Lighting Cost Comparison - Incandescent vs. CFL

***Update - 10/4/09 - I have an improving lighting cost comparison that includes a lighting calculator and includes a residential LED bulb.  See the incandescent, CFL, and LED lighting cost comparison and calculator.

In the last few months I've heard this statement twice: "I want to conserve energy. I plan on changing out my incandescent bulbs to CFLs as soon as they burn out."

While thinking of CFLs is a great start, there is no need to wait until your old bulbs burn out.  If you do a life-cycle analysis (which I have done below) it makes much more sense to replace the incandescent bulbs immediately!  This is not just from a "save the Earth" perspective, but especially a cost savings one.

Based on the cost of electricity at .09 cents/kwh, a regular old 60 watt light bulb would cost you $10.80 over its 2,000 hr life.  The 14 watt CFL equivalent's electricity cost would only be $2.34 over the same 2,000 hrs (plus the CFL will last another 4,000 hrs after that)!   The only way it would not make sense for you to immediately change that old bulb is if the CFL cost  $8.46 or more, which I can assure you they don't ( I get mine for around $1.50 a pop).  So what are you waiting for?

The figure below displays 3 different scenarios for a 10-year lighting analysis.  The light is assumed to stay on for 4 hours a day, 365 days/year, for 10 years.  The first case is all incandescent, the second case is all CFL, and the third case is you replace the incandescent after it burns out, and use CFLs after that.  As you can see, immediately replacing the regular bulbs with CFLs provides the best payback!

-click on the thumbnail below, then move it around the screen if necessary


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I agree completely about emissions, in fact that is the point I make on that website... Basically, Markets can deal with energy depletion since the price rises anyway and encourages switching to renewable or (long-lasting) nuclear energy I have taken out the emission section on my site cause I am rewriting it in view of the current House Bill, but the main point is that markets can't deal with emissions because there is no incentive to cut back on them - cap and trade is a (wrongly) artificial; way to create a market in them. So political intervention is certainly necessary, if we accept the climate change problem(what used to be called "global warming" except it sounded too good!). That's why direct action via renewable energy development and spread in new grid systems as well as CCS (carbon capture and storage, ie put simply "cleaning up coal") solutions should be explored. That's dealing with the problem. Banning inefficient products (via efficiency legislation) is not. Does your light bulb give out any gases? There you go! In fact, any consumption cutback -if really needed- is achieved by fossil fuel price rise with mitigating action for consumers as explained, and/or efficiency based product taxation giving the double whammy of lowering related emissions and of funding emission reduction more than remaining product use causes them. Taxation is still not a good idea for many reasons but it is better for all concerned -and for emission reduction- than bans, if direct action (emission-free energy spread / CCS solutions) is felt to take too long.
...continued... (think there's a spam block on links, understandable enough!) "If it is just saving money then the CFL is the hands down winner." No, that's not true, the power factor argument alone (as discussed on other lighting posts here) halves the advantage, added to lifespan issues etc as on, heat factor as discussed is in several studies in temperate climates halving the advantage again, and so on... cutting dowwn the advantage all the time. Typically 3% of total energy usage is saved by a switchover of all lights hardly a hands down reason for a switch - I have no reason to favour one figure over another, but so many sources question the "status quo" that it at least should be open to question ...continued....
Re "Peter, thanks for the comment, but I was merely doing the cost analysis from a consumer standpoint, not a life-cycle analysis from an environmental standpoint." Well, if you did read onwards it's clearly from a consumer standpoint, including why the savings arguments don't hold up. Lifecycle only starts at ! ....continued.....
...continued.... Many like yourself see it as a challenge to save energy, fair enough - and interesting site here too, just exploring it more now -as long as it's an individual decision by the paying consumer, not subject to regulation by politicians... Society doesn't need to force people to save: See the "Why all energy efficiency regulation is wrong" from onwards and summary of why light bulb bans are wrong In short, energy supply is not a problem, emissions can be dealt with directly as described on the website (light bulbs don't give out any gases!) and consumers can consider cost savings against all the <b>usage advantages</b> that inefficient products have, or noone would buy them...
Peter, I'm getting ready to go to the Pub (by the way, isn't it pretty late in Ireland right now), so I'll have to give you a more detailed analysis later, but one point: You say society doesn't need to force people to save, but I dont know that this is true. Society doesn't pay the true cost of Electricity because externalities are not taken into account. Does the power company pay for the Emissions that I have to breathe in? Does the power company pay for the mountain that was destroyed to get at the precious coal? Society pays for these externalities, not the power company, so the true cost is not passed on to the user. This is the argument for Energy Efficiency Regulation. But, I will say that I am generally against forcing people to buy CFLs....
I did not know that I was questioning your statements but rather I felt I was contributing further knowledge. As to the rightness of my comments I am sure that wherever you have an incandescent bulb shining on your body, that radiant heat is superior to almost any other kind for keeping you comfortably warm at the lowest temperature. This is why heat lamps work so well in the bath, and why even small fake electric fireplaces close to you body allows you to turn down the central heating system. I am always colder than my wife and if I do something like this I can turn down the temperature at least 1 degree and still feel comfortable. Comfort is not a point on a graph. It is a complex set of relationships, including activity, air temperature and humidity, temperature of surfaces in the room, method of delivering heating, air movemenmt, and your own preferences. Of course CFLs are better in all locations in a warmer climate, since they do not add heat. I replace my incandescent bulb with a CFL in the summer. I go back to incandescent in winter. I love studies by Rocky Moiuntyain Institute but I think they would tell you I was correct for my individual case , which is what we all have to be to really save energy. I just believe that if we think for ourselves we will save a lot more than trying to met some average or most often situation. I will always learn from brilliant people like Amory Lovins , but I can hardly expect him to design the best system for me. So when I tweak my own system a little I do it because I am sure, from 60 years of living on this earth and having a fascination with efficient heating systems for the last 30 years, of my decision.
Ed, I will concede that incandescents do help heating in the winter, but they also help heating in the summer, which most people don't want! I would like to see if Rocky Mountain Institute or any of the other organizations have done an analysis comparing which saves more energy: using incandescents in winter (helping use less heat) and CFLs all other times, or just using all CFLs. I'm sure this depends on which region of the country you are in, but it would be nice to see several different scenarios.
The scenarios ignored one thing. How are you heating? If like many people it is winter and you are using electric baseboard heating, the lighting energy use is just part of the heat delivered to your home. I personally believe the radiant heat from an incandescent light is more efficient at warming my body than the convected heat of baseboard heat. I have replaced almost all my incandescents with CFLs but I keep the one next to my reading, tv watching, computer using chair, an incandescent. I also have began to replace some CFLs with solar powered LEDs that I assemble from solar garden lights, leaving the solar panel outside and bulbs inside connected by long wire. I also have installed a switch so these are on only when I want. This appears to work well, and avoids a lot of the mercury waste of the CFLs, CFLs are great when applied [properly but daylighting and LEDs are the true energy champios we need to embrace.


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