We answer some of the common queries - and dispel some popular myths - about energy-saving light bulbs. Mostly, we're talking about CFL (compact fluorescent) bulbs unless we specify otherwise.


Does switching lights on and off use more energy than leaving them running?
No. Switching on an energy saving bulb only uses the same amount of power as leaving it on for a minute or two. Turning the bulb on and off repeatedly may shorten its life, but normal household use shouldn't cause any problems. In fact, Energy Saving Trust Recommended bulbs are tested through thousand of cycles of switching.

Do energy-saving light bulbs take a long time to light up?
Originally they did, but most modern energy saving bulbs take little more than a few seconds to warm up to full brightness.

Producing an energy-saving bulb must take more energy in the first place than making a standard bulb. Does that make it inefficient?
An energy saving bulb may indeed take more energy to make than a traditional bulb. But the energy saved by the bulb over its lifetime far outweighs this energy consumption. This applies even more to LED lighting where bulbs can last for 50,000 hours, 50 times as long as incandescent bulbs.

Do traditional bulbs give a better quality of light?
The light quality of CFLs and LEDs does vary. If you want a light that looks the same as a traditional bulb, buy a "warm white" or "soft white" bulb, with a Colour Rendering Index (CRI) of at least 0.8. You should find the CRI somewhere in the small print on the packaging.


Are halogen bulbs more efficient than traditional bulbs?
Halogen bulbs are slightly more efficient than traditional bulbs, and most domestic halogens have a lower power rating (typically 20W-50W for halogen bulbs compared with 40W-100W for traditional bulbs). However, rooms lit with halogen bulbs usually have more fittings than rooms lit with traditional bulbs or energy saving bulbs. So they will use more energy. If you have halogen lighting in your home you can buy Energy Saving Trust Recommended halogen bulbs. To save much more energy, replace halogens with the new generation of LED lamps.

Lots of my lights have dimmer switches. Can I fit them with energy saving bulbs?
Most energy-saving bulbs aren't fully compatible with dimmer switch circuits at the moment. However a growing range of dimmable CFLs is emerging to address this problem. There are also energy-saving bulbs that can be used with 'staged dimming'. This requires a special sort of dimmer with three separate settings - high, low and off.

Is the government really banning traditional incandescent bulbs?
In effect, yes. The government, energy suppliers and many major UK retailers have lead a voluntary initiative to phase out incandescent light bulbs, where there is a suitable low energy replacement. The UK voluntary phase-out is now being followed up by legal restrictions on bulb sales across Europe.

Do CFLs contain mercury? And isn't that bad for the environment?
Yes, CFL bulbs contain tiny traces of mercury. However in the long term, they will reduce mercury pollution. This is because burning fossil fuels like coal is the biggest source of mercury in the air. Because energy saving bulbs use 80% less electricity than a traditional bulb, this means far less mercury overall.

How can I recycle my energy saving light bulbs?
Energy-saving light bulbs are part of the Waste Electrical and Electronic Equipment (WEEE) initiative. This means retailers must provide information to the public on how they can be recycled. Alternatively, contact your local authority to see whether they recycle energy saving light bulbs. If you don't know who your local authority is, check at Directgov. You can also find out more about recycling energy saving light bulbs at Recolight.co.uk


Low energy lights work in a completely different way to traditional lighting, and this has a number of implications. Obviously, the main one is that they use less electricity to produce the same amount of light, but some of the other differences are less helpful.

Here are some of the main concerns that have been raised about CFLs and LEDs, the two main types of low-energy lighting:

Are they as bright?
If you buy the right low energy bulb, it will be just as bright as the one you're replacing

Do they take ages to get up to full brightness?
All CFLs and other fluorescent tubes take some time to reach full brightness after they are switched on. However, some are much better than others. If you choose an Energy Saving Trust Recommended bulb, you can be assured that it meets strict criteria on lighting up period, as well as all the other standards.

LEDs reach full brightness just as quickly as old-fashioned bulbs. If you want instant full brightness everywhere in your house, then you could consider LEDs throughout. LEDs for standard light fittings are still expensive and not widely available, but prices are expected to come down.

Do they still give off a harsh light?
When buying any low-energy light, you have a choice about the quality of light it will produce. This is mainly to do with the colour of the light - when we buy a white light bulb we don't actually want pure white light, and we would be disappointed if that was what we got.

Is it true that they contain poisonous chemicals?
CFLs contain tiny amounts of mercury. This cannot possibly harm you while the light is working. Even if you break the bulb in your house, the amount of mercury that can escape is tiny and not considered a hazard. Nevertheless, we would recommend that you clear up carefully after breaking a CFL. Like all electronic appliances, CFLs should be disposed of by taking to an approved recycling point. LEDs do not contain mercury though, as with all electronic appliances, they should be recycled at an approved facility.

Can you see these lights flicker?
No, you can't. Unless you've got a really ancient CFL that looks like an old jam jar, your CFL will be turning on and off about 50,000 times a second. This is about 1,000 times faster than the human eye can recognise.

I've heard that if I use efficient lights, they will give out less heat and I will have to use my central heating more
This is actually true, but the effect is quite small. Most of the energy from lighting in UK homes does not contribute to space heating - it is either emitted at times when heat isn't needed, or it goes straight out of the windows, or it leads to overheating and so doesn't save fuel.

Nonetheless in all our cost and energy saving figures for lighting, the Energy Saving Trust have taken account of this "Heat Replacement Effect". We assume that you'll pay a little bit more for heating, at the same time as you pay a lot less for lighting.

Have they banned traditional light bulbs?
Old-fashioned GLS light bulbs are being phased out across the European Union and in many other countries. In the UK, the government has acted ahead of EU legislation, and most types of GLS bulb are no longer produced. Some may still be available in shops for a while until existing stocks run out.

All types of halogen bulb are still being manufactured, though there are plans to phase out the least efficient models.