Compact Fluorescent (CFL) bulbs are the ones people think of first when they think of low energy bulbs.

They contain fluorescent tubes that contain a vapour that emits ultraviolet light when electricity is applied. The tubes are coted inside with a coating inside that ‘fluoresces’ - turns the ultraviolet rays into visible light - hence ‘fluorescent’ light.

Fluorescent tubes were first invented in the 1940’s but it wasn’t until the energy crises of the 1970s when traditional fluorescent tubes were wrestled into more compact shapes.

Early versions were slow to light and tended to be cumbersome – modern versions are becoming increasingly smaller and more efficient. The ’starter’ units associated with traditional fluorescent tubes have been replaced by electronic circuitry which means that these bulbs will never be quite as small as their traditional incandescent couterparts.

They remain, however, highly efficient, with less of the energy being coverted into heat (and thus wasted), requiring, as a general guide, about one fifth of the power of a traditional incandescent bulb. It goes beyond that now, with additional energy ratings, an 11w ”A” rated bulb will produce more light than an equivalent “B” rated bulb.

There are other benefits, as well as using around a fifth of the power to produce the same light output, CFL bulbs last around seven times as long as their traditional counterparts. There is a downside though, some of the compounds used in CFL bulbs are not particularly friendly to the environment, an issue that recycling centres will need to come to terms with in the future.