the curse of the GU10 halogen bulb

Posted by : S

Sabtu, 11 Juli 2009

I know more than I want to about these light bulbs. While the UK Government is waging war on the 100 watt incandescent light bulb, they have, typically, ignored the growing trend of using these bulbs. I guess they pay people to change bulbs for them.

We had our house gutted and rebuilt in 2000, and as a consequence had around 40 recessed lights fitted, each of which take the GU10 mains voltage (240v) GU10 light bulbs.

At first, the main issue was that the halogen bulbs had a very short life span and cost a lot to buy, around �5. I seemed to be changing a couple a week. Things have improved and now the bulbs are relatively cheap ( �1-�2) and have a fairly long life expectancy.

So what is my gripe ? Well these bulbs are rated at a hefty 35 or 50 watts. The packaging even implies that they are energy saving in some way, but of course watts are watts. i
If you have 5 * 50 watts halogen bulbs in your kitchen, then you are using a unit every 4 hours they are on. If I turn on all the halogens (assuming the bulbs are 50 watts) then I'm using 2Kw. that's the same as my washing machine

So my point is that 2 * 50 watts GU10 bulbs = 1 * 100 watts bulb .

The other thing to note about these bulbs is they get very hot. The recessed light fittings are supposed to have a heat cowl fitted above them if in open loft space to prevent insulation or other material touching the back of the bulbs which get quite hot.

While the light from these bulbs is good quality I was unhappy with the energy consumption and nervous that a couple of installations might create a fire risk above. I looked into low energy versions and here is what I found:

The bulbs above are all GU10-fittings, but use a range of technologies. You can also see that while they share the same diameter and lugs at the top, they vary in length.

These are from the left :

11watt Compact Florescent (CFL) Megaman brand cost �8
7 watt Compact Florescent (CFL) Farnell brand �8
1.5 watt LED unknown brand �9
50 watt halogen Sylvania brand �2

So the three technologies for GU10 bulbs are LED, CFL and Halogen.

The Megaman I got from B&Q and it's the best of the CFLs and probably the best alternative. gives reasonable light instantly. In common with all CFLs the light quality is a bit bleached or cold, but they work well. The only issue is that they are physically much longer, and depending on the light fitting , they may not fit. Most of my recessed fittings are backless. the bulb is gripped by the rim and the electricity is connected by a loose cable connector at the back. This means the depth of the bulb can be accommodated. You may find that your fittings will not accept a bulb this deep, so it's important to check before buying.
The Farnell bulb is closer to the form-factor of a standard GU10 bulb and can be used where the depth problem described above is an issue. Even so the dimensions are not *exactly* the same around the 'neck'. These do not give good light from switch on, and need a few minutes to warm up, initially giving a pinkish light. However once warm they work well, and I have a set of these in my utility room.
I had high hopes for LED technology as this appears to provide the cheapest running costs. However the light quality is very poor. A dim cold bluish light which is not good for spotlights. I also noted that some of the individual LEDS' have failed over a 2 year period, so reliability is not great. I have high hopes for LED lighting, and I have seen some bulbs on the web which use a single high power LED rather than an array of 20 smaller ones. However these are currently around �23 per bulb, too much to be practical
Finally you see a halogen bulb for reference. excellent light quality, but heavy power consumption and they get very hot.

So in conclusion the Megaman variety wins as the best allround replacement if you want to use less energy and generate less CO2. the Farnell offers a viable alternative where space is an issue. LED bulbs have yet to be a viable alternative. I noticed that all the display units in B&Q use LED bulbs. This is , I assume, to reduce their energy costs, but it also provides a way to see the type of light they provide.

update 9/01/10

yesterday I visited the local B&Q, and noticed they had a number of LED bulbs. They had the standard ones as I'd used and dismissed above, but they also had a much more expensive 'alpha' range. Two types, one was a 20watt equivalent for around �16 ! This appeared to have a single large LED at the centre, and the light was described as brilliant white.

the second was a 10 watt equivalent which uses 24 SMD white (Surface Mount Device). the dome is difuse so it's hard to see what the LED's look like but I can make out that they are yellow. I have seen pictures on the web of a new type of LED bulb which uses rectangular yello LED's , not the tiny spherical ones , found in the cheaper LED bulbs.This was around �12 and the light was described as soft white.

Because I now appear to have an obsession with finding an energy efficient GU10 bulb, I got the one of the second type to try. �12 is a high price for a bulb, but in the persuit of science ....

Anyway I used it to replace a standard GU10 that had failed in my bathroom, and the light quality is excellent. Better than either brand of CFL and a million miles from the previous LED bulb. Light quality is warmer , like a regular GU10 halogen. Perhaps it's a little diffuse as it does not have a single light source, but very good. It only consumes 2.8 watts around 1/20th of a 50watt GU10.

Update 10/07/2010

I recently aquired a number of another type of LED GU10 bulb. These have 3 high powered LED's and are suited as spotlights. They use only 2.8watts and cost around �12 each. These work very well where the earlier Alpha type are too diffuse.