How Eco is an eco-halogen light bulb?

A friend of mine asked me to investigate so-called 'eco' halogen light bulbs she had seen in various outlets. Halogen bulbs use a little less power than incandescents but are not nearly as efficient as compact fluorescents  (CFLs) or LEDs - eco is a relative term. It turns out that the eco-halogens (from Osram) have energy rating C whereas compact fluorescents and LED light bulbs are normally rated A and there is a world of difference between A and C - a factor of at least 3 in electricity use.


I find it is a while since I last discussed lighting in any detail (Should I buy LED light bulbs?, Nov. 2011) and I did not mention lights in my previous posts on energy ratings, though lights have had energy ratings since 1998 [1]. Most light bulbs should have this displayed on the packaging, though reflector bulbs are exempt for some reason, which means lots of halogens are not labelled. The chart below shows the maximum watts allowed for different energy ratings. There is a big jump even between A and B. An old style incandescent would be rated E and a C rating is only about 20% less. In this case the eco halogen uses 46 W for a nominal 60 W whereas an A-rated CFL equivalent would use at most 13 W. If you used this bulb 1 hour per day the difference between the 13  W CFL and the 46 W halogen would save you 12 kWh/year. I am currently paying 13.4p/kWh so this would save me £1.60 over the year. It should last 20 years.

Energy use for light bulbs with different energy ratings, by nominal wattage. A standard incandescent would be class E.

The only eco advantage of the halogens is that they do not contain mercury whereas CFLs do. However, if you take your dead bulbs to an appropriate recycling point this is not a problem. Cambridge City Council uses Recolight for their recycling and they recapture up to 95% of the materials including the mercury. If you break a bulb at home then there is a risk of mercury escaping but the quantity in each bulb is tiny - much less than in mercury thermometers and barometers.

As well as EU legislation for energy labelling there is also legislation for phasing out inefficient bulbs [2]. It is not an easy read but if I understand it correctly C rated bulbs will be allowed up until September 2016, when the final stage of the phase out occurs and even then B rated will still be allowed (34 W for a 60 W equivalent). I dare say halogen bulbs will remain a popular alternative to incandescents because they have a 'colour' very similar to the old incandescents and they warm up very quickly. Some CFLs take a while to warm up though they are better now than they used to be. Also, CFLs can still suffer from premature old age if you switch them on and off a lot, particularly if you switch them on when they are still warm from earlier use. For this reason they are not recommended for toilets where they are not on for very long anyway. Finally CFLs suitable for dimmer switches are much less energy efficient.

LEDs come on instantly, are endlessly switchable and often dimmable. Spots and reflectors are available for around £6 now but general purpose bulbs are more expensive. It is worth looking out for special offers: here is a 60 W equivalent globe LED dimmable bulb currently on offer for £13.75. The cost is less outrageous when you consider the long lifetime - this one is rated for 50000 hours so at 4 hours/day it should last 34 years. It uses just 12W so at  6 hours/day this costs £6.60/year less than the halogen - payback for the higher up front cost in 2 years. LED technology continues to improve. Philips recently announced a new bulb using half the energy of normal LEDs.

This EU website has good explanations of various bulb parameters including colour temperature, lifetime and luminous output.

By the way, if you have ever wondered why LED light bulbs need big heat sinks even though they use much less power and hence generate less heat, I understand now it is because the electronics in the bulb is delicate. With an incandescent it did not matter how hot it got as long as it did not set the lamp shade on fire.

Also relating to fires, if you are considering replacing halogen downlighters with LEDs in an insulated ceiling you might think that because the LEDs generate less heat you don't need to cut away the insulation around them. This is not true however, as there does have to be somewhere for the heat to go and even if you don't start a fire you will shorten the lifetime of your bulb. You can get downlight covers which make it easy to roll the insulation over or  you can get lights like this one which dump the heat into the room below.


[1] COMMISSION DIRECTIVE 98/11/EC of 27 January 1998 ...with regard to energy labelling of household lamps

[2] COMMISSION REGULATION (EC) No 244/2009 of 18 March 2009 ...with regard to ecodesign requirements for non-directional household lamps