On the Economy of Light Bulbs

This compact fluorescent lightbulb lasted 11,400 hours

On May 17th, 2003, I bought this compact fluorescent light bulb for $5.99. A couple days ago it finally stopped working, ending it’s 76 month career of generating photons. I’m pretty sure this was one of the first compact fluorescent bulbs that I’ve ever bought. And, as far as I know, this has been the longest lasting. Over the last few years, I have purchased about 50 CFL’s. I’ve replaced every bulb in my house with CFL’s, except two or three that are infrequently used. This one I bought for full price, but my local nationwide non-independent retailer will sometimes sell CFL bulbs for 99¢ as part of some government program.

I was and still am a bit skeptical about CFL bulbs. Why? Well, about half of the CFL bulbs that I have bought (especially the 99¢ ones) only last about three to nine months, which is no better than an incandescent bulb. Sure, they have a “5 year warranty”, but it sure seems like an awful lot of work to get a light bulb replaced under warranty. Not to mention that the shipping charges for the replacement bulb are probably equal to the cost of a new one. But what really burns me up is that you can’t throw them away. Each bulb has between 1 and 5 mg of mercury in them (less than 1/10000 oz.). That doesn’t seem like much, but environmental mercury is highly toxic and already a huge problem. Each little bit that gets in the ground water quickly travels up the food chain. Those at the top of the food chain get the highest concentrations (hint: people are the top of the food chain). Last year, about 100 million CFL bulbs were sold. Those bulbs contain about 50,000 lbs. of mercury, all of which will likely be tossed in the trash. Oh, and most of them emit ultraviolet radiation. You’re probably fine if you stay more than a foot a way from the bulb.

I am also skeptical about power savings, and being a numbers guy, I wondered what the savings actually are. Here are the results.

Compact Fluorescent Incandescent
Cost $5.99 about 50¢
Power Consumption 20 watts 60 watts
Operating Time 11,400 hours about 1000 hours
Total # of bulbs needed 1 about 12
Total bulb cost $5.99 50¢ * 12 = $6.00
Power Used 20W * 11,400 hours = 228 kilowatt hours 60W * 11,400 hours = 684 kilowatt hours
Total Operating Cost 228 kWh * 8.8¢ / kWh = about $20 684 kWh * 8.8¢ = about $60
Total Cost of Ownership about $26 about $66

Estimated Savings: about $40, about 450 kWh, and about 1000 pounds of CO2.

So, there you have it. Even if your CFL bulb burns out after a year, you still save about a dollar when compared with an incandescent. I have about 30 CFL light bulbs in my house. This means every year I’m saving about $100. Not bad.

I’m still upset about the mercury. I already trashed a number of bulbs before realizing that they all contained mercury. Now I’m just saving them in a box until I can find a recycler.

I look forward to LED bulbs. They aren’t made with mercury, they don’t emit ultraviolet radiation, and they use 1/4 as much power as a CFL. Unfortunately, right now they are so expensive that I would have to run one for 6 years just to break even with my $5.99 CFL bulb (9 years for a 99¢ model). And they aren’t really bright enough. Most are less than half as bright as an incandescent 60W bulb. As time goes by though, they will get less expensive and brighter. And just one LED bulb can potentially replace 100 incandescent bulbs, saving about $500 in energy over it’s lifetime. Not bad for a bunch of diodes.

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