1.3 LED Basic Parameters

Light Output

LEDs provide much higher light output on the same input power as comparable incandescent or fluorescent sources, because of their high efficiencies. This is also because the light emitted from the LED is naturally directional, and in almost all applications less light is lost in the fixture compared to traditional light sources. Colour quality is a key challenge facing LEDs as a light source for general lighting.

Various light sources versus LED, part 1:

Lamp Type	Incandescent bulb	Halogen lamp	Metal halide lamp	Mercury vapor lamp	LED
Technical	Incandescent bulb makes light by heating metal filament wire to light temperature until it glows.	Halogen gas increases the lifetime of the wolfram filament and avoid the darkening of the bulb. The bulb can be operated on higher temperatures, which allows warmer CCT	Adding rear earth metal salts to mercury vapor lamp enables high efficiency. It works on high pressure and temperatures, so special fixtures are required. The advantage is the compact size in comparison to fluorescents and incandescents lamps. Mixture of halides influences the CCT. After 10 000 hours the lumen output is approx. 83% of nominal.	The outer bulb is coated with a phosphor for thermal insulation and converts some UV emissions into red light. After 2000 hours only 50% of nominal light output.	Compact and highly durable light source enables both new designs and advantages in the light control. LEDs are switched on instantly and this makes applications with frequent switching easy. Tunable white  and RGB versions are already on the market. LEDs offer several benefits  which can be employed in combination with all well being applications.
Efficacy (lm/W)	6 - 16	16 - 30	75 - 125	40 - 75	80 - 140
Input power: (W)	20 - 60	55 - 100	20 - 24 000	50 - 500	0,2 - 100
Hazardous chemical content:	no	Halogens	Argon, Mercury	Argon, Mercury	no*
Electronic ballast:	no	in general no	needed to control the current	needed	needed
CRI:	100	100	70 - 95	40 - 60	65 - 97
Application:	Indoor, outdoor	Indoor applications like shops, residential	Floodlight, outdoor, shops	Outdoor applications, streetlights, facade	Indoor, Outdoor
Additional information:	high IR radiation	high IR radiation	High UV radiation	High light pollution	little UV and IR radiation
Lifetime: (hours)	1000	1000 - 3000	6000 - 20 000	4000	50 000
CCT: (K)	2700	2700 - 3500	3800 - 7000	3200 - 4200	2700 - 8000
Dimmable	yes  0 - 100%	yes 0 - 100%	yes 50 - 100%	no	yes 5 - 100%

*LEDs have to be, as all semiconductor devices, disposed in a correct way, otherwise hazardous chemicals such as arsenic or phosphorus may occur.

Various light sources versus LED, part 2:

Lamp Type	Compact fluorescent lamp - CFL	Fluorescent lamp - FL	Low pressure sodium - LPS	High pressure sodium - HPS	LED
Technical	Light output decreases shortly after first use 5-10%, end of lifetime is approx. 70-80%. Full power is not reached after 1 second. The latest versions are CCFL (cold cathode). In general, for outdoor applications all FLs have problems at lower ambient temperatures, sometimes it is not possible to start lamp.	The lamp reaches best efficacy if the temperature of lamp cold-spot is around 35°C. A problem is stroboscopic effect in some applications. Problems occur at lower ambient temperatures, sometimes it is not possible to start the lamp. After 25 000 hours lumen output decreases down to 50%.	LPS lamps have an outer glass vacuum envelope around the inner discharge tube for thermal insulation. Yellow light is very insect maintenance friendly. The fact is the light source is quite spacious and the recycling process costs a lot of money. Practically, this type of the lamp is running out version because of low CRI.	Smaller than LPS. Yellow light is very insect maintenance friendly.	Compact and highly durable light source enables both new designs and advantages in the light control. LEDs are switched on instantly and this makes applications with frequent switching easy. Tunable white  and RGB versions are already on the market. LEDs offer several benefits  which can be employed in combination with all well being applications.
Efficacy (lm/W)	46 - 80	70 - 120	up to 200	100 - 150	80 - 140
Input power (W)	10 - 50	8 - 80	10 - 180	50 - 600	0,2 - 100
Hazardous chemical content	Small amount of Mercury	mercury, neon	Sodium, Neon, Argon	Sodium, Neon, Argon, Mercury	no*
Electronic ballast	needed or build in	needed	needed	needed	needed
CRI	80 - 90	80 - 99	30	25 - 85	65 - 97
Application	Indoor applications	Indoor	Outdoor, streetlight, security	Outdoor, streetlight, security	Indoor, Outdoor
Additional information	Frequently on/off reduce lifetime; high UV radiation	Frequently on/off reduce lifetime; high UV radiation	Full brightness rapidly; no lumen degradation over lifetime; relative big light source.	Less light pollution as Mercury vapor lamps; Frequently on/off reduce lifetime	little UV and IR radiation
Lifetime (hours)	15 000	15 000 - 45 000	16 000 - 23 000	10 000 - 24 000	50 000
CCT (K)	2700 - 5000	2700 - 8000	difficult to describe	2000 - 3000	2700 - 8000
Dimmable	yes,  3 - 100%, continues dim damage the light source	yes, 3 - 100%, continues dim damage the light source	no	yes 50 - 100%	yes 5 - 100%

*LEDs have to be, as all semiconductor devices, disposed in a correct way, otherwise hazardous chemicals such as arsenic or phosphorus may occur.

Correlated Colour Temperature (CCT) CCT describes the relative colour appearance of a white light source, indicating whether it appears more yellow/gold or bluer, in terms of the range of available shades of white. The most efficient (up to 140 lm/W) high-output white LEDs are phosphor-converted devices based on blue LEDs, characterized by very high CCTs of 5000K or above. Warm white (from 2700K to 4000K) devices are now available at efficacies comparable with FLs (up to 120 lm/W).
Color Rendering Index (CRI) CRI is a measure of the ability of a light source to render colors, relative to a reference light source (incandescent bulb). CRI may be compared only for light sources of equal CCTs.