Your utility company charges 15 cents per kilowatt-hour of electricity.

Question

What is the daily cost of keeping lit a 100-watt light bulb for 9 hours each day? How much will you save in a year if you replace the bulb with an LED bulb that provides the same amount of light using only 15 watts of power

Answer 1

365.25)(100-15)(9)(.15)/1000

1 kw= watt/1000

=365.25(85)(9)(.15)1000

= $41,912.44/1000

= $41.91 yearly savings

9(100)(.15)/1000= about 14 cents per day cost for 100 watts per day

9(15)(.15)/1000=$20.25/1000=about 2 cents per day for 15 watts per day

saving 12 cents per day

365.25(12)= about $43.83 per year savings

go with $41.91