Posted by Luke Fishback

Compact Fluorescent Light bulbs (CFLs) are presently being pushed pretty aggressively by energy efficiency organizations, retailers, and even governments. When we go to the hardware store to buy some new light bulbs, though, we find that CFLs often cost 10 times as much as the good old-fashioned incandescent bulbs. In order to see if CFLs are worth their price tag, I compared the total cost of purchase and operation for CFLs and standard incandescent light bulbs over a long period of time. The results show that CFLs will pay for themselves in savings on your electric bill in a matter of months. Keep in mind that the costs shown below are for just one light fixture operated 4 hours per day.

Let’s do a little math. At your local hardware store you can probably find 40, 60, 75, and 100W incandescent bulbs for as little as 25 cents apiece. At the same store, it will likely cost you about $2.50 per comparable CFL. The average life on the incandescent will be about 750 hours, whereas you can expect around 8000 hours out of the CFL. So, when we look at the cost, it only makes sense to do so over a nice long period of time.Otherwise we would neglect the cost of replacing the incandescent several times over the life time of the CFL.

In the graph below I’ve shown the total cost of buying and operating the light bulbs for one light fixture for 8 different scenarios. In this case the light is turned on for 4 hours every day. I intend to delve a little more into this data in a subsequent post, but I hope this plot makes it clear that over a reasonable time horizon (a few months), the CFL will save way more than the purchase cost.

* To get the same amount of light as a 40W incandescent, it only takes 10W for a CFL. For 60W, it takes 13W; for 75W it takes 20W; and for 100W it takes 26W.

To the quality point, there are some CFLs on the market that offer nice, soft lighting. The dimming capability may still need a little work though. The NY Times put together a decent energy efficient bulb comparison table here.