Compact Fluorescent Bulbs Pay Off Handsomely


Typical compact
fluorescent bulb.

Over the past two years, I have gradually replaced most my light bulbs with compact fluorescent bulbs.

Many claim these bulbs save a ton of money, but they cost a lot. Try $8 for a new compact fluorescent bulb that is equivalent to a $0.50 100W incandescent. Do they really pay off?

Here’s the math:

Bulb Type Incandescent Compact Fluorescent
Wattage 100 27
Bulb lifetime 1500 10000
Initial cost $0.50 $8
Cost per hour of usage $0.00874 $0.00080
Cost per year of typical usage $25.53 $2.34

Two assumptions using this math:

  1. Electricity costs $0.0841 per kWh, which is the 1998-2003 average according to the US Department of Energy (link).
  2. “typical usage” is 8 hours a day: 2 hours in the morning and 6 hours at night.

Regardless of one’s typical usage, it is abundantly clear that, even after accounting for the initial cost, compact fluorescent bulbs overall cost about a tenth to run as traditional bulbs. Most of this is due to their lower energy usage, but part is due to their dramatically increased life span.

90% of the energy consumed by incandescent bulbs are kicked off as heat. This calculation does not catch two things related to that:

  1. If you live in a warm climate, you run the A/C far more than you run the heater. If you create more heat in the house, guess what happens to your electricity bills? They go up because you have to use the A/C even more.
  2. Even if you live in a cold climate–where you run the heat far more than A/C–you are still better off running compact fluorescents unless you have a house exclusively heated by electricity. Gas/propane/oil heating cheaper than electric heat, so while the incandescent bulbs could slightly reduce central heater utilization, you are effectively supplementing a “cheaper to operate” heater with a more expensive one.

CF bulbs have even more advantages. By reducing demand, they can extend the usable life of lower capacity electrical systems that are common in older houses. Thanks to lower heat output, they are safer, especially in lamps or in older houses where certain exposed light fixtures are installed in locations where they wouldn’t be allowed today.

Compact fluorescent bulbs definitely pay off!

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