Hello folks! Today I am going to address a question I get asked quite often. In todays market what are the differences and advantages of LED and CFL lighting and which is better?
Leaving the second question for later lets start with a review of the two types of lights.
CFL stands for “compact fluorescent light”, these are like the big overhead fluorescent lights but now in a compact form that is compatible with the standard screw base. These produce light by passing an electric current through a mercury vapor. To do this they have to generate a high voltage, this voltage is generated in that big ceramic bulge at the base. This produces ultraviolet light which is changed to visible light by the phosphor (the white coating) on the sides of the tube. To make the bulbs compact the actual glass tube is twisted into a tight spiral. To change the color of the light from warm (reddish) to cool (blueish) the chemical elements in the phosphor are changed.
LED stands for “light emitting diode”, these are small semiconductor chips. Inside the chip are two types of material where the energy of the current on one side is much higher than the other. When the current goes through the chip is like each electron jumping off a cliff and releasing energy. This energy comes out as a specific color of light due to the quantum mechanical nature of the device. To make a white LED, three actual chips are combined that have red, green, and blue output. Blue LEDs are a relatively recent invention and made possible white lights for residential purposes. The LED chips have a reflector built into them so that the light is emitted in one direction.
The brightness of a light is measured in lumens. This is how bright it looks at a standard distance averaged over all directions. So even if a light is 10 times brighter in one direction it may be the same lumens as one that seems to be less bright but emits light in all directions.
Because this is EarthSTEPS, one of the first considerations is efficiency. The most obvious measurement would be the number of lumens for each watt of power consumed. In this case both LEDs and CLFs are about the same and produce about 70 lumens per watt. Standard incandescent lights produce about 16 lumens per watt so the LEDs and CFLs are 4 times more efficient. However there is a difference between LEDs and CFLs when one considers the use. CFLs are better for wide area lighting and globe fixtures. LEDs are much better for spot lighting type situations. A fixture around the bulb can absorb up to 30% of the total light. CFLs are available in higher powers than LEDs and are better in situations where a brighter light is needed. LEDs can be bought in strings that can provide accent indirect lighting over large areas. LEDs can be used for spotlights and display lighting.
LEDs are naturally colored and do not use filters. For colored lights a filter can block up to 90% of your light and reduce and savings. For colored lights, LEDs are much more efficient.
Efficiency for 100W (1500 lumens) 6 hrs/day usage
| Type | Lifetime (hrs) | Replacement Time (yrs) | Bulb Cost | Electric Cost | Total Cost |
|---|---|---|---|---|---|
| Incandescent | 1000 hrs | 0.46 yrs | $0.75/bulb | $28.47$/yr | $30.11/yr |
| Compact Fluorescent Lamp | 10,000 hrs | 4.6 yrs | $3.34/bulb | $6.55/yr | $7.28/yr |
| LED – 3 bulbs @510 lumens each | 40,000 hrs | 18.4 yrs | $86.85/3 bulbs | $7.26/yr | $11.98/yr |
CFLs Pros: Cheapest to operate, replace less often than incandescents
Cons: Contains mercury, needs special disposal, light can be lost in fixture
LEDs Pros: Cheap to operate, seldom needs replacing
Cons: Expensive to buy, need multiple bulbs to get same brightness, focussed light
The answer to the second question, it “it depends”. It depends on your needs the type of light, the hassle of disposing of hazardous waste etc.
As a last note, the new laws generating so much political hot air will not ban incandescent bulbs, but merely require a certain level of efficiency. This can be met with halogen incandescent bulbs but without as much energy savings as the options I discuss. As of January 2012 all bulbs in the reange of 1490 to 2600 lumens must consume 72 watts or less and last for at least 1000 hours.