How confusing can buying a light bulb be?
According to the Environmental Protection Agency lighting consumes 12% of total in home energy use, so focusing on new energy efficient lighting makes a lot of sense. Today’s lighting has a number of technologies to choose from, including the original Edison incandescent everyday bulb, the newer compact florescent lamps (CFL) and the even newer Light Emitting Diode (LED) bulbs.
Before evaluating the types of light bulbs we should understand the components associated with lighting selection. The basic incandescent bulb is the standard that all others are compared. The labeling only shows its energy requirement in Watts (60W etc.), but it has other components not generally specified; one is its brightness or efficacy level in lumens per Watt, its color rendition index or the quality of light to render colors correctly and its color temperature in degrees Kelvin that describes its relative color appearance. These components are important when purchasing newer CFL or LED bulbs when matching the brightness and color of the incandescent bulb you wish to replace.
Incandescent bulbs were introduced for residential use more than 125 years ago. They have the lowest initial cost and are the most inefficient of modern lighting technologies. They have short life spans and use significantly more energy to produce an acceptable light output. Incandescent lamps produce light by heating a metal filament enclosed within a vacuum glass envelope. More than ninety percent of the energy used escapes as heat, with less than 10% producing light. Incandescent bulbs are being phased out as they consume a large amount of energy for the light they produce.
Compact Florescent Lamps
First generation replacement technology for incandescent bulbs was florescent tubes; the glass tube is coated with a fluorite coating and filled with a small amount of mercury. Small heating filaments at each end of the tube are used to warm the mercury into a vapor. When electric current flows through this vapor the atoms get excited and give off ultraviolet light. When the ultraviolet light is absorbed by the fluorite coating, it fluorescences, which in turn causes it to give off visible light. The light output is regulated by an electronic ballast circuit built into be base of the bulb.
Florescents come in two forms Linear Tube Florescents used in workshops and utility rooms, and Compact Florescent Lamps (CFL) used in more stylish fixtures, including ceiling floodlights, spiral lamps, standard lamps with a dome cover, candelabra torpedo-shape lamps, triple tube bright short lamps and globe lamps for bathroom fixtures.
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The advantage of CFLs is their low power consumption and long life. They are around 400% more efficient using 25% the energy of a standard incandescent bulb and last up to ten times as long; unfortunately, they have a few disadvantages as well.
One issue is that mercury is a toxic metal that can lead to adverse health affects and need to be disposed of responsibly, which requires effort. They also transmit ultra violet light which can be harmful to some people; its best not to use spiral and triple tube CFLs close to your skin for desk or reading lights, it’s best to use dome covered lamps that attenuate the UV light. CFLs also have initial inrush currents (1/2 cycle) and long start-up times (1-3 minutes); are not readily dimmable, do not like high or low temperature swings, and reliability and life-span drops when switched on and off rapidly or used over short intervals. They are affected by heat and are relatively inefficient with 85% of their energy lost as heat. The only reason they don’t appear as hot compared to incandescent bulbs is because they use less energy 13W instead of 60W for the same visible light level.
CFLs are ideally suited for low cost lights where switch on to full light intensity time is not critical (1 to 3 minutes), on times are long and used in kitchens, hallways, sitting rooms and outside lights etc. They are not suited to closets, pantries and toilets where on times are short (less than 15 minutes).
Most come from China and China has had many manufacturing quality and reliability problems; one way to minimize these potential problems is to invest in an Energy Star certified product. The design and manufacturing process of an Energy Star product has to be tested and certified by a third party before the Energy Star label can be attached.
Light Emitting Diode Bulbs
An alternative to a CFL is the newer Light Emitting Diode (LED) bulb, which is extremely energy efficient. The DOE stated that in 2012, about 49 million LEDs were installed in the U.S. -- saving about $675 million in annual energy costs. Until recently, LEDs were too expensive for most in home lighting applications; however, as with all semiconductor based products the price halves every eighteen months. As an example between 2011 and 2012, the cost of a 60-watt equivalent LED bulb fell by nearly 40 percent, and by 2030.
LEDs emit light in a specific direction; however, when combined in clusters with diffusers they spread the light for normal area lighting. LEDs produce a number of colors including red, green and blue, but are primarily used as white light generators. The standard and most stable solution uses a phosphor conversion technique where phosphors are used to convert the LEDs ultraviolet light into white light. The phosphors allow for color tuning and produce higher lumens per Watt over incandescent and CFLs.
LEDs have all the advantages associated with CFLs and incandescents and none of the disadvantages. They are more than twice as efficient as CFLs and have between two and a half and five times longer life than CFls; they do not contain toxic materials, produce negligible heat, are more resistance to breakage than CFLs and incandescents, are dimmable and have instant high intensity light unlike CFLs. The only discernable disadvantage has been price and aesthetic design, both of which are being addressed.
LEDs now come in a number of forms including directionally focused flashlights and desk lamps, diffused bulbs for area lighting, track lighting, recessed down-lights and spotlights, floodlights, candelabra bulbs and tube lights. Because of their low power they are also being used in portable battery and solar cell applications. They do have a slight vulnerability to junction meltdown at high temperatures when the design has poor heat sinking.
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As with CFLs Energy Star-certified LED bulbs signify third party verified reliability and performance as well as energy-saving. The relevant tests, devised by the Illuminating Engineering Society quantifies light output and distribution, as well as electrical power; allowing the calculation of efficacy in lumens/watts. It also identifies the light's color characteristics, such as its appearance, and its ability to render colors accurately. The lamp must also achieve 170 degrees of radial flux or light consistency.
All LED bulbs at some point are going to lose their original light intensity; the industry has set 70 percent lumen depreciation as the end of life for a LED bulb. However, instead of a 25,000 hour life test (2.8 years) a 6000 hour (6.8 months) test is performed and an algorithm used to simulate the 25,000 hour decline. For an average operating use of 3 hours a day according to the EPA the natural life of the bulb would be 22.8 years.
To pass the Energy Star benchmarks, products must perform robustly as well as demonstrate long life. Non Energy Star rated products have not been verified and may fail long before the stated life time.
As the only verified tested life cycle by Energy Star is for 25,000 hours we based all our following data on 25,000 and not the 50,000 hours claimed by some manufacturers.