30 Sep 2014

On LED Lighting

Last week, I was in my local Medlock's looking for a replacement lamp for a downlighter. The one which had gone was about five years old and was a compact fluorescent — not a comfy fit in a GU10 lamp but it worked OK until it died. I showed the dead lamp to the man behind the counter and he said they did have a replacement but that it would be both cheaper and better to switch to an LED. "They are just about the only lamps we sell now" he said. "The halogen bulb has all but disappeared and the compact fluorescent seems to be going the same way."

Then on Sunday I am at the Homebuilding & Renovating show at Olympia in London and I visit a stand called SavingCO2 which sold nothing but LED lamps. LED GU10s for downlighters, LED bulbs for where we used to put tungsten bulbs, even LED tube lights. Just about any and every bulb and fitting you have ever come across is now available in an LED version at a wattage around half of that achieved by compact fluorescents, and close on a tenth of what we have been using with tungsten and halogen, and with a light quality that most people would readily prefer.

Now admittedly, these LEDs are still a lot more than a halogen lamp — TLC is selling these for less than £2 — but the promise is that these LED lamps will last longer and, if anything, give off a better light. What is more, an interesting article online on Optics.org states that LED prices are falling by about 9% a year, but speculates that quality may suffer in the race to the bottom. There is a danger that if the quality remains too high, then manufacturers will lose the replacement market.

There is also significant money to be saved here. If a typical house has 40 lights and each light runs for an average of 800hrs/annum (about 2.5hrs per day), then the house will consume
• 2,000 kWh/annum if everything was lit with tungsten bulbs (cost £250/annum)
• 1,000 kWh/annum if it's a mix of halogen, CF and tungsten (cost £125/annum)
• 250 kWh/annum if every light fitting was replaced by an LED (cost £30/annum)

And 40 LED bulbs would currently cost around £500, so there is a reasonable payback on offer.

It's interesting to compare LEDs with PV. PV installation costs have also fallen significantly during the past few years so that, today, PV is costing around £1,500/kW to install and each kW of PV produces about 800kWh/annum in the UK climate. That 800kWh/annum is similar to the amount of energy saved per annum by converting all your lamps to LEDs, for a third of the cost.

It's also interesting to note that the building regs have been left behind by the onward march of LED lighting. Currently, the lighting requirements for Part L in England are covered in a supplement called the Domestic Buildings Services Compliance Guide: 2013 edition. It is still batting on about having to have dedicated light fittings to stop recalcitrant consumers ditching their unpopular CF lamps and reverting to tungsten bulbs at the drop of a hat. The guide requests that 75% of the light fittings in  a new build should be  energy-efficient (defined as at least 40 lumens per circuit-watt). But with LEDs achieving over 100 lumens per circuit-watt, this definition is already looking out of date.

To its credit, there is a supplementary clause in the guidance which sates that light fittings whose supplied power is less than 5 circuit-watts are excluded from the overall count of total numbers of light fittings. As most of the halogen-replacing LED GU10 lamps are rated at 3 or 4 circuit-watts, this neatly side steps the issue and allows you to put in as many as you want. My guess is that then next version of this guide will probably do away with lighting guidance altogether, as by then LED lighting will have become ubiquitous in new installations.

The big question is will LED lamps really last the 40,000 hours or so the manufacturers claim? Or will the market take them down a route towards built-in obsolescence?


3 comments:

  1. Mark,

    Interesting paper on life of LEDs and issues with LEDs below.

    LEDs are the panacea – and other fairy tales
    http://arrow.dit.ie/sdar/vol1/iss3/2/

    We are still in the rough ground where manufacurers can claim things without validated test backups. Shades of the Phoebus Conspiracy i think.

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  2. Having converted my house use almost exclusively LEDs over the past 3 years, it's certainly true that the right LEDs can easily match or better the performance of traditional lamps. However during that time I've tried a number of models that were unsatisfactory - you can't yet reliably select any LED replacement and expect to be happy with the end result (but see below).

    Key among my findings is that I've not yet found a LED lamp rated 5W or less that is bright enough to be a direct replacement for an existing fitting - except for accent lighting - though you can, of course, double the number of fittings to keep below the 5W limit.

    However the 5W limit refers to "light fittings" with a "supplied power" of less than 5W, not to lamps with a usage of less than 5W. That means that only fittings with a restricted power supply quality for the exemption, and a 3W or 4W GU10 doesn't - i.e. you still need "dedicated light fittings to stop recalcitrant consumers" ditching their LEDs too. In practice, that means using MR16 LEDs via a LED driver, rather than mains-replacement lamps. Consequently I don't see the regulations changing any time soon - not until LEDs become the dominant bulb on the market.

    Anyway, my recommendations for those wishing to convert right now are:
    50W GU10 replacement - Philips Master 7W GU10 3000K 40D Dimm
    50W MR16 replacement - 8 Watt COB MR16 warmweiss (Greenline / Lichtrevolution.de)
    40W MR16 replacement - 6 Watt COB MR16 warmweiss (Greenline / Lichtrevolution.de)
    5' fluorescent tube replacement - Auraglow 27w T8

    Hopefully it will be some time before I can report on their longevity, though.

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  3. LEDs don't achieve 100 lm/W at the end of their life
    They achieve about 70.

    T5 fluorescent do achieve nearly 100.

    T5s are still a good deal in circumstances where CFL are not.

    On the other hand, I trust the quality of a T5 from a good manufacturer more than I trust 99% of LEDs.

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