It’s hard to gauge the true cost of compact fluorescent lamps (CFLs) because of the incentive subsidies currently being offered by utilities, but suffice it to say that a CFL generally costs significantly more to manufacture and buy than the equivalent incandescent lamp. The packaging for CFLs typically shows a comparison of light output in lumens vs. power consumed in watts, as well as color temperature information. The comparison for one 120 V, 800 Lumen (60-watt incandescent equivalent) CFL indicates that it will use one-fourth the energy (15 watts), and that it is guaranteed to last 5 years when used for 3 hours a day. It is suggested that this is eight times the life of the equivalent incandescent lamp, and that with the savings in power used the overall cost of ownership will be lower.
The least expensive CFLs have some disadvantages with respect to incandescent units. They cannot be used with dimmer controls. There are now dimmable CFLs offered, but these come at a premium price. Also, the first CFLs generated high-frequency noise that could affect am radio reception. This problem has been reduced by later units that incorporate noise filter technology.
How about the power quality effects of CFLs?
I recently ran a series of tests on energy-saving CFL and LED replacement lamps to see how they compare as loads relative to the incandescent bulbs they are to replace. Suffice it to say that they are nonlinear in their use of current, gulping their power in short bursts. The following three figures show the current used by a 60-watt-equivalent CFL, the harmonic spectrum of that current, and the watts vs. volt-amp efficiency that results in a power factor (PF) of 0.55. The 60-watt incandescent bulbs linear load would have a power factor near 1.0.
Note: All current and power readings are 10 times the actual because of my measurement setup using 10 turns in the current measuring loop, while the harmonic percentages and power factor numbers are correct as shown.