How Many Dollars Does it Take to Change a Light Bulb?

Like most people I've heard repeatedly how switching my lights to compact florescent bulbs can save you money and helps save the environment and I actually have a couple.  I've always really wondered though, is it REALLY worth it?  Am I going to save a significant amount, or even enough to cover the cost of the bulb?  I wanted to find out how much I'd save by switching all my incandescent lights to florescent.

I have an average size house (1300 sqft) and was somewhat shocked when I counted up all the light bulbs in the house and it came to 24!  The house is occupied by someone most of the day so I'm estimating each bulb spends an average of 6 hours each day turned on.

Incandescent Lights 

First let’s calculate out the cost of operating my lights currently.  One of the key selling points with the florescent bulbs is that they last for 7 years, so I'm going to calculate all the costs on a seven year scale.

Operating each bulb for 6 hours a day, 365 days a year is 2,190 hours a year per bulb.  The average bulb lasts for 1,000 hours so it will have to be replaced 2.2 times a year.  You can buy a 4 pack of bulbs for $2.99 (about $0.75 per bulb).  This makes the total cost of replacing each light bulb $1.65 per year. 

These are all 60 watt bulbs, and where I live electricity runs for $0.08 per kilo-watt hour.  60 watts at 2,190 hours a year is 131.4 kilowatt hours.  At $0.08 per kilowatt hour that makes the total annual cost of electricity $10.51 per bulb.

So $1.65 in bulbs plus $10.51 for electricity is $12.16 per bulb, per year.  Multiply that out times 24 bulbs and 7 years, that is $2,042.88 I spend every 7 years on lighting. 

Florescent Lights

The compact florescent have the startup cost of buying 24 bulbs.  Just checked the prices at walmart.com and it looks like it's going to cost me $40 total. 

Since I won't need to change these bulbs for the next 7 years, there won't be any charge for replacement bulbs this time.  I'm still going to run each bulb for 2,190 hours per year, but since they only take 13 watts instead of 60m they'll only consume 28.47 kilo-watt hours per year.  That make the annual electricity cost $2.28 per bulb.

The end result is a $40 up front investment + 2.28 per bulb, per year.  With 24 bulbs running for 7 years that is $423.04 to light my house for 7 years.


The Results
 
End result is $423.04 with compact florescent compared to $2,042.88 for incandescent.  That's a savings of $1,619.84.  Seems to be a worthwhile investment to me!  The environmental savings are bonus.