And Let There Be More Light For Less Money: Save Money On Light Bulbs

by golbguru on November 13, 2006

For many years I have been using those “soft white” bulbs that never seemed to give anything else than “dull yellow” light. The only reason I bought them was they were really cheap at Walmart….ok one more reason was that I was too lazy to check out those other lights on the aisle..and never made any kind of comparison.

I have finally managed to put some numbers to the cost of light from at least two different types of light bulbs. The results (along with some general knowledge stuff) are explained below. Make sure you understand the costs on the graphs below.

20W, 40W, 60W, or 100W? Which bulb will give me more light?
-Ok, first of all, that is a wrong question. The ‘W’ stands for “Watt” (after James Watt of the steam engine fame), which is a unit of energy consumption. It does not tell you how much “light” a light bulb will give you. It just tells you how much it will cost you to use the light bulb.

So how do I figure out which bulb will give me more light?
-Look for the value under the word “Lumen” or “Lumens”. Lumen is a measure of light intensity or light output. Higher Lumens value implies brighter light. This value is very clearly displayed on all light bulb packages. See the image below.

So what is the right way to choose a light bulb?
This is in fact written on most packages as something like this: “To save energy costs, find the bulb with the light output you need, then choose the one with the lowest watts”. Here is an image showing where this is typically displayed:

60Wlightbulb-1 saving-tips

What kind of bulbs will give me more Lumens for less Watts?
This is a no brainer. Compact fluorescent (CF) lights (yeah those spiral ones) give a lot more light for much less wattage. Typically a 15W CF light is equivalent to a 60W regular light, a 26W CF light is equivalent to 100W regular light. When I say equivalent, I mean “gives almost the same Lumens value”.

[Image of a lit CF bulb; source:]

But CF bulbs are damn expensive! aren’t they?
Yeah that’s what I thought, until I ran the numbers myself. In the graph below, I have compared the cost of using a regular bulb against a CF bulb. These calculations are based on a 15W CF bulb (900 Lumens) and a 60W regular bulb (850 Lumens). I am assuming a 4 hour per day use and 10 cents per kWh (kilo Watt hour). I have assumed the cost of the 15W CF bulb to be $5.58 and the cost of the 60W regular bulb to be $0.615 (yeah 61.5 cents). The buying cost of the bulb is reflected in the “year 0″ in the graph. One bulb of each kind is compared:

costsavings-1 saving-tips

The graph shows that you will save about $2.13 per year per bulb by using the CF type bulb. If you have about 15 bulbs in your house, you will save about $31.95 per year. The step in the graph for the regular bulb between months 8 and 9 is because the bulb reached it’s rated life (usually 1400 hours) during that time and a regular replacement bulb was needed which resulted in additional costs. The rated life of most CF bulbs is about 8000 hours so you don’t need to change them for about 5~6 years.

Things become really dramatic when you consider the cost of using 15 bulbs over a period of 5 years. This is shown in the graph below:

costsavings-2 saving-tips

For this graph, I have assumed that we changed the regular bulbs every year (you may need to change them more often). In, this case you will end up saving about $480 over 5 years by using CF bulbs. In 5 years, it will be time to change your CF bulbs; but by this time you will have saved so much that this additional cost will not matter much. Also, I am pretty sure that some bulbs get used for much more than 4 hours a day and some houses have many more than just 15 light bulbs :)

Btw, those cost savings numbers on the CF bulb packaging are not too stretched out; however, they do potray slightly higher cost savings because I don’t think they include the buying cost of the CF bulb in their calculations.

The other good thing I like about these CF bulbs is their “white” light; the “soft white” or yellow light of the regular bulbs is too depressing for me now-a-days.

So what are you waiting for ! Go ahead and get those CF bulbs for your homes right now and start saving money!

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{ 28 comments… read them below or add one }

1 Frugal Frugalson 11.13.06 at 11:39 am

Around here, Lowe’s and Home Depot often have 99¢ CF bulbs that are subsidized by the local electric utilities. It’s definitely worth looking into…

CF bulbs also seem to last a long time too, since I have some that have been in service for 8+ years. That factor alone made them a great choice for my attic light that is a real PITA to change.

2 Dimes 11.13.06 at 1:23 pm

Oh CF lights are so unaesthetic, and they flicker, which you don’t notice most of the time but when you have a migraine wow do you see! I have a few for the lights I hope never burn out, but that’s about it.
Maybe the technology will improve in time, and we’ll make the switch.

3 GolbGuru 11.13.06 at 1:49 pm

frugal frugalson: man 99 cents is awesome deal for these lights. Wish they come out with something like that in our Lowe’s here.

dimes: yeah I didn’t look at them with a migraine yet :)..but “unaesthetic” ?…man I love that spirally shape, and if you look at them often, you will love it too :)

4 sun 11.13.06 at 2:38 pm

How did you calculate all the costs? I didn’t do any cost comparsion before and swithed to CF light bulbs at the time when I read on the packages that “a 26W CF light is equivalent to 100W regular” one. Now all the lights in our house are using CF bulbs. However, I guess as every other products, there are brand difference as some I bought at Costco didn’t really last that long as it promised. I lost several in less than a year.

5 GolbGuru 11.13.06 at 3:09 pm

sun: It’s strange to loose many CF bulbs in a year, because these things don’t have a filament like normal bulbs have…and hence they don’t “burn” up. I have been using a couple of CF 40W lamps for about 4 years now. The light has faded a bit over time, but none died out. Try a different supplier and see if that solves the problem.

calculation was bare minimum. here is an example:

Cost of use for one 60W regular light bulb:

Cost of bulb = $0.615

Wattage = 60 W = 0.060 kW

Number of hours per day = 4

Number of hours per month = 30 * 4 = 120

Therefore, kW-hour usage per month = 0.060*120 = 7.2 kW-hr/month

Per year usage roughly = 12 *7.2 = 86.4 kW-hr/year

Cost of electricity roughly = $0.10 per kW-hr

Therefore, cost of electricity per year = 0.10*86.4 = $8.64

Add to this the buying cost of one bulb to get: $8.64 + $0.615 = $9.255

However, this one bulb will die in about 8 months since it is rated only for about 1000 hrs. So you will need to buy another regular bulb at this time which will cost another $0.615.

Hence, total cost per year = $9.215 + $0.615= $9.87

If you have 15 places in your house where you use such bulbs, multiply this by 15 to get $148.05 as the total cost.

Similar calculations were done for the CF bulb and the difference was displayed as savings. :)

6 mapgirl 11.14.06 at 7:51 am

Hi! I got your message. Email me at mapgirlsfiscalchallenge at gmail’s mail service and we can talk some more about migration. Thanks! m.

7 nku 11.14.06 at 10:45 am

I agree. The Phillips CF bulb that I replaced in my bedroom last year is still burning (metaphorically), and the regular GE bulbs in the living room need replacement once in 3/4 months. But lot of people go for low initial investment, especially those desi who are here for short term, say a year or so. They don’t give a damn about long term energy saving or sh*t.

♯No product placemnet was intended.

8 knowhimwell 11.14.06 at 3:09 pm

Wow, you did a lot of research on this. I wrote a post about changing lightbulbs too.


9 GolbGuru 11.14.06 at 4:20 pm

mapgirl: thanks, I will get in touch.

nku: product placement is excused :), well even for a year that CF thing is cheaper. Not to mention that it gets less hot which means less entropy (forgive the engineering term).

knowhimwell: thanks for the link. I am glad this topic is being blogged about.

10 Super Saver 11.14.06 at 5:16 pm

Another great mathematical analysis of a personal finance tip. I didn’t realize the savings could be that high.

11 jagular 11.15.06 at 10:53 am

My name is Jagular and I wholeheartedly endorse this event or product.

12 knowhimwell 11.15.06 at 1:49 pm

golbguru: I think I found your blog by clicking on a blog carnival application. Could that be it? LMK, I am interested in a carnival. We have two carnivals that we are accepting applications for. One is on thanksgiving & recipes, another is on healthy families. I couldn’t find a place on your site to email all this info to you. That’s why I put it in a comment. Great site!


13 GolbGuru 11.15.06 at 6:40 pm

knowhimwell: thanks for the info. :)

14 Sun 11.16.06 at 9:24 pm

That’s an excellent explanation! It’s amazing that you put so much efforts in such a small thing as calculating the costs of a light bulb.

15 Golbguru 11.17.06 at 9:46 am

Sun: it didn’t take much time :) I am anyways working with Excel all the time …so just putting in a few different numbers is easy :)

16 Lisa 11.24.06 at 9:00 am

We have made the switch to the CF bulbs, and am looking forward to the savings that will appear on the electric bill. The lights do flicker a bit but after they warm up they are good to go.

17 John Daltrey 04.12.07 at 10:33 pm

I visited a neighbors house a month ago and immediately commented on how nice their lighting colors looked. They told me their entire house was retrofitted with screw in compact fluorescents in full spectrum color. They were using 20 watt bulbs in sockets I was using 100 watts all over my house. Amazing. I felt uneducated and humiliated. I took their recommendation and now my house has these cfl bulbs in every socket. I bought at bulborama, highly recommended, they have a website too -

I have to believe in the near future all homes will have cfl’s. I can’t imagine standard light bulbs surviving much longer, too much energy and money can be saved.

18 Daryn 04.25.07 at 5:11 pm

I tried these bulbs. The color is horrible and completely unacceptable. It casts a green hue over everything and the color doesn’t even come close to bulbs like the GE Reveal.

How about simply turning off your lights when not in use? Or putting motion senors in your sockets.

My CF bulbs have been relegated to the garage and back porch.

19 David 04.27.07 at 1:05 am

Please also tell everyone that Compact Flourescents have quite a bit of mercury (powder) in them. If they should break, which they easily can, one should be very careful to avoid the powder/mercury and how to go about cleaning them up (don’t use a vacuum).

This is a major drawback of CF bulbs, that makes L.E.D. bulbs much more appealing, should they eventually be able to compete with CF bulbs in light output.

20 Yama 05.27.07 at 11:28 am

Just to let you guys know that even-though CF bulb have a long lifespan but in general after 2+ years or so the light quality is kinda degraded. CF might be something new in the US (not exactly, I believe it’s been around a lot longer than that just that no one ever pay attention to it.) I have been using CF for ~ 12-15 years.

21 Tom 06.29.07 at 8:31 am

I am a fan of CF through and through. At my office, we have a light that remains on 24/7. After replacing an incan bulb every 3 weeks here at my office I decided to buy a CF and give it a try. I paid $8.37 for a 19w CF (1,100 lumens/75w equivalent). The box stated that it would run for 10,000 hours so I saved the box and receipt expecting to get a refund. Well, it has been running ever since 5/6/2003 or 36,360 hours! Although I don’t have a means to test it, it does seem to have dimmed some (maybe to a 60 watt?) over time.

The newer CF bulbs are dimmable and you can buy them based on the color temperature so that you can really create moods with your CF bulbs. I learned a lot browsing on and really like their selection and layout … no, I don’t work for them! :-)

Looking forward to LED progression. Many years ago I remember reading about fiber optic lighting where a home would have one bulb for the entire house and fiber optic cables running to the rooms to transmit the light … would love to see that too.

22 jake 12.13.07 at 7:28 pm

I havn’t turned a light on for more than a minute at a time for a while now. I use lamps….talk about a savings. The best way to save money, and energy is to just not use it. My electric bill is consistently around a 150 kW-hr per month in a 2200 sq-ft house, with electric stove and dryer. The question is…what is it worth to you?

My house runs between 42 degrees and 50 degrees (F) right now and I hang dry my clothes. My total utilities (including internet) per month are under $125 (electric, water, propane, and internet). And so you know I do weld at least a couple things a month on a 200 Amp GMAW welder plugged into 220V 50 Amp circuit.

So, with that said, I am not really in this to save energy, but money. So what’s it worth to you?

23 JP 02.11.08 at 12:39 am

These new CF bulbs are great, but I am even more excited about LEDs. LEDs use 1/10 the energy of a regular bulb and last for many, many years. Right now they cost too much, but in the next 5-10 years, I bet LEDs will be everywhere.

24 shirteesdotnet 07.01.08 at 2:27 pm

Unfortunately for all of us, these bulbs are toxic and dangerous. Doing some research we find that these bulbs contain mercury, and also have a brighter white light than a regular bulb which can cause headaches (even migraines) in many people. Mercury in vaccines have, in some studies, been linked to autism.

The EPA offers a detailed, 11-step procedure you should follow.. something along the lines of: Air out the room for a quarter of an hour. Wear gloves. Double-bag the refuse. Use duct tape to lift the residue from a carpet. Don’t use a vacuum cleaner, as that will only spread the problem. The next time you vacuum the area, immediately dispose of the vacuum bag.

If we have to go through all of that… is it safe for our environment? Forget Al Gore for a second… is it safe for us? Our children?

In the future our landfills are going to be littered with glass and metal, but with plastics leeching chemicals and other more dangerous and hazardous stuff like mercury.

I was all for CF bulbs until I educated myself further.

25 Paul D 06.06.09 at 8:37 am

Great post! I used to be all about the watts, but now I’ll be checking the lumens. Cheers!

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