Question

(Power and Energy) If electricity costs $0.09 per kilowatt hour, find the cost (in dollars) of running each of the following electrical devices six hours per day for 30 days:

a. A 60 watt incandescent light bulb
b. An LED light bulb that emits the same light intensity as a 60 W incandescent light bulb, but uses 80 mA from a 120 V residential power wall outlet
c. A 1500 W electric space heater that runs continuously over the six-hour daily period

Answer 1

a) $0.97

b) $0.16

c) $24.30

Explanation:

$0.09 per kilowatt hour = $0.09/kWh

6h/day 30 days = 180h

a) 60W*180h = 10800 Wh = 10.8kWh

10.8kWh * $0.09/kWh = $0.97

b) P = V*I

V = 120V

I = 80mA = 80/1000 = 0.08A

P = 120*0.08 = 9.6W

9.6W*180h = 1728 Wh = 1.728kWh

1.728kWh * $0.09/kWh = $0.16

c) 1500W*180h = 270000 Wh = 270kWh

270kWh * $0.09/kWh = $24.30