The strength of light given out depends on the wattage of the bulb and also how efficiently it converts energy into light, known as the lamp’s efficacy. It is important to know how energy efficient a bulb is, how long it will last and the color of light it gives out. There are two main types of bulb, filament and fluorescent.

Filament bulbs

Low voltage tungsten halogen: these are very small and compact and so good for discreet display and accent lighting. They are the same color and have a similar lifespan to mains halogen but to make them work you need a transformer to convert from mains to a lower voltage.

Mains voltage tungsten halogen: matter from the tungsten filament interacts with halogen gas and redeposit on the filament, which glows through quartz surround. The bulb does not blacken so has a longer life than a tungsten or incandescent bulb at about 2,000 hours. It gives out a cool light, so is good in spotlights.

Tungsten or incandescent: ranging from 8 to 200 watts, the filament glows white hot and radiates light through a pearlised or clear glass surround, eventually blackening the bulb and burning it out. The light is warm and flattering, like natural light. But it has a low life span of around 1,000 hours and is less efficient than other types because it produces a lot of heat.