What is an LED and how does it work?
LED refers to "light emitting diode." A diode is a special semiconductor that emits a bright light when an electrical current passes through it. Diodes are relatively small (about 1/3 of an inch square), so to create adequate light, many are clustered together in one luminaire. LEDs are undergoing the most vigorous advancement of the electric lighting technologies. What was once used as the indicator light on your VCR has now been reborn into a nearly full-spectrum source used for its red-blue-green color mixing capabilities and as a neutral source for tasks and accents.
What are the advantages of LEDs?
LEDs have several advantages over conventional incandescent lamps. For one thing, they don't have a filament that will burn out, so they last much longer. Additionally, their small plastic bulb makes them very durable. They also fit more easily into modern electronic circuits. But the main advantage is efficiency. With conventional incandescent bulbs a filament is heated to create light. But unless the bulb is used specifically as a heater (an incubator or heat lamp, for instance), this is inefficient because a large portion of the energy isn't going directly to producing light. Conversely, LEDs don't create heat to produce light, thereby greatly increasing the light output of each watt of energy consumed. This is often referred to as lumens per watt.
How efficient are LEDs compared to incandescent bulbs?
The efficacy of newer LEDs is more than five times as great as comparable incandescent bulbs. In other words, LEDs use only about 20% as much electricity to produce the same amount of light. However, because LEDs direct a larger percentage of light where it is needed, in many applications they are as much as ten times as effective as incandescent bulbs, reducing energy use by 90%.
How does the brightness of LEDs compare to incandescent lighting?
Brightness is measured in lumens, while the energy a bulb consumes is measured in watts. To produce similar amounts of light, LED and fluorescents bulbs consume far fewer watts than incandescent or halogen bulbs. A standard 60W incandescent produces 800 lumens, whereas LEDs consume 13-15 watts to produce 800 lumens.
Energy Star guidelines recommend the following:
- If you used to buy a 100-watt incandescent, look for a LED watt range of 23-30 (1600 lumen output)
- If you used to buy a 75-watt incandescent, look for an LED watt range of 18-25 (1100 lumen output).
- If you used to buy a 60-watt incandescent, look for an LED watt range of 13-15 (800 lumen output).
- If you used to buy a 40-watt incandescent, look for an LED watt range of 9-13 (450 lumens output).
How do LEDs compare to fluorescent lighting?
Both LED and fluorescent lighting are more efficient than incandescents: LEDs consume up to 90% less energy and fluorescents consume up to 75% less. Fluorescents are made of glass tubes and can shatter if dropped, whereas LEDs are more durable. Also, fluorescents contain trace amounts of mercury and several states have special recycling rules.
Are there potential drawbacks to LEDs?
LEDs have a higher initial cost relative to traditional lamps, however people typically make back the cost in a couple of years because of LEDs' energy efficiency and long life. Also, earlier LEDs emitted directional light making them more suitable for task lighting than ambient glow. These days, omni-directional LED luminaires have become more common, pointing light at reflective surfaces or through high-quality lenses to give off an even and diffused glow. And although the first LEDs were associated with poor color accuracy and crispness, measured by the color rendering index (CRI), they have improved in recent years. Look for LEDs with a minimum of 80 CRI.
Why do LEDs cost more than other lighting options?
The components are costly: LEDs are made of circuit boards and require drivers, and some use yellow phosphor, a rare earth compound. However, with advances in technology and growing popularity the prices have been steadily dropping. Keep in mind that the quality of LEDs varies greatly, which will affect the price. Look for ones that provide the best color and light output over time from a reputable manufacturer.
Where should I use LEDs?
LEDs have excellent directionality, making them a great option for the following lighting applications:
- Task and reading lamps
- Pendants and overhead
- Accent and display lighting
- Cove lighting
- Outdoor and landscape accent lighting
- Linear strip lighting (under kitchen cabinets)
- Recessed lighting/ceiling cans
- Stair and walkway lighting
- Difficult to reach places (due to their long life and low maintenance)
- Art lighting (unlike incandescent and fluorescents, LEDs don't produce UV radiation, making them safe for artwork.)
LEDs at a glance
Energy efficient LED bulbs typically use only 2-10 watts of electricity, 1/3 to 1/30 the electricity that incandescent or fluorescents use.
Longevity LED bulbs last up to 10 times as long as fluorescents, and far longer than a typical incandescent.
Compact form Fixtures using LEDs offer unique design capabilities due to their small size.
Cool to the touch LEDs convert electricity to light and do not cause heat build-up.
Durable LEDs don't have a filament or glass bulb so they are less susceptible to damage and breakage than a regular incandescent or fluorescent bulb.
Mercury-free No mercury is used in the manufacturing of LEDs.
Low-maintenance costs LEDs save in maintenance and replacement costs because of their long lifetime.
Slow failure Unlike an incandescent or fluorescents, which burn out abruptly, LEDs slowly dim over time.
Higher upfront cost LEDs typically cost more than incandescent, halogen, or fluorescent bulbs. However, that cost can be recouped in energy savings.
Directional light LEDs light a smaller area of space, making them better candidates for task lighting. However, newer designs better reflect and diffuse light, providing indirect and glare-free illumination.
How long will an LED last?
A quality LED lamp can last anywhere from 20,000 to 50,000 hours. If you operate the lamp for 6 hours per day, 365 days a year, your LED lamp could last 20 years.
Do I have to replace individual LED diodes?
An LED does not burn out like a standard lamp, so individual diodes do not need to be replaced. Instead, the diodes gradually produce lower output levels over a very long period of time. An LED is typically considered "dead" at 70% of initial light output.
Can LEDs produce a warm light?
Color is measured as temperature on the Kelvin scale and interpreted as "warm" or "cool." Incandescent fixtures produce warm light and are low on the Kelvin scale with a color temperature of 2700K. The earliest LEDs produced a bluish/green color at temperatures around 5500K, but are now readily available in warmer temperatures.
Can LEDs replace the conventional incandescent and compact fluorescent light bulbs in my existing fixtures?
The ability to purchase an LED bulb and screw it into an existing incandescent fixture (like you can with a CFL) is known as retrofitting. Retrofitting is more popular these days and many options are available. However, you may find an LED module that can physically fit into an existing incandescent but the fixture won't necessarily maximize the LED's efficiency.
Are LED lights dimmable?
Some can be dimmed, but you'll need to consult manufacturer specifications for compatibility with your current system because some may not be able to handle the lower wattage on which LEDs operate.
Do LEDs generate noise when in use?
No. Unlike some incandescent, halogen and fluorescent lamps, LEDs do not "buzz" when powered on or when dimmed.
Consider the following factors when evaluating LED, fluorescent, halogen, and incandescent bulbs:
|Most Efficient||Least Efficient|
|Efficiency||Uses up to 80% less energy than an incandescent||Uses up to 75% less energy than an incandescent||Uses up to 30% less energy than an incandescent||90% of energy is wasted as heat|
|Average Life Span (Hours)||50,000||10,000||1,000||1,000|
|Annual Operating Cost||Low||Medium-Low||Medium||High|
|Light Output (Watts/800 Lumens)||6-8W||13-15W||45W||60W|
|Color Temperature||Varies by product; select high-quality LEDs for consistency||Ranges from warm (3,000K) to cool (6,000K)||Ranges from warm (2,700K) to cool (5,500K)||Warm (2,700K)|
|Color Rendering Index (CRI)||80-90+||Most are 60-70+||100||100|
|Turns On Instantly||Yes||Needs to warm up||Yes||Yes|
|Other Considerations||Higher initial purchase cost||Contains mercury||Operates at very high temperature||Manufacturing of 40W, 60W and 100W lamps has been phased out|