What's the current state of play with these? Having just had to replace yet another from the array of allegedly long-life 35W tungsten MR16s which festoon our kitchen ceiling :-( I'm interested...
eg, lots here:
What wattage do you realistically need to replace an 35W conventional bulb? What's the colour temperature like? Payback time? etc etc. Anyone made the 'jump'?
Thanks David
There isn't one. In those consumer products, the white efficiency is not much better than the halogen lamp, so you'd need something like a 30W one. They don't exist, because there's no way to run an MR16 at 30W without cooking the LED. Best you can get is a few watts, and that's the equivalent of a few watts of halogen lighting. Efficiency and lifetime of LEDs plumets when they get warm.
Cold white (5000K or so). 3000K ones are only half the efficiency, so you won't find them in cheap consumer products.
I'm playing with Luxeon ones I've made myself. If you want to buy ready made products containing professional quality lighting LEDs, they seem to start at around £50 each, with most nearer £80.
Bummer. but thanks for the info.
I came across a diy site yesterday actually: this sort of thing?:
David
Not the same as that. (Can't see much point making that -- you can buy them easily enough.)
I'm using proper Luxeon lighting LEDs (3W), not little 5mm LEDs. Also, the MR16 lamp just isn't suitable for anything other than decorative/toy lighting -- it's too small to dissipate the required power without getting far too hot. There's scope for designing replacement bulbs with the same front flange fitting, and a much larger rear for a heatsink, which would fit in some MR16 fittings. But I think LED retrofit is unlikely to be where LED lighting is going to succeed, unless someone works out how to make LEDs work efficiently very much hotter than they can today.
The newer Cree XR-E is more efficient than the Luxeons. (Not to the point where you can equal a 35W halogen with 3W of LED, but enough that 3W of LED may be enough for some MR-16 applications.)
We bought one of these to evaluate at work...They state LED output is 660Lux at 1m, same as 35W halogen.
But in practice the halogen is much brighter and in our tests does not even replace a 35W light, certainly greater than 20W halogen, but not 35W. I think the spread was certainly bigger than the 38° quoted as well.
Other thing to watch out is light is a lot bluer and harsher, might be OK for a "show room" but for general lighting is harsh.
One other gotcha is must be freely ventilated or else seriously reduces the life. We bust our LED light as the downlighter in our "test kitchen" had glass fibre insulation running across the back of it. The existing halogens (50W 38°) just all get very very hot, but all 15 have worked fine for the last 12 years. The LED downlighter did not last very long before failing completely, probably less than a week. In between it got progressively dimmer. Yes we did know about this and just wanted to see what happens.
So, I will not be replacing my halogen downlighters with LED's just yet...
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