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Starting a new type of post here called “Do the Math”.  Everyone likes to save money and everyone likes to make good decisions, but that often involves math and most people don’t have the time or patience to do the math at the time the decision needs to be made.  On top of that, retailers know that even math nerds don’t haul around all the formulas and when they helpfully calculate for you, it’s never in equivalent amounts – one shampoo will be in cents per ounce, the next in cents per quart, another in liters (just in case you are down with imperial but don’t have a handy conversion to metric tool).  Makes me nuts.  So, I’m gonna pick something and do the math ahead of time so that I (and you) can make that call and feel GOOD about it.

First up – incandescent vs. CFL (compact fluorescent) vs. LED light bulbs.  Now, these guys have a lot of math associated with them and they also have some preference decisions (direction, time to warm up, general aesthetics, heat produced).  I’m sticking with the money numbers here.  So what you need to do the math is:

  • Cost of the bulb (I’m going to use a 65W incandescent equivalent)
  • Lifespan of the bulb (going with 24 hours per day – most aren’t on that long, but hey, it’s the number of hours in a day)
  • Cost of a Kilowatt hour (I’m using $0.11 – you may need to check your power bill if you really want to do your cost instead of a general comparison)
  • Hours in a year – 8760

I’m interested in my recessed lighting bulbs since they seem to be burned the most and stay on the longest   Plus, I’ve got a snotload of them – including four that burn constantly.  I’ll take on the “regular bulbs” and “ceiling fan bulbs” in later articles just to see if the numbers are different based on the cost of the bulbs themselves.CFL Bulb

For this post I’m using Home Depot online prices simply because they are easy to find.  Not using dimmable bulbs and I’m going to include the lumens (brightness) since well, light is what light bulbs are all about.

First the standard old school lightbulb (630 lumens).

  • Cost – $4.49/bulb (Philips DuraMax)
  • Lifespan of the bulb (2500 hours or 3.5 bulbs per year)
  • Annual energy cost – $62.64
  • Total cost/year (3.5 bulbs + energy) = 78.35


Now the CFL bulb (what I currently have) (695 lumens)

  • Cost – $3.83/bulb (Feit Electric EcoBulb)
  • Lifespan of the bulb (7665 hours or about 1.15 bulbs per year)
  • Annual energy cost – $14.48
  • Total cost/year (1.15 bulbs + energy) = $18.88

OK, that’s a bit better, but dang – those fixtures are running me nearly $80 per year! (Time to look at timers since the switches are hard to reach, LOL!)

How about the new LED bulbs? (650 lumens)

  • Cost – $15.88/bulb (eeek!) (EcoSmart)
  • Lifespan of the bulb (24966 hours or about .35 bulbs per year)
  • Annual energy cost – $9.04
  • Total cost/year (.35 bulbs + energy) = $14.59

Looks like I’d save another $16 per year per bulb (though I wouldn’t see a savings for about 15 months based on the cost of the bulbs) to go to the LED bulbs though my big gain was dumping the incandescent bulbs.  So how about a “big number”?  Let’s say you have 4 bulbs per room in a 6 room house (obviously adjust – this is just a comparison) that are on 3 hours per day.  (Total cost x 3)

  • Incandescent = $235.05
  • CFL = $151.04
  • LED = $43.77

Looks like it will be worthwhile to start investing in those LED bulbs with the only problem being the 22 year lifespan at 3 hours per day given the *much* higher cost of the bulbs themselves.  Unless you are going to be in your house for 22 years or plan to yank all those bulbs and carry them with you when you move (I may well be cheap enough to do that, LOL!), it’s gonna take a while to realize the full benefit of the cost and “the next great thing” will probably come along.  LED bulbs have dropped in price dramatically since their introduction as have CFLs.  LEDs don’t have the disposal hazards of CFLs, however.

LED BulbLooks like my strategy will be to start slowly replacing those “always on” and “hard to get to” bulbs with LEDs the same way I did with CFLs, hoping that by the time I get to replacing all the bulbs, the price of LEDs will have dropped another tier or two.  It’s also time to start talking to folks about turning out the lights (again).

Summary – if you are still using incandescent bulbs, you are pretty well tossing money away.  CFL bulbs are hazardous waste (bad) but a lot cheaper and last much longer (good).  LED bulbs are not hazardous waste (good), last waaay longer at lower cost but cost substantially more to buy (meaning that it may take a long time to realize the return on mass replacement).

Update:  Today I purchased 7 LED bulbs (4 40W recessed track lights for the 2 display cabinets, 2 flames for the back hall sconces and 1 standard for my bedside table light since I regularly fall asleep with it on and forget to turn it off in the morning) for “always on” lights at a total cost of $101.79.  This changes the numbers just a little as the total was $10 less than the sample bulbs I used in my calculations.  The “always on” cost for the bulbs plus the electric for a year is $165.07 (hence the next purchase of timers) or $13.75/mo.  To run CFLs in those for a year, the cost would be $132.16 (bulb plus energy cost) or 11.03/mo.  The LED bulbs will be paid for in savings at 14 months, leaving me with 31 months of bulb life.   The monthly pure energy savings for 7 bulbs for 31 months will be $3.17/month for a total of $98.27 in savings over the life of the bulbs.  Not too shabby for replacing 7 light bulbs.