Updated Aug 2012
Shorter life than promised
One of the most common complaints from disgruntled customers is premature failure after only a few hours, days, weeks or years, way short of the life rate stated on the package; sometimes due to poor lamp quality, sometimes from using good lamps in the wrong luminaires so they overheat, or switching them on-and-off too often.
In real scenarios, what causes CFLs to fall short of their rated life?
As anyone who frequently replaces CFLs in closets or hallways has likely discovered, rapid cycling can prematurely kill a CFL. Repeatedly starting the lamp shortens its life, Snyder explains, because high voltage at start-up sends the lamp’s mercury ions hurtling toward the starting electrode, which can destroy the electrode’s coating over time. Snyder suggests consumers keep this in mind when deciding where to use a compact fluorescent. The Lighting Research Center has published a worksheet [PDF] for consumers to better understand how frequent switching reduces a lamp’s lifetime. The sheet provides a series of multipliers so that consumers can better predict a bulb’s longevity. The multipliers range from 1.5 (for bulbs left on for at least 12 hours) to 0.4 (for bulbs turned off after 15 minutes). Despite any lifetime reduction, Snyder says consumers should still turn off lights not needed for more than a few minutes.
Another CFL slayer is temperature. “Incandescents thrive on heat,” Baker says. “The hotter they get, the more light you get out of them. But a CFL is very temperature sensitive.” He notes that “recessed cans”—insulated lighting fixtures—prove a particularly nasty compact fluorescent death trap, especially when attached to dimmers, which can also shorten the electronic ballast’s life. He says consumers often install CFLs meant for table or floor lamps inside these fixtures, instead of lamps specially designed for higher temperatures, as indicated on their packages. Among other things, these high temperatures can destroy the lamps’ electrolytic capacitors—the main reason, he says, that CFLs fail when overheated.
Chen W, Davis R, and Ji Y. 1998, in “An Investigation of the Effect of Operating Cycles on the Life of Compact Fluorescent Lamps” wrote:
A study published in 1998 examined CFL performance with five different operating cycles. It found that when the length of time the lamps were on was reduced from 3 hours to 1 hour, the lamp lasted for 80 percent of its rated life. When reduced to 15 min and 5 min, the lamp lasted for 30 percent and 15 percent, respectively, of its rated life.
A spokesman for the (pro-CFL) Energy Saving Trust confirms that frequent switching may reduce CFL life:
Regularly flicking a bulb on for a brief moment and then off again is not recommended as it can shorten the lifetime of the bulb.
When CFLs fail prematurely, calculated long-term savings of course go down the drain. As noted in this New York Times article: Do New Bulbs Save Energy if They Don’t Work?
Irritation seems to be rising as more consumers try compact fluorescent bulbs, which now occupy 11 percent of the nation’s eligible sockets, with 330 million bulbs sold every year. Consumers are posting vociferous complaints on the Internet after trying the bulbs and finding them lacking.
Bulb makers and promoters say the overall quality of today’s compact fluorescents is high. But they also concede that it is difficult to prevent some problem bulbs from slipping through.
Experts say the quality problems are compounded by poor package instructions. Using the bulbs incorrectly, such as by screwing low-end bulbs into fixtures where heat is prone to build up, can greatly shorten their lives.
Some experts who study the issue blame the government for the quality problems, saying an intensive federal push to lower the price essentially backfired by encouraging manufacturers to use cheap components.
According to the few consumer tests that test CFLs for that long, life span seems to have improved over the last decade for the best lamps, though not all CFLs work as long as promised.
• In a German test published January 2009, Osram & Philips CFLs lasted the full 15 500 hours – though with decreasing output – whereas 20% of IKEAs lamps went out before 3000 hrs and most reflector lamps died fairly soon. The tendency was for cheaper lamps to go out sooner. Konsumo: Energiesparlampen-Test: – Zweifel beseitigt
• Another German test from Dec 2008 gave “less than good results”. The first lamps went out after 1500 hours. (However, the exact details were not presented.) Öko-test Online: Energiesparlampe versus Glühbirne
• In a Swiss test from November 2007, Noser, IKEA and Megaman had fallouts before 3000 hrs, whereas the other 11 kept burning. Arcotronic AG: 14 Sparlampen im Test
• In a Swedish test from 2008, various lamp models and wattages from 3 common brands were tested for 6000 hours. 3 of the 4 tested IKEA lamps lasted the 6000 hrs, but one model an average of only 4398 hours. 11 of 14 Osram models (promising 6-15 000 hrs) passed the 6000 hour test, and the remaining 3 (sold as ‘6000 hrs’) lasted 4984 – 5911 hours. 8 of 15 Philips lamps kept burning at 6000 hrs and the other 7 went out between 3189 and 5837 hours, of which one (marked ’10 000 hrs’) lasted only 4244 hrs and 4 of 8 sold as ‘8000 hrs’ lasted only between 5178 and 5837 hours. Råd & Rön: Lågenergilampor, 1/2008
And this is when tested in lab conditions with bulbs burning openly without shades, at optimal temperature etc. In home luminaires with insufficient air flow and real life situations, e.g. when turned on and off often, life rate may turn out to be significantly shorter.
Edit 2012: Since I wrote this article, Råd & Rön tests have been made annually and published online (see Consumer Tests – CFL in pages section), but only the 2009 cycle tested CFLs for as long as 8 000 hours. Quoting myself:
Lamp life: Quite a few burned out long before stated life. Of the Osram ‘Miniball’ 11W (marked 6 000 h), all had gone out by half that time! And of a less known brand, North Light (marked 10 000 h), 40 % had gone out by 6 000 hours. Bulb models were least durable while spiral models gave most light and lasted longest.
Improvements seem to have been made in the amount of on-off cycles top brand CFLs can withstand, but when I mailed and asked, it turned out that on-off cycles were: 2 hours 45 minutes on, 15 minutes off, meaning that not even this Swedish consumer agency wants to test more frequent switching than that.
This in essence makes CFLs useless for many if not most sockets in an average home, except perhaps a continuously burning porch light. Humorously illustrated by this youtube video where visits to different rooms were actually timed (thanks to Freedom Lightbulb for recommending it):
And making 20 000 hour incandescent bulbs is clearly possible since they can be bought at Aero-Tech Light Bulb Co, it’s only a matter of wanting to. [Thanks to Freedom Lightbulb and Argumente für die Glühbirne for finding the link.]