(I posted this elsewhere on the internet and thought I would also share it here . . . )
Why Choose LED lamps over CFLs?
LED lamps typically use less power (watts) per unit of light generated (lumens). A good LED lamp can generate twice as many lumens per watt as a CFL (50-100+ versus 40-80).
- less greenhouse gas emissions from power plants
- lower electric bills
LED lamps last much longer than CFLs, as much as 10x longer (50,000 hours versus 5,000 hours).
- fewer spent lamps in the landfill
- less frequent lamp purchasing/changing, especially important for hard-to-reach lamp locations
LED lamps generate less heat than CFLs.
- decreased load on Air Conditioning systems
- reduced danger of burns from touching lamps
- reduced fire hazards
LED lamps typically are RoHS compliant, meaning that they have no or at most negligible amounts of hazardous substances within the scope of that compliance (lead, cadmium, mercury, ...). CFLs on the other hand all have 1mg-5mg of Mercury (even more in tubular fluorsecent lamps), and no doubt many people are not properly disposing of spent CFLs, resulting in Mercury making its way into the environment, with serious consequences. And if a CFL were to break in your house you might be exposed to Mercury.
- virtually no risk of environmental contamination
- no risk of personal exposure to hazardous materials
LED lamps tend not to have unpredictable failure modes. There are stories of CFLs catching fire, emitting smoke and odors, exploding, etc. The ballast circuitry in CFLs can fail in a variety of ways, some not so pleasant for anyone in the same room/house. This is especially the case when market pressure causes the designers to cut corners to save production costs. LED drivers are not nearly as unstable and usually fail by just no longer supplying power to the LEDs themselves.
- virtually no risk of fire/smoke/odor
LED lamps emit no Infrared or Ultraviolet radiation. CFLs (and tubular fluorescent lamps) generate light by exciting the Mercury vapor inside the lamp with electricity, generating Ultraviolet radiation, which stimulates the phosphor coating on the inner surface of the glass bulb, causing it to re-radiate most of the Ultraviolet radiation as visible light. LED lamps generally create "white" light by using blue LEDs and a phosphor coating which re-radiates some of the blue light as longer wavelength light (yellow range of the spectrum), together appearing as white.
- no personal exposure to Ultraviolet radiation, which can cause cell damage
- artwork and other sensitive items are not degraded as a result of exposure to Ultraviolet radiation
LED lamps are not sensitive to frequent power cycling. The lifetime of CFLs (and tubular fluorescent lamps) is reduced by turning them on/off more than a certain number of times per day. The "rated" lifetimes of such lamps are usually based on assumptions that they will be left on, say 3-4 hours, each time they are turned on, rather than having that 3-4 hours be spread out over many on/off cycles. The actual lifetime of a fluorescent lamp will suffer compared to its "rated" lifetime if this "on-time" assumption is not adhered to. This can lead to people thinking they should not turn off their lights as often as might be best for energy conservation purposes, leading to wasted energy.
- no concern about how often you turn on/off your lights
LED lamps have better control over the direction(s) in which their light is emitted. This is advantageous in applications where you only want the light to go in one general direction (unidirectional) rather than in all directions (omnidirectional). Think of recessed ceiling lighting where any light not directed downward is wasted. LEDs tend to generate light in one direction. By using lenses in the LED lamp, this light can be spread out to achieve various specified beam angles. To do that with incandescent or fluorescent light sources, which emit light in all directions, a reflector must be used (the 'R' part of 'PAR38' for example), and these reflectors are never perfect, causing some light loss in the process. This further increases the efficiency advantage of LED lamps over traditional light sources.
- less wasted light
LED lamps turn on instantly (reaching full brightness immediately). CFLs tend to have a warm-up period which may range from a few seconds to over a minute. During this warm-up period they are not as bright as they eventually become. This can lead to problems ranging from having to wait for light levels to increase to a useful level, wasting your time, to turning the lights on before you really need them, in anticipation of the warm-up period, wasting electricity.
- no wasted time or electricity
LED lamps can be used in colder temperatures than CFLs. Most CFLs will not turn on or will only emit very low levels of light in the cold (near freezing). I have not heard of a low-temperature limit for LED lamps although there may be one, but I'm sure it's much lower than that of CFLs.
- effective in cold temperatures
LED lamps are typically far more robust than CFLs. CFLs, with their thin glass tubing, are easily broken, such as by dropping them on a hard surface from just a few feet up. LED lamps are solid-state devices, and as such can handle impacts with far less risk of breakage/damage.
- much less easily broken
Why Choose CFLs over LED lamps?
LED lamps are still quite expensive compared to CFLs of similar light output ($50-$100+ versus $5-$10). This initial expense is not as bad though, if you consider both the extended lifetime of LED lamps over CFLs, and their efficiency advantage, allowing them to generate more light from less electricity. I have developed a formula that takes all those factors into account and can give you a cost-per-million-lumen-hours number for any lamp for which you have all the necessary specifications (and the cost of electricity). Recently I ran the numbers on some newly-introduced LED lamps and it is getting closer and closer to being able to justify the use of LED lamps over CFLs purely on the basis of total cost of ownership, without even considering any of the other advantages listed above.
LED lamps are still not as bright and/or small (for their brightness) as you can get CFLs. This means that some applications simply will not have a bright and small enough LED lamp available to fit them (when the lamp must fit in an enclosure).
Very few LED lamps currently available are dimmable. There are dimmable CFLs on the market now, at a somewhat higher price than their non-dimmable versions.
LED lamps are not as commonly available for omnidirectional applications (the classic "light bulb" shape). Due to the unidirectional nature of the light emitted by LEDs, it is a more difficult design challenge to build an LED lamp that can emit light in all directions.
LED lamps do not tend to emit so-called "Full Spectrum" light. Incandescent light by its nature is full spectrum, fluorescent light can be made to approximate full-spectrum light by appropriate use of different phosphors (at increased cost). This approach to achieving full-spectrum light could also be used for LED lamps, but I have yet to see it. People generally cannot see the difference between full-spectrum light of a given Correlated Color Temperature (CCT) and more narrow-spectrum light of that same CCT. Our eyes just average out all the frequencies of light they see and arrive at a single color, whether that color was achieved through many small levels of widely-spread-out frequencies of light (bell-shaped curve) or a couple of large spikes.
Edited by bobkart - 12/7/09 at 1:00am