Should I Replace My Light Bulbs With Compact Fluorescent Lamps (CFLs) Today, Or Wait Until They Burn Out?
When doing household financial calculations, the math is easy.
It is the assumptions behind the math where people differ.
Take the question, "Should I Replace My Light Bulbs With Compact Fluorescent Lamps (CFLs) Today, Or Wait Until They Burn Out?"
On one hand, you have the waste-not, want-not crowd. You paid good money for the old bulbs, so you lose money by replacing them early. But after playing with the light bulb comparison calculator at MilkYourMoney, I’m thinking every day of keeping the old bulbs is a false economy.
So… what numbers are relevant?
The most obvious is the ongoing monthly cost of electricity. With 30 bulbs, the average savings from switching are around $20 per month. (Less if you live in the Midwest. More if you live in the Northeast. Ignore for now…)
Then there is the issue of replacement costs. At $1.34 per bulb, the old batch cost $40. At $2.98 per bulb, the new batch would cost $90 (rounded).
Now how to make sense of these costs to arrive at a solution?
First, the cost of the old batch of bulbs is sunk and irrelevant.
However, their remaining life could delay the expense of new bulbs.
Average lifespan of old bulbs = 300 days, new bulbs = 2,000 days
If the old bulbs are half-used, they save 150 days of new bulb cost. Whereas 150 days of old bulbs was "worth" (i.e. cost) $20, it only translates to $6.70 worth of new bulbs, which cost more but last longer.
Overall, 5 more months of the old bulbs will delay $6.70 in hardware expense, but cost $100 in extra energy usage. Looks like I should switch the remaining incandescents with CFL (ASAP!) unless someone can overturn these calculations…
(That raises the issue of what to do with the old bulbs. I might offer them to a neighbor. It seems weird to offer the gift of energy inefficiency. However, if they use old bulbs with no intention of switching anytime soon, it is still a savings, right?)
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$20 a month savings seems high to me. I don’t have that many bulbs in my house, but I recently switched the majority to CFLs and have not noticed a difference. I waited for the old ones to burn out. I expect more savings from not having to buy new bulbs all the time and the convenience of not having to replace them. It also feels good to know I am doing something to save energy in my drafty old house.
I recently replaced some burnt out bulbs with CFLs and now I thumb my nose at everyone else who uses the antiquated, energy hogging old bulbs. Ok, just kidding. Maybe.
I suggest buying a package of the CFLs and replace the bulbs in the most frequently used lights (burnt out or not). This is where you will get the most savings. Replacing a bulb in a closet or hallway won’t pay for itself in decades. Save the still-good old bulbs and use them in less used areas until they are all burnt out and replaced with CFLs.
If you live in an apartment or rental, save all the old bulbs (burnt out or not) and replace all the CFLs when you move out. You don’t want to give the next tenant a freebie.
@SeeMyMoney - like you, I have already changed the majority of bulbs, and have not seen the full $20 per month. Although these days it is refreshing to see any decrease in utilities, even $8 to $12. Surprised by $0… although eventually I may end up there, too… the utilities company sent a letter saying they want to raise rates by roughly the amount of the CFL savings.
@Hondo - good call. I stopped short of changing lights in the basement, for now.
Wait - this is the age of make do and mend. It seems from anecdotal evidence that the savings are overestimated so keep the cost of changing in your pocket until it is absolutely necessary.
@Uncommonadvice - thanks for the different viewpoint.
The spreadsheet might be aggressive in its assumptions, but I don’t think that makes the actual savings any less real. If you use less energy, it must pass through to savings, right? Even if obscured by rising rates, seasonality, etc.
re: “make do and mend” — that is a good point, we do not want to squander resources. And I try to do that with most products, when replacements are a net-drain on resources. But here we can conserve one of two ways: materials for bulbs vs. energy at power plants. I guess what I’m trying to say… does “make do and mend” apply to our energy, the same as physical products?
I’ve been thinking a lot about this one myself - my only problem is that most of my fixtures have unusual light bulbs (floods, dimmers, candelabras) so the CFLs are expensive. I am working on replacing them all though!
Quality of CFL bulbs is an issue that can affect the calculations. Please see below an article we did a while back based on our experience:
http://www.onefamilysblog.com/2008/05/feit-electric-energy-saving-bulbs.html
Regards,
ofb
We bought our CFLs in packages of 8, on sale, for $8.59 per package. We replaced all the bulbs in our home, and we notice a savings of about $18 a month during the winter (when we use the lights more) and $7-$10 per month in the summer, when we rely on natural lighting more — of course the occasional times we fire up the AC negates those savings…
Anyway, I have found CFLs worth the effort. And we do enjoy the intangible warm fuzzies that we get as well.
My decision re: CFLs is based in part on the size of the carbon footprint from the power plants as much as it is the savings. In the big picture it is savings for all of us.
Frugal is not cheap, rather judicious in my mind.
I do the change to CFL one package at a time. So the ceiling fan has 3 incandescent bulbs and I bought one CFL each month (that is what fit my budget) and changed all of the bulbs for that fan. Working one room at a time.
Any old bulbs with life left are put in a box for two purposes: emergency replacements and giveaways. Often there are churches or other groups that provide housing or goods for people whose homes are burned out or who just need a helping hand.
For the most part, I think the old bulbs are a sunk cost like you do. (Unless you plan on reselling used bulbs on Craiglist or something.)
However, I still keep my old bulbs. You might run out one day, or there are some applications where incandescents work better. (In high vibration environments, I’ve found CFLs crack/break very fast.)
As someone who sells light bulbs for a living, I am constantly bombarded with questions about how much energy is actually being saved by using compact fluorescents and whether they live up to all of the hype that they receive. It seems to me that a lot of the negative things said about incandescent bulbs and their energy usage is borne out of a poor understanding of basic physics. The law of conservation of energy states that energy cannot be created or destroyed, just changed from one form to another. So many people speak of incandescent bulbs “wasting” energy as though they are defying the laws of physics and destroying energy. I live in a fairly cool climate and during the winter I use an electric heater to heat the particular room that I am in. If I use an incandescent bulb and 90% of its energy usage is for the production of heat, then it is simply generating heat that I would have to generate anyway with my 1000W heater. It’s June here and we are still dealing with cold and rainy weather, so there is a significant portion of the year where the heat energy produced by incandescent bulbs indoors is useful and not “wasted.” For me, it is an obvious choice given the mercury content and poor light quality that comes from compact fluorescents.