The following is an article from the United Sustainable Energy Agency.
Energy saving light bulb myth buster
Why use them?
Compact fluorescent light bulbs (CFLs) use 80% less electricity, save you about £3 a year each, and last up to 12 times longer than old fashioned tungsten bulbs.
What are they?
Think of them as compact versions of the strip lights in work places since the 1950s.
Have they improved?
You can now get all shapes and sizes, fittings and levels of brightness, including 150W equivalent and dimmable options. A recent blind test of 761 shoppers found that 64% preferred the light from them.
Is it better to leave them running?
No, switching them on uses the equivalent electricity as leaving them on for a few minutes. Most now light instantaneously.
How should I dispose of them?
Use the service your municipal tip provides for the safe disposal of fluorescent tubes.
Is mercury an issue?
Ironically, installing CFLs ought to help reduce the need for coal-fired electricity production - a major cause of global mercury emissions. CFLs contain mercury - about 5mg. Locked into its tube, this is harmless.
What should I do if I smash one?
Ventilate the room for 15 minutes. Put on your rubber gloves, brush the bits into a bag, seal it and drop it at the tip next time you go.
Are tungsten bulbs banned?
No. Manufacturers have agreed to withdraw them from sale, starting with 100W this year, 60W in 2010 and 40W in 2001.
Where can I find out more?
Contact the Energy Saving Trust on 0800 512 012