How long do LEDs last?

Unlike conventional light sources (light bulbs, fluorescent lamps, discharge lamps …) LEDs do not burn out suddenly, but gradually decrease the illumination intensity. LEDs duration equals the number of hours until the LED illuminates with the 70% of its original brightness. Good quality LEDs used in well-designed lamps and lighting systems achieve lifetime of 30 000 – 50 000 hours. For example, a standard bulb may run for about 1,000 hours and fluorescent tubes over a period 8000-10000 hours. The quality and quantity of light and LEDs lifetime is strongly dependent on temperature. LEDs must be used in lighting systems transferring heat from the diode structures. These can be either dedicated heat sinks or a suitably designed lamp housing.

Are LEDs energy-efficient?

High-quality LED lamps using LEDs and electronic components from renowned manufacturers are more energy-efficient and emit more light than fluorescent or discharge lamps (HID). However, many LED products currently available in stores and online only slightly decrease power consumption . Many of them emit much less light than incandescent bulbs or fluorescent lamps.

Do LEDs provide high quality lighting?

Light color and color reproduction is a very important aspect of light quality. Until recently, the overwhelming majority were LEDs with Correlated Color Temperature (CCT)  above 5000K. Light with high CCT is perceived as “cool” blue – white. Although the diodes with high CCT are still very popular, there are more and more LEDs emitting neutral white and warm white (compatible with incandescent and halogen). They are less efficient than “cold” LEDs, but the technology of their production is constantly improving, which makes the difference in efficiency between  “cold” white light  and “warm” white light LEDs slowly blurred. LEDs emitting warm white light(2700-3000K) are most suitable for use in dwellings. LEDs emitting neutral – white color (3500-4000K) are more popular in commercial applications. Color Rendering Index (CRI) used for measuring conventional light sources turned out to be inadequate to define the color reproduction by the LEDs. Therefore, the LEDs, where possible, should be selected individually for specific applications.

Are LEDs cost-effective?

It is difficult to put a price on LEDs. Good quality LED lamps are more expensive in comparison to conventional light sources. However, production costs of LED technology are falling rapidly. It is important to consider the overall costs and savings, including the cost of the lamp, the cost of power consumption and maintenance costs. This approach shows that the initial purchase price of LED lighting pays for  itself after about 3 years at current electricity prices and the cost of LED lamps (March 2012).

It is assumed that:

The average cost of kWh all charges included [Euro] 0,16
Average daily use of light [h]   4
lifetime [h] Power [W] The cost of bulbs / lamps [net Euro]
Halogen 50W 2000 50 2,5
LED 12W 50000 12 40

The graph shows the total operating cost  of a 50W halogen bulb and its 12W LED equivalent, the cost of electricity, the purchase price of halogen lamps and LED lamps included (22 halogen bulbs and 1 LED light during 30 years).

    

How are LED lighting products different from other lighting, like fluorescent or incandescent?

LEDs emit light in a certain direction while the incandescent lamps and fluorescent lamps emit light and heat in all directions. For lighting applications which will use a directional light, LEDs are much more effective and energy-efficient.

For example, an incandescent lamp or a compact fluorescent lamp (CFL) used in the lamp built into the ceiling will be wasting about half of the emitted light. In the case when LED lights are built into the ceiling, they emit light only in the direction where it is needed, i.e. the room below the lamp.

An incandescence lamp produces light by conducting current in a metal filament that heats up to such high temperatures that it starts glowing. Incandescent lamps emit 90% of the electricity consumed in the form of heat.

In fluorescent lamps the current flows through the fluorescent tube containing a variety of gases. This reaction causes the emission of ultraviolet (UV), which is converted to white, visible light by a fluorescent coating (called phosphorus), which is located on the inner walls of the tube. Fluorescent lamps emit about 80% of consumed electricity as heat.

LED lamps use light-emitting diodes (LEDs) to produce light in a very efficient manner. The movement of electrons in a semiconductor structure emits light in small electronic components known as LEDs. A small amount of heat which is produced in the diode structure is transferred from the back of the semiconductor to the heat sink.

Well-designed LED lighting is more energy-efficient, durable, versatile and has longer lifetime as compared with incandescent and fluorescent lamps.

Aren`t all LED lights highly efficient and long-lasting?

Not necessarily. LEDs are used in electronic devices as indicator lamps and have been energy-efficient and reliable for years. However, creating white, stable light of high-quality from LEDs is a completely new challenge. The most important factor influencing the LED lamps energy-efficiency and long life is a well-thought-out design of the lamp. LED lamps must undergo a series of tests to be recognized as more efficient and longer lasting than conventional lighting (incandescent, fluorescent). The following requirements should also be met:

  • The lamp brightness is equal to or greater than in comparable conventional technologies (incandescent, fluorescent lamps). Additionally, the light is well dispersed in the area illuminated by the lamp.
  • The amount of emitted light is constant during the lamp use. Only reducing the amount of light at the end of lifetime is permissible
  • Very high color quality of light. The shade of white light is not changed during the lamp use
  • The lamp is at least as much or more energy-efficient as fluorescent lamps
  • Light appears immediately after turning on the lamp
  • The light does not blink when dimming / brightening
  • The lamp does not take power when it is off. The exception is the lamp with the external control system, which should not consume more than 0.5W when disabled.

A poorly designed lamp can cause a large number of problems that are visible at once, and some appear only after some (often after less than a year). These include:

  • flickering light
  • change of the light color
  • poorer intensity of light
  • uneven light emission
  • taking power even when disabled