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Light Bulb Evaluations

Evaluation of CFL and LED bulbs led to the conclusion that CFL bulbs are more economical to use due to their substantially lower price. Furthermore, it is easier to allow for dimming functionality with CFL bulbs. LED bulbs consume roughly 75% less power than their CFL equivalent, but are 15 to 20 times as expensive. Also, most LED bulbs are not dimmable (many of those that claim they are actually functioning as 3-way bulbs with no smooth dimming capability). Older dimmer switches worked by changing the voltage (using a rheostat) going to the light bulb. This type of dimmer would not work with LED bulbs (since the diode does not have a linear response to change in voltage). However, most new dimming switches work by cycling the lights on and off (~120 times per second). But in order for the LEDs to appear dim, cycling frequencies of 400+Hz may have to be used. It also must be noted that for proper performance (as well as a more efficient use of a CFL), dimmable CFL bulbs should be used on dimming circuits (check the package).

LED bulbs are great in locations such as closets (where lights are often turned on, then immediately off). In order for CFL bulbs to perform most efficiently, they should in locations where they are on for more than 15 minutes. Therefore, CFL use in closets is not ideal. It also should be noted that LED bulbs offer much longer average lifetime than CFLs (50,000+ hours vs. 10,000 hours for CFL).

After looking at the comparative data, halogen light bulbs are quite expensive without the same energy savings as CFLs. They also tend to have a shorter life and more focused light. The nice thing is that they are dimmable however this trade off is not quite sufficient to argue for the use of halogens over CFLs or LEDs.

High Pressure Sodium lamps are relatively inexpensive however the accompanying ballast is quite expensive. They offer longer lives and while their ratings are seemingly high (35-50W) the amount of lumens they output make them equivalent to 150-300W incandescants. These bulbs are very practical for outdoor lighting but the yellow color may not be as suitable for indoor applications.

Mercury Vapor lamps do not offer much selection for low wattage lighting. Their lifetimes are a bit shorter than CFLs and only consume about 50% less energy than incandescents. The price per bulb and ballast is more expensive than high pressure sodium lamps. One plus side of these lamps is the color is categorized as cool white.

Metal Halide bulbs are the most expensive of those that require a ballast. Their lifetime and energy savings make them comparable to CFLs (35W bulb equivalent to a 100W incandescent). One plus side is that their color is halogen white which is better than most CFLs.

Overall, the metal halide bulbs seem to be the most competitive with the CFLs and LEDs for indoor use however any of the last three are possible options for outdoor use.

Joseph Galambos
Samantha Gunter

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