Here we summarize the key features of the main types of low-energy light bulbs now available for domestic situations.
CFLs (Compact Fluorescent Lamps)
These work on same principle as fluorescent strip lighting, and contain an integral electronic ballast, which regulates current flow through the fluorescent tube.
- Power: most in the range 8 to 24 watts; some delay in reaching full brightness
- Light quality: earlier designs criticized for 'cold' light; warmer toned designs now available
- Styles: various, including sticks, spirals, traditional bulbs, globes, candles and reflectors
- Dimmable: Yes, but certain designs only
- Lifetime: varies, usually in range 6000 to over 20,000 hours
- Environmental: contain small amounts of mercury vapour inside the tube - no more than 5 milligrams, and in some designs less than 1 mg. Broken or obsolete bulbs should be disposed of appropriately (see Disposal of low-energy light bulbs).
Halogen bulbs
Consist of a tungsten filament surrounded by inert gas plus traces of a halogen such as iodine or bromine. More efficient light producers than normal tungsten filament bulbs, so need less powerful bulb for same light output. Energy-efficient versions use about 30% less energy than standard halogen bulbs.
- Power: 40 to 150 watts (less than 30 watts for some 'eco' energy-saving designs); full brightness achieved at switch-on
- Light quality: bright or 'cool' tone
- Styles: various, including traditional bulb, candle, globe, reflector
- Dimmable: yes
- Lifetime: typically 2000 hours
- Environmental: contain no mercury or lead
NOTE: handle without touching the glass envelope to avoid damaging the bulb.
GE's latest HaloSpherical halogen bulb
Light-Emitting Diode (LED) bulbs
Widely used in vehicle lights, traffic lights, and electrical equipment, and increasingly for decorative spot and space lighting in the home. Note that both low-voltage DC and 240 volt AC versions are available, so make sure you have the correct type for your fitting.
- Power: current versions range from 1 to 7 watts
- Light quality: typically a 'cool' white light, but 'warm' designs increasingly available; also, various single colours, and sequential multicoloured giving a mini light show!
- Styles: reflectors most common, but new designs include LED clear or frosted globes and candles, and LED cove lighting to replace fluorescent units
- Dimmable: only certain designs; otherwise, dimmers greatly reduce the lifetime of the bulb
- Lifetime: typically from 15,000 to over 25,000 hours, although some decorative styles may have a shorter lifetime
- Environmental: contain no mercury, although LED semiconductors may contain small amounts of lead, nickel, arsenic and other potentially toxic metals