Compact Fluorescent Lamps (CFLs) are a modern type of light bulb that will fit into a standard light fitting, usually a bayonet fitting in the UK , but CFLs are also available with Edison screw fittings. Most CFLs either consist of a number of short glass sticks, or two or three small tubular loops. Sometimes, these are enclosed in a glass bowl or made to look like a traditional bulb. There are also some older CFLs that look light a clear or white glass jam-jar and are much heavier, but these are less efficient and are not recommended. CFLs work in much the same way as a fluorescent strip light: the inside is coated with a phosphor that gives off the light and there is an electronic ballast to start the lamp operating.
CFLs are often called low energy lamps because they use less energy than the traditional tungsten filament bulbs that they replace. As they plug in directly to the normal light fittings they work off the UK 's standard 230V supply and should not be confused with low-voltage lamps which do not offer significant energy or cost savings.

Compact Fluorescent Lamps are sold by the wattage, in much the same way as normal bulbs. However because they use a lot less energy, a lower wattage bulb will be needed to give out the same amount of light. The table below gives the approximate equivalents that can be used:

Although CFLs cost more to buy, they save money because they use less electricity.

Ordinary Bulbs	CFLs
40W	7 - 10W
60W	15 -18W
100W	20 - 25W
150W	32W

No! There used to be a general belief that because fluorescent strip lights used more power in their warm-up phase, then it was better to leave them on all the time. This was never true - an old style strip light (or non-electronic CFL) only uses as much energy in the warm-up phase as it does whilst operating for a minute or so, and modern electronic ballast CFLs use even less energy at the start. Although CFLs do not use much electricity it is still best to keep them switched off when not wanted - why throw money away on anything that not needed?

The Government's Market Transformation Unit has tested 1 several leading brands (including retailers' own-brands) of CFLs and conventional, tungsten bulbs. It found that, generally, around 8 of 10 bulbs of either type exceed the median (average) life stated on the box. Specifically, at least 90% of bulbs from all brands of CFLs with a claimed average life of 6,000 hours or less exceeded this average life. Even where much longer lives were claimed - of 12,000 to 15,000 hours - over 70% of bulbs exceeded the claimed average life. So the overall conclusion was the CFLs do really last - on average - at least as long as the life stated on the box.

When the same team tested conventional bulbs they found a similar result for bulbs that were claimed to last for in excess of 1,000 hours - these bulbs typically lasted for 1,150 hours. Cheaper tungsten filament bulbs, that did not claim to be long life, still met their manufacturers' claims, but rarely lasted for more than about 900 hours and some brands only lasted for 600 hours on average.

This testing means that you CAN believe the claims on the boxes. What is more, it confirms that even the cheapest energy saving CFLs will typically last for 5,000 hours of use, compared to only just over 1,000 hours on average for the best conventional bulbs.

The same team tested the energy efficiency ratings of the bulbs as well. All bulbs were within one grade of the measured efficiency, and most were correctly reported. Some CFLs that claimed to be "B" rated were found to be rated "A" (and a few vice versa), and similarly some "E" rated ordinary bulbs actually achieved "D" status. But the message was clear - CFLs use very much less power and are a lot cheaper to run, over their lifetime, than ordinary tungsten bulbs.

Again, No! Low voltage lights are usually small bright halogen bulbs, often needing a transformer to work. They are commonly used in kitchens where they give a bright narrow beam, often requiring several lights on a single unit. Although each halogen bulb uses less power than a conventional light bulb, they use a great deal more than a CFL and if several halogen bulbs are used, they will use more energy in total than conventional lights.