Can anyone give me a percentage efficiency figure for the types of LEDs found in car or other high end lighting systems please? It does not need to be super accurate, just a ball park percentage figure will do. It is for use in a discussion with some pupils at school tommorrow, comparing different lighting types (incandescent), Low energy and modern LEDs. Thanks in advance, Ambrose the stressed!!

They're not actually THAT good really, because they produce a LOT of heat too, unlike little "indicator" LEDs that are much better. AFAIK power LEDs are not much more efficient than CFLs

why not make an experiment out of it? You can measure the energy in and the heat out, the left over energy is how much light they give out and then do the maths from there.

Google is your friend. Modern high power LEDs are very efficient. They get hot because of a lot of power in a small space and are still not that effcient – but far more than most other light sources. xpgs are over 100 lumen / watt now edit – so twice as efficient as CFLs

http://www.ecoledlighting.com/docs/LEDEfficiencyComparison.pdf

http://www.plantedtank.net/articles/Light-Bulb-Comparison/29/

TJ – as above, about similar to CFLs, not THAT efficient.

Onzadog – you'd need a bomb calorimeter to get a reasoably accurate heat power output, measuring temp isn't indicative.

100 lumen / watt

=~ 15%

sfb – what's the (maths behind the) relationship between lumen and energy? (curious, not looked into it)

Coffeking – twice as efficient. CFLs up to 55 l/watt leds up to 110 l/watt

TJ – by your own links:

Link1:
CFL 25-60
LED 20-55
Link2:
LED 80
CFL 75

? Have I missed something? Though obviously there are the odd spike above that (P7's at 90l/W etc), the general rule is as above?

Coffeking – xpgs are hitting 110 l/watt now

Those tables are out of date – LED tech moves on so quick

XP-G's (for example, but one of the most efficient today) are 130 l/watt per Cree's own datasheet, per this link that's 22% efficient.

http://en.wikipedia.org/wiki/Luminous_efficacy

Automotive LED's seem to produce a much lower l/watt figure but this is a compromise for other more desirable traits, there's some interesting reading on the latest automotive LED's for headlamp use on CPF . . .

Fd

what's the (maths behind the) relationship between lumen and energy? (curious, not looked into it)

684 lumens = 1W of light power

I'll work on approx 60% then. Many thanks folks.

I'll work on approx 60% then

of what ? Unless you say it's utterly meaningless!

Defining efficiency as

useful energy transfer
—————————- X 100%
total energy input

(Sorry, I can't format it very well on here).

All I want is the percentage of the electricity provided to the LED that then is converted to light, as opposed to wasted as heat.

So thus, I think it is OK to say that a certain device (whatever it may be) has an efficiency expressed as a percentage.

60% efficiency may not be even theoretically possible for light generation. The best figure I've ever seen was 22% for organic LEDs

taken from TJ's first link, 'table of characteristics etc', fudging in 'recent advances'

fergusd – Member

XP-G's (for example, but one of the most efficient today) are 130 l/watt per Cree's own datasheet, per this link that's 22% efficient.

http://en.wikipedia.org/wiki/Luminous_efficacy

22% wffwecient is the vvery best you get from LEDs from this

I was surprised that the sodium, orange colour street lights are about as efficient as the latest LEDS. At least we've been using something relatively efficient for a while there.