Wesley J. Smith, as part of his coverage of environmental news he calls "Global Warming Hysteria" recently discussed a $ 50 LED light bulb. I commented on the article, saying that he didn't mention that CFLs were much cheaper than the one he described and that that the improved energy efficiency made up for much of the cost. The article and some of the comments made me want to see for myself how much savings CFL bulbs represent.
Sources for Starting Numbers
From an October 2010 Consumer Reports article*, I discovered a 60-watt incandescent bulb is equivalent to a 16-watt CFL or 12-watt LED. Incadescents have an average life expectancy of 1,000 hours and CFL's 8,000.
From the Department of Energy's statistics, I found the average cost per kilowatt hour is 9.62 cents.
By skimming various online sites, I chose 60 cents as a reasonable average cost for an incandescent and 5 dollars for the CFL.
I estimated that an average bulb is probably lit for about 5 hours daily. I didn't try to find specific statistics because a) this affects all the bulbs equally and b) it would probably be difficult to find.
Results
From this data, I determined the average cost to power a single incandescent bulb to be $11.62 over a year, compared with $ 3.94 for a CFL.
For the sake of argument, I also compared the best-case scenario for incandescents with the worst-case for fluorescent bulbs. To do this, I basically cherry-picked the numbers most favorable to incandescents and those least favorable to CFLs. Even still, the CFLs won, $ 5.90 beating out $ 9.63.
People interested in looking at my math can examine the spreadsheet I used, complete with the formulas. You will note I ran the numbers for LEDs, but since I was less confident of the numbers I plugged in, I didn't put the results in this post.
Cross-checking
How accurate was my estimate? I found three other cost comparisons. The first is a U.S. News and World Report article. It claims changing 30 fixtures results in savings of $ 440 to 1,500 over 5 years. I show an $ 8.05 savings over one year for one bulb. Multiplying that by 150 gives $1207.50, meaning my result was perhaps a bit on the high end.
Next, I found GE Lighting's savings calculator. It too suggested my estimate was high: it gave a one-year savings of $ 5.91.
According to Energystar.gov, CFLs save $ 40 over the bulb's lifetime. If they last five years, that puts savings at $ 8, close to my estimate.
From all this, I think we can be reasonably confident fluorescents save money.
More Information
As it happens, both Factcheck.org and Politifact looked at closely related claims. Factcheck responded to the question: "Will energy efficient light bulbs cost $ 50 each next year?" with the following:
Some light emitting diode bulbs may cost that much, but some halogen incandescent bulbs and compact fluorescent bulbs go for about $1.50 to $3 each.Politifact did a slew of articles on the subject. Here they are:
- Whether or not fluorescents are safe & environmentally friendly
- On the cost of non-incandescent bulbs—alegedly six times more expensive
- What exactly the government is mandating.
- And more...
*Full, official citation:
Lightbulbs. (2010). Consumer Reports, 75(10), 26.
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