Still Good Incandescents ?

Kim,

I work for an energy utility in Britain. In terms of what to do with old incandescents, maybe keep hold of one in case a CFL otherwise discard. The energy saving from the new versions of CFL's far outweigh any resource issue of throwing away a still working incandescent. Consulting with my colleague on this he notes; In terms of purely finances a 20W CFL replacing a 100W bulb will pay for itself in 3 months, saving over 100 in it's lifetime. Also CFLs general last ten times longer. Hope this helps.

Anna.

As someone who hates to throw anything away, I share the distaste for discarding the not-yet-burned-out incandescents. I use them in rarely used locations -- cellar and attic lights. Here in a heating climate, the waste heat is less a waste in the winter when the heat is wanted anyway, so using them in the heating season and not in the summer would make sense, especially if electricity is used for heat (and I certainly don't advocate that extremely wasteful practice). It sometimes makes sense to use electric heat to heat just one room, reducing the need to heat the rest of the house, and using the lights to help accomplish that would be using the electricity for a dual purpose -- as efficient as combining cfls with an electric heater.

Joel Gagnon

When CFLs first came out, I immediately put them into my rarely used locations around the house since it was in these rooms or places that a light accidently left on could stay that way for days or weeks. In my mind, energy savings to be made by CFLs were greatest in these rarely used locations.

Bernie Masters

Good point. I had forgotten about the risk of leaving such lights on since I installed switches with pilot lights years ago to solve this problem. If you are one of the people who finds yourself forgetting to turn lights off in rarely-used places, cfls would be a better bet than incandescents, but installing those indicator switches would be better still. I got an off-list reply from Dan that I think is worth sharing on this point as well. He noted that cfls do not cope well with either high or low temperatures, which shorten lamp life. Ditto with frequent cycling, especially with only brief on times, such as in closets and pantries. My own experience has been that cfls have a much shortened lamp life when used in enclosed fixtures -- but they are getting better. I wish someone would objectively rate lamp life based on "severe use" scenarios and post the information. Of course, lamp life is now so long that such testing would itself take quite a while!

Joel

Out of the twenty or so CFL's I've installed in my house, two failed early in their use cycle, due, I suspect, to ballast failure. Does anyone know what the "cause of death" of a CFL is after it's been on for its allotted 10,000 hours (or 8,000 or 5,000 - I've noticed that different bulbs are rated differently, although all promise lots of money saved).

Thx!
Adam

From a High School Science Teacher's best friend: the Mythbusters. (I'm sure it'd be relatively easy to recreate the second part of this experiment to calculate bulb longevity under those 'severe' conditions. Anyone know if it's been done, or should I ask a local High School teacher to do it?)

Lights On or Off Myth:

You save on energy bills by leaving lights on. Some people believe that the energy to turn on lights exceeds savings of turning lights off. They talked to Mark Reisfelt, manager of the Independent Electric Supply where they purchased their light bulbs. He felt that it was best to turn the lights off. To test the myth, they needed to measure energy usage during startup, maintenance (steady state), and shutdown. For steady state energy consumption, they turned on several different types of bulbs for 60 minutes and measured their consumption using a Kill A Watt : *Incandescent 90 Wh *Compact Fluorescent (CFL): 10 Wh *Halogen: 70 Wh *Metal halide 60 Wh *LED: 1 Wh *Fluorescent: 10 Wh For startup energy consumption, Grant hooked up an inductive current loop to a computer and measured the amount of energy used when the turned on the bulbs. With an inductive current loop, you run a wire through the center, which induces a current in the loop. This current is then measured by a digital sampling oscilloscope. Based on the amount of energy consumed turning on the bulb, they were able calculated how long the bulb would have to be turned off in order to make it worth the energy savings, i.e. "It's best to turn off the bulb if you are leaving the room for": *Incandescent: 0.36 seconds *CFL: 0.015 seconds *Halogen: .51 seconds *LED: 1.28 seconds *Fluorescent: 23.3 seconds

In other words, its almost always best to turn the bulb off. Even the 23 seconds for the fluorescent lights isn't very long, and the rest of the times are pretty much blinks of an eye.

Bulb Longevity

They tested one final element of this myth: frequently turning lights on and off decreases their life span, thus leading to greater costs. Grant setup a timer and relay to turn the bulbs on and off repeatedly every 2 minutes. After six weeks, only the LED bulb was still working. Based on this test, they extrapolated that it would take five years of ordinary usage to cause the bulbs to burn out. (Source: http://kwc.org/mythbusters/2006/12/episode_69_22000_foot_fall_lig.html)

Mary Morse

Associate Environmental Services Specialist
City of San Jose Watershed Protection
170 W. San Carlos Street,
San Jose CA 95113
phone: 408-277-2767
fax 408-277-5775
are you water aware?

This is very good information, Mary. Thanks for sharing it. Of course, it is in the nature of scientific inquiry that the answer to one question raises several more questions to pursue. The longevity test in particular suggests several follow-up questions. Notice that after 6 weeks (that is 1008 hours) all but the LED lights had failed. 1000 hours is the expected lifespan of most incandescents, but way shy of the expected lifespan of cfls. We can't tell from the reported information whether the incandescents quit early in that period relative to the cfls or not. My guess is that their life was shortened significantly as well, but whether the shortening is proportional isn't apparent. Here then is the question: Is the life of a cfl shortened more than the life of an incandescent by short cycling? The answer may depend on the length of the cycle and, as Barry Hooper pointed out, the manufacturer, making the answer less than straightforward, but investigations would help us gain insight into how best to treat cfls to minimize life-shortening and maximize energy efficiency. cfls are more expensive to produce and purchase. I expect they take more energy to produce as well. If their lifespan is seriously shortened by frequently turning them off and on, at some point it makes no sense to use them instead of an incandescent. The more insight we can gain into where the tradeoff point lies, the more confident we can be in advocating what we believe to be more sustainable behavior.

Joel Gagnon

Hi all,

According to ENERGY STAR specifications, CFL ballasts are designed to last for one on/off cycle for every two hours of life (http://energystar.gov/ia/partners/product_specs/program_reqs/cfls_prog_req.pdf ). Given a 10,000 hour lifespan, the ballast should last for 5,000 on/off cycles (10,000 hours/2 hours). The Mythbusters experiment included one on/off cycle every two minutes. Over a six week period, this would be over 30,000 on/off cycles (60/2*24*7*6). If the CFL lasted a week under the experiment conditions, the ballast would have lasted for 10,000 hours of operating time under "normal" conditions.

Gareth

Gareth Clarke
BC Hydro Power Smart -
Residential Marketing
Suite #900 4555 Kingsway,
Burnaby, BC, V5H 4T8
P: 604 453-6392
C: 604 725-2759
F: 604 453-6505
E: [email protected]