I've just replaced half of the LED downlighters in a kitchen, and
realised that the new ones are exactly the same make and model as the
old ones that were installed in 2014.
These are the downlighters:
In 2012 I remember seeing LED efficiency improvements each year, but
here there's been no improvement in more than five years. So has the
LED lighting efficiency reached a limit?
The 200 lm/W was first reported back in 2010 in the lab.
At the time I thought this technology would eventually make its way
into real-world lamps, but it's been ten years now so maybe that won't
100 lm/W has been my go-to efficiency level for about five years now.
I didn't realise that Philips offered up to 126 lm/W though.
On Thu, 9 Jan 2020 14:01:00 +0000, Andy Burns wrote:
Ikea's are poor things - low luminous efficacy (l/W) and hot.
4 years ago I was replacing luminaires and set the line at 100l/w for all
but GU10s (the GU10 has a hard life, cap up and in a hole); 3 years ago I
was buying 3W 320l COB lamps, 4W 470l, 5W 600l and 6W 800l COBs.
Last year's GU10 were 3W 420 lm.
A lot of places are still 5W 400l etc., although Home Bargains' 12W 1500l is
OK and cheap.
I've plenty of stock so will wait until there's an improvement - at my age
it'd better be soon!
I'm replacing them due to failure. Not sure whether it's the driver
or the LEDs that are failing though.
They have a five-year guarantee which appears to be about equal to
their actual life.
The replacement downlighters are significantly brighter than the
remaining old ones though, so I'm not sure I'd want to run them for
ten years even if they would last that long.
If that is the case it is a bit surprising so many modern downlights
don't have replaceable bulbs. I doubt many people want to rewire a new
downlight every five years as opposed to just replacing a £2 gu10 bulb.
It's an easy job if the original installation left enough slack in the
cables to pull the lamp and transformer through the hole.
The only potential problem I find is that the edge of the hole in the
plasterboard ceiling is fragile, and can be easily damaged by the
retaining clips as the lamp is removed and replaced.
The efiiciency of an LED depends on its emitted wavelength, and the most
efficient part of the visible spectrum is at the near ultraviolet end
where the theoretical limit is around 680lm/W (at 380nm).
For a reasonable colour rendition visible 'white' LED the theoretical
limit is around 400 lm/W so we are getting very close!
An equivalent brightness to a 60W tungsten lamp would consume about 2W
In practical terms yes. There are advances in maximum brightness LEDs in
the laboratory but they are unlikely to make it into mass production
until someone finds a way to make them at a high enough yield and
reliability. The PSU efficiency is already a factor in consumer devices.
They dim over time as defects in the crystal accumulate. See:
The luminous flux at the surface of an LED die is approximately the same
as the sun's photosphere and the phosphors are quite close to their
limit. Push them much harder and you either need very good heat sinking
or a much more robust expensive phosphor. You can never say never in
this game - people are working on improved phosphors and better CRI.
I am a bit puzzled why you need to replace so many LED units though.
The ones in my house are a mixture from different eras using a replace
on fail policy. All the spotlights are now LED based. A few filament
bulbs persist in seldom used fittings (as do much older CFLs).
I can see that dimming effect myself, as the replacement lamps are
significantly brighter than the remaining originals. Given the eye's
logarithmic brightness perception they may be more than twice as
I've got 12 downlighters in the kitchen. I've replaced five due to
failure over the past year. Given the difference in brightness after
five years, I wouldn't want to keep the originals for ten years even
if they lasted that long.
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