We all know the general idea “compact florescent bulbs may cost more than traditional incandescent bulbs but they will last way longer and use less energy.”
That may be true but let’s get down with the numbers and find out how and how much more efficient compact florescent bulbs are than incandescent. While we’re at it we’ll also what other differences are there between compact florescent bulbs and incandescent bulbs?
When you buy a light bulb we often equate wattage to the amount of light omitted.
That would be **wrong**! Wattage is the amount of electricity used while lumen is the unit of measurement used when referring to the amount of light flow or luminous flux. Let’s compare lumens to wattage in both incandescent and compact florescent bulbs.
| Lumens | Incandescent | Compact Florescent |
|---|---|---|
| >450 | 40 watts | 14 watts |
| >800 | 60 watts | 15 watts |
| >1,100 | 75 watts | 20 watts |
| >1,600 | 100 watts | 28 watts |
| >2,600 | 150 watts | 40 watts |
To achieve the same amount to light (lumens) as a compact florescent bulb an incandescent uses between 3-4 times the amount of electricity. To really drive that idea home let’s chart out the difference between the two kinds of bulbs.
##Chart: 6 Hours a Day##
Assuming a bulb is run 6 hours a day for calculating daily watt hour usage
##Chart: 365 Days a Year##
Converting that to kilowatt hour (1 watt hour = 0.001 kilowatt hours) usage over the course of a year assuming those bulbs are on 6 hours a day 365 days a year.
Over the course of a year switching just one 60 watt light bulb that is on 6 hours a day, 365 days a year from incandescent to compact fluorescent would take that bulb’s kilowatt hour usage from 131 kWh to 33 kWh. That’s a savings of 98 kWh which with electric charges at an average of $0.19 / kWh would save almost $20/year per bulb. Using a conversion factor of 0.537[^1] that change of one bulb saves 53kgCo2 / year.
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##Differences in Use##
Now that we know more about how the different kinds of bulbs add up electrically and mathematically let’s compare some other details about the bulbs to help you weigh the decision between compact florescent and incandescent bulb usage for your lifestyle.
| Compact Florescent Bulbs | Incandescent Bulbs | |
|---|---|---|
| Dimmers | Must buy a special compact florescent bulb to work with a dimmer switch, which are on average $13 ea. | Can be used in a dimmer without problem |
| Cost | 4 pack of 60W – $8 avg. | 4 pack of 60W – $3 avg. |
| 3-Way Lamps | Must buy a special compact florescent bulb to work in a 3 way lamp which are on average $11 ea. | Must buy a special incandescent bulb to work in a 3 way lamp which are on average $3 ea. |
| Lifespan | 60W equivalent lasts 8000 hours avg. | 60W lasts 750-1000 hours avg. |
| Disposal | Must be disposed of properly since it contain mercury in concentrations that exceed the toxicity characteristic leaching procedure’s (TCLP) limit | Must be disposed of properly since bulbs contain lead at levels that exceed hazardous waste limits |
| Recessed lighting | They cannot be used in recessed lighting enclosures or enclosed globes | Can be used in recessed lighting of globe enclosures |
##Learn more##
* [Safe removal of broken CF bulbs – consumerreports.com](http://www.consumerreports.org/cro/home-garden/home-improvement/hardware-building-supplies/lightbulbs/compact-fluorescent-lighting-10-07/safe-removal-of-broken-cfls/bulbs-safe.htm)
* [General Electric Lighting Compact florescent FAQ](http://www.gelighting.com/na/home_lighting/ask_us/faq_compact.htm#dimmer)
* [Dane County Wisconsin DPW](http://www.countyofdane.com/pwht/recycle/lamps_bulbs.aspx)
* [EPA Provides information about Mercury](http://www.epa.gov/mercury/)
* [Department for Environment, Food and Rural Affairs: Conversion Factors](http://www.defra.gov.uk/environment/business/envrp/conversion-factors.htm)
[^1]: [Simple Carbon Calculator](http://www.nef.org.uk/greencompany/co2calculator.htm) from the UK National Energy Foundation