Yes, we’ve safely banned the bulb and got rid of old fashioned, energy guzzling ‘incandescent’ bulbs. Just so you know what’s watt (geddit?), here’s a handy guide to deciphering the language of lighting: from halogen to LED and beyond.

The basics

Wattage – The wattage tells you how much electricity the light bulb uses – and therefore how much you’ll pay in running costs. Note that different lighting technologies produce light through different processes (see later), with some using a lot less electricity to produce the same light output. For example, a 22-watt compact fluorescent lamp can provide a similar level of lighting to the old 100-watt incandescent bulbs that have been phased out. But within the CFL family, a larger wattage means a brighter light.

Voltage –  ‘Voltage’ refers to electrical potential difference. Household lights are either mains voltage (240V) or low voltage. Note that ‘low voltage’ does NOT mean low energy – it’s the watts that count.

Lumens – A measure how much visible light a bulb emits. In other words, the brightness of the bulb.

Colour temperature – Colour temperature is a characteristic of visible light; think of it as a measure of how warm or cool the light from a bulb looks. Colour temperatures over 5000 K (Kelvin – the unit of absolute temperature) are a ‘cool’, blueish-white, while those of 2700-3500 K are a ‘warm’, yellowish-white. You’ll often see compact fluorescent bulbs marked ‘warm white’ or ‘cool white’. Traditional fluoro tubes were typically cool white, giving fluorescent light the reputation of looking like sterile, hospital lighting! If you prefer warmer tones, don’t give up on CFLs – warm white versions are commonly available.

Warm white or cool white?

Lighting types

Incandescent (aka filament) – In these lights, electricity is passed through a tungsten filament, producing heat until it’s hot enough for some of that energy to be emitted as visible light (think ‘white hot’). This technology is over a century old, produces waste heat (not good in summer) and is very inefficient.

Halogen – Halogen lamps are a type of filament light, producing light by producing heat first. They have halogen gas inside the bulb to prevent evaporated tungsten from depositing on the glass bulb. Halogen downlights are the most common in homes. A typical halogen ceiling downlight is 50-watt bulb, but they are commonly used in multiples to provide general room lighting. If you have eight in your living room, that’s 400 watts worth of electricity use to do the job that a single pendent 22-watt CFL could do. One writer called the trend of rooms full of halogen downlights ‘ceiling acne’!

‘Energy-saver’ halogen – Some manufacturers are producing halogen lamps with pear-shaped outer bulbs that look like traditional incandescent bulbs but use up to 30% less electricity. They are dimmable and produce a warm-looking light. However, they’re not as energy efficient as fluorescent alternatives.

Infrared coated (IRC) halogen – As the name suggests, IRC halogen downlights have a coating on the inside of the lamp that reflects infrared (heat) radiation back to the filament so that less electricity is needed to heat the filament to the point where it produces visible light. Hence a 35W IRC can produce a similar light output to a standard 50W halogen.

Heat lamps – With these incandescent lamps, the heat produced at the filament is the aim of the game. They are designed to give off radiant heat as well as light. They are a popular heat source for bathrooms where forced air heaters tend to have a cooling effect. Heat lamps for bathrooms are often sold as a complete heater, light and exhaust fan unit, such as the IXL Tastic units. Keep in mind that each lamp is typically a whopping 275-watt lamp and most units use two or four of them. If you use the ‘heat’ switch when you only need light, you’ll be effectively turning on a 550- or 1100-watt light source (and paying for it through electricity bills). Make sure your kids or housemates know this. Don’t forget to turn heat lamps off and don’t use them when you only need light.

The many options for household lighting. Image from a rather brilliant book called ‘Greeniology 2020’

Fluorescent – These tube-like lights use a completely different technology to filament bulbs to produce light. They fall into the category of ‘gas-discharge’ lamps. They use electricity to excite mercury vapour enclosed inside the tube. These excited mercury atoms then get a phosphor coating inside the tube to join the party and fluoresce, producing visible light. This conversion of electrical energy to visible light is much more efficient than filament lights. Traditionally, fluorescent lamps have been long fluoro-tubes, but they’re also available in ring shapes, and others.

Compact fluorescent (CFL) – CFL stands for compact fluorescent lamp – the convenient little brother of the fluoro tube.

Light emitting diode (LED) – LEDs are a completely different technology again. These are the lights of the future. They are very efficient and long-lasting – in the future the need to change light bulbs may become extinct (along with light bulb jokes, heaven forbid)! Each diode is a point light source. Many practical applications of LEDs use multiple diodes. For example, modern traffic lights use LED lighting, which is why they look like a cluster of light dots when viewed closely – each dot of light is a single light-emitting diode. LED downlights are now available and the range of home LED products is growing. They’re currently relatively expensive, but prices will come down as the technology takes off. And keep in mind the savings from their tiny energy use – particularly as electricity prices increase.

So that’s a brief look at lighting. If you want a further look at the past, present and future of lighting, see my ABC Catalyst story Changing the Globe. Or if you have some other lighting lingo you want illuminated, let us know by commenting.