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Do Compact Fluorescent Bulbs really make a difference in your energy usage and cost?

An article by Plainsboro.COM owner Kennedy Lemke
September, 2009



Update: 12/8/2009: Today a CF bulb that I installed just a few months ago burned out. This is the second CF bulb that has stopped functioning for me in the space of just a few months. Both of these bulbs were GE 13-watt (replaces 60-watt) CF bulbs from the same 8-pack that I purchased from Sam's Club sometime in 2008, and both of the two that burned out had been installed in the same light bulb socket in a fixture in my hallway.

Now the question is, since these bulbs are labelled as being "5-year" bulbs, rated for a life of 8000 hours, why have two of them burned out within the first 12 months or so of purchase? Since they both burned out in the same socket in my home, I therefore tend to think that the socket is more to blame than the light bulbs themselves. However, my limited electrical experience makes it difficult for me to believe that a particular socket could be responsible for causing CF bulbs to malfunction so quickly after installation. If anyone has a theory about this, please contact me. In the meantime I'll likely install a non-CF bulb in that socket for now.

I don't particularly mind from an expense point of view that two of these bulbs have burned out so quickly. But what does tick me off is that even though they are light-duty bulbs, they're advertised to last at least 20 times as long as they actually did last. And it's also a bit of a pain in the butt to have to replace them since it requires using a ladder, and having to carefully remove and replace a delicate glass fixture.


The quick answer to whether or not Compact Flourescent Bulbs can really make a difference in energy usage and cost is "Yes", and I will describe my evidence of this in this brief article.

I moved into a newly-built house in April of 2006, so as of the time I'm writing this, I've been here about three and a half years. For the first year or so in my house, I wasn't really paying too much attention to my energy usage and thus, for example, all of my light bulbs were incandescent bulbs (the kind we have used for over a century). I had been aware of electricity usage issues all my life, so it had already been ingrained into my psyche to do things like turn off lights and appliances when not in use, and I've always done this as long as I can remember.

Of course the past few years have really brought energy consumption to the forefront of our national attention, and as such plenty of articles and news stories have focused on what we as consumers can do to reduce our energy usage. Many of the stories suggested purchasing and using "compact fluorescent" light bulbs as a quick and easy way to immediately reduce electricity usage. Compact fluorescents bulbs are fluorescent, but they work in "regular" light bulb sockets.

I didn't investigate these new bulbs too much other than to note that the packaging would indicate that the bulbs would cast as much light as incandescent bulbs, but would only use about a quarter of the electricity.

So over the course of a couple years I heeded the advice of these stories and, I gradually replaced many of the incandescent light bulbs in my home. I started with the bulbs I used most frequently, the main floor lamp in my living room, my bed's night light, and the bulbs in my garage. Over time, I'd pick up various sizes and styles of CF bulbs whenever I visited discount stores like Sam's Club or Walmart. As of September 2009, I have replaced 27 of the 47 light bulbs in my home with CF bulbs.

My electricity provider in Wyoming is Rocky Mountain Power. One of the features of their billing procedure is that they track your average daily electricity usage, and over time they give you a graph of this data for the previous 13 months. I recently collected enough of my bills with these graphs on them so that I could plot the past three and a half years (40 months), and I came up with this graph of my average daily electricity usage:

Chart showing my daily kilowatthour usage for the past 40 months

It doesn't take a math whiz to look at this graph and see a trend toward lower usage. At the beginning of my time in my house, I would average 12 or 13 Kilowatt hours of electricity usage with an occasional month of 14. But recently my daily averages have dropped to 10 or 11 Kwh's.

In fact, what I did is I averaged my daily usage over the first 12 months living in my house and compared that to the past 12 months. What I found is that for the first 12 months my average daily Kwh usage was 12.83 Kwh's, and for the most recent 12 months (September 2008 through August 2009), I have averaged 10.58 Kwh's of electricity usage per day. That's a difference of 2.25 Kwh's per day, or a reduction of about 17.5%. In real dollars, this adds up to a savings of between $32.00 to $81.00 per year depending on how you calculate the price of a Kwh. I have very likely already paid for all the CF light bulbs I have purchased over the past couple years, and this is an annual savings I will continue to enjoy as long as I continue to use CF light bulbs.

One important question to ask is whether or not the decrease in average daily Kwh usage is due exclusively to replacing incandescent bulbs with CF's, or whether there might be another explanation. The answer to this is that as far as I can remember, my electricity usage is about the same today as it was 3.5 years ago in terms of my major appliances (have not replaced any). So my conclusion is that the savings I have achieved can be attributed almost exclusively to replacing incandescent bulbs with CF's.

Not everything about Compact Fluorescent Light Bulbs is perfect. In fact, here are a few items that are on the negative side of using CF's:

  • When you first turn on a CF bulb, some light comes on immediately, but not 100% of the light capacity of the bulb. In fact, depending mostly on the temperature of the surrounding air, a CF can take up to 2 minutes to light to its full capacity. At first this is rather distracting, but you get used to it over time.

  • CF's contain a small amount of mercury (I've heard about 5 milligrams). Therefore you need to be more careful not to break them and release the mercury into the environment. If you do break one and the detritus ends up all over your house you may need to have an expensive mercury cleanup done. (I broke a CF bulb once, but it was entirely contained in a light fixture so I did no cleanup.) And, because of the mercury, burned out or broken CF bulbs should be taken to a recycling center, not dumped in the garbage.

Conclusion: Despite these few potential negatives, the answer is "Yes", simply replacing incandescent bulbs with CF's will produce real savings in electricity costs over time.