Compact fluorescent lamps were in the news recently when U.S. legislators passed a Bill that mandated energy-efficiency standards light bulbs must meet by 2014.
The Bill would make it impossible to sell the incandescent bulbs we have today. Coincidentally, EC&M Magazine, a publication for electrical contractors, published letters to the editor expressing alarm that legislators are enacting laws favoring CFLs. “I am as much for greening the world as anyone,” said one letter writer, who then pointed out numerous problems with CFLs, before concluding that, “mandated stupidity is not the way to go.”
It is interesting that electrical contractors, who should know a thing or two about working with bulbs of all kinds, would not be enthralled with CFLs. One issue the EC&M letter mentioned was that CFL actual lifetime can be far less than what ratings would lead consumers to believe. I tend to agree with the letter writer because of my own experience with these bulbs. I installed one in my garage that cost three times as much as an equivalent incandescent. It was dead after just six months of occasional use, though CFL makers advertise lifetimes that are eight times longer than those of incandescent lamps.
I decided to get some answers. So I spoke with a fluorescent-systems engineer at GE about how CFL makers come up with lifetime ratings. It turns out that the median of the distribution curve for all lamp lifetimes (in other words, where 50% of the lamps die) is defined as the lamp life. Even incandescent bulbs are rated this way and have been since the days of Edison.
GE says the spread of CFL lifetimes is a Weibull distribution though with relatively few bulbs on the infant mortality tail. Still, only 50% of bulbs will give the life listed on their packaging. There is another caveat in how this lifetime curve data get measured. It is through an ANSI standard procedure that powers sample bulbs on for 3 hours and off for 20 minutes at room temperature. This test in no way resembles the situation in my garage. There I was more likely to flip on the light for just a few minutes several times a day, and temperatures could vary from below freezing to 100°F.
Could temperature changes like this diminish bulb life? Cold temperatures shouldn’t, says GE, but higher temperatures might. And what about short duty cycles? That’s a relatively important issue as consumers install timers and other energy-saving devices that shut off room lights automatically a few minutes after occupants leave. My GE contact says the company doesn’t have a lot of data on this question, but admits some studies suggest CFL life drops with quicker duty cycles.
Energy Star tests would tend to confirm this impression. Bulbs earning Energy Star ratings must pass a fast cycling test with periods consisting of 5 minutes on/5 minutes off. But the bulb need only last half as long as its rated life under these conditions to earn an Energy Star rating.
All in all, I am not rushing out to buy more CFLs. I would rather wait until 2010 for GE to introduce the production version of its highefficiency incandescent lamp. GE is showing a prototype of the bulb now, though with frosted glass so you can’t make out the details of the filament. The HEI promises to give the same efficiency as CFLs, and do so without using 5 milligrams of mercury.