Random Thoughts of Chris Tilley

I read yesterday that Australia is going to phase out incandescent bulbs, replacing them with compact fluorescents, over the next three years with goal of having them eliminated by 2012. They are expecting that will reduce their CO2 emissions by 4 million tons a year. California is looking at doing something similar. With governments now stepping up to the plate and requiring energy standards on light bulbs we will see improvements. I hope other governments will follow suit.

I have been replacing incandescent light bulb with compact fluorescents for about 5 years so I was wondering how much I am saving and what the carbon savings are.

First I counted all my compact fluorescents, 24 total. Most are 13 watt replacing 60 watt. So that is what I use for the numbers. I'm not going for accuracy here just a general picture. Next I estimated that each bulb was on an average of 4 hours. So 24 bulbs * 60 watts * 4 hours * 365 equals 2102 kWh / year. I pay 6 cents/kWh so 2102 kWh * 6 cents/kWh equals $126.12 per year. The bulbs are guaranteed for 5 years this is less time than the number of hours that I used compared to 10,000 lifespan but I'm using the the lower number. So 5years * 126.12 equals $630.60. For the replacement bulbs running the same calculations we get 456kWh, $27.33/year and $136.65 for 5 years.

The carbon calculations are derived from the website Environmentaldefense.org. They have a table that told me that for 15 watt replacing a 60 watt save between 806 and 884 lbs over the life of the bulb that they state is 15,000 hours. So I use 4 hours * 365 day for 1460 hours a year. That is 9.8% of the 15,000 hours. 9.8% of the 884lbs equals 87lbs/year/bulb. Times that by 24 bulbs and you get 2088 lbs per year or roughly 1 ton. Using the lower 806 lbs still works out roughly to 1 ton. So 5 tons over the 5 years.

So 24 60 watt incandescent bulbs replace with 13 watt compact fluorescent bulbs final results.

60 watt bulb -- 2102 kWh/year -- $126.12/year -- $630.60 over 5 years
13 watt bulb -- 456 kWh/year -- $27.33/year -- $136.65 over 5 years

Total savings over 5 years is almost $500 plus reducing CO2 emissions by 5 tons. I have not included the cost of bulbs. Compact Fluorescent cost more but last longer, plus compared to the overall saving the costs are negligible.