A family replaces 10 60-watt incadescent bulbs with 10 30-watt flourescent lamps. If each light was used for 4 hours a day and the cost of electricity was 10.0 cents/kWh, how much money would they...

A family replaces 10 60-watt incadescent bulbs with 10 30-watt flourescent lamps. If each light was used for 4 hours a day and the cost of electricity was 10.0 cents/kWh, how much money would they save in a year?

how much money would they save in a year?

Expert Answers
lemjay eNotes educator| Certified Educator

First, determine the total power of the incandescent bulbs in kW as well as the total power of fluorescent lamps.

For 10 pcs. of 60W incandescent bulb, 

`Total Power = 10* 60W = 600W= 0.6kW`

For 10 pcs. of  30W fluorescent, 

`Total Power = 10* 30W = 300W = 0.3kW`

Next, determine the power consumption (kWh) of the family in one day. Use the formula:

Total power * number of hours used per day = kWh per day

Note that each bulb is used 4 hours per day.

For 10pcs of 60W incandescent bulb,

`0.6 * 4 = 2.4` kWh per day

And, for 10 pcs of 30W fluorescent bulb,

`0.3* 4 = 1.2` kWh per day

Next, let's determine the power consumption (kWh) per year.

For 10pcs of 60W incandescent bulb,

`2.4 (kWh)/(day)xx (365 days)/(1 year) = 876` kWh per year

And, for 10 pcs of 30W fluorescent bulb,

`1.2(kWh)/(day)xx (365 days)/(1 year) = 438` kWh per year

Then, let's compute the annual electricity cost.

For 10pcs of 60W incandescent bulb,

`876 kWh xx 10 (cents)/ (kWh) = 8760 cents`
 
And, for 10 pcs of 30W fluorescent bulb,
 
`438xx 10 (cents)/ (kWh) = 4380 cents`
 
To solve amount saved, subtract the annual electricity cost of  fluorescent bulb from incandescent bulb.
 
`8760 - 43820 = 4380`
 
Hence, the amount saved in electricity cost is 4380 cents.