The standard incandescent light bulb found in most homes is extremely inefficient in that 90% of the energy it uses is given off as heat. Efficiency is a measure of how much visible light is produced (measured in lumens), against the amount of electricity it requires (in watts (W)). Therefore a 100W incandescent bulb, which produces 1200 lumens, only produces 12 lumens of light per watt. A fluorescent lamp is rather more efficient - a 20W tube gives 60 lumens per watt. It is therefore 5 times more efficient than the incandescent bulb, and only uses 20% of the electricity.

This difference in efficiency has led to the development of compact fluorescent lamps (CFL's). These use one quarter of the electricity of a standard light bulb, and last up to 13 times longer. These lamps also give a warmer light than older fluorescents, making them more pleasant to work under. Although they are initially more expensive, their greater efficiency and long life makes them a much cheaper option in the long term.

CFL's are designed to be fitted to standard lamp fixtures. Because CFL's work differently to incandescent bulbs, they are best used in areas that remain lit for long periods, such as kitchens and living areas. They are not as suitable for areas which are only lit for very short periods of time, such as closets, as they take a burst of energy when they are first switched on, and can take up to 5 minutes to 'warm up' and reach full brightness. Repeated switching on and off can also reduce their life span. They also have a rapid flicker, which could make them less suitable for accent lighting in an office, for example.

Also available are a new generation of incandescent lamps which give a bright white light close to daylight quality. Tungsten-halogen lamps come in two types - high voltage lamps used for general illumination, and more energy efficient low-voltage halogen lamps used for accent lighting. This type is expensive but more efficient (they can save up to 60% of the running cost of a standard incandescent lamp), and they last up to 2000 hours.