How Do LED Light Bulbs Compare In Savings and Construction To Incandescent (Regular) Light Bulbs?

Given the need to conserve energy in our energy hungry world, newer technologies tend to penetrate the market as energy costs rise. Today, the LED (light-emitting diode) has made its presence known, especially with the advent of clusters to power larger lights. With the price of oil rising, and the emphasis on less carbon emitting technologies, we can expect new technologies for providing illumination, and tweaks and revisions to older technologies.

This article will address the following questions:

1. How do LEDs work?

2. How is an LED constructed?

3. Why do LEDs use so much less energy?

4. What are average power savings?

The LED is a relatively small source, perhaps less than 1 square millimeter. It can emit light of different colors, but for home use soft white light is the focus today. I do not profess to be a physicist, but will describe the action of electrons in an LED in a way that can help to illustrate the difference in function against that of the incandescent light bulb.

In an atom (element), electrons can be put into an "excited" state (moving differently from their usual positions). When this happens by, for instance, the application of heat, the electron(s) jump and leave behind a "hole." Jumping to a different level in the atom, these electrons can resonate until some action brings the atoms back to their holes (the hole is just a name for the position the electron used to be in). As electrons return to their pre-excited lower energy state holes, energy is given off in the form of light! This process of changing electron energy levels is what is harnessed by the LED. The color (or wavelength) of the light depends upon the atomic structure of material being used in the LED, and its temperature.

So of what value is this last paragraph? Put very simply, light is emitted from a semiconductor in an LED just by the movement or flow of electrons. From techtarget.com, the material the electrons flow through, or semiconductor, is a substance, usually a solid chemical element or compound, that can conduct electricity under some conditions but not others, making it a good medium for the control of electrical current. Its conductance varies depending on the current and voltage applied to a control electrode. This is what sets the LED apart from our old-fashioned incandescent light bulbs.

In an incandescent light bulb, there is a filament which is intentionally designed out of tungsten to increase the resistance to electron flow. This resistance causes the filament to glow hot giving off 95% heat and 5% light. An LED generates most of its light by "allowing" electrons to flow through a semiconductor which does not create a lot of heat. The result of allowing the electrons to flow, light emission, produces only 3% of the heat of an incandescent bulb.

Imagine an LED as having a strip of material inside its bulb. One half of the strip is made of one semiconductor, while the other side is made of another kind of semiconductor. Electrons flow from one side to the other (in one direction only) and this movement causes electrons to change their energy levels. As electrons drop from one level of energy to a lower level of energy, the difference in energy winds up being given off as light.

The following picture is for assisting in understanding the CONCEPT.

Because of the physical properties of the LED it saves energy, and hence, lowers the cost of electricity. For instance, at holiday time the traditional C7 Christmas tree bulb uses 6 watts of electricity. An LED uses 0.08 watts. Running a 50 light strand at the national average cost for electricity for 5 hours per day for a month would cost $4.50. I usually use 3 or more strands outside - $13.50 for a holiday season. A comparable calculation for LED strands would be less than 60 cents per strand per month. My 3 strands would run $1.80. Here we are talking about 13% of the cost to run C7 strands! You can see why widespread use of LEDs could someday save this country hugely!

LEDs typically use less than 10% of an equivalent incandescent bulb (10% of the power used in an incandescent bulb to produce the same light). Put another way, an LED producing the equivalent of 40 watts of incandescent light uses less than 4 watts! That is a pretty easy formula to remember if you are trying to get a handle on savings. A 75 watt incandescent bulb (most common used) would only require less than 7.5 watts in an LED.

The average amount of electricity used by a 1200 square foot home (I chose this as an average U.S. home) according to http://michaelbluejay.com is 30.6 kWh per day. Of that total, 6-10% is the average wattage used for lighting (usage can be as high as 25%). So on the high side we are talking about 3.06 kWh per day for light. If you were to go to your electric utility home page (or thereabouts) you will find the price you pay per kWh for electricity. Multiply 3.06 kWh x cost per kWh and that will be approximately the incandescent cost rate to light your house per day.

MULTIPLY THAT by 13% (0.13) and you will find the cost of electricity to power LEDs giving off the same amount of light per day. Subtract the two products and you will have the savings if you could replace all incandescents with LEDs. By the way, as an aside, the average home has about 45 light bulbs in approximately 30 fixtures.

But things aren't that simple. LED lamps are rather expensive. Even though LEDs will have a life 5 times greater than CFLs and 41 times greater than an incandescent bulb, there is a Sticker Shock when buying them!

An LED bulb producing a 60 watt equivalent of light is $39.95. The CFL runs $3.95. The incandescent bulb runs $1.25

But wait! This translates to $95.95 for 50,000 hours on an LED, $159.75 for CFLs for 50,000 hours, and $652.50 for incandescent light bulbs over the same period of time (remember, you would have to replace bulbs sooner).

In general, an LED is 10 times the price of a CFL and 32 times the price of an incandescent.

This discussion shows why LEDs are the wave of the future. The savings on electricity are phenomenal. Cities are taking the lead in large use of LEDs; some cities are changing to LED street lights because it can save up to 80% on energy use. By way of another concluding remark, battery life can be extended 10-15 times if powering LEDs.

Work is underway to lower the unit price of LEDs and headway is being made at Purdue University where new and enhanced materials may lower the initial cost of LED lights. The future looks bright for the LED light.

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