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.
4 comments:
I'm wondering if there are hidden environmental costs to CFL's? Is there anything really toxic or rare that's required to make them? Also, nice graph!
Good question Ron. As I understand it there is about 5 mg of mercury in a CFL. As a point of comparison old school thermometers had ~500 mg. A more relevant comparison though is the amount of mercury released during the most common form of electricity generation, coal power. Apparently over a 5 year period, an incandescent bulb will use enough energy to release 10 mg of mercury into the air. Over the same period, a comparable CFL will only use enough energy to release around 2.4 mg. So, all told, the CFL (5+2.4= 7.2 mg) represents less cumulative mercury than the incandescent. The small amount of mercury inside the CFL is, of course, only released if the bulb is broken. Please follow these clean-up instruction if you break a CFL: http://www.energystar.gov/ia/partners/promotions/change_light/downloads/Fact_Sheet_Mercury.pdf
Thanks Ron for the 'toxic' question. This mercury problem has been discussed several times on NPR. Luke's reference to mercury release by incandescent bulbs surprised me. The graph is great, but too large to print. My computer screen is small.
luke, thanks for simplifying thingsfor 55 yr old,prematurely senile people.im off to the hardware store
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