There are three main types of energy-saving light bulb. Note that the 'energy saving' described below is as compared to an old-fashioned, incandescent bulb.
These are the most common energy-saving light bulbs.
Price: £2 - £10
Energy saving: up to 80%
Durability: 10 years
These are the cheapest energy-saving light bulbs. They are also the least energy-efficient and the least durable.
Price: £2 - £3
Energy saving: up to 30%
Durability: 2 years
These are the most expensive energy-saving light bulbs. They are also the most energy-efficient and the most durable. An LED light should pay for itself in 5-10 years.
Price: £10 - £35
Energy saving: up to 90%
Durability: 20 years
Old-fashioned bulbs had either a bayonet or a screw cap (there are three sizes of each). Energy-saving bulbs that are designed to replace them have the same range of fittings. UK ceiling lights generally have bayonet fittings, but some lamps and lamp holders have screw fittings. CFL, halogen and LED bulbs are available in a two-pin fitting for use in specialist lamp holders.
You can get energy-saving light bulbs in most shapes - even spotlight bulbs. There's no difference between the different shapes of light bulbs, so you can get whichever one you prefer. However, for some light fittings and shades, you'll need to be careful to get a bulb that fits. In other cases, you might want a specific shape, such as a candle.
Stick-shaped bulbs do not give much light from the end, which may make it quite dark directly under a ceiling light. Spiral bulbs are better. Enclosed bulbs (top row) have the best light distribution, but are less bright for a given wattage.
Last updated: June 2014