Easy to understand buyers guide
1. Buy the light bulb that gives off the amount of light you need
In the past we bought light bulbs based on the amount of power it used: “Bring me a couple of 100 Watt bulbs from the shop”. In reality, however, we were buying a certain amount of light and chose between 40, 60, 75 or 100 Watt (W) incandescent bulbs by knowing from experience how much light they produced.
Now we have an increasing range of new lighting technologies available to us (compact fluorescent lamps (CFL), LED, Halogen), each with a different level of efficiency. This means that it no longer makes sense to buy a bulb solely on its power rating – we now need to shift to buying ‘lumens’, which is the measurement of the total amount of light produced by a light bulb. For example, a typical 60 W incandescent light bulb produces around 720 lumens (lm), but the CFL that produces 720 lm only uses 12 W (a significant energy saving).
2. Adjust the mood with warm and cool colour
Two ratings are used to describe the colour of white light sources. Correlated Colour Temperature (CCT) describes the ‘shade’ of white light emitted, while the Colour Rendering Index (CRI) rates the ability of the light to accurately portray colours of objects in the space being lit.
CCT, measured in Kelvin (K), is a scale to describe how ‘warm’ or ‘cool’ the light source appears. In theory, as an object (e.g. a piece of metal) is heated, it glows changing colour from a red to orange to yellow to white to bluish-white as the temperature of the object increases toward 7000 K (to convert to Celsius minus approximately 300).
A standard incandescent bulb operates by heating the filament to 2700 K, which is warm white coloured light. Fluorescent, CFL and LED light bulbs, however, are available in a wide range of colour temperatures, which allows you to customise the mood of your space. As a guide (and see Figure 1; not to be confused with colour temperature which is the shade of white light).
A bulb’s CRI will be between 0 and 100, where 100 represents true natural colour reproduction for that particular colour temperature. Anything higher than 80 is usually adequate, but for specialised tasks where colour is important (e.g. food preparation, applying makeup, painting) it is advisable to choose bulbs with a CRI above 90.
In the past we bought light bulbs based on the amount of power it used: “Bring me a couple of 100 Watt bulbs from the shop”. In reality, however, we were buying a certain amount of light and chose between 40, 60, 75 or 100 Watt (W) incandescent bulbs by knowing from experience how much light they produced.
Now we have an increasing range of new lighting technologies available to us (compact fluorescent lamps (CFL), LED, Halogen), each with a different level of efficiency. This means that it no longer makes sense to buy a bulb solely on its power rating – we now need to shift to buying ‘lumens’, which is the measurement of the total amount of light produced by a light bulb. For example, a typical 60 W incandescent light bulb produces around 720 lumens (lm), but the CFL that produces 720 lm only uses 12 W (a significant energy saving).
2. Adjust the mood with warm and cool colour
Two ratings are used to describe the colour of white light sources. Correlated Colour Temperature (CCT) describes the ‘shade’ of white light emitted, while the Colour Rendering Index (CRI) rates the ability of the light to accurately portray colours of objects in the space being lit.
CCT, measured in Kelvin (K), is a scale to describe how ‘warm’ or ‘cool’ the light source appears. In theory, as an object (e.g. a piece of metal) is heated, it glows changing colour from a red to orange to yellow to white to bluish-white as the temperature of the object increases toward 7000 K (to convert to Celsius minus approximately 300).
A standard incandescent bulb operates by heating the filament to 2700 K, which is warm white coloured light. Fluorescent, CFL and LED light bulbs, however, are available in a wide range of colour temperatures, which allows you to customise the mood of your space. As a guide (and see Figure 1; not to be confused with colour temperature which is the shade of white light).
A bulb’s CRI will be between 0 and 100, where 100 represents true natural colour reproduction for that particular colour temperature. Anything higher than 80 is usually adequate, but for specialised tasks where colour is important (e.g. food preparation, applying makeup, painting) it is advisable to choose bulbs with a CRI above 90.
The CCT of a light bulb determines the shade of white light. A cool white bulb is used on the left and warm white bulb on the right.
The difference in colour rendering by light bulbs with a CRI of 60, 80 and 100.
3. Choose the shape of light you need
Most rooms need two types of lighting: general/ambient lighting and task/accent lighting (Figure 3). Different bulbs and light fittings should be used for these two purposes.
3. Choose the shape of light you need
Most rooms need two types of lighting: general/ambient lighting and task/accent lighting (Figure 3). Different bulbs and light fittings should be used for these two purposes.
Combination of general and accent lighting.
General/Ambient Lighting
Ambient lighting provides overall, general lighting which radiates a comfortable level of brightness. Having a central source(s) of ambient light in all rooms is fundamental to a good lighting plan.
• Use omni-directional (light in all directions) light bulbs in pendants, chandeliers, ceiling or wall-mounted fixtures.
• Use light fittings that allow most of the light through so a lower wattage light bulb can be used (more energy efficient). Some light fittings can block/absorb 50% or more of light.
• Avoid using downlights for general illumination as they provide bright ‘pools’ of light on the floor (most floor surfaces absorb as much as 80% of all the light) without directly illuminating the rest of the space.
-- Up to six downlights may be required to light the same area as one pendant light. Think about other ways of lighting with fluorescent light bulbs before installing halogen downlights. If you do have halogen downlights, install lower wattage, more efficient bulbs (infra-red coated (IRC) halogen or LED). Downlights are much better suited to spot-lighting.
Task/Accent Lighting
Task lighting is used to illuminate specific tasks such as reading, sewing or cooking. Accent lighting adds drama to a room by creating visual interest. This might mean emphasising paintings, house plants, or collectables.
• Directional light bulbs such as LED or halogen reflector lamps (downlights) are best employed for this purpose.
• By installing task lighting on different switching to the general room lighting you can choose when to use it, avoiding unnecessary energy consumption.
The spread of light from a directional light bulb can range from a narrow spotlight to a very wide floodlight. When selecting a directional light bulb, look for the Beam Angle, which gives a sense of how wide the beam spreads out when emitted from the bulb (in technical terms, this is the angle where light intensity drops to 50% of the centre beam intensity). Virtually all of the light from a directional light bulb is inside the beam – very little light reaches other surfaces outside the path of the beam (i.e. this provides a quite dark ambience).
• Rule: for the same wattage bulb the smaller the beam angle the brighter the illuminated surface will be, but in a smaller area.
• Select the beam angle by determining the largest dimension of the feature to be lit and the distance from the feature (Figure 4). The packaging of most directional light bulbs generally provides a simple graphic to assist with selecting the appropriate beam angle.
Note: A PAR spotlight will typically have a beam angle of twenty degrees or less while a PAR floodlight can range from the low twenty degree range all the way to sixty degrees. It's almost a guarantee that you'll be dissatisfied with your purchase if, for example, you mistakenly buy a PAR spotlight when replacing a PAR floodlight (regardless of bulb technology such as LED, CFL or halogen) as the area of illumination will be quite different.
General/Ambient Lighting
Ambient lighting provides overall, general lighting which radiates a comfortable level of brightness. Having a central source(s) of ambient light in all rooms is fundamental to a good lighting plan.
• Use omni-directional (light in all directions) light bulbs in pendants, chandeliers, ceiling or wall-mounted fixtures.
• Use light fittings that allow most of the light through so a lower wattage light bulb can be used (more energy efficient). Some light fittings can block/absorb 50% or more of light.
• Avoid using downlights for general illumination as they provide bright ‘pools’ of light on the floor (most floor surfaces absorb as much as 80% of all the light) without directly illuminating the rest of the space.
-- Up to six downlights may be required to light the same area as one pendant light. Think about other ways of lighting with fluorescent light bulbs before installing halogen downlights. If you do have halogen downlights, install lower wattage, more efficient bulbs (infra-red coated (IRC) halogen or LED). Downlights are much better suited to spot-lighting.
Task/Accent Lighting
Task lighting is used to illuminate specific tasks such as reading, sewing or cooking. Accent lighting adds drama to a room by creating visual interest. This might mean emphasising paintings, house plants, or collectables.
• Directional light bulbs such as LED or halogen reflector lamps (downlights) are best employed for this purpose.
• By installing task lighting on different switching to the general room lighting you can choose when to use it, avoiding unnecessary energy consumption.
The spread of light from a directional light bulb can range from a narrow spotlight to a very wide floodlight. When selecting a directional light bulb, look for the Beam Angle, which gives a sense of how wide the beam spreads out when emitted from the bulb (in technical terms, this is the angle where light intensity drops to 50% of the centre beam intensity). Virtually all of the light from a directional light bulb is inside the beam – very little light reaches other surfaces outside the path of the beam (i.e. this provides a quite dark ambience).
• Rule: for the same wattage bulb the smaller the beam angle the brighter the illuminated surface will be, but in a smaller area.
• Select the beam angle by determining the largest dimension of the feature to be lit and the distance from the feature (Figure 4). The packaging of most directional light bulbs generally provides a simple graphic to assist with selecting the appropriate beam angle.
Note: A PAR spotlight will typically have a beam angle of twenty degrees or less while a PAR floodlight can range from the low twenty degree range all the way to sixty degrees. It's almost a guarantee that you'll be dissatisfied with your purchase if, for example, you mistakenly buy a PAR spotlight when replacing a PAR floodlight (regardless of bulb technology such as LED, CFL or halogen) as the area of illumination will be quite different.
Illuminance (lux) at various distances from a light bulb with a 24 degree beam angle – the further the target surface is from the directional light source, the wider the area of illumination and lower the level of light.
4. Expand your definition of cost
Choose the light bulb that will cost you the least in the long run, not just the lowest first cost.
One of the fundamental differences between lighting technologies is their lifetime. A second is the power consumption – they both have a significant impact on the true cost of providing light over an extended period of years.
• The initial price of a halogen bulb, for example, is far lower than the price of an equivalent LED bulb. But when you consider that a good quality LED lasts 5-10 times longer and consumes 1/5th of the energy, the true dollar cost becomes clear.
Figure 5 provides an example of the costs for replacement light bulb alternatives (halogen, linear fluorescent, LED and CFL) to a 75 W tungsten filament incandescent bulb.
4. Expand your definition of cost
Choose the light bulb that will cost you the least in the long run, not just the lowest first cost.
One of the fundamental differences between lighting technologies is their lifetime. A second is the power consumption – they both have a significant impact on the true cost of providing light over an extended period of years.
• The initial price of a halogen bulb, for example, is far lower than the price of an equivalent LED bulb. But when you consider that a good quality LED lasts 5-10 times longer and consumes 1/5th of the energy, the true dollar cost becomes clear.
Figure 5 provides an example of the costs for replacement light bulb alternatives (halogen, linear fluorescent, LED and CFL) to a 75 W tungsten filament incandescent bulb.
Costs for replacement light bulb alternatives to a 75 W tungsten filament incandescent bulb. Cost figures based on lifetimes of 25,000 hours for LED, 8000 hours for linear fluorescent and CFL, 2000 hours for halogen and 1000 hour for incandescent bulbs; an LED price of $50, linear fluorescent and CFL price of $6, halogen price of $4 and incandescent price of $1; and electricity rate of 22.759¢ per kilowatt-hour (kWh).
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The material on this website is copyright Commonwealth of Australia, except where otherwise indicated.
Commonwealth copyright material on this website is licensed under the Creative Commons Attribution 3.0 Australia Licence.
You are free to copy, communicate and adapt the Commonwealth copyright material, so long as you attribute the Commonwealth of Australia (Department of Industry and Science) as the author of the original material.
Permission to use third party copyright content in this publication can be sought from the relevant third party copyright owner/s.
Wherever a third party holds copyright in material presented on this website, the copyright remains with that party. Their permission may be required to use the material.
Please contact the Department of Industry and Science before making use of this material.