Answer:
(A) For incandescent bulb, your break even cost is $32.67
(B) With LED bulb, your break even cost is $3.8115
Conclusion: It makes financial sense to use LED bulbs.
Explanation:
We start by checking the cost of your electricity bill when you use incandescent bulb and when you use LED bulb.
Since your answers are to be in kilowatt hour, we transform the watt measurement of the bulbs into kilowatt thus:
60watt incandescent bulb = 0.06kw
7watt led bulb = 0.007kw
National average cost of electricity per kilowatt hour is $1.21
Cost per kWh using incandescent bulb is 1.21 × 0.06 = $0.0726
Cost per kWh using led bulb is 1.21 × 0.007 = $0.00847
(A) WITH INCANDESCENT
0.06kw × 500hrs/year = 30kwhrs/year
Cost of electricity bill = 1.21 × 30 =$36.3
Your 10% return = $3.63
Break even cost per year, in kWh is = 36.3 - 3.63 = $32.67
(B) WITH LED
0.007kw × 500hrs/year = 3.5kwhrs/year
Cost of electricity bill = 1.21 × 3.5 = $4.235
Your 10% return = $0.4235
Break even cost per year in kWh is = 4.235 - 0.4235
(C) The incandescent bulb costs $0.45 but draws you a bill of $32.67 a year WHILE the led bulb costs $2.25 but draws you a bill of $3.8115
We conclude hence, that light-emitting diode bulbs make financial sense. Overlook the cost of purchasing the bulb because it uses less kilowatts per hour and draws you a very low bill, compared to the incandescent bulb!
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