $25.55 = $44.

Trades & Technology

You might also like to view...

Extension agents disseminate the most recent recommendations by researchers to people at no cost

Indicate whether the statement is true or false

Trades & Technology

In 2009, _____ sold 54 percent of all organic food

a. Mass market retailers c. Producers at farmers' markets b. Internet retailers d. Specialty stores

Trades & Technology

Which statement below is correct concerning asbestos and automotive service?

A) Asbestos was once used to make friction material for clutches and brake linings B) Exposure to even low levels of asbestos may cause a disease known as mesothelioma. C) A technician cannot be certain when he/ she is working with asbestos-containing products. D) All of the statements above are correct.

Trades & Technology

Technician A says that a symptom may be corrected without correcting the cause of the problem. Technician B says that verifying the repair will determine if the root cause of the problem has been repaired. Which technician is correct?

A) Technician A only B) Technician B only C) Both technicians A and B D) Neither technician A nor B

Trades & Technology